Synthesis of 5-unsubstituted dihydropyrimidinone-4-carboxylates from deep eutectic mixtures
- Sangram Gore,
- Sundarababu Baskaran and
- Burkhard König
Beilstein J. Org. Chem. 2022, 18, 331–336, doi:10.3762/bjoc.18.37
Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones
- Girish Suresh Yedase,
- Sumit Kumar,
- Jessica Stahl,
- Burkhard König and
- Veera Reddy Yatham
Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121
Graphical Abstract
Scheme 1: Photocatalyzed aerobic oxidation of aromatic alcohols.
Scheme 2: Substrate scope. Reaction conditions as given in Table 1 (entry 1). Yields are isolated yields, average of...
Scheme 3: Selective oxidation of 3-bromobenzyl alcohol in the presence of 3-phenylpropanol. Compound 1af was ...
Figure 1: Mechanistic studies. (A): UV–vis spectra of the CeIV(OBn)Cln complex in CH3CN under blue light irra...
Activated carbon as catalyst support: precursors, preparation, modification and characterization
- Melanie Iwanow,
- Tobias Gärtner,
- Volker Sieber and
- Burkhard König
Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104
Graphical Abstract
Figure 1: Experimental setup of ultrasonic spray pyrolysis. Reprinted with permission from [95], copyright 2006 T...
Figure 2: Overview of nitrogen-containing functional groups on the surface of activated carbons. Scheme was d...
Azologization of serotonin 5-HT3 receptor antagonists
- Karin Rustler,
- Galyna Maleeva,
- Piotr Bregestovski and
- Burkhard König
Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74
Graphical Abstract
Scheme 1: Approach of the direct azologization of reported [60,61] serotonin 5-HT3R antagonists via replacement of a...
Scheme 2: Synthesis of the differently substituted quinoxaline azobenzene derivatives 5a and 5b via Baeyer [62]–M...
Scheme 3: Synthesis of the methoxy-substituted quinoxaline derivative 12a via diazotization [66-69].
Scheme 4: General procedure for the synthesis of purine- and thienopyrimidine-substituted arylazobenzenes and...
Scheme 5: Synthesis of the thiomethyl-linked purine azobenzene 23 [62,63,72-74].
Scheme 6: Synthesis of the amide-linked azobenzene purine 28 [62,63,75-77].
Figure 1: UV–vis absorption spectra measured at 50 µM in DMSO. Left: purine derivative 16c; right: azo-extend...
Figure 2: On the left panel representative traces of currents induced by the application of 3 µM 5HT (black t...
Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis
- Amrita Das,
- Mitasree Maity,
- Simon Malcherek,
- Burkhard König and
- Julia Rehbein
Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228
Graphical Abstract
Figure 1: Selected examples of sulfenylated heterocycles used in pharmaceuticals and material chemistry.
Scheme 1: Synthetic routes to organosulfur compounds.
Scheme 2: Aryl sulfide synthesis.
Scheme 3: Substrate scope for arylthiol syntheses. The reaction was performed with 1a–g (0.1 mmol) and 2a–d (...
Figure 2: Crystal structures of compounds 3a, 3d, 3e and 3i.
Scheme 4: Radical trapping experiments.
Figure 3: (a) Changes in the fluorescence spectra (in this case intensity, λEx = 455 nm) of [Ir(dF(CF3)ppy)2(...
Scheme 5: Proposed mechanism for visible light mediated direct C–H sulfenylation.
Figure 4: Black line: UV–vis spectrum of the degassed [Ir] + 1,3,5-TMB mixture (solution A) in ACN. Blue and ...
Photocatalytic formation of carbon–sulfur bonds
- Alexander Wimmer and
- Burkhard König
Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4
Graphical Abstract
Scheme 1: General overview over the sulfur-based substrates and reactive intermediates that are discussed in ...
Scheme 2: Photoredox-catalyzed radical thiol–ene reaction, applying [Ru(bpz)3](PF6)2 as photocatalyst.
Scheme 3: Photoredox-catalyzed thiol–ene reaction of aliphatic thiols with alkenes enabled by aniline derivat...
Scheme 4: Photoredox-catalyzed radical thiol–ene reaction for the postfunctionalization of polymers (a) and n...
Scheme 5: Photoredox-catalyzed thiol–ene reaction enabled by bromotrichloromethane as redox additive.
Scheme 6: Photoredox-catalyzed preparation of β-ketosulfoxides with Eosin Y as organic dye as photoredox cata...
Scheme 7: Greaney’s photocatalytic radical thiol–ene reaction, applying TiO2 nanoparticles as photocatalyst.
Scheme 8: Fadeyi’s photocatalytic radical thiol–ene reaction, applying Bi2O3 as photocatalyst.
Scheme 9: Ananikov’s photocatalytic radical thiol-yne reaction, applying Eosin Y as photocatalyst.
Scheme 10: Organocatalytic visible-light photoinitiated thiol–ene coupling, applying phenylglyoxylic acid as o...
Scheme 11: Xia’s photoredox-catalyzed synthesis of 2,3-disubstituted benzothiophenes, applying 9-mesityl-10-me...
Scheme 12: Wang’s metal-free photoredox-catalyzed radical thiol–ene reaction, applying 9-mesityl-10-methylacri...
Scheme 13: Visible-light benzophenone-catalyzed metal- and oxidant-free radical thiol–ene reaction.
Scheme 14: Visible-light catalyzed C-3 sulfenylation of indole derivatives using Rose Bengal as organic dye.
Scheme 15: Photocatalyzed radical thiol–ene reaction and subsequent aerobic sulfide-oxidation with Rose Bengal...
Scheme 16: Photoredox-catalyzed synthesis of diaryl sulfides.
Scheme 17: Photocatalytic cross-coupling of aryl thiols with aryl diazonium salts, using Eosin Y as photoredox...
Scheme 18: Photocatalyzed cross-coupling of aryl diazonium salts with cysteines in batch and in a microphotore...
Scheme 19: Fu’s [Ir]-catalyzed photoredox arylation of aryl thiols with aryl halides.
Scheme 20: Fu’s photoredox-catalyzed difluoromethylation of aryl thiols.
Scheme 21: C–S cross-coupling of thiols with aryl iodides via [Ir]-photoredox and [Ni]-dual-catalysis.
Scheme 22: C–S cross-coupling of thiols with aryl bromides, applying 3,7-bis-(biphenyl-4-yl)-10-(1-naphthyl)ph...
Scheme 23: Collin’s photochemical dual-catalytic cross-coupling of thiols with bromoalkynes.
Scheme 24: Visible-light-promoted C–S cross-coupling via intermolecular electron donor–acceptor complex format...
Scheme 25: Li’s visible-light photoredox-catalyzed thiocyanation of indole derivatives with Rose Bengal as pho...
Scheme 26: Hajra’s visible-light photoredox-catalyzed thiocyanation of imidazoheterocycles with Eosin Y as pho...
Scheme 27: Wang’s photoredox-catalyzed thiocyanation reaction of indoles, applying heterogeneous TiO2/MoS2 nan...
Scheme 28: Yadav’s photoredox-catalyzed α-C(sp3)–H thiocyanation reaction for tertiary amines, applying Eosin ...
Scheme 29: Yadav’s photoredox-catalyzed synthesis of 5-aryl-2-imino-1,3-oxathiolanes.
Scheme 30: Yadav’s photoredox-catalyzed synthesis of 1,3-oxathiolane-2-thiones.
Scheme 31: Li’s photoredox catalysis for the preparation of 2-substituted benzothiazoles, applying [Ru(bpy)3](...
Scheme 32: Lei’s external oxidant-free synthesis of 2-substituted benzothiazoles by merging photoredox and tra...
Scheme 33: Metal-free photocatalyzed synthesis of 2-aminobenzothiazoles, applying Eosin Y as photocatalyst.
Scheme 34: Metal-free photocatalyzed synthesis of 1,3,4-thiadiazoles, using Eosin Y as photocatalyst.
Scheme 35: Visible-light photoredox-catalyzed preparation of benzothiophenes with Eosin Y.
Scheme 36: Visible-light-induced KOH/DMSO superbase-promoted preparation of benzothiophenes.
Scheme 37: Jacobi von Wangelin’s photocatalytic approach for the synthesis of aryl sulfides, applying Eosin Y ...
Scheme 38: Visible-light photosensitized α-C(sp3)–H thiolation of aliphatic ethers.
Scheme 39: Visible-light photocatalyzed cross-coupling of alkyl and aryl thiosulfates with aryl diazonium salt...
Scheme 40: Visible-light photocatalyzed, controllable sulfenylation and sulfoxidation with organic thiosulfate...
Scheme 41: Rastogi’s photoredox-catalyzed methylsulfoxidation of aryl diazonium salts, using [Ru(bpy)3]Cl2 as ...
Scheme 42: a) Visible-light metal-free Eosin Y-catalyzed procedure for the preparation of vinyl sulfones from ...
Scheme 43: Visible-light photocatalyzed cross-coupling of sodium sulfinates with secondary enamides.
Scheme 44: Wang’s photocatalyzed oxidative cyclization of phenyl propiolates with sulfinic acids, applying Eos...
Scheme 45: Lei’s sacrificial oxidant-free synthesis of allyl sulfones by merging photoredox and transition met...
Scheme 46: Photocatalyzed Markovnikov-selective radical/radical cross-coupling of aryl sulfinic acids and term...
Scheme 47: Visible-light Eosin Y induced cross-coupling of aryl sulfinic acids and styrene derivatives, afford...
Scheme 48: Photoredox-catalyzed bicyclization of 1,7-enynes with sulfinic acids, applying Eosin Y as photocata...
Scheme 49: Visible-light-accelerated C–H-sulfinylation of arenes and heteroarenes.
Scheme 50: Visible-light photoredox-catalyzed β-selenosulfonylation of electron-rich olefins, applying [Ru(bpy)...
Scheme 51: Photocatalyzed preparation of β-chlorosulfones from the respective olefins and p-toluenesulfonyl ch...
Scheme 52: a) Photocatalyzed preparation of β-amidovinyl sulfones from sulfonyl chlorides. b) Preparation of β...
Scheme 53: Visible-light photocatalyzed sulfonylation of aliphatic tertiary amines, applying [Ru(bpy)3](PF6)2 ...
Scheme 54: Reiser’s visible-light photoredox-catalyzed preparation of β-hydroxysulfones from sulfonyl chloride...
Scheme 55: a) Sun’s visible-light-catalyzed approach for the preparation of isoquinolinonediones, applying [fac...
Scheme 56: Visible-light photocatalyzed sulfonylation/cyclization of vinyl azides, applying [Ru(bpy)3]Cl2 as p...
Scheme 57: Visible-light photocatalyzed procedure for the formation of β-ketosulfones from aryl sulfonyl chlor...
Scheme 58: Zheng’s method for the sulfenylation of indole derivatives, applying sulfonyl chlorides via visible...
Scheme 59: Cai’s visible-light induced synthesis of β-ketosulfones from sulfonyl hydrazines and alkynes.
Scheme 60: Photoredox-catalyzed approach for the preparation of vinyl sulfones from sulfonyl hydrazines and ci...
Scheme 61: Jacobi von Wangelin’s visible-light photocatalyzed chlorosulfonylation of anilines.
Scheme 62: Three-component photoredox-catalyzed synthesis of N-amino sulfonamides, applying PDI as organic dye....
Scheme 63: Visible-light induced preparation of complex sulfones from oximes, silyl enol ethers and SO2.
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
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.
Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view
- Qiu Sun,
- Jörg Heilmann and
- Burkhard König
Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28
Graphical Abstract
Figure 1: Structure of 4-hydroxybenzyl alcohol (HBA, 1).
Figure 2: Structure–activity relationship of curcumin analogs.
Scheme 1: Synthesis of curcumin (3). Reagents and conditions: (a) vanillin, 1,2,3,4-tetrahydroquinoline, HOAc...
Figure 3: Backbone and substitution of monocarbonyl analogs of curcumin (MACs) showing their structural diver...
Scheme 2: Exemplary synthesis of MAC representatives. Reagents and conditions: (a) 40% KOH, EtOH, 5 °C; stirr...
Scheme 3: Synthesis of ellagic acid (7). Reagents and conditions: (a) H2SO4, CH3OH; (b) (1) o-chloranil, Et2O...
Figure 4: Structure of resveratrol and its analogs.
Scheme 4: Synthesis of quinolone-substituted phenol 20. Reagents and conditions: (a) Ac2O, 2-hydroxybenzaldeh...
Scheme 5: Synthesis of quinolone-substituted phenol 23. Reagents and conditions: (a) Ac2O, 2-hydroxybenzaldeh...
Figure 5: Design of 4-amino-2-sulfanylphenol derivatives and their structure–activity relationship.
Scheme 6: Synthesis of 4-amino-2-sulfanylphenol derivatives. Reagents and conditions: (a) R1SO2Cl, pyridine, ...
Figure 6: Structures of two series of natural-like acylphloroglucinols.
Scheme 7: Synthesis of acylphloroglucinol derivatives 35–41. Reagents and conditions: (a) acyl chloride, AlCl3...
Scheme 8: Synthesis of acylphloroglucinol derivatives 43–51. Reagents and conditions: (a) isoprene, Amberlyst...
Figure 7: Analogs of (−)-EGCG for the prevention of oxidation and improvement of the bioavailability of the c...
Scheme 9: Synthesis of xanthohumol 58. Reagents and conditions: (a) MOMCl, diisopropylethylamine, CH2Cl2; (b)...
Scheme 10: Synthesis of genistein 60. Reagents and conditions: (a) 4-hydroxyphenylacetonitrile, anhydrous HCl,...
Scheme 11: Synthesis of fisetin (67) and quercetin (68). Reagents and conditions: (a) 3,4-dimethoxybenzaldehyd...
Figure 8: Structure of (2S)-7,2’,4’-trihydroxy-5-methoxy-8-(dimethylallyl)flavanone (69).
Studies on the photodegradation of red, green and blue phosphorescent OLED emitters
- Susanna Schmidbauer,
- Andreas Hohenleutner and
- Burkhard König
Beilstein J. Org. Chem. 2013, 9, 2088–2096, doi:10.3762/bjoc.9.245
Graphical Abstract
Figure 1: Structures of the investigated phosphorescent triscyclometalated iridium complexes.
Figure 2: Photodegradation of the different compounds in toluene under ambient atmosphere. Plotted is the rat...
Figure 3: Photodegradation behavior of the iridium complexes in CH2Cl2 and toluene solution and in a spin-coa...
Figure 4: Mass spectra of the identified halogenated degradation products of a) Ir(ppy)3 after 200 min of irr...
Figure 5: Degradation curves of Ir(piq)3 in benzene and benzene-d6 under ambient and inert conditions (left)....
Figure 6: DAD chromatogram showing the formation of two main degradation products (left) and their assigned m...
Figure 7: Degradation curves of Ir(ppy)3 in benzene and benzene-d6 under ambient and inert conditions, and ma...
Figure 8: (a) Degradation curves of Ir(Me-ppy)3 in benzene and benzene-d6 under ambient and inert conditions....
Figure 9: Degradation curves of Ir(F,CN-ppy)3 in benzene, benzene-d6 and toluene under ambient conditions and...
New GABA amides activating GABAA-receptors
- Peter Raster,
- Andreas Späth,
- Svetlana Bultakova,
- Pau Gorostiza,
- Burkhard König and
- Piotr Bregestovski
Beilstein J. Org. Chem. 2013, 9, 406–410, doi:10.3762/bjoc.9.42
Graphical Abstract
Figure 1: The neurotransmitter GABA.
Scheme 1: Synthesis of GABA-amide hydrochlorides 4a–c and 6a–f. (i) THF, reflux; (ii) MeOH, HCl (5%); (iii) T...
Figure 2: Effect of 7b on GABAA-receptor activation. (A) Superimposed traces of whole-cell currents induced b...
Figure 3: Absence of GABAA-receptor activation on application of 4c. Top traces: Examples of whole-cell curre...
Figure 4: Variation of EC50 values with the number n of methylene units separating the amide and the ammonium...
Figure 5: Effect of 7d on GABAA-receptor activation. (A,B) Superimposed traces of whole-cell currents induced...
Parallel solid-phase synthesis of diaryltriazoles
- Matthias Wrobel,
- Jeffrey Aubé and
- Burkhard König
Beilstein J. Org. Chem. 2012, 8, 1027–1036, doi:10.3762/bjoc.8.115
Graphical Abstract
Scheme 1: Terphenyl scaffold 1 [13,14]; oxazole-pyridazine-piperazine 2 [14,15] and aryl-triazoles 3 and 4 [15,16] as α-helix mime...
Scheme 2: Synthesis of azido-functionalized resins 7 and 9.
Reduction of benzylic alcohols and α-hydroxycarbonyl compounds by hydriodic acid in a biphasic reaction medium
- Michael Dobmeier,
- Josef M. Herrmann,
- Dieter Lenoir and
- Burkhard König
Beilstein J. Org. Chem. 2012, 8, 330–336, doi:10.3762/bjoc.8.36
Graphical Abstract
Scheme 1: Mechanism of the alcohol reduction and recycling of iodine.
Molecular recognition of organic ammonium ions in solution using synthetic receptors
- Andreas Späth and
- Burkhard König
Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32
Graphical Abstract
Figure 1: Biologically important amines and quaternary ammonium salts: histamine (1), dopamine (2) and acetyl...
Figure 2: Crown ether 18-crown-6.
Figure 3: Conformations of 18-crown-6 (4) in solvents of different polarity.
Figure 4: Binding topologies of the ammonium ion depending on the crown ring size.
Figure 5: A “pseudorotaxane” structure consisting of 24-crown-8 and a secondary ammonium ion (5); R = Ph.
Figure 6: Typical examples of azacrown ethers, cryptands and related aza macrocycles.
Figure 7: Binding of ammonium to azacrown ethers and cryptands [111-113].
Figure 8: A 19-crown-6-ether with decalino blocking groups (11) and a thiazole-dibenzo-18-crown-6-ether (12).
Figure 9: 1,3-Bis(6-oxopyridazin-1-yl)propane derivatives 13 and 14 by Campayo et al.
Figure 10: Fluorescent azacrown-PET-sensors based on coumarin.
Figure 11: Two different pyridino-cryptands (17 and 18) compared to a pyridino-crown (19); chiral ammonium ion...
Figure 12: Pyridino-18-crown-6 ligand (21), a similar acridino-18-crown-6 ligand (22) and a structurally relat...
Figure 13: Ciral pyridine-azacrown ether receptors 24.
Figure 14: Chiral 15-crown-5 receptors 26 and an analogue 18-crown-6 ligand 27 derived from amino alcohols.
Figure 15: C2-symmetric chiral 18-crown-6 amino alcohol derivatives 28 and related macrocycles.
Figure 16: Macrocycles with diamide-diester groups (30).
Figure 17: C2-symmetric chiral aza-18-crown-6 ethers (31) with phenethylamine residues.
Figure 18: Chiral C-pivot p-methoxy-phenoxy-lariat ethers.
Figure 19: Chiral lariat crown ether 34.
Figure 20: Sucrose-based chiral crown ether receptors 36.
Figure 21: Permethylated fructooligosaccharide 37 showing induced-fit chiral recognition.
Figure 22: Biphenanthryl-18-crown-6 derivative 38.
Figure 23: Chiral lariat crown ethers derived from binol by Fuji et al.
Figure 24: Chiral phenolic crown ether 41 with “aryl chiral barriers” and guest amines.
Figure 25: Chiral bis-crown receptor 43 with a meso-ternaphthalene backbone.
Figure 26: Chromogenic pH-dependent bis-crown chemosensor 44 for diamines.
Figure 27: Triamine guests for binding to receptor 44.
Figure 28: Chiral bis-crown phenolphthalein chemosensors 46.
Figure 29: Crown ether amino acid 47.
Figure 30: Luminescent receptor 48 for bis-alkylammonium guests.
Figure 31: Luminescent CEAA (49a), a bis-CEAA receptor for amino acids (49b) and the structure of lysine bindi...
Figure 32: Luminescent CEAA tripeptide for binding small peptides.
Figure 33: Bis crown ether 51a self assembles co-operatively with C60-ammonium ion 51b.
Figure 34: Triptycene-based macrotricyclic dibenzo-[24]-crown-8 ether host 52 and guests.
Figure 35: Copper imido diacetic acid azacrown receptor 53a and the suggested His-Lys binding motif; a copper ...
Figure 36: Urea (54) and thiourea (55) benzo crown receptor for transport and extraction of amino acids.
Figure 37: Crown pyryliums ion receptors 56 for amino acids.
Figure 38: Ditopic sulfonamide bridged crown ether receptor 57.
Figure 39: Luminescent peptide receptor 58.
Figure 40: Luminescent receptor 59 for the detection of D-glucosamine hydrochloride in water/ethanol and lumin...
Figure 41: Guanidinium azacrown receptor 61 for simple amino acids and ditopic receptor 62 with crown ether an...
Figure 42: Chiral bicyclic guanidinium azacrown receptor 63 and similar receptor 64 for the enantioselective t...
Figure 43: Receptors for zwitterionic species based on luminescent CEAAs.
Figure 44: 1,10-Azacrown ethers with sugar podand arms and the anticancer agent busulfan.
Figure 45: Benzo-18-crown-6 modified β-cyclodextrin 69 and β-cyclodextrin functionalized with diaza-18-crown-6...
Figure 46: Receptors for colorimetric detection of primary and secondary ammonium ions.
Figure 47: Porphyrine-crown-receptors 72.
Figure 48: Porphyrin-crown ether conjugate 73 and fullerene-ammonium ion guest 74.
Figure 49: Calix[4]arene (75a), homooxocalix[4]arene (75b) and resorcin[4]arene (75c) compared (R = H, alkyl c...
Figure 50: Calix[4]arene and ammonium ion guest (R = H, alkyl, OAcyl etc.), possible binding sites; A: co-ordi...
Figure 51: Typical guests for studies with calixarenes and related molecules.
Figure 52: Lower rim modified p-tert-butylcalix[5]arenes 82.
Figure 53: The first example of a water soluble calixarene.
Figure 54: Sulfonated water soluble calix[n]arenes that bind ammonium ions.
Figure 55: Displacement assay for acetylcholine (3) with a sulfonato-calix[6]arene (84b).
Figure 56: Amino acid inclusion in p-sulfonatocalix[4]arene (84a).
Figure 57: Calixarene receptor family 86 with upper and lower rim functionalization.
Figure 58: Calix[6]arenes 87 with one carboxylic acid functionality.
Figure 59: Sulfonated calix[n]arenes with mono-substitution at the lower rim systematically studied on their r...
Figure 60: Cyclotetrachromotropylene host (91) and its binding to lysine (81c).
Figure 61: Calixarenes 92 and 93 with phosphonic acids groups.
Figure 62: Calix[4]arene tetraphosphonic acid (94a) and a double bridged analogue (94b).
Figure 63: Calix[4]arene tetraphosphonic acid ester (92c) for surface recognition experiments.
Figure 64: Calixarene receptors 95 with α-aminophosphonate groups.
Figure 65: A bridged homocalix[3]arene 95 and a distally bridged homocalix[4]crown 96.
Figure 66: Homocalix[3]arene ammonium ion receptor 97a and the Reichardt’s dye (97b) for colorimetric assays.
Figure 67: Chromogenic diazo-bridged calix[4]arene 98.
Figure 68: Calixarene receptor 99 by Huang et al.
Figure 69: Calixarenes 100 reported by Parisi et al.
Figure 70: Guest molecules for inclusion in calixarenes 100: DAP × 2 HCl (101a), APA (101b) and Lys-OMe × 2 HC...
Figure 71: Different N-linked peptido-calixarenes open and with glycol chain bridges.
Figure 72: (S)-1,1′-Bi-2-naphthol calixarene derivative 104 published by Kubo et al.
Figure 73: A chiral ammonium-ion receptor 105 based on the calix[4]arene skeleton.
Figure 74: R-/S-phenylalaninol functionalized calix[6]arenes 106a and 106b.
Figure 75: Capped homocalix[3]arene ammonium ion receptor 107.
Figure 76: Two C3 symmetric capped calix[6]arenes 108 and 109.
Figure 77: Phosphorous-containing rigidified calix[6]arene 110.
Figure 78: Calix[6]azacryptand 111.
Figure 79: Further substituted calix[6]azacryptands 112.
Figure 80: Resorcin[4]arene (75c) and the cavitands (113).
Figure 81: Tetrasulfonatomethylcalix[4]resorcinarene (114).
Figure 82: Resorcin[4]arenes (115a/b) and pyrogallo[4]arenes (115c, 116).
Figure 83: Displacement assay for acetylcholine (3) with tetracyanoresorcin[4]arene (117).
Figure 84: Tetramethoxy resorcinarene mono-crown-5 (118).
Figure 85: Components of a resorcinarene based displacement assay for ammonium ions.
Figure 86: Chiral basket resorcin[4]arenas 121.
Figure 87: Resorcinarenes with deeper cavitand structure (122).
Figure 88: Resorcinarene with partially open deeper cavitand structure (123).
Figure 89: Water-stabilized deep cavitands with partially structure (124, 125).
Figure 90: Charged cavitands 126 for tetralkylammonium ions.
Figure 91: Ditopic calix[4]arene receptor 127 capped with glycol chains.
Figure 92: A calix[5]arene dimer for diammonium salt recognition.
Figure 93: Calixarene parts 92c and 129 for the formation molecular capsules.
Figure 94: Encapsulation of a quaternary ammonium cation by two resorcin[4]arene molecules (NMe4+@[75c]2 × Cl−...
Figure 95: Encapsulation of a quaternary ammonium cation by six resorcin[4]arene molecules (NMe3D+@[130]6 × Cl−...
Figure 96: Structure and schematic of cucurbit[6]uril (CB[6], 131a).
Figure 97: Cyclohexanocucurbit[6]uril (CB′[6], 132) and the guest molecule spermine (133).
Figure 98: α,α,δ,δ-Tetramethylcucurbit[6]uril (134).
Figure 99: Structure of the cucurbituril-phthalhydrazide analogue 135.
Figure 100: Organic cavities for the displacement assay for amine differentiation.
Figure 101: Displacement assay methodology for diammonium- and related guests involving cucurbiturils and some ...
Figure 102: Nor-seco-Cucurbituril (±)-bis-ns-CB[6] (140) and guest molecules.
Figure 103: The cucurbit[6]uril based complexes 141 for chiral discrimination.
Figure 104: Cucurbit[7]uril (131c) and its ferrocene guests (142) opposed.
Figure 105: Cucurbit[7]uril (131c) guest inclusion and representative guests.
Figure 106: Cucurbit[7]uril (131c) binding to succinylcholine (145) and different bis-ammonium and bis-phosphon...
Figure 107: Paraquat-cucurbit[8]uril complex 149.
Figure 108: Gluconuril-based ammonium receptors 150.
Figure 109: Examples of clefts (151a), tweezers (151b, 151c, 151d) and clips (151e).
Figure 110: Kemp’s triacid (152a), on example of Rebek’s receptors (152b) and guests.
Figure 111: Amino acid receptor (154) by Rebek et al.
Figure 112: Hexagonal lattice designed hosts by Bell et al.
Figure 113: Bell’s amidinium receptor (156) and the amidinium ion (157).
Figure 114: Aromatic phosphonic acids.
Figure 115: Xylene phosphonates 159 and 160a/b for recognition of amines and amino alcohols.
Figure 116: Bisphosphonate recognition motif 161 for a colorimetric assay with alizarin complexone (163) for ca...
Figure 117: Bisphosphonate/phosphate clip 164 and bisphosphonate cleft 165.
Figure 118: N-Methylpyrazine 166a, N-methylnicotinamide iodide (166b) and NAD+ (166c).
Figure 119: Bisphosphate cavitands.
Figure 120: Bisphosphonate 167 of Schrader and Finocchiaro.
Figure 121: Tweezer 168 for noradrenaline (80b).
Figure 122: Different tripods and heparin (170).
Figure 123: Squaramide based receptors 172.
Figure 124: Cage like NH4+ receptor 173 of Kim et al.
Figure 125: Ammonium receptors 174 of Chin et al.
Figure 126: 2-Oxazolin-based ammonium receptors 175a–d and 176 by Ahn et al.
Figure 127: Racemic guest molecules 177.
Figure 128: Tripods based on a imidazole containing macrocycle (178) and the guest molecules employed in the st...
Figure 129: Ammonium ion receptor 180.
Figure 130: Tetraoxa[3.3.3.3]paracyclophanes 181 and a cyclophanic tetraester (182).
Figure 131: Peptidic bridged paraquat-cyclophane.
Figure 132: Shape-selective noradrenaline host.
Figure 133: Receptor 185 for binding of noradrenaline on surface layers from Schrader et al.
Figure 134: Tetraphosphonate receptor for binding of noradrenaline.
Figure 135: Tetraphosphonate 187 of Schrader and Finocchiaro.
Figure 136: Zinc-Porphyrin ammonium-ion receptors 188 and 189 of Mizutani et al.
Figure 137: Zinc porphyrin receptor 190.
Figure 138: Zinc porphyrin receptors 191 capable of amino acid binding.
Figure 139: Zinc-porphyrins with amino acid side chains for stereoinduction.
Figure 140: Bis-zinc-bis-porphyrin based on Tröger’s base 193.
Figure 141: BINAP-zinc-prophyrin derivative 194 and it’s guests.
Figure 142: Bisaryl-linked-zinc-porphyrin receptors.
Figure 143: Bis-zinc-porphyrin 199 for diamine recognition and guests.
Figure 144: Bis-zinc-porphyrin crown ether 201.
Figure 145: Bis-zinc-porphyrin 202 for stereodiscrimination (L = large substituent; S = small substituent).
Figure 146: Bis-zinc-porphyrin[3]rotaxane and its copper complex and guests.
Figure 147: Dien-bipyridyl ligand 206 for co-ordination of two metal atoms.
Figure 148: The ligand and corresponding tetradentate co-complex 207 serving as enantioselective receptor for a...
Figure 149: Bis(oxazoline)–copper(II) complex 208 for the recognition of amino acids in aqueous solution.
Figure 150: Zinc-salen-complexes 209 for the recognition tertiary amines.
Figure 151: Bis(oxazoline)–copper(II) 211 for the recognition of amino acids in aqueous solution.
Figure 152: Zn(II)-complex of a C2 terpyridine crown ether.
Figure 153: Displacement assay and receptor for aspartate over glutamate.
Figure 154: Chiral complex 214 for a colorimetric displacement assay for amino acids.
Figure 155: Metal complex receptor 215 with tripeptide side arms.
Figure 156: A sandwich complex 216 and its displaceable dye 217.
Figure 157: Lanthanide complexes 218–220 for amino acid recognition.
Figure 158: Nonactin (221), valinomycin (222) and vancomycin (223).
Figure 159: Monesin (224a) and a chiral analogue for enantiodiscrimination of ammonium guests (224b).
Figure 160: Chiral podands (226) compared to pentaglyme-dimethylether (225) and 18-crown-6 (4).
Figure 161: Lasalocid A (228).
Figure 162: Lasalocid derivatives (230) of Sessler et al.
Figure 163: The Coporphyrin I tetraanion (231).
Figure 164: Linear and cyclic peptides for ammonium ion recognition.
Figure 165: Cyclic and bicyclic depsipeptides for ammonium ion recognition.
Figure 166: α-Cyclodextrin (136a) and novocaine (236).
Figure 167: Helical diol receptor 237 by Reetz and Sostmann.
Figure 168: Ammonium binding spherand by Cram et al. (238a) and the cyclic[6]metaphenylacetylene 238b in compar...
Figure 169: Receptor for peptide backbone and ammonium binding (239).
Figure 170: Anion sensor principle with 3-hydroxy-2-naphthanilide of Jiang et al.
Figure 171: 7-bromo-3-hydroxy-N-(2-hydroxyphenyl)naphthalene 2-carboxamide (241) and its amine binding.
Figure 172: Naturally occurring catechins with affinity to quaternary ammonium ions.
Figure 173: Spiropyran (244) and merocyanine form (244a) of the amino acid receptors of Fuji et al.
Figure 174: Coumarin aldehyde (245) and its iminium species with amino acid bound (245a) by Glass et al.
Figure 175: Coumarin aldehyde appended with boronic acid.
Figure 176: Quinolone aldehyde dimers by Glass et al.
Figure 177: Chromogenic ammonium ion receptors with trifluoroacetophenone recognition motifs.
Figure 178: Chromogenic ammonium ion receptor with trifluoroacetophenone recognition motif bound on different m...
Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties
- Harald Schmaderer,
- Mouchumi Bhuyan and
- Burkhard König
Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26
Graphical Abstract
Scheme 1: Flavin–guanidinium ion conjugates 1 and 2 and tetraacetyl riboflavin (3).
Scheme 2: Synthesis of flavins 1 and 2. Conditions: (i) DMAP, H2O, Δ, 20 h, 71–78%, (ii) HOBt, EDC, NEt(iPr)2...
Figure 1: X-ray crystal structures of the flavin-Kemp’s acids 6 (left) and 9 (right).
Figure 2: Structure of compound 1 in the solid state.
Figure 3: Calculated lowest energy conformation of 1 in the gas phase (AM1, Spartan program package).
Scheme 3: Oxidative photocleavage of dibenzyl phosphate.
Scheme 4: Photoreduction of 4-nitrophenyl phosphate.
Scheme 5: Photo Diels–Alder-reaction of anthracene with N-methyl-maleinimide.
Synthesis of new Cα-tetrasubstituted α-amino acids
- Andreas A. Grauer and
- Burkhard König
Beilstein J. Org. Chem. 2009, 5, No. 5, doi:10.3762/bjoc.5.5
Graphical Abstract
Figure 1: Proposed reaction mechanism for the formation of Cα-tetrasubstituted tetrahydrofuran α-amino acids.
Scheme 1: Cyclisation reaction forming the tetrahydrofuran amino acid (TAA).
Figure 2: Structure of compound 15 in the solid state determined by X-ray analysis [21].
