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Search for "Knoevenagel condensation" in Full Text gives 63 result(s) in Beilstein Journal of Organic Chemistry.
Mannich base-connected syntheses mediated by ortho-quinone methides
- Petra Barta,
- Ferenc Fülöp and
- István Szatmári
Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43
- ortho-amidoalkylation of phenols in which a tandem Knoevenagel condensation occurs through o-QM followed by the formation of an unstable oxazine intermediate [64]. Later, the same research group published a similar reaction extended by various lactams carried out in trifluoroacetic acid in water [65
Graphical Abstract
Scheme 1: Formation of amidoalkylnaphthols 4 via o-QM intermediate 3.
Scheme 2: Asymmetric syntheses of triarylmethanes starting from diarylmethylamines.
Scheme 3: Proposed mechanism for the formation of 2,2-dialkyl-3-dialkylamino-2,3-dihydro-1H-naphtho[2,1-b]pyr...
Scheme 4: Cycloadditions of isoflavonoid-derived o-QMs and various dienophiles.
Scheme 5: [4 + 2] Cycloaddition reactions between aminonaphthols and cyclic amines.
Scheme 6: Brønsted acid-catalysed reaction between aza-o-QMs and 2- or 3-substituted indoles.
Scheme 7: Formation of 3-(α,α-diarylmethyl)indoles 52 in different synthetic pathways.
Scheme 8: Alkylation of o-QMs with N-, O- or S-nucleophiles.
Scheme 9: Formation of DNA linkers and o-QM mediated polymers.
Curcuminoid–BF2 complexes: Synthesis, fluorescence and optimization of BF2 group cleavage
- Henning Weiss,
- Jeannine Reichel,
- Helmar Görls,
- Kilian Rolf Anton Schneider,
- Mathias Micheel,
- Michael Pröhl,
- Michael Gottschaldt,
- Benjamin Dietzek and
- Wolfgang Weigand
Beilstein J. Org. Chem. 2017, 13, 2264–2272, doi:10.3762/bjoc.13.223
- avoid a Knoevenagel condensation at the C-3 atom (Scheme 1a), the β-diketone moiety needs to be fixed into the enol form. In principle, this can be achieved by two different methods. The first one described by Pabon et al. utilises boric oxide in ethyl acetate as an intermediate agent (Scheme 1a) [8
Graphical Abstract
Scheme 1: Synthesis of the curcumin structure motif using (a) boric oxide or (b) boron trifluoride.
Figure 1: ORTEP drawings in side view (left) and top view (right) of complexes 2f (a), 2g (b) and 2h (c). Hyd...
Scheme 2: BF2 group hydrolysis of complex 2b.
Scheme 3: Suggested mechanism of BF2 complex hydrolysis.
Figure 2: Absorbance (left) and emission (right) spectra of compounds 2a (orange), 2b (black), 2c (blue), 2d ...
Figure 3: Absorbance spectra of 2b in methanol (orange), tetrahydrofuran (red), toluene (black), dichlorometh...
Figure 4: Compounds 2a–h in dichloromethane solution in daylight (top) and under 365 nm irradiation (bottom).
The effect of milling frequency on a mechanochemical organic reaction monitored by in situ Raman spectroscopy
- Patrick A. Julien,
- Ivani Malvestiti and
- Tomislav Friščić
Beilstein J. Org. Chem. 2017, 13, 2160–2168, doi:10.3762/bjoc.13.216
- of reactive encounters between the particles. In contrast, ex situ gas chromatography studies of the Knoevenagel condensation between vanillin and barbituric acid in a planetary mill revealed a sigmoidal dependence of reaction yield with time [22]. Similarly, sigmoidal dynamics were detected by in
- that the reaction progress adopts a sigmoidal profile at milling frequencies higher than 25 Hz, which is consistent with the results of earlier ex situ studies of a Knoevenagel condensation reaction [22]. At milling frequencies below 25 Hz, however, the reaction appears to exhibits linear behavior
Graphical Abstract
Scheme 1: Milling synthesis of 2,3-diphenylquinoxaline from benzil and ortho-phenylenediamine [40].
Scheme 2: Movement of the milling jar and sample holder under milling conditions.
Figure 1: Time-resolved Raman spectrum for the double condensation of o-phenylenediamine and benzil to form 2...
Figure 2: Section of the time-resolved Raman spectrum for the model mechanochemical reaction conducted at 30 ...
Figure 3: (Left) Estimated contribution of each component for each Raman spectrum over time of the synthesis ...
Figure 4: The effect of milling frequency on the milling condensation of benzil and o-phenylenediamine to for...
Figure 5: The reproducibility of varying milling frequency on the neat mechanochemical condensation of benzil...
Figure 6: The effect of milling frequency on the internal jar temperature measured immediately after reaction...
Mechanochemical Knoevenagel condensation investigated in situ
- Sebastian Haferkamp,
- Franziska Fischer,
- Werner Kraus and
- Franziska Emmerling
Beilstein J. Org. Chem. 2017, 13, 2010–2014, doi:10.3762/bjoc.13.197
- .13.197 Abstract The mechanochemical Knoevenagel condensation of malononitrile with p-nitrobenzaldehyde was studied in situ using a tandem approach. X-ray diffraction and Raman spectroscopy were combined to yield time-resolved information on the milling process. Under solvent-free conditions, the reaction
- process both result in crystalline products suitable for single crystal X-ray diffraction. Keywords: ball milling; C–C coupling; in situ; Knoevenagel condensation; mechanochemistry; Introduction Mechanochemical syntheses have gained increasing popularity in different areas such as materials science
- interactions such as hydrogen bonds, halogen bonds, and π∙∙∙π interactions [16][17][18][19]. For example, Toda et al. reported yields of 97% for Aldol condensations in the absence of any solvents [20]. Kaupp et al. described the first Knoevenagel condensation in a ball mill [21]. Compared to conventional
Graphical Abstract
Scheme 1: Knoevenagel condensation of p-nitrobenzaldehyde (1) with malononitrile (2) yielding p-nitrobenzylid...
Figure 1: X-ray diffraction patterns of the reactants p-nitrobenzaldehyde (1) and malononitrile (2) and the p...
Figure 2: a) Schematic diagram of the in situ setup for investigating mechanochemical reactions in a tandem a...
Solvent-free sonochemistry: Sonochemical organic synthesis in the absence of a liquid medium
- Deborah E. Crawford
Beilstein J. Org. Chem. 2017, 13, 1850–1856, doi:10.3762/bjoc.13.179
- that alternative products can be formed using this technique, as with ball milling. The Knoevenagel condensation [18], Michael addition [19] and Biginelli reactions [20] amongst others have been instigated by ultrasonic irradiation in the presence of solvents such as pyridine and methanol, resulting in
Graphical Abstract
Figure 1: Typical laboratory employed planetary ball mill and ultrasonic bath.
Scheme 1: Reaction between o-vanillin and 1,2-phenylenediamine by ultrasonic irradiation for 60 minutes.
Figure 2: o-Vanillin in its flake form and 1,2-phenylenediamine in its bead form.
Figure 3: Clear separation of the reagents observed, with orange coated beads of 1,2-phenylenediamine residin...
Figure 4: Chemical structures of the products obtained from the reaction between o-vanillin and 1,2-phenylene...
Figure 5: Reaction mixture before and after ultrasonic irradiation for 60 minutes.
Figure 6: 1H NMR spectrum of diimine 1 in CDCl3/EtOD.
Scheme 2: Aldol reaction between ninhydrin and dimedone to form 2.
Figure 7: 1H NMR spectrum of 1,3-indandione 2 in DMSO-d6.
Synthesis of 1-indanones with a broad range of biological activity
- Marika Turek,
- Dorota Szczęsna,
- Marek Koprowski and
- Piotr Bałczewski
Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48
- (62), followed by a Knoevenagel condensation with a variety aromatic aldehydes to give chalcone derivatives 63 (Scheme 21). The reaction of the latter with hydroxylamine hydrochloride, followed by intramolecular 1,4-addition gave 1-indanone derivatives 64a–l which were further tested for in vitro
- -Benzylidene-1-indanones 126a–o were obtained by a Knoevenagel condensation of 1-indanone 125 with various aromatic aldehydes. Hydrogenolysis of 2-benzylidene-1-indanone 126b using Pd/C allowed to obtain 2-benzyl substituted 1-indanone 127 (Scheme 40). 2-Bromo-6-methoxy-3-phenyl-1-indanone 130, as an
Graphical Abstract
Figure 1: Biologically active 1-indanones and their structural analogues.
Figure 2: Number of papers about (a) 1-indanones, (b) synthesis of 1-indanones.
Scheme 1: Synthesis of 1-indanone (2) from hydrocinnamic acid (1).
Scheme 2: Synthesis of 1-indanone (2) from 3-(2-bromophenyl)propionic acid (3).
Scheme 3: Synthesis of 1-indanones 5 from 3-arylpropionic acids 4.
Scheme 4: Synthesis of kinamycin (9a) and methylkinamycin C (9b).
Scheme 5: Synthesis of trifluoromethyl-substituted arylpropionic acids 12, 1-indanones 13 and dihydrocoumarin...
Scheme 6: Synthesis of 1-indanones 16 from benzoic acids 15.
Scheme 7: Synthesis of 1-indanones 18 from arylpropionic and 3-arylacrylic acids 17.
Scheme 8: The NbCl5-induced one-step synthesis of 1-indanones 22.
Scheme 9: Synthesis of biologically active 1-indanone derivatives 26.
Scheme 10: Synthesis of enantiomerically pure indatraline ((−)-29).
Scheme 11: Synthesis of 1-indanone (2) from the acyl chloride 30.
Scheme 12: Synthesis of the mechanism-based inhibitors 33 of coelenterazine.
Scheme 13: Synthesis of the indane 2-imidazole derivative 37.
Scheme 14: Synthesis of fluorinated PAHs 41.
Scheme 15: Synthesis of 1-indanones 43 via transition metal complexes-catalyzed carbonylative cyclization of m...
Scheme 16: Synthesis of 6-methyl-1-indanone (46).
Scheme 17: Synthesis of 1-indanone (2) from ester 48.
Scheme 18: Synthesis of benzopyronaphthoquinone 51 from the spiro-1-indanone 50.
Scheme 19: Synthesis of the selective endothelin A receptor antagonist 55.
Scheme 20: Synthesis of 1-indanones 60 from methyl vinyl ketone (57).
Scheme 21: Synthesis of 1-indanones 64 from diethyl phthalate 61.
Scheme 22: Synthesis of 1-indanone derivatives 66 from various Meldrum’s acids 65.
Scheme 23: Synthesis of halo 1-indanones 69.
Scheme 24: Synthesis of substituted 1-indanones 71.
Scheme 25: Synthesis of spiro- and fused 1-indanones 73 and 74.
Scheme 26: Synthesis of spiro-1,3-indanodiones 77.
Scheme 27: Mechanistic pathway for the NHC-catalyzed Stetter–Aldol–Michael reaction.
Scheme 28: Synthesis of 2-benzylidene-1-indanone derivatives 88a–d.
Scheme 29: Synthesis of 1-indanone derivatives 90a–i.
Scheme 30: Synthesis of 1-indanones 96 from o-bromobenzaldehydes 93 and alkynes 94.
Scheme 31: Synthesis of 3-hydroxy-1-indanones 99.
Scheme 32: Photochemical preparation of 1-indanones 103 from ketones 100.
Scheme 33: Synthesis of chiral 3-aryl-1-indanones 107.
Scheme 34: Photochemical isomerization of 2-methylbenzil 108.
Scheme 35: Synthesis of 2-hydroxy-1-indanones 111a–c.
Scheme 36: Synthesis of 1-indanone derivatives 113 and 114 from η6-1,2-dioxobenzocyclobutene complex 112.
Scheme 37: Synthesis of nakiterpiosin (117).
Scheme 38: Synthesis of 2-alkyl-1-indanones 120.
Scheme 39: Synthesis of fluorine-containing 1-indanone derivatives 123.
Scheme 40: Synthesis of 2-benzylidene and 2-benzyl-1-indanones 126, 127 from the chalcone 124.
Scheme 41: Synthesis of 2-bromo-6-methoxy-3-phenyl-1-indanone (130).
Scheme 42: Synthesis of combretastatin A-4-like indanones 132a–s.
Figure 3: Chemical structures of investigated dienones 133 and synthesized cyclic products 134–137.
Figure 4: Chemical structures of 1-indanones and their heteroatom analogues 138–142.
Scheme 43: Synthesis of 2-phosphorylated and 2-non-phosphorylated 1-indanones 147 and 148 from β-ketophosphona...
Scheme 44: Photochemical synthesis of 1-indanone derivatives 150, 153a, 153b.
Scheme 45: Synthesis of polysubstituted-1-indanones 155, 157.
Scheme 46: Synthesis of 1-indanones 159a–g from α-arylpropargyl alcohols 158 using RhCl(PPh3)3 as a catalyst.
Scheme 47: Synthesis of optically active 1-indanones 162 via the asymmetric Rh-catalyzed isomerization of race...
Scheme 48: Mechanism of the Rh-catalyzed isomerization of α-arylpropargyl alcohols 161 to 1-indanones 162.
Figure 5: Chemical structure of abicoviromycin (168) and its new benzo derivative 169.
Scheme 49: Synthesis of racemic benzoabicoviromycin 172.
Scheme 50: Synthesis of [14C]indene 176.
Scheme 51: Synthesis of indanone derivatives 178–180.
Scheme 52: Synthesis of racemic pterosin A 186.
Scheme 53: Synthesis of trans-2,3-disubstituted 1-indanones 189.
Scheme 54: Synthesis of 3-aryl-1-indanone derivatives 192.
Scheme 55: Synthesis of 1-indanone derivatives 194 from 3-(2-iodoaryl)propanonitriles 193.
Scheme 56: Synthesis of 1-indanones 200–204 by cyclization of aromatic nitriles.
Scheme 57: Synthesis of 1,1’-spirobi[indan-3,3’-dione] derivative 208.
Scheme 58: Total synthesis of atipamezole analogues 211.
Scheme 59: Synthesis of 3-[4-(1-piperidinoethoxy)phenyl]spiro[indene-1,1’-indan]-5,5’-diol hydrochloride 216.
Scheme 60: Synthesis of 3-arylindan-1-ones 219.
Scheme 61: Synthesis of 2-hydroxy-1-indanones 222.
Scheme 62: Synthesis of the 1-indanone 224 from the THP/MOM protected chalcone epoxide 223.
Scheme 63: Synthesis of 1-indanones 227 from γ,δ-epoxy ketones 226.
Scheme 64: Synthesis of 2-hydroxy-2-methylindanone (230).
Scheme 65: Synthesis of 1-indanone derivatives 234 from cyclopropanol derivatives 233.
Scheme 66: Synthesis of substituted 1-indanone derivatives 237.
Scheme 67: Synthesis of 7-methyl substituted 1-indanone 241 from 1,3-pentadiene (238) and 2-cyclopentenone (239...
Scheme 68: Synthesis of disubstituted 1-indanone 246 from the siloxydiene 244 and 2-cyclopentenone 239.
Scheme 69: Synthesis of 5-hydroxy-1-indanone (250) via the Diels–Alder reaction of 1,3-diene 248 with sulfoxid...
Scheme 70: Synthesis of halogenated 1-indanones 253a and 253b.
Scheme 71: Synthesis of 1-indanones 257 and 258 from 2-bromocyclopentenones 254.
Scheme 72: Synthesis of 1-indanone 261 from 2-bromo-4-acetoxy-2-cyclopenten-1-one (260) and 1,2-dihydro-4-viny...
Scheme 73: Synthesis of 1-indanone 265 from 1,2-dihydro-7-methoxy-4-vinylnaphthalene (262) and bromo-substitut...
Scheme 74: Synthesis of 1-indanone 268 from dihydro-3-vinylphenanthrene 266 and 4-acetoxy-2-cyclopenten-1-one (...
Scheme 75: Synthesis of 1-indanone 271 from phenylselenyl-substituted cyclopentenone 268.
Scheme 76: Synthesis of 1-indanone 272 from the trienone 270.
Scheme 77: Synthesis of the 1-indanone 276 from the aldehyde 273.
Scheme 78: Synthesis of 1-indanones 278 and 279.
Scheme 79: Synthesis of 1-indanone 285 from octa-1,7-diyne (282) and cyclopentenone 239.
Scheme 80: Synthesis of benz[f]indan-1-one (287) from cyclopentenone 239 and o-bis(dibromomethyl)benzene (286)....
Scheme 81: Synthesis of 3-methyl-substituted benz[f]indan-1-one 291 from o-bis(dibromomethyl)benzene (286) and...
Scheme 82: Synthesis of benz[f]indan-1-one (295) from the anthracene epidioxide 292.
Scheme 83: Synthesis of 1-indanone 299 from homophthalic anhydride 298 and cyclopentynone 297.
Scheme 84: Synthesis of cyano-substituted 1-indanone derivative 301 from 2-cyanomethylbenzaldehyde (300) and c...
Scheme 85: Synthesis of 1-indanone derivatives 303–305 from ketene dithioacetals 302.
Scheme 86: Synthesis of 1-indanones 309–316.
Scheme 87: Mechanism of the hexadehydro-Diels–Alder (HDDA) reaction.
Scheme 88: Synthesis of 1-indenone 318 and 1-indanones 320 and 321 from tetraynes 317 and 319.
Scheme 89: Synthesis of 1-indanone 320 from the triyn 319.
Scheme 90: Synthesis 1-indanone 328 from 2-methylfuran 324.
Scheme 91: Synthesis of 1-indanones 330 and 331 from furans 329.
Scheme 92: Synthesis of 1-indanone 333 from the cycloadduct 332.
Scheme 93: Synthesis of (S)-3-arylindan-1-ones 335.
Scheme 94: Synthesis of (R)-2-acetoxy-1-indanone 338.
Figure 6: Chemical structures of obtained cyclopenta[α]phenanthrenes 339.
Scheme 95: Synthesis of the benzoindanone 343 from arylacetaldehyde 340 with 1-trimethylsilyloxycyclopentene (...
Effects of solvent additive on “s-shaped” curves in solution-processed small molecule solar cells
- John A. Love,
- Shu-Hua Chou,
- Ye Huang,
- Guilllermo C. Bazan and
- Thuc-Quyen Nguyen
Beilstein J. Org. Chem. 2016, 12, 2543–2555, doi:10.3762/bjoc.12.249
- cyanoactates in the final synthetic step via Knoevenagel condensation [15][31][32][33][34][35], we chose to begin with (E)-octyl 3-(5-bromothiophen-2-yl)-2-cyanoacrylate as the starting material to ensure good solubility. Intermediate 1 was prepared by palladium-mediated stannylation [36] and then subjected to
Graphical Abstract
Figure 1: a) Molecular structures and b) energy levels of p-SIDT(FBTTh2)2 and p-SIDT(FBTThCA8)2 highlighting ...
Scheme 1: Synthetic route towards p-SIDT(FBTThCA8)2. (i) Sn2Me6, Pd(PPh3)4, toluene, 85 °C; (ii) 4,7-dibromo-...
Figure 2: a) Solid-state absorption profiles of neat p-SIDT(FBTThCA8)2 (dashed line) and p-SIDT(FBTThCA8)2:PC...
Figure 3: Light intensity dependence of photocurrent as a function of the effective voltage, V0 − V, for devi...
Figure 4: Current voltage curves for devices cast from pure chlorobenzene (yellow) and with 1.5% DIO (blue) w...
Figure 5: Dynamic secondary ion mass spectrometry (DSIMS) profile showing scaled nitrogen (solid) and deuteri...
Figure 6: a) A schematic diagram of inverted architecture and b) J–V curves of device cast with no DIO in the...
Solvent-free, visible-light photocatalytic alcohol oxidations applying an organic photocatalyst
- Martin Obst and
- Burkhard König
Beilstein J. Org. Chem. 2016, 12, 2358–2363, doi:10.3762/bjoc.12.229
- for mechanochemical syntheses include stoichiometric reactions such as the Knoevenagel condensation and the Wittig reaction, but also reactions catalyzed by metal catalysts, like the Sonogashira coupling and the Suzuki coupling [1]. Photocatalysis, as a part of Ostwald’s sub-discipline photochemistry
Graphical Abstract
Figure 1: Rod mill, schematic (left) and photographs (middle and right).
Scheme 1: Oxidation of 4,4’-dimethoxybenzhydrol (1a) to 4,4’-dimethoxybenzophenone (1b).
Scheme 2: Scope for benzylic alcohol oxidation and obtained yields.
Scheme 3: Oxidation of 4-methoxyphenyl methyl carbinol (6a) to 4-methoxyacetophenone (6b).
Figure 2: 1H NMR (crude) of 4-methoxyacetophenone 6b.
High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension
- Paul B. Geraghty,
- Calvin Lee,
- Jegadesan Subbiah,
- Wallace W. H. Wong,
- James L. Banal,
- Mohammed A. Jameel,
- Trevor A. Smith and
- David J. Jones
Beilstein J. Org. Chem. 2016, 12, 2298–2314, doi:10.3762/bjoc.12.223
- -dialdehydes 14, Scheme 5, which were purified by a combination of silica chromatography and size exclusion chromatography (SEC). A final Knoevenagel condensation coupling the BXx-dialdehydes with N-hexyl-rhodanine resulted in the required series of products, both BXR and BTxR. The new materials have been
Graphical Abstract
Figure 1: Chemical structures of molecular materials with the following variations; BTxR, alkyl side chains o...
Scheme 1: Synthesis of the key intermediates TMS-Tx-BPin (3), i) diisopropylamine (DIA), THF, n-BuLi, −78 °C ...
Scheme 2: Oligothiophenes 4–11 synthesised through reaction of the commercially available 5-bromo-2-thiophene...
Scheme 3: Synthesis of the bithiophene through palladium catalyzed direct arylation, a) i) Pd(OAc)2, PCy3, Pi...
Scheme 4: Synthesis of the key bis-borylated BDT core 13, i) 1.5 equiv B2Pin2, 0.025 equiv [Ir(COD)OMe]2, 0.0...
Scheme 5: Synthesis of the BXR and BTXR series of materials, i) 5-bromothiophene carboxaldehyde, 5b, 7a–c, 9b...
Figure 2: BQR thermal and POM properties. a) DSC thermogram of BQR under nitrogen at a ramp rate of 10 °C min...
Figure 3: BT4R thermal and POM images. a) DSC thermogram of BT4R under nitrogen at a ramp rate of 10 °C min−1...
Figure 4: UV–vis absorption spectra of the BXXR series in CHCl3. An expansion of the peak area is shown in th...
Figure 5: Normalised thin film UV–vis absorption profiles for the BXxR series for, a) as-cast films (from CDCl...
Figure 6: Normalised thin film UV–vis absorption profiles for a) BBR, b) BTR and c) BQR showing as-cast (blac...
Figure 7: Normalised thin film fluorescence emission profiles for BXxR series after excitation at 580 nm, a) ...
Figure 8: Variable temperature thin film UV–vis absorption profiles for BQR, collected using the transmission...
Figure 9: Variable temperature thin-film fluorescence emission profiles for BQR, a) heating and b) cooling, c...
Figure 10: BQR thin film UV–vis (solid lines) and fluorescence emission spectra (dashed lines) collected at rt...
Figure 11: Optimized geometry and molecular orbital surfaces of HOMO (bottom) and LUMO (top) for the BXR serie...
Figure 12: J–V characteristics of BXR:PC71BM BHJ solar cells. (a) device structure, (b) J–V curves for as-cast...
Figure 13: J–V characteristics of BTxR:PC71BM ternary BHJ solar cells, a) device architecture, and b) J–V curv...
Figure 14: J–V characteristics of PTB7-Th:BQR:PC71BM ternary BHJ solar cells. (a) PTB7-Th chemical structure, ...
Robust C–C bonded porous networks with chemically designed functionalities for improved CO2 capture from flue gas
- Damien Thirion,
- Joo S. Lee,
- Ercan Özdemir and
- Cafer T. Yavuz
Beilstein J. Org. Chem. 2016, 12, 2274–2279, doi:10.3762/bjoc.12.220
- Knoevenagel condensation of benzyl nitriles and aldehydes produces C–C bonded products with labile nitrile functionalities. In fact, nitrile groups have been shown in porous polymers (particularly in polymers of intrinsic microporosity (PIMs)) to be good precursors to several functionalities like carboxylic
- highly porous cyanovinylene networks could be obtained through Knoevenagel condensation of benzylic nitriles and aldehydes by choosing appropriate building blocks. The resulting nitrile functionalities in COP-156 could be easily modified into free amine or amidoxime groups. The amine functionalities in
Graphical Abstract
Scheme 1: Synthesis route for COP-156 and COP-157, and the post-modification of COP-156.
Figure 1: FTIR spectra of COP-156 (black), COP-156-amine (blue) and COP-156-amidoxime (red). The dotted lines...
Figure 2: Gas adsorption (filled dots)-desorption (empty dots) isotherms and pore size distribution of COP-15...
Figure 3: CO2 uptake under moist conditions at 40 °C of COP-156 (black) and COP-156-amine (blue).
Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides
- Franziska Hemmerling and
- Frank Hahn
Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148
- units, reductive PKS release and Knoevenagel condensation yield the benzaldehyde intermediate 88. Oxidative dearomatisation of 88 catalysed by the salicylate monooxygenase AteafoD gives 89, which is hydroxylated at C8 by the oxygenase AteafoF. The positioning of this newly formed hydroxy group forces
Graphical Abstract
Scheme 1: Schematic description of the cyclisation reaction catalysed by TE domains. In most cases, the nucle...
Scheme 2: Mechanisms for the formation of oxygen heterocycles. The degree of substitution can differ from tha...
Scheme 3: Pyran-ring formation in pederin (24) biosynthesis. Incubation of recombinant PedPS7 with substrate ...
Scheme 4: The domain AmbDH3 from ambruticin biosynthesis catalyses the dehydration of 25 and subsequent cycli...
Scheme 5: SalBIII catalyses dehydration of 29 and subsequent cyclisation to tetrahydropyran 30 [18].
Figure 1: All pyranonaphtoquinones contain either the naphtha[2,3-c]pyran-5,10-dione (32) or the regioisomeri...
Scheme 6: Pyran-ring formation in actinorhodin (34) biosynthesis. DNPA: 4-dihydro-9-hydroxy-1-methyl-10-oxo-3H...
Scheme 7: Pyran formation in granaticin (36) biosynthesis. DNPA: 4-dihydro-9-hydroxy-1-methyl-10-oxo-3H-napht...
Scheme 8: Pyran formation in alnumycin (37) biosynthesis. Adapted from [21].
Scheme 9: Biosynthesis of pseudomonic acid A (61). The pyran ring is initially formed in 57 after dehydrogena...
Scheme 10: Epoxidation–cyclisation leads to the formation of the tetrahydropyran ring in the western part of t...
Scheme 11: a) Nonactin (70) is formed from heterodimers of (−)(+)-dimeric nonactic acid and (+)(−)-dimeric non...
Figure 2: Pamamycins (73) are macrodiolide antibiotics containing three tetrahydrofuran moieties, which are a...
Scheme 12: A PS domain homolog in oocydin A (76) biosynthesis is proposed to catalyse furan formation via an o...
Scheme 13: Mechanism of oxidation–furan cyclisation by AurH, which converts (+)-deoxyaureothin (77) into (+)-a...
Scheme 14: Leupyrrin A2 (80) and the proposed biosynthesis of its furylidene moiety [69,70].
Scheme 15: Asperfuranone (93) biosynthesis, adapted from [75].
Figure 3: The four major aflatoxins produced by Aspergilli are the types B1, B2, G1 and G2 (94–97). In the di...
Scheme 16: Overview on aflatoxin B1 (94) biosynthesis. HOMST = 11-hydroxy-O-methylsterigmatocystin [78,79,82-106].
Scheme 17: A zipper mechanism leads to the formation of oxygen heterocycles in monensin biosynthesis [109-111].
Scheme 18: Formation of the 2,6-dioxabicyclo[3.2.1]octane (DBO) ring system in aurovertin B (118) biosynthesis ...
Figure 4: Structures of the epoxide-containing polyketides epothilone A (119) and oleandomycin (120) [123-125].
Scheme 19: Structures of phoslactomycin B (121) (a) and jerangolid A (122) (b). The heterocycle-forming steps ...
Scheme 20: a) Structures of rhizoxin (130) and cycloheximide (131). Model for the formation of δ-lactones (b) ...
Scheme 21: EncM catalyses a dual oxidation sequence and following processing of the highly reactive intermedia...
Figure 5: Mesomeric structures of tetronates [138,139].
Figure 6: Structures of tetronates for which gene clusters have been sequenced. The tetronate moiety is shown...
Scheme 22: Conserved steps for formation and processing in several 3-acyl-tetronate biosynthetic pathways were...
Scheme 23: In versipelostatin A (153) biosynthesis, VstJ is a candidate enzyme for catalysing the [4 + 2] cycl...
Scheme 24: a) Structures of some thiotetronate antibiotics. b) Biosynthesis of thiolactomycin (165) as propose...
Scheme 25: Aureusidine synthase (AS) catalyses phenolic oxidation and conjugate addition of chalcones leading ...
Scheme 26: a) Oxidative cyclisation is a key step in the biosynthesis of spirobenzofuranes 189, 192 and 193. b...
Scheme 27: A bicyclisation mechanism forms a β-lactone and a pyrrolidinone and removes the precursor from the ...
Scheme 28: Spontaneous cyclisation leads to off-loading of ebelactone A (201) from the PKS machinery [163].
Scheme 29: Mechanisms for the formation of nitrogen heterocycles.
Scheme 30: Biosynthesis of highly substituted α-pyridinones. a) Feeding experiments confirmed the polyketide o...
Scheme 31: Acridone synthase (ACS) catalyses the formation of 1,3-dihydroxy-N-methylacridone (224) by condensa...
Scheme 32: A Dieckmann condensation leads to the formation of a 3-acyl-4-hydroxypyridin-2-one 227 and removes ...
Scheme 33: a) Biosynthesis of the pyridinone tenellin (234). b) A radical mechanism was proposed for the ring-...
Scheme 34: a) Oxazole-containing PKS–NRPS-derived natural products oxazolomycin (244) and conglobatin (245). b...
Scheme 35: Structure of tetramic acids 251 (a) and major tautomers of 3-acyltetramic acids 252a–d (b). Adapted...
Scheme 36: Equisetin biosynthesis. R*: terminal reductive domain. Adapted from [202].
Scheme 37: a) Polyketides for which a similar biosynthetic logic was suggested. b) Pseurotin A (256) biosynthe...
Figure 7: Representative examples of PTMs with varying ring sizes and oxidation patterns [205,206].
Scheme 38: Ikarugamycin biosynthesis. Adapted from [209-211].
Scheme 39: Tetramate formation in pyrroindomycin aglycone (279) biosynthesis [213-215].
Scheme 40: Dieckmann cyclases catalyse tetramate or 2-pyridone formation in the biosynthesis of, for example, ...
Creating molecular macrocycles for anion recognition
- Amar H. Flood
Beilstein J. Org. Chem. 2016, 12, 611–627, doi:10.3762/bjoc.12.60
- a difunctional building block for the Knoevenagel condensation that forms cyanostilbenes. Treating the material to carbonate base-catalyzed conditions, he acquired the product in high yields, now optimized to 80% and scaling nicely up to 10 g quantities. The effectiveness of the central binding
Graphical Abstract
Figure 1: The design and building of a house is just as satisfying as that of a new molecule and often takes ...
Figure 2: Timeline of anion-binding macrocycles.
Figure 3: Click chemistry’s copper-catalyzed azide–alkyne cycloaddition (CuAAC) forms 1,2,3-triazoles that st...
Figure 4: These molecular compounds are the same and not the same.
Figure 5: (a, b, c) Sequence of chemical sketches leading to triazolophanes. (d) The precursor that led, by C...
Figure 6: Variation in phenylene substituents weakens chloride affinity from 1 to 4.
Figure 7: (a) Pyridyl triazolophane and (b) its high-fidelity sandwich around iodide (crystal). Adapted with ...
Figure 8: Testing the (a) macrocyclic effect, and (b) effect of rigidity against (c) the parent triazolophane....
Figure 9: (a) Representations of the four equilibria that dominate in dichloromethane for which the (b) propy...
Figure 10: Representations of (a) aryl–triazole–ether macrocycle 12 and (b) the ion-pair crystal structure of ...
Figure 11: Chloride is used as a comparator for (a) cyanide and (b) biflouride. (c) Computer-aided receptor de...
Figure 12: (a) One-pot synthesis of cyanostars. (b) Volcano plot of anion affinities (40:60 methanol/dichlorom...
Figure 13: (a) Representation and (b) crystal structure of cyanostar-based [3]rotaxane.
Figure 14: Crystal structures of cyanostar sandwich around (a) perchlorate and (b) diglyme (molecules shown wi...
Figure 15: (a) Star-extended cyanostar and an (b) STM image cropped from a 2D lamellar lattice. Part (b) adapt...
Figure 16: (a) Synthesis and one-pot macrocyclization of the tricarb macrocycle. (b) Volcano plot of anion aff...
Figure 17: (a) Tricarb binds iodide. (b) Tricarb’s single-molecule STM image resembles a donut. (c) Honeycomb ...
Figure 18: Timeline of crescent-shaped anion receptors.
Figure 19: Timeline of anion-binding foldamers.
Figure 20: Family portrait of 3D-printed molecular receptors.
(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers
- Giorgos Koutoulogenis,
- Nikolaos Kaplaneris and
- Christoforos G. Kokotos
Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48
- good yield and stereoselectivity, given the high molecular complexity that is being achieved in one step (Scheme 64). The researchers suggested that diketone 204 and benzaldehyde 205 reacts through Knoevenagel condensation, to produce 2-arylidene-1,3-indanediones, which is subsequently attacked by the
Graphical Abstract
Scheme 1: Activation of carbonyl compounds via enamine and iminium intermediates [2].
Scheme 2: Electronic and steric interactions present in enamine activation mode [2].
Scheme 3: Electrophilic activation of carbonyl compounds by a thiourea moiety.
Scheme 4: Asymmetric synthesis of dihydro-2H-pyran-6-carboxylate 3 using organocatalyst 4 [16].
Scheme 5: Possible hydrogen-bonding for the reaction of (E)-methyl 2-oxo-4-phenylbut-3-enoate [16].
Scheme 6: Asymmetric desymmetrization of 4,4-cyclohexadienones using the Michael addition reaction with malon...
Scheme 7: The enantioselective synthesis of α,α-disubstituted cycloalkanones using catalyst 11 [18].
Scheme 8: The enantioselective synthesis of indolo- and benzoquinolidine compounds through aza-Diels–Alder re...
Scheme 9: Enantioselective [5 + 2] cycloaddition [20].
Scheme 10: Asymmetric synthesis of oxazine derivatives 26 [21].
Scheme 11: Asymmetric synthesis of bicyclo[3.3.1]nonadienone, core 30 present in (−)-huperzine [22].
Scheme 12: Asymmetric inverse electron-demand Diels-Alder reaction catalyzed by amine-thiourea 34 [23].
Scheme 13: Asymmetric entry to morphan skeletons, catalyzed by amine-thiourea 37 [24].
Scheme 14: Asymmetric transformation of (E)-2-nitroallyl acetate [25].
Scheme 15: Proposed way of activation.
Scheme 16: Asymmetric synthesis of nitrobicyclo[3.2.1]octan-2-one derivatives [26].
Scheme 17: Asymmetric tandem Michael–Henry reaction catalyzed by 50 [27].
Scheme 18: Asymmetric Diels–Alder reactions of 3-vinylindoles 51 [29].
Scheme 19: Proposed transition state and activation mode of the asymmetric Diels–Alder reactions of 3-vinylind...
Scheme 20: Desymmetrization of meso-anhydrides by Chin, Song and co-workers [30].
Scheme 21: Desymmetrization of meso-anhydrides by Connon and co-workers [31].
Scheme 22: Asymmetric intramolecular Michael reaction [32].
Scheme 23: Asymmetric addition of malonate to 3-nitro-2H-chromenes 67 [33].
Scheme 24: Intramolecular desymmetrization through an intramolecular aza-Michael reaction [34].
Scheme 25: Enantioselective synthesis of (−)-mesembrine [34].
Scheme 26: A novel asymmetric Michael–Michael reaction [35].
Scheme 27: Asymmetric three-component reaction catalyzed by Takemoto’s catalyst 77 [46].
Scheme 28: Asymmetric domino Michael–Henry reaction [47].
Scheme 29: Asymmetric domino Michael–Henry reaction [48].
Scheme 30: Enantioselective synthesis of derivatives of 3,4-dihydro-2H-pyran 89 [49].
Scheme 31: Asymmetric addition of α,α-dicyano olefins 90 to 3-nitro-2H-chromenes 91 [50].
Scheme 32: Asymmetric three-component reaction producing 2,6-diazabicyclo[2.2.2]octanones 95 [51].
Scheme 33: Asymmetric double Michael reaction producing substituted chromans 99 [52].
Scheme 34: Enantioselective synthesis of multi-functionalized spiro oxindole dienes 106 [53].
Scheme 35: Organocatalyzed Michael aldol cyclization [54].
Scheme 36: Asymmetric synthesis of dihydrocoumarins [55].
Scheme 37: Asymmetric double Michael reaction en route to tetrasubstituted cyclohexenols [56].
Scheme 38: Asymmetric synthesis of α-trifluoromethyl-dihydropyrans 121 [58].
Scheme 39: Tyrosine-derived tertiary amino-thiourea 123 catalyzed Michael hemiaketalization reaction [59].
Scheme 40: Enantioselective entry to bicyclo[3.2.1]octane unit [60].
Scheme 41: Asymmetric synthesis of spiro[4-cyclohexanone-1,3’-oxindoline] 126 [61].
Scheme 42: Kinetic resolution of 3-nitro-2H-chromene 130 [62].
Scheme 43: Asymmetric synthesis of chromanes 136 [63].
Scheme 44: Wang’s utilization of β-unsaturated α-ketoesters 87 [64,65].
Scheme 45: Asymmetric entry to trifluoromethyl-substituted dihydropyrans 144 [66].
Scheme 46: Phenylalanine-derived thiourea-catalyzed domino Michael hemiaketalization reaction [67].
Scheme 47: Asymmetric synthesis of α-trichloromethyldihydropyrans 149 [68].
Scheme 48: Takemoto’s thiourea-catalyzed domino Michael hemiaketalization reaction [69].
Scheme 49: Asymmetric synthesis of densely substituted cyclohexanes [70].
Scheme 50: Enantioselective synthesis of polysubstituted chromeno [4,3-b]pyrrolidine derivatines 157 [71].
Scheme 51: Enantioselective synthesis of spiro-fused cyclohexanone/5-oxazolone scaffolds 162 [72].
Scheme 52: Utilizing 2-mercaptobenzaldehydes 163 in cascade processes [73,74].
Scheme 53: Proposed transition state of the initial sulfa-Michael step [74].
Scheme 54: Asymmetric thiochroman synthesis via dynamic kinetic resolution [75].
Scheme 55: Enantioselective synthesis of thiochromans [76].
Scheme 56: Enantioselective synthesis of chromans and thiochromans synthesis [77].
Scheme 57: Enantioselective sulfa-Michael aldol reaction en route to spiro compounds [78].
Scheme 58: Enantioselective synthesis of 4-aminobenzo(thio)pyrans 179 [79].
Scheme 59: Asymmetric synthesis of tetrahydroquinolines [80].
Scheme 60: Novel asymmetric Mannich–Michael sequence producing tetrahydroquinolines 186 [81].
Scheme 61: Enantioselective synthesis of biologically interesting chromanes 190 and 191 [82].
Scheme 62: Asymmetric tandem Henry–Michael reaction [83].
Scheme 63: An asymmetric synthesis of substituted cyclohexanes via a dynamic kinetic resolution [84].
Scheme 64: Three component-organocascade initiated by Knoevenagel reaction [85].
Scheme 65: Asymmetric Michael reaction catalyzed by catalysts 57 and 211 [86].
Scheme 66: Proposed mechanism for the asymmetric Michael reaction catalyzed by catalysts 57 and 211 [86].
Scheme 67: Asymmetric facile synthesis of hexasubstituted cyclohexanes [87].
Scheme 68: Dual activation catalytic mechanism [87].
Scheme 69: Asymmetric Michael–Michael/aldol reaction catalyzed by catalysts 57, 219 and 214 [88].
Scheme 70: Asymmetric synthesis of substituted cyclohexane derivatives, using catalysts 57 and 223 [89].
Scheme 71: Asymmetric synthesis of substituted piperidine derivatives, using catalysts 223 and 228 [90].
Scheme 72: Asymmetric synthesis of endo-exo spiro-dihydropyran-oxindole derivatives catalyzed by catalyst 232 [91]....
Scheme 73: Asymmetric synthesis of carbazole spiroxindole derivatives, using catalyst 236 [92].
Scheme 74: Enantioselective formal [2 + 2] cycloaddition of enal 209 with nitroalkene 210, using catalysts 23 ...
Scheme 75: Asymmetric synthesis of polycyclized hydroxylactams derivatives, using catalyst 242 [94].
Scheme 76: Asymmetric synthesis of product 243, using catalyst 246 [95].
Scheme 77: Formation of the α-stereoselective acetals 248 from the corresponding enol ether 247, using catalys...
Scheme 78: Selective glycosidation, catalyzed by Shreiner’s catalyst 23 [97].
Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity
- Louis P. Sandjo,
- Victor Kuete and
- Maique W. Biavatti
Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183
- synthesis [65]. This preparation started with a Knoevenagel condensation of 2-fluoroacetophenone with malononitrile. The product of the condensation reacted with an excess of N,N-dimethylformamide dimethyl acetal to afford an enamine. This latter was treated with hydrochloric acid in acetic acid gave 4-aryl
Graphical Abstract
Figure 1: Fragments produced by the FAB–MS of dehydrokuanoniamine B (20) [42].
Figure 2: Fragments produced by the EIMS of sagitol (26) [55].
Figure 3: Fragments produced by the EIMS of styelsamine B (4) [45].
Figure 4: Fragments produced by the EIMS of styelsamine D (6) [45].
Figure 5: Fragments produced by the EIMS of subarine (37) [40].
Scheme 1: Synthesis of styelsamine B (4) and cystodytin J (1) [58].
Scheme 2: Synthesis of sebastianine A (38) and its regioisomer 39 [59].
Scheme 3: Synthesis route A of neoamphimedine (12) [61].
Scheme 4: Synthesis route B of neoamphimedine (12) [62].
Scheme 5: Synthesis of arnoamines A (40) and B (41) [63].
Scheme 6: Synthesis of ascididemin (42) [65].
Scheme 7: Synthesis of subarine (37) [66,67].
Scheme 8: Synthesis of demethyldeoxyamphimedine (9) [68].
Scheme 9: Synthesis of pyridoacridine analogues related to ascididemin (42) [70].
Scheme 10: Synthesis of analogues of meridine (56) [71].
Scheme 11: Synthesis of bulky pyridoacridine as eilatin (58) [72].
Scheme 12: Synthesis of AK37 (59), analogue of kuanoniamine A (60) [73].
Figure 6: Biosynthesis pathway I [74].
Figure 7: Reaction illustrating catechol and kynuramine as possible biosynthetic precursors [75].
Figure 8: Biosynthesis pathway B deduced from the feeding experiment A using labelled precursors [76].
Figure 9: Proposed biosynthesis pathway [47].
Figure 10: 4H-Pyrido[2,3,4-kl]acridin-4-one as a cytotoxic pharmacophore.
Figure 11: 7H-Pyrido[2,3,4-kl]acridine as a cytotoxic pharmacophore.
Figure 12: 9H-Quinolino[4,3,2-de][1,10]phenanthrolin-9-one as a cytotoxic pharmacophore.
Figure 13: 8H-Benzo[b]pyrido[4,3,2-de][1,7]phenanthrolin-8-one as a cytotoxic pharmacophore.
Figure 14: Pyrido[4,3,2-mn]pyrrolo[3,2,1-de]acridine as a cytotoxic pharmacophore.
Figure 15: 9H-Pyrido[4,3,2-mn]thiazolo[4,5-b]acridin-9-one and 8H-pyrido[4,3,2-mn]thiazolo[4,5-b]acridine: cyt...
Figure 16: 9H-quinolino[4,3,2-de][1,10]phenanthrolin-9-one as an anti-mycobacterial pharmacophore.
Figure 17: 9H-Quinolino[4,3,2-de][1,10]phenanthrolin-9-one as an antibacterial pharmacophore.
Figure 18: Saturated and less saturated pyridine moieties as aspartyl inhibitor cores.
Figure 19: Iminobenzoquinone and acridone cores as intercalating and TOPO inhibitor motifs found in pyridoacri...
A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells
- Gleb Sorohhov,
- Chenyi Yi,
- Michael Grätzel,
- Silvio Decurtins and
- Shi-Xia Liu
Beilstein J. Org. Chem. 2015, 11, 1052–1059, doi:10.3762/bjoc.11.118
- Discussion Synthesis Under Knoevenagel condensation reaction conditions, the corresponding aldehydes 4 and 7 can readily react with cyanoacetic acid leading to the target sensitizers 1 and 2, as depicted in Scheme 1. For the synthesis of the aldehyde precursor 4, the Horner–Wadsworth–Emmons (HWE) reaction
Graphical Abstract
Figure 1: Chemical structures of the target dyes 1 and 2.
Scheme 1: Synthetic routes to the target dyes 1 (top) and 2 (bottom).
Figure 2: Cyclic voltammograms of 1 (blue line), 2 (red line) and 6 (black line) in CH2Cl2 (0.1 M Bu4NPF6; Pt...
Figure 3: Electronic absorption spectra of 1 (blue line) and 2 (red line) in CH2Cl2 solutions.
Figure 4: Photovoltaic performance of the two sensitizers. Photocurrent density (J) as a function of voltage ...
Multicomponent reactions in nucleoside chemistry
- Mariola Koszytkowska-Stawińska and
- Włodzimierz Buchowicz
Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179
- considerable number of pacidamycin analogues. 4. The multicomponent domino reactions initiated by the Knoevenagel condensation The Knoevenagel condensation can be considered as one of the most useful tools for the formation of C=C double bonds. The condensation products, i.e., electron-deficient alkenes
- , readily act in subsequent reactions as Michael acceptors, Diels–Alder (hetero)dienes or dienophiles, or dipolarophiles. Multicomponent domino reactions initiated by the Knoevenagel condensation are a valuable tool for the construction of many compounds with complex molecular structures [90]. The syntheses
- shown in Scheme 23 and Scheme 24 represent examples of the Knoevenagel condensation-initiated domino reactions where the nucleoside aldehyde (i.e., 5-formyl-3',5'-di-O-acetyl-2'-deoxyuridine (14) or 5-formyl-2'-deoxyuridine (27)) acted as the Knoevenagel acceptor. Compounds 61 to 65 were prepared by the
Graphical Abstract
Figure 1: Selected chemical modifications of natural ribose or 2'-deoxyribose nucleosides leading to the deve...
Scheme 1: (a) Classical Mannich reaction; (b) general structures of selected hydrogen active components and s...
Scheme 2: Reagents and reaction conditions: i. H2O or H2O/EtOH, 60–100 °C, 7 h–10 d; ii. H2, Pd/C or PtO2; ii...
Scheme 3: Reagents and reaction conditions: i. H2O, 90 °C, overnight.
Scheme 4: Reagents and reaction conditions: i. AcOH, H2O, 60 °C, 12 h-5 d; ii. AcOH, H2O, 60 °C, 8 h.
Scheme 5: Reagents and reaction conditions: i. CuBr, THF, reflux, 0.5 h; ii. n-Bu4NF·3H2O, THF, rt, 2 h.
Scheme 6: Reagents and reaction conditions: i. [bmim][PF6], 80 °C, 5–8 h.
Scheme 7: Reagents and reaction conditions: i. EtOH, reflux, 24 h.
Scheme 8: Reagents and reaction conditions: i. NaOAc, H2O, 95 °C, 1–16 h; ii. NaOAc, H2O, 95 °C, 1 h.
Scheme 9: Reagents and reaction conditions: i. a. 37% aq HCl, MeOH; b. NaOAc, 1,4-dioxane, H2O, 100 °C, overn...
Scheme 10: Reagents and reaction conditions: i. DMAP, DCC, MeOH, rt, 1 h.
Scheme 11: The Kabachnik–Fields reaction.
Scheme 12: Reagents and reaction conditions: i. 60 °C, 3 h; ii. 80 °C, 2 h.
Scheme 13: The four-component Ugi reaction.
Scheme 14: Reagents and reaction conditions: i. MeOH, rt, 2–3 d, yields not given.
Scheme 15: Reagents and reaction conditions: i. MeOH/CH2Cl2 (1:1), rt, 24 h, yield not given; ii. 6 N aq HCl, ...
Scheme 16: Reagents and reaction conditions: i. MeOH/H2O, rt, 26 h; ii. aq AcOH, reflux, 50%; iii. reversed ph...
Scheme 17: Reagents and reaction conditions: i. MeOH, rt, 24 h; ii. HCl, MeOH, 0 °C to rt, 6 h, then H2O, rt, ...
Scheme 18: Reagents and reaction conditions: i. DMF/Py/MeOH (1:1:1), rt, 48 h; ii. 10% HCl/MeOH, rt, 30 min.
Scheme 19: Reagents and reaction conditions (R = CH3 or H): i. CH2Cl2/MeOH (2:1), 35–40 °C, 2 d; ii. HF/pyridi...
Scheme 20: Reagents and reaction conditions: i. MeOH, 76%; ii. 80% aq TFA, 100%.
Scheme 21: Reagents and reaction conditions: i. EtOH, rt, 72 h; ii. Zn, aq NaH2PO4, THF, rt, 1 week; then 80% ...
Scheme 22: Reagents and reaction conditions: i. EtOH, rt, 48 h, then silica gel chromatography, 33% for 57 (30...
Scheme 23: Reagents and reaction conditions: i. [bmim]BF4, 80 °C, 4 h; ii. [bmim]BF4, 80 °C, 3 h; iii. [bmim]BF...
Scheme 24: Reagents and reaction conditions: i. [bmim]BF4, 80 °C.
Scheme 25: Reagents and reaction conditions: i. H3PW12O40 (2 mol %), EtOH, 50 °C, 2–15 h; ii. H3PW12O40 (2 mol...
Scheme 26: General scheme of the Biginelli reaction.
Scheme 27: Reagents and reaction conditions: i. EtOH, reflux.
Scheme 28: Reagents and reaction conditions: i. Bu4N+HSO4−, diethylene glycol, 120 °C, 1.5–3 h.
Scheme 29: Reagents and reaction conditions: i. BF3·Et2O, CuCl, AcOH, THF, 65 °C, 24 h; ii. Yb(OTf)3, THF, ref...
Scheme 30: Reagents and reaction conditions: TCT (10 mol %), rt: i. 100 min; ii. 150 min; iii. 140 min.
Scheme 31: Reagents and reaction conditions: i. EtOH, microwave irradiation (300 W), 10 min; ii. EtOH, 75 °C, ...
Scheme 32: The Hantzsch reaction.
Scheme 33: Reagents and reaction conditions: TCT (10 mol %), rt, 80–150 min.
Scheme 34: Reagents and reaction conditions: i. Yb(OTf)3, THF, 90 °C, 12 h; ii. 4 Å molecular sieves, EtOH, 90...
Scheme 35: Reagents and reaction conditions: i. MeOH, 50 °C, 48 h.
Scheme 36: Reagents and reaction conditions: i. MeOH, 25 °C, 5 d.
Scheme 37: Bu4N+HSO4−, diethylene glycol, 80 °C, 1–2 h.
Scheme 38: The three-component carbopalladation of dienes on the example of buta-1,3-diene.
Scheme 39: Reagents and reaction conditions: i. 5 mol % Pd(dba)2, Bu4NCl, ZnCl2, acetonitrile or DMSO, 80 °C o...
Scheme 40: Reagents and reaction conditions: i. 2.5 mol % Pd2(dba)3, tris(2-furyl)phosphine, K2CO3, MeCN or DM...
Scheme 41: Reagents and reaction conditions: i. 2.5 mol % Pd2(dba)3, tris(2-furyl)phosphine, K2CO3, MeCN or DM...
Scheme 42: The three-component Bucherer–Bergs reaction.
Scheme 43: Reagents and reaction conditions: i. MeOH, H2O, 70 °C, 4.5 h; ii. (1) H2, 5% Pd/C, MeOH, 55 °C, 5 h...
Scheme 44: Reagents and reaction conditions: i. pyridine, MgSO4, 100 °C, 28 h, N2; ii. DMF, 70–90 °C, 22–30 h,...
Scheme 45: Reagents and reaction conditions: i. Montmorillonite K-10 clay, microwave irradiation (600 W), 6–10...
Scheme 46: Reagents and reaction conditions: i. Montmorillonite K-10 clay, microwave irradiation (560 W), 6–10...
Scheme 47: Reagents and reaction conditions: i. CeCl3·7H2O (20 mol %), NaI (20 mol %), microwave irradiation (...
Scheme 48: Reagents and reaction conditions: i. PhI(OAc)2 (3 mol %), microwave irradiation (45 °C), 6–9 min.
Scheme 49: Reagents and reaction conditions: i. 117, ethyl pyruvate, TiCl4, dichloromethane, −78 °C, 1 h; then ...
Chemistry of polyhalogenated nitrobutadienes, 14: Efficient synthesis of functionalized (Z)-2-allylidenethiazolidin-4-ones
- Viktor A. Zapol’skii,
- Jan C. Namyslo,
- Mimoza Gjikaj and
- Dieter E. Kaufmann
Beilstein J. Org. Chem. 2014, 10, 1638–1644, doi:10.3762/bjoc.10.170
- thiazolidinone atropisomers, due to hindered rotation between the trichlorovinyl and the arylamino groups. X-ray analysis proved the Z-configuration of the nitrovinylidene group of 11. Subsequent reactions of the thiazolidinones, such as the SNVin thiolation in 2-position of the allylidene backbone, Knoevenagel
- condensation of the heterocyclic rings with aromatic aldehydes, and an unusual formation of persubstituted pyrazoles demonstrate the chemical versatility of these heterocyclic systems. The newly formed thiazolidinones deserve additional synthetic interest as starting materials, also due to their trichlorovinyl
Graphical Abstract
Scheme 1: SNVin reactions of pentachloro-2-nitro-1,3-butadiene (1).
Scheme 2: Formation of thiazolidin-4-ones 7–19.
Figure 1: Hindered rotation in the case of ortho- or meta-substituted aniline precursors.
Figure 2: X-ray analysis of thiazolidin-4-one 11.
Scheme 3: Assumed mechanism for the formation of thiazolidin-4-ones 7–18.
Scheme 4: Substitution reactions of the precursors 3 and 5 with additional amines.
Scheme 5: Synthesis of 5-arylmethylidenethiazolidin-4-ones 22–26 and 1H-pyrazoles 27, 28.
Scheme 6: Assumed mechanism for the formation of 1H-pyrazole 27.
Scheme 7: Formation of ethyl propanoate 29 and subsequent reactions.
Primary-tertiary diamine-catalyzed Michael addition of ketones to isatylidenemalononitrile derivatives
- Akshay Kumar and
- Swapandeep Singh Chimni
Beilstein J. Org. Chem. 2014, 10, 929–935, doi:10.3762/bjoc.10.91
- involves the initial formation of isatylidenemalononitrile by Knoevenagel condensation of isatin with malononitrile followed by the addition of acetone to provide Michael adduct 4a. Thus, catalyst 1a also finds its successful application in the multicomponet version of this reaction without compromising
- isatylidenemalononitrile. Substrate scope of the addition of 2 with 3 catalyzed by 1a D-CSA. One-pot, three-component Knoevenagel condensation–Michael addition. Cascade reduction–cyclization for the synthesis of spirooxindole. Solvent screening the Michael addition of acetone (2a) to isatylidenemalononitrile (3a
Graphical Abstract
Figure 1: Oxindole based Michael acceptors.
Figure 2: Primary-tertiary diamine organocatalysts.
Scheme 1: Diamine catalyzed Michael addition of acetone to isatylidenemalononitrile.
Scheme 2: Substrate scope of the addition of 2 with 3 catalyzed by 1a D-CSA.
Scheme 3: One-pot, three-component Knoevenagel condensation–Michael addition.
Scheme 4: Cascade reduction–cyclization for the synthesis of spirooxindole.
Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study
- Shinichi Yamabe,
- Guixiang Zeng,
- Wei Guan and
- Shigeyoshi Sakaki
Beilstein J. Org. Chem. 2014, 10, 259–270, doi:10.3762/bjoc.10.21
- (C=O → C=C, alkene) conversion reaction, the Knoevenagel condensation [12] was utilized. While the condensation is traditionally base-catalyzed, it was found to proceed readily in water even without any catalyst [13][14]. Not only can this synthesis be considered as clean (green chemistry), but also
- conversion? An investigation about the role of the proton transfers along the hydrogen bonds may be of interest. Is a base-free W-K reduction comparable to the Knoevenagel condensation possible? Which path (a) or (b) in Scheme 2 is more favorable? Is the carbanion R1(R2)HC− a probable intermediate? Is the
- uncatalyzed (without base) Knoevenagel condensation in water. Experimental conditions and yields are taken from a) ref. [13] and b) ref. [14], respectively. Reaction models of neutral (a) and anionic (b) systems. Water molecules are linked to oxygen lone-pair orbitals and to H–N bonds of hydrazine. In the
Graphical Abstract
Scheme 1: The Wolff–Kishner (W-K) reduction. DEG, diethylene glycol (HO–C2H4–O–C2H4–OH), is usually used as a...
Scheme 2: Mechanism of the Wolff–Kishner reduction. The route (a) is taken from ref. [6] and (b) from refs. [5,7,8].
Scheme 3: An uncatalyzed (without base) Knoevenagel condensation in water. Experimental conditions and yields...
Scheme 4: Reaction models of neutral (a) and anionic (b) systems. Water molecules are linked to oxygen lone-p...
Figure 1: Geometric changes of the neutral Wolff–Kishner reduction reaction. The employed model is shown in Scheme 4a ...
Scheme 5: A CT complex between R1R2C=O and H2N–NH2 assisted by two hydrogen networks. R3–OH is an alcohol mol...
Figure 2: Energy changes of the neutral W-K reaction of acetone. Geometric changes are shown in Figure 1 and Figure S...
Figure 3: Geometric changes of the base-promoted Wolff–Kishner reduction reaction. The model employed is show...
Figure 4: Energy changes of the OH− containing W-K reaction of acetone calculated by B3LYP/6-311+G**. Geometr...
Scheme 6: The main part of TS6. The N1···H26 hydrogen bond is converted into the C1–H26 covalent bond.
Figure 5: A trans-diimine → propane conversion step corresponding to TS6 in Figure 3. The system is composed of trans...
Figure 6: Geometric changes of the base-promoted Wolff–Kishner reduction reaction of acetophenone [Me–C(=O)–P...
Figure 7: Energy changes of the OHˉ containing W-K reaction of acetophenone. Geometric changes are shown in Figure 6....
Scheme 7: Elementary processes of the W-K reduction obtained by DFT calculations. From the diimine intermedia...
Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis
- Sebastian Krüger and
- Tanja Gaich
Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14
- ozonolysis to give aldehyde 136 [123]. Knoevenagel condensation with 4-iodooxindole was achieved in the next step. Pfitzner–Moffatt oxidation [124] followed by elimination furnished trans-divinylcycloproane 137. Submission of this compound to elevated temperature initiated a very smooth DVCPR yielding
Graphical Abstract
Scheme 1: Vogel’s first approach towards the divinylcyclopropane rearrangement [4] and characterization of cis-d...
Scheme 2: Transition states for the Cope rearrangement and the related DVCPR. Ts = transition state.
Scheme 3: Two possible mechanisms of trans-cis isomerizations of divinylcyclopropanes.
Scheme 4: Proposed biosynthesic pathway to ectocarpene (21), an inactive degradation product of a sexual pher...
Scheme 5: Proposed biosynthesis of occidenol (25) and related natural compounds.
Scheme 6: Gaich’s bioinspired system using the DVCPR to mimick the dimethylallyltryptophan synthase. DMAPP = ...
Scheme 7: Iguchi’s total synthesis of clavubicyclone, part 1.
Scheme 8: Iguchi’s total synthesis of clavubicyclone, part 2.
Scheme 9: Wender’s syntheses of the two pseudoguainanes confertin (50) and damsinic acid (51) and Pier’s appr...
Scheme 10: Overman’s total synthesis of scopadulcic acid B.
Scheme 11: Davies’ total syntheses of tremulenolide A and tremulenediol A.
Scheme 12: Davies formal [4 + 3] cycloaddition approach towards the formal synthesis of frondosin B.
Scheme 13: Davies and Sarpongs formal [4 + 3]-cycloaddition approach towards barekoxide (106) and barekol (107...
Scheme 14: Davies formal [4 + 3]-cycloaddition approach to 5-epi-vibsanin E (115) containing an intermediate c...
Scheme 15: Echavarren’s total synthesis of schisanwilsonene A (126) featuring an impressive gold-catalzed casc...
Scheme 16: Davies early example of a formal [4 + 3]-cycloaddition in alkaloids synthesis.
Scheme 17: Fukuyama’s total synthesis of gelsemine, part 1.
Scheme 18: Fukuyama’s total synthesis of gelsemine, featuring a divinylcyclopropane rearrangement, part 2.
Scheme 19: Kende’s total synthesis of isostemofoline, using a formal [4 + 3]-cycloaddition, including an inter...
Scheme 20: Danishefsky’s total synthesis of gelsemine, part 1.
Scheme 21: Danishefsky’s total synthesis of gelsemine, part 2.
Scheme 22: Fukuyama’s total synthesis of gelsemoxonine.
Scheme 23: Wender’s synthetic access to the core skeleton of tiglianes, daphnanes and ingenanes.
Scheme 24: Davies’ approach towards the core skeleton of CP-263,114 (212).
Scheme 25: Wood’s approach towards actinophyllic acid.
Scheme 26: Takeda’s approach towards the skeleton of the cyanthins, utilitizing the divinylcyclopropane rearra...
Scheme 27: Donaldson’s organoiron route towards the guianolide skeleton.
Scheme 28: Stoltz’s tandem Wolff/DVCPR rearrangement.
Scheme 29: Stephenson’s tandem photocatalysis/arylvinylcyclopropane rearrangement.
Scheme 30: Padwa’s rhodium cascade involving a DVCPR.
Scheme 31: Matsubara’s version of a DVCPR.
Scheme 32: Toste’s tandem gold-catalyzed Claisen-rearrangement/DVCPR.
Scheme 33: Ruthenium- and gold-catalyzed versions of tandem reactions involving a DVCPR.
Scheme 34: Tungsten, platinum and gold catalysed cycloisomerizations leading to a DVCPR.
Scheme 35: Reisman’s total synthesis of salvileucalin B, featuring an (undesired) vinylcyclopropyl carbaldehyd...
Scheme 36: Studies on the divinylepoxide rearrangement.
Scheme 37: Studies on the vinylcyclopropanecarbonyl rearrangement.
Scheme 38: Nitrogen-substituted variants of the divinylcyclopropane rearrangement.
Investigating the continuous synthesis of a nicotinonitrile precursor to nevirapine
- Ashley R. Longstreet,
- Suzanne M. Opalka,
- Brian S. Campbell,
- B. Frank Gupton and
- D. Tyler McQuade
Beilstein J. Org. Chem. 2013, 9, 2570–2578, doi:10.3762/bjoc.9.292
- complicate downstream operations. We immediately recognized the water formed in the Knoevenagel condensation would quench the DMF-DMA in the second step. In addition, our batch Knoevenagel condensation was base catalyzed and we discovered that base increased dimer byproducts in the enamine step. Therefore
- of normal process windows [45]. Attempts to increase the reaction concentration beyond 1.0 M led to reactor clogging due to the limited of solubility of 5. We proceeded to develop a continuous process by coupling the enamine step with the Knoevenagel condensation (Scheme 4). To achieve this, we
- that the Knoevenagel condensation occurred primarily in the Al2O3 column, we only varied the temperature of the Al2O3 column. The Al2O3 column temperature was initially set to 25 °C which yielded 91% of 5 from acetone and malononitrile (Table 2, entry 2). We observed that the Al2O3 column reactor
Graphical Abstract
Figure 1: The estimated demand of for nevirapine until 2015 [6].
Scheme 1: Commercial building blocks to nevirapine.
Scheme 2: a) Current commercial process to CAPIC and b) newly developed batch synthesis to CAPIC and its brom...
Scheme 3: Proposed synthesis to 2-bromo-4-methylnicotinonitrile using a continuous approach with the consider...
Figure 2: a) Flow scheme to produce the enamine intermediate 5 from isopropylidenemalononitrile (4) (see Supporting Information File 1 for...
Scheme 4: Flow scheme to produce the enamine 5 starting from acetone and malononitrile (See Supporting Information File 1 for details).
Figure 3: Comparing the long-term stability of the Al2O3 and 3 Å MS columns when the Al2O3 column temperature...
Scheme 5: Several byproducts were observed when producing 5 starting from acetone and malononitrile. 7 is for...
Scheme 6: Flow scheme to produce 2-bromo-4-methylnicotinonitrile (6b) in 81% yield from 4 with a 1 M concentr...
Scheme 7: Reactor scheme for the continuous synthesis of 2-bromo-4-methylnicotinonitrile (6b) with an average...
An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles
- Marcus Baumann and
- Ian R. Baxendale
Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265
- readily prepared by chlorination of 2-pyridone (1.42) with phosphorous oxychloride (Scheme 8) [31][32]. The resulting primary alcohol 1.45 is then subjected to a second SNAr reaction with 4-fluorobenzaldehyde [33]. A Knoevenagel condensation of the aldehyde functionality in compound 1.47 with
- chromium(VI) oxide yielded the aldehyde 1.67 required for the previously described Knoevenagel condensation. The five membered heterocycle 2,4-thiazolidinedione (1.68) is readily available commercially, but can be easily prepared at scale via a simple cyclocondensation between thiourea and chloroacetic
- crude material in the subsequent Knoevenagel condensation with thiazolidinedione 1.68. In order to reduce the intermediate benzylidene double bond in this example sodium borohydride is used in the presence of cobalt chloride efficiently delivering pioglitazone in high purity. Other syntheses of
Graphical Abstract
Scheme 1: Scaled industrial processes for the synthesis of simple pyridines.
Scheme 2: Synthesis of nicotinic acid from 2-methyl-5-ethylpyridine (1.11).
Scheme 3: Synthesis of 3-picoline and nicotinic acid.
Scheme 4: Synthesis of 3-picoline from 2-methylglutarodinitrile 1.19.
Scheme 5: Picoline-based synthesis of clarinex (no yields reported).
Scheme 6: Mode of action of proton-pump inhibitors and structures of the API’s.
Scheme 7: Hantzsch-like route towards the pyridine rings in common proton pump inhibitors.
Figure 1: Structures of rosiglitazone (1.40) and pioglitazone (1.41).
Scheme 8: Synthesis of rosiglitazone.
Scheme 9: Syntheses of 2-pyridones.
Scheme 10: Synthesis and mechanism of 2-pyrone from malic acid.
Scheme 11: Polymer-assisted synthesis of rosiglitazone.
Scheme 12: Synthesis of pioglitazone.
Scheme 13: Meerwein arylation reaction towards pioglitazone.
Scheme 14: Route towards pioglitazone utilising tyrosine.
Scheme 15: Route towards pioglitazone via Darzens ester formation.
Scheme 16: Syntheses of the thiazolidinedione moiety.
Scheme 17: Synthesis of etoricoxib utilising Negishi and Stille cross-coupling reactions.
Scheme 18: Synthesis of etoricoxib via vinamidinium condensation.
Figure 2: Structures of nalidixic acid, levofloxacin and moxifloxacin.
Scheme 19: Synthesis of moxifloxacin.
Scheme 20: Synthesis of (S,S)-2,8-diazabicyclo[4.3.0]nonane 1.105.
Scheme 21: Synthesis of levofloxacin.
Scheme 22: Alternative approach to the levofloxacin core 1.125.
Figure 3: Structures of nifedipine, amlodipine and clevidipine.
Scheme 23: Mg3N2-mediated synthesis of nifedipine.
Scheme 24: Synthesis of rac-amlodipine as besylate salt.
Scheme 25: Aza Diels–Alder approach towards amlodipine.
Scheme 26: Routes towards clevidipine.
Figure 4: Examples of piperidine containing drugs.
Figure 5: Discovery of tiagabine based on early leads.
Scheme 27: Synthetic sequences to tiagabine.
Figure 6: Structures of solifenacin (2.57) and muscarine (2.58).
Scheme 28: Enantioselective synthesis of solifenacin.
Figure 7: Structures of DPP-4 inhibitors of the gliptin-type.
Scheme 29: Formation of inactive diketopiperazines from cis-rotameric precursors.
Figure 8: Co-crystal structure of carmegliptin bound in the human DPP-4 active site (PDB 3kwf).
Scheme 30: Improved route to carmegliptin.
Figure 9: Structures of lamivudine and zidovudine.
Scheme 31: Typical routes accessing uracil, thymine and cytosine.
Scheme 32: Coupling between pyrimidones and riboses via the Vorbrüggen nucleosidation.
Scheme 33: Synthesis of lamivudine.
Scheme 34: Synthesis of raltegravir.
Scheme 35: Mechanistic studies on the formation of 3.22.
Figure 10: Structures of selected pyrimidine containing drugs.
Scheme 36: General preparation of pyrimidines and dihydropyrimidones.
Scheme 37: Synthesis of imatinib.
Scheme 38: Flow synthesis of imatinib.
Scheme 39: Syntheses of erlotinib.
Scheme 40: Synthesis of erlotinib proceeding via Dimroth rearrangement.
Scheme 41: Synthesis of lapatinib.
Scheme 42: Synthesis of rosuvastatin.
Scheme 43: Alternative preparation of the key aldehyde towards rosuvastatin.
Figure 11: Structure comparison between nicotinic acetylcholine receptor agonists.
Scheme 44: Syntheses of varenicline and its key building block 4.5.
Scheme 45: Synthetic access to eszopiclone and brimonidine via quinoxaline intermediates.
Figure 12: Bortezomib bound in an active site of the yeast 20S proteasome ([114], pdb 2F16).
Scheme 46: Asymmetric synthesis of bortezomib.
Figure 13: Structures of some prominent piperazine containing drugs.
Figure 14: Structural comparison between the core of aplaviroc (4.35) and a type-1 β-turn (4.36).
Scheme 47: Examplary synthesis of an aplaviroc analogue via the Ugi-MCR.
Scheme 48: Syntheses of azelastine (5.1).
Figure 15: Structures of captopril, enalapril and cilazapril.
Scheme 49: Synthesis of cilazapril.
Figure 16: Structures of lamotrigine, ceftriaxone and azapropazone.
Scheme 50: Synthesis of lamotrigine.
Scheme 51: Alternative synthesis of lamotrigine (no yields reported).
Figure 17: Structural comparison between imiquimod and the related adenosine nucleoside.
Scheme 52: Conventional synthesis of imiquimod (no yields reported).
Scheme 53: Synthesis of imiquimod.
Scheme 54: Synthesis of imiquimod via tetrazole formation (not all yields reported).
Figure 18: Structures of various anti HIV-medications.
Scheme 55: Synthesis of abacavir.
Figure 19: Structures of diazepam compared to modern replacements.
Scheme 56: Synthesis of ocinaplon.
Scheme 57: Access to zaleplon and indiplon.
Scheme 58: Different routes towards the required N-methylpyrazole 6.65 of sildenafil.
Scheme 59: Polymer-supported reagents in the synthesis of key aminopyrazole 6.72.
Scheme 60: Early synthetic route to sildenafil.
Scheme 61: Convergent preparations of sildenafil.
Figure 20: Comparison of the structures of sildenafil, tadalafil and vardenafil.
Scheme 62: Short route to imidazotriazinones.
Scheme 63: Alternative route towards vardenafils core imidazotriazinone (6.95).
Scheme 64: Bayer’s approach to the vardenafil core.
Scheme 65: Large scale synthesis of vardenafil.
Scheme 66: Mode of action of temozolomide (6.105) as methylating agent.
Scheme 67: Different routes to temozolomide.
Scheme 68: Safer route towards temozolomide.
Figure 21: Some unreported heterocyclic scaffolds in top market drugs.
Raman spectroscopy as a tool for monitoring mesoscale continuous-flow organic synthesis: Equipment interface and assessment in four medicinally-relevant reactions
- Trevor A. Hamlin and
- Nicholas E. Leadbeater
Beilstein J. Org. Chem. 2013, 9, 1843–1852, doi:10.3762/bjoc.9.215
- conversion using NMR spectroscopy. Comparison of the values shows a good correlation (Table 1). Expanding the technique to other reactions The Knovenagel condensation We turned our attention next to the Knoevenagel condensation of ethyl acetoacetate with a range of aromatic aldehydes (Scheme 2). Our
- )-one (4a) across a range of reaction conditions (scan time = 15 s, integration = 10 s). The reaction between salicylaldehyde and ethyl acetoacetate to form 3-acetyl coumarin (1). The Knoevenagel condensation of benzaldehyde and ethyl acetoacetate to yield (Z)-ethyl 2-benzylidene-3-oxobutanoate (2a
Graphical Abstract
Figure 1: (a) Flow cell and (b) Raman interface used in the present study.
Scheme 1: The reaction between salicylaldehyde and ethyl acetoacetate to form 3-acetyl coumarin (1).
Figure 2: The Raman spectrum of 3-acetylcoumarin (1) generated using Gaussian 09 [40] at the B3LYP/6-31g(d) level...
Figure 3: Monitoring an aliquot of 3-acetyl coumarin (1) as it passes through the flow cell (scan time = 15 s...
Figure 4: Monitoring the conversion of salicylaldehyde and ethyl acetoacetate to 3-acetylcoumarin (1) across ...
Figure 5: Plot of Raman intensity of the peak arising at 1608 cm-1 vs concentration of 3-acetyl coumarin (1),...
Scheme 2: The Knoevenagel condensation of benzaldehyde and ethyl acetoacetate to yield (Z)-ethyl 2-benzyliden...
Figure 6: Monitoring the conversion of benzaldehyde and ethyl acetoacetate to (Z)-ethyl 2-benzylidene-3-oxobu...
Scheme 3: Claisen-Schmidt condensation of benzaldehyde with acetophenone to yield chalcone, 3a.
Figure 7: Monitoring the conversion of benzaldehyde with acetophenone to chalcone, 3a, across a range of reac...
Scheme 4: The Biginelli cyclocondensation of benzaldehyde, ethyl acetoacetate, and urea to yield 5-ethoxycarb...
Figure 8: Monitoring the conversion of benzaldehyde, ethyl acetoacetate, and urea to 5-ethoxycarbonyl-6-methy...
Enhancement of efficiency in organic photovoltaic devices containing self-complementary hydrogen-bonding domains
- Rohan J. Kumar,
- Jegadesan Subbiah and
- Andrew B. Holmes
Beilstein J. Org. Chem. 2013, 9, 1102–1110, doi:10.3762/bjoc.9.122
- ] followed by a Knoevenagel condensation provided the target compound 2 in excellent yield. The solubilizing strategy of incorporating alkyl groups on the thiophene unit provided the compound with excellent solubility in a wide range of common solvents. Optoelectronic properties In chloroform solution the UV
Graphical Abstract
Figure 1: N-ethylhexyl-substituted (1) [20] and target free N–H (2) cyanopyridone structures.
Scheme 1: Synthesis of the cyanopyridone 2, reagents and conditions: (i) Pd(PPh3)4, Cs2CO3, toluene, reflux, ...
Figure 2: (a) Chloroform (solid line) and thin-film (dashed line) UV–vis absorption and emission spectra and ...
Figure 3: The concentration dependence of (a) the NH 1H NMR chemical shift and (b) the vinyl proton chemical ...
Figure 4: AFM height image of observed nanostructures of films drop cast from (a) 10 mg/mL and (b) 1 mg/mL ch...
Figure 5: Dimeric structures of 2. (a) centrosymmetric dimer of 2; (b) bond-rotated centrosymmetric dimer of 2...
Figure 6: Schematic representation of self-complementary interactions leading to one-dimensional chains.
Synthesis of functionalized spiro[indoline-3,4’-pyridines] and spiro[indoline-3,4’-pyridinones] via one-pot four-component reactions
- Li-Juan Zhang,
- Qun Wu,
- Jing Sun and
- Chao-Guo Yan
Beilstein J. Org. Chem. 2013, 9, 846–851, doi:10.3762/bjoc.9.97
- ester A from the addition of arylamine to methyl propiolate. The second reaction is a Knoevenagel condensation of isatin with malononitrile or ethyl cyanoacetate under the catalysis of triethylamine to give the isatylidene deriatives B. The third reaction is a Michael addition of β-enamino ester
Graphical Abstract
Figure 1: Molecular structure of the spiro compound 1c.
Figure 2: Molecular structure of the spiro compound 1h.
Figure 3: Molecular structure of spiro compound 2b.
Figure 4: Molecular structure of spiro compound 3b.
Scheme 1: The proposed mechanism for the domino reaction.
