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Search for "atropisomers" in Full Text gives 19 result(s) in Beilstein Journal of Organic Chemistry.
Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes
- Michio Yamada
Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13
- determined the absolute configurations of these atropisomers through the X-ray crystallographic analyses of (Sa)-59 and (Ra)-60. Surprisingly, heating the enantiomers of 69 and 60 at 80 °C for 3 h resulted in negligible thermally induced racemization. Meanwhile, in O2-free toluene solution under illumination
Graphical Abstract
Scheme 1: Pathway of the [2 + 2] CA–RE reaction of an electron-rich alkyne with TCNE or TCNQ. EDG = electron-...
Scheme 2: Reaction pathway for DMA-appended acetylene and TCNEO.
Scheme 3: Pathway of the [2 + 2] CA–RE reaction between 1 and DCFs.
Scheme 4: Sequential double [2 + 2] CA–RE reactions between 1 and TCNE.
Scheme 5: Divergent chemical transformation pathways of TCBD 6.
Scheme 6: Synthesis of 12.
Scheme 7: [2 + 2] CA–RE reaction of 1 with 14. TCE = 1,1,2,2-tetrachloroethane.
Scheme 8: Autocatalytic model proposed by Nielsen et al.
Scheme 9: Synthesis of anthracene-embedded TCBD compound 19.
Scheme 10: Sequence of the [2 + 2] CA–RE reaction between dibenzo-fused cyclooctyne or cyclooctadiyne and TCNE...
Scheme 11: [2 + 2] CA–RE reaction between the CPP derivatives and TCNE. THF = tetrahydrofuran.
Scheme 12: [2 + 2] CA–RE reaction between ethynylfullerenes 31 and TCNE and subsequent thermal rearrangement.
Scheme 13: Pathway of the [2 + 2] CA–RE reaction between TCNE and 34, followed by additional skeletal transfor...
Scheme 14: Synthesis scheme for heterocycle 38 from the reaction between TCNE and 1 in water and a surfactant.
Scheme 15: Synthesis scheme of the CDA product 41.
Scheme 16: Synthesis of rotaxanes 44 and 46 via the [2 + 2] CA–RE reaction.
Scheme 17: Synthesis of a CuI bisphenanthroline-based rotaxane 50.
Figure 1: Structures of the chiral push–pull chromophores 51–56.
Figure 2: Structures of the axially chiral TCBD 57 and DCNQ 58 bearing a C60 core.
Figure 3: Structures of the axially chiral SubPc–TCBD–aniline conjugates 59 and 60 and the subporphyrin–TCBD–...
Figure 4: Structures of 63 and the TCBD 64.
Figure 5: Structures of the fluorophore-containing TCBDs 65–67.
Figure 6: Structures of the fluorophore-containing TCBDs 68–72.
Figure 7: Structures of the urea-containing TCBDs 73–75.
Figure 8: Structures of the fullerene–TCBD and DCNQ conjugates 76–79 and their reference compounds 80–83.
Figure 9: Structures of the ZnPc–TCBD–aniline conjugates 84 and 85.
Figure 10: Structures of the ZnP–PCBD and TCBD conjugates 86–88.
Figure 11: Structures of the porphyrin-based donor–acceptor conjugates (89–104).
Figure 12: Structures of the porphyrin–PTZ or DMA conjugates 105–112.
Figure 13: Structures of the BODIPY–Acceptor–TPA or PTZ conjugates 113–116.
Figure 14: Structures of the corrole–TCBD conjugates 117 and 118.
Figure 15: Structure of the dendritic TCBD 119.
Figure 16: Structures of the TCBDs 120–126.
Figure 17: Structures of the precursor 127 and TCBDs 128–130.
Figure 18: Structures of 131–134 utilized for BHJ OSCs.
Unexpected chiral vicinal tetrasubstituted diamines via borylcopper-mediated homocoupling of isatin imines
- Marco Manenti,
- Leonardo Lo Presti,
- Giorgio Molteni and
- Alessandra Silvani
Beilstein J. Org. Chem. 2022, 18, 303–308, doi:10.3762/bjoc.18.34
- diffraction analysis and proved to be single diastereoisomers and atropisomers. A plausible mechanism for the one-pot Cu(II)-catalyzed Bpin addition to the isatin-derived ketimine substrate and subsequent homocoupling is described. Keywords: atropoisomer; bis(pinacolato)diboron; 3,3′-bisoxindole; N-tert
Graphical Abstract
Scheme 1: Reaction conducted according to the Ellman protocol.
Figure 1: Asymmetric unit of 2a, with the atom-numbering scheme. The crystallographic reference system is als...
Figure 2: Substrate scope of the borylcopper-mediated homocoupling of oxindole-based N-tert-butanesulfinyl im...
Scheme 2: Proposed mechanism for the borylcopper-mediated homocoupling of ketimines 1.
Peptide stapling by late-stage Suzuki–Miyaura cross-coupling
- Hendrik Gruß,
- Rebecca C. Feiner,
- Ridhiwan Mseya,
- David C. Schröder,
- Michał Jewgiński,
- Kristian M. Müller,
- Rafał Latajka,
- Antoine Marion and
- Norbert Sewald
Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1
- diastereomers, i.e. cis/trans isomers or conformers with a high interconversion barrier. For complestatin-based macrocyclic peptides, the existence of biaryl atropisomers caused by the indole of tryptophan has been reported [82]. Recently, the occurrence of isomers was also observed in our group for SMC
- cyclised RGD peptides. It could be proven that an isomerisation is not caused by the cross-coupling but by the presence of stable isomers/conformers. Molecular dynamics (MD) simulations verified the appearance of stable, distinct conformers or atropisomers, which were in accordance with the experimental
Graphical Abstract
Scheme 1: Synthesis of SMC stapled axin CBD peptides. Reaction conditions: (a) Pd2(dba)3, sSPhos, KF, DME/EtO...
Scheme 2: Overview of the different cross-linkages obtained by intramolecular SMC. A) General structure of SM...
Figure 1: Analysis of the secondary structure by circular dichroism: CD spectra of both isomers of stapled pe...
Figure 2: In vitro binding affinities to β-catenin determined by competitive fluorescence polarisation assays....
Figure 3: Cleavage sites of Proteinase K digestion indicated by a red arrow.
Figure 4: Principal component analysis (PCA) of the macrocycle’s non-hydrogen atoms in the two isomers of P5....
Figure 5: Molecular modelling of the conformational preferences of the SMC stapled peptides P5 (with cis or t...
Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds
- Alemayehu Gashaw Woldegiorgis and
- Xufeng Lin
Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185
- (Brønsted acidity/basicity, hydrogen-bonding units, and counter-anions toward metals) [48][49]. In 2019, Shi, Lin, and co-workers achieved an enantioselective synthesis of axially chiral quinoline-derived biaryl atropisomers via Pd-catalyzed C–H olefination of 8-phenylquinoline (11) using a novel chiral
- of axially chiral N-arylindole atropisomers from azonaphthalene 54 and indole substrates 59 in the presence of chiral phosphoric acid CPA 17. The atropisomeric adducts were obtained in moderate to good yields (up to 93%) with good to excellent enantioselectivity (up to >99% ee, Scheme 20b). Therefore
- restricted rotation around an N–C single bond. There are few strategies for the catalytic atroposelective construction of N–C nonbiaryl atropisomers, which mainly consist of enantioselective cyclization [35], N-functionalization [93], and desymmetrization [94] of the existing achiral N–C bond. In this
Graphical Abstract
Figure 1: Representative examples of axially chiral biaryls, heterobiaryls, spiranes and allenes as ligands a...
Figure 2: Selected examples of axially chiral drugs and bioactive molecules.
Figure 3: Axially chiral functional materials and supramolecules.
Figure 4: Important chiral phosphoric acid scaffolds used in this review.
Scheme 1: Atroposelective aryl–aryl-bond formation by employing a facile [3,3]-sigmatropic rearrangement.
Scheme 2: Atroposelective synthesis of axially chiral biaryl amino alcohols 5.
Scheme 3: The enantioselective reaction of quinone and 2-naphthol derivatives.
Scheme 4: Enantioselective synthesis of multisubstituted biaryls.
Scheme 5: Enantioselective synthesis of axially chiral quinoline-derived biaryl atropisomers mediated by chir...
Scheme 6: Pd-Catalyzed atroposelective C–H olefination of biarylamines.
Scheme 7: Palladium-catalyzed directed atroposelective C–H allylation.
Scheme 8: Enantioselective synthesis of axially chiral (a) aryl indoles and (b) biaryldiols.
Scheme 9: Asymmetric arylation of indoles enabled by azo groups.
Scheme 10: Proposed mechanism for the asymmetric arylation of indoles.
Scheme 11: Enantioselective synthesis of axially chiral N-arylindoles [38].
Scheme 12: Enantioselective [3 + 2] formal cycloaddition and central-to-axial chirality conversion.
Scheme 13: Organocatalytic atroposelective arene functionalization of nitrosonaphthalene with indoles.
Scheme 14: Proposed reaction mechanism for the atroposelective arene functionalization of nitrosonaphthalenes.
Scheme 15: Asymmetric construction of axially chiral naphthylindoles [65].
Scheme 16: Enantioselective synthesis of axially chiral 3,3’-bisindoles [66].
Scheme 17: Atroposelective synthesis of 3,3’-bisiindoles bearing axial and central chirality.
Scheme 18: Enantioselective synthesis of axially chiral 3,3’-bisindoles bearing single axial chirality.
Scheme 19: Enantioselective reaction of azonaphthalenes with various pyrazolones.
Scheme 20: Enantioselective and atroposelective synthesis of axially chiral N-arylcarbazoles [73].
Scheme 21: Atroposelective cyclodehydration reaction.
Scheme 22: Atroposelective construction of axially chiral N-arylbenzimidazoles [78].
Scheme 23: Proposed reaction mechanism for the atroposelective synthesis of axially chiral N-arylbenzimidazole...
Scheme 24: Atroposelective synthesis of axially chiral arylpyrroles [21].
Scheme 25: Synthesis of axially chiral arylquinazolinones and its reaction pathway [35].
Scheme 26: Synthesis of axially chiral aryquinoline by Friedländer heteroannulation reaction and its proposed...
Scheme 27: Povarov cycloaddition–oxidative chirality conversion process.
Scheme 28: Atroposelective synthesis of oxindole-based axially chiral styrenes via kinetic resolution.
Scheme 29: Synthesis of axially chiral alkene-indole frame works [45].
Scheme 30: Proposed reaction mechanism for axially chiral alkene-indoles.
Scheme 31: Atroposelective C–H aminations of N-aryl-2-naphthylamines with azodicarboxylates.
Scheme 32: Synthesis of brominated atropisomeric N-arylquinoids.
Scheme 33: The enantioselective syntheses of axially chiral SPINOL derivatives.
Scheme 34: γ-Addition reaction of various 2,3-disubstituted indoles to β,γ-alkynyl-α-imino esters.
Scheme 35: Regio- and stereoselective γ-addition reactions of isoxazol-5(4H)-ones to β,γ-alkynyl-α-imino ester...
Scheme 36: Synthesis of chiral tetrasubstituted allenes and naphthopyrans.
Scheme 37: Asymmetric remote 1,8-conjugate additions of thiazolones and azlactones to propargyl alcohols.
Scheme 38: Synthesis of chiral allenes from 1-substituted 2-naphthols [107].
A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium
- Shun Saito,
- Kota Atsumi,
- Tao Zhou,
- Keisuke Fukaya,
- Daisuke Urabe,
- Naoya Oku,
- Md. Rokon Ul Karim,
- Hisayuki Komaki and
- Yasuhiro Igarashi
Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97
- comparison of experimental and simulated ECD spectra [26][27]. Quite interestingly, the DFT calculation suggested that 1a and 1b would possess the opposite axial chirality around the biaryl bond between C-6 and C-7'': Ra for 1a and Sa for 1b as dominant atropisomers (Figure 4). This conformational difference
Graphical Abstract
Figure 1: Structures of pseudosporamide (1) and pseudosporamicins A–C (2–4).
Figure 2: COSY, key HMBC and ROESY correlations of pseudosporamide (1).
Figure 3: 1H NMR ΔδS−R values for PGME amides 5a and 5b obtained from compound 1.
Figure 4: The opposite axial chirality around the biaryl C-6–C-7'' bond influenced by the C-2 configuration i...
Figure 5: The experimental and calculated ECD spectra in MeCN.
Figure 6: COSY, key HMBC and NOESY correlations of compound 2.
Figure 7: NOESY correlations for the spiroacetal moiety of compound 2.
Figure 8: Selected examples of oligomycin-class metabolites from actinomycetes.
Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence
- Vânia F. Pais,
- Tristan Neumann,
- Ignacio Vayá,
- M. Consuelo Jiménez,
- Abel Ros and
- Uwe Pischel
Beilstein J. Org. Chem. 2019, 15, 2612–2622, doi:10.3762/bjoc.15.254
- the syn and anti atropisomers because of the slow rotation around the chiral axis at this temperature. Free rotation around the C–C bond was observed at 80 °C and hence, variable-temperature 1H NMR studies showed coalescence of the signals to give an average spectrum (see Supporting Information File 1
- (toluene/EtOAc 7:1), 16 was obtained as a light-yellow foam (70 mg, 62% yield). NMR spectra recorded at 25 °C showed a ca. 0.45:0.55 diastereomeric mixture of atropisomers. To simplify the spectra the measurements were undertaken at 80 °C. 1H NMR (400 MHz, C6D6, 80 °C) δ 8.80 (d, J = 5.6 Hz, 0.5H), 8.78 (d
- borylation starting from 13 (95 mg, 0.25 mmol) and after flash chromatography on silica gel (n-hexane/EtOAc 4:1), 17 was obtained as light-yellow foam (105 mg, 83% yield). NMR spectra recorded at 25 °C showed a ca. 0.45:0.55 diastereomeric mixture of atropisomers. To simplify the spectra the measurements
Graphical Abstract
Figure 1: Structures of the dyes 16–19.
Scheme 1: Synthesis of the precursors 2, 3, and 5.
Scheme 2: Synthesis of the precursor triflates 8–11.
Scheme 3: Synthesis of 12–15 and the organoboron dyes 16–19.
Figure 2: UV–vis absorption (solid line) and fluorescence (dashed line) spectra of a) 16, b) 17, c) 18, and d...
Scheme 4: Jablonski diagram representing the photophysical processes in the dyes 16–19.
Figure 3: Transient absorption spectrum (600 ns delay) of dye 17 in nitrogen-purged acetonitrile on excitatio...
Figure 4: Fluorescence titrations of the dyes (ca. 4–11 μM) with Bu4NF in acetonitrile. a) 16 (up to 156 equi...
Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis
- Zhen Cao,
- Aline Lacoudre,
- Cybille Rossy and
- Brigitte Bibal
Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239
- bis-alkylaryl thioether ligand to control the directionality and spatial orientation of its coordination to silver(I). Besides, 9,10-diphenylanthracenes (DPA) with ortho-substituted 9- and 10-aryl groups can exist as syn- or anti-atropisomers whose rotational barrier [46][47] ranges from 21 (ortho-H
- ) to 25–29 kcal/mol (ortho-CH3). A few ortho-substituted DPA atropisomers have been described as potent molecular switches [48][49], building-blocks for self-assembled capsules [50][51] or optical materials [52][53][54]. However, due to their partially frozen structure, syn-isomers of DPA are ideal
Graphical Abstract
Scheme 1: Synthesis of ligand 1, as its syn-atropisomer.
Figure 1: X-ray structures of complex 1a, as two diastereoisomeric macrocycles (R,S-1)2·(AgOTf)2 with ligands...
Figure 2: X-ray structure of complex 1c, as a (R,S-1)4·(AgNO3)6 cage with three nitrate anions as coordinatin...
Figure 3: X-ray structure of complex 1d, as a racemic mixture of (R,R)- and (S,S)-(syn-1)·(PPh3AgOTf)2.
Figure 4: Variable temperature 1H NMR of complex 1a in CDCl3 (7 mM) from −30 °C to 60 °C.
Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols
- Chi-Tung Yeung,
- Wesley Ting Kwok Chan,
- Wai-Sum Lo,
- Ga-Lai Law and
- Wing-Tak Wong
Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92
- highest reactivity and enantioselectivity with trimethylacetaldehyde as a substrate. Opposite absolute configurations of the catalytic products of benzaldehyde from atropisomers of 5 showed that axial chirality contributes significantly to high enantioselectivities. Further works on organocatalyst
Graphical Abstract
Scheme 1: Chiral biphenyl diol organocatalysts 1–6.
Scheme 2: Synthesis of 3.
Figure 1: (a) Single crystal X-ray structure of 3: showing intra- and intermolecular hydrogen bonds (green da...
Scheme 3: Synthesis of 4.
Scheme 4: Synthesis of 6.
Figure 2: X-ray crystal structure of (P)-(S,S)-6 at two different orientations to show (a) P atropselectiviti...
Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine
- Piotr Pomarański,
- Piotr Roszkowski,
- Jan K. Maurin,
- Armand Budzianowski and
- Zbigniew Czarnocki
Beilstein J. Org. Chem. 2018, 14, 2384–2393, doi:10.3762/bjoc.14.214
- , Poland 10.3762/bjoc.14.214 Abstract Background: Atropisomers are very interesting stereoisomers having axial chirality resulting from restricted rotation around single bonds and are found in various classes of compounds. ortho-Substituted arylpyridines are an important group of them. A regio- and
- conclusions about the order of substitution. Also, the observed selectivity in the case of ortho-methoxyphenylboronic acid suggested an additional metal O-chelation effect in the transition state, apparently not present in the ortho-chloro analogues. The rotational barrier in selected atropisomers was
- determined on the basis of HT NMR and thermal epimerisation experiments. The structure of most presented atropisomeric derivatives of 2,6-dimethylpyridine was confirmed by single-crystal X-ray analysis. Racemic chiral, differently substituted atropisomers were also examined by 1H NMR spectroscopy in the
Graphical Abstract
Figure 1: Structures of stereoisomers of 3,4,5-tris(2-methoxyphenyl)-2,6-dimethylpyridines determined by X-ra...
Figure 2: Graphical representation of kinetic, time-dependent 1H NMR analysis of (syn)-7 (100 °C).
Figure 3: Graphical representation of kinetic, time-dependent 1H NMR analysis of (syn)-10 (120 °C).
Figure 4: HT-NMR (300 MHz, DMSO-d6) spectra of A) (syn)-7. B) (syn)-10. Only the upfield (ca. 3.4–4 ppm) regi...
Figure 5: Summary of the results for coupling with ortho-substituted phenylboronic acid for triaryl products.
Figure 6: Summary of results for coupling with ortho-substituted phenylboronic acid for diaryl products.
Figure 7: Proposed intermediates for the 1,2-addition of 5 with methoxy group. A) Oxidative addition step. B)...
Figure 8: Proposed intermediates for the 1,3-addition with methoxy group. A) Oxidative addition step. B) Tran...
Figure 9: Proposed intermediates for the 1,2-addition with chlorine atom. A) Oxidative addition step. B) Tran...
Figure 10: Proposed intermediates for the 1,3-addition with chlorine atom. A) Oxidative addition step. B) Tran...
Conjugate addition–enantioselective protonation reactions
- James P. Phelan and
- Jonathan A. Ellman
Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116
- er) (Scheme 23b) [46]. This enantioselective addition process could be applied to a racemic mixture of axially chiral N-(2-tert-butylphenyl)itaconimide (98), furnishing atropisomers 99a and 99b as a stable and separable 1:1 mixture. A higher enantioselectivity was observed for the anti-diastereomer
Graphical Abstract
Figure 1: Two general pathways for conjugate addition followed by enantioselective protonation.
Scheme 1: Tomioka’s enantioselective addition of arylthiols to α-substituted acrylates.
Scheme 2: Sibi’s enantioselective hydrogen atom transfer reactions.
Scheme 3: Mikami’s addition of perfluorobutyl radical to α-aminoacrylate 11.
Scheme 4: Reisman’s Friedel–Crafts conjugate addition–enantioselective protonation approach toward tryptophan...
Scheme 5: Pracejus’s enantioselective addition of benzylmercaptan to α-aminoacrylate 20.
Scheme 6: Kumar and Dike’s enantioselective addition of thiophenol to α-arylacrylates.
Scheme 7: Tan’s enantioselective addition of aromatic thiols to 2-phthalimidoacrylates.
Scheme 8: Glorius’ enantioselective Stetter reactions with α-substituted acrylates.
Scheme 9: Dixon’s enantioselective addition of thiols to α-substituted acrylates.
Figure 2: Chiral phosphorous ligands.
Scheme 10: Enantioselective addition of arylboronic acids to methyl α-acetamidoacrylate.
Scheme 11: Frost’s enantioselective additions to dimethyl itaconate.
Scheme 12: Darses and Genet’s addition of potassium organotrifluoroborates to α-aminoacrylates.
Scheme 13: Proposed mechanism for enantioselective additions to α-aminoacrylates.
Scheme 14: Sibi’s addition of arylboronic acids to α-methylaminoacrylates.
Scheme 15: Frost’s enantioselective synthesis of α,α-dibenzylacetates 64.
Scheme 16: Rovis’s hydroheteroarylation of α-substituted acrylates with benzoxazoles.
Scheme 17: Proposed mechanism for the hydroheteroarylation of α-substituted acrylates with benzoxazoles.
Scheme 18: Sodeoka’s enantioselective addition of amines to N-benzyloxycarbonyl acrylamides 75 and 77.
Scheme 19: Proposed catalytic cycle for Sodeoka’s enantioselective addition of amines.
Scheme 20: Sibi’s enantioselective Friedel–Crafts addition of pyrroles to imides 84.
Scheme 21: Kobayashi’s enantioselective addition of malonates to α-substituted N-acryloyloxazolidinones.
Scheme 22: Chen and Wu’s enantioselective addition of thiophenol to N-methacryloyl benzamide.
Scheme 23: Tan’s enantioselective addition of secondary phosphine oxides and thiols to N-arylitaconimides.
Scheme 24: Enantioselective addition of thiols to α-substituted N-acryloylamides.
Scheme 25: Kobayashi’s enantioselective addition of thiols to α,β-unsaturated ketones.
Scheme 26: Feng’s enantioselective addition of pyrazoles to α-substituted vinyl ketones.
Scheme 27: Luo and Cheng’s addition of indoles to vinyl ketones by enamine catalysis.
Scheme 28: Curtin–Hammett controlled enantioselective addition of indole.
Scheme 29: Luo and Cheng’s enantioselective additions to α-branched vinyl ketones.
Scheme 30: Lou’s reduction–conjugate addition–enantioselective protonation.
Scheme 31: Luo and Cheng’s primary amine-catalyzed addition of indoles to α-substituted acroleins.
Scheme 32: Luo and Cheng’s proposed mechanism and transition state.
Figure 3: Shibasaki’s chiral lanthanum and samarium tris(BINOL) catalysts.
Scheme 33: Shibasaki’s enantioselective addition of 4-tert-butyl(thiophenol) to α,β-unsaturated thioesters.
Scheme 34: Shibasaki’s application of chiral (S)-SmNa3tris(binaphthoxide) catalyst 144 to the total synthesis ...
Scheme 35: Shibasaki’s cyanation–enantioselective protonation of N-acylpyrroles.
Scheme 36: Tanaka’s hydroacylation of acrylamides with aliphatic aldehydes.
Scheme 37: Ellman’s enantioselective addition of α-substituted Meldrum’s acids to terminally unsubstituted nit...
Scheme 38: Ellman’s enantioselective addition of thioacids to α,β,β-trisubstituted nitroalkenes.
Scheme 39: Hayashi’s enantioselective hydroarylation of diphenylphosphinylallenes.
Scheme 40: Hayashi’s enantioselective hydroarylation of diphenylphosphinylallenes.
Figure 4: Togni’s chiral ferrocenyl tridentate nickel(II) and palladium(II) complexes.
Scheme 41: Togni’s enantioselective hydrophosphination of methacrylonitrile.
Scheme 42: Togni’s enantioselective hydroamination of methacrylonitrile.
A convenient route to symmetrically and unsymmetrically substituted 3,5-diaryl-2,4,6-trimethylpyridines via Suzuki–Miyaura cross-coupling reaction
- Dariusz Błachut,
- Joanna Szawkało and
- Zbigniew Czarnocki
Beilstein J. Org. Chem. 2016, 12, 835–845, doi:10.3762/bjoc.12.82
- the phenyl rings (or naphthalene ring for 26) with three methyl groups of the pyridine ring. Consequently, the inhibited rotation of the phenyl rings led to the formation of stable diastereomeric atropisomers which could be detected in NMR spectroscopy. The interconversion barrier is probably
- remarkably high in 3,5-bis(2-trifluromethylphenyl)-2,4,6-trimethylpyridine [79], since both atropisomers of this compound could be observed during GC–MS analysis as a pair of well-separated Gaussian peaks at the temperature of elution approaching 290 °C. A similar phenomenon was observed for pyridine 8 and
- efficient techniques (preparative HPLC). The library of synthesized compounds will be used as a reference standard during our study on impurity markers in illegally produced amphetamine analogues. In several cases of ortho-aryl-substituted pyridines, stable atropisomers were observed and this phenomenon
Graphical Abstract
Figure 1: Types of aryl pyridines and pyrimidines already prepared in our group [23-27].
Scheme 1: Synthesis of diarylpyridines 4–29.
Scheme 2: Synthetic routes leading to unsymmetrically substituted arylpyridines.
Scheme 3: Preparation of unsymmetrical 3,5-diaryl-2,4,6-trimethylpyridines 46–56.
Scheme 4: Preparation of unsymmetrical 3,5-diaryl-4-chloro-2,6-dimethylpyridines 68–71.
Organocatalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones with bifunctional amine-thiourea catalysts bearing multiple hydrogen-bond donors
- Ming-Liang Zhang,
- Deng-Feng Yue,
- Zhen-Hua Wang,
- Yuan Luo,
- Xiao-Ying Xu,
- Xiao-Mei Zhang and
- Wei-Cheng Yuan
Beilstein J. Org. Chem. 2016, 12, 295–300, doi:10.3762/bjoc.12.31
- and position of the substituents on the phenyl ring (Table 3, entries 3–10). When the substituent was in the ortho-position of the phenyl ring of the R2 group, a diastereoselectivity was observed that may be due to the steric hindrance of ortho substituents led to the atropisomers (Table 3, entry 3
Graphical Abstract
Scheme 1: The strategy to construct chiral 3-substituted-3-hydroxy-1H-pyrrol-2(3H)-ones.
Figure 1: The X-ray structure of compound 4i.
Figure 2: A proposed transition state for the asymmetric Henry reaction.
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
- for their application in optoelectronics. Keywords: atropisomers; cyclization; 2-nitroperchlorobutadiene; 1H-pyrazoles; thiazolidin-4-ones; Introduction Preliminary studies in the field of polyhalogenated nitrobutadienes have already shown the enormous potential of pentachloro-2-nitro-1,3-butadiene
- -substituted anilines 16–18 two atropisomers were generated. This phenomenon is due to a less hindered rotation of the C–N bond of the former anilines (Figure 1). The steric hindrance is additionally forcing by the s-cis conformation of the nitrobutadiene moiety (cf. Figure 2). A DFT calculation of the energy
- 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
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.
Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics
- Gijs Koopmanschap,
- Eelco Ruijter and
- Romano V.A. Orru
Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50
Graphical Abstract
Scheme 1: The proposed mechanism of the Passerini reaction.
Scheme 2: The PADAM-strategy to α-hydroxy-β-amino amide derivatives 7. An additional oxidation provides α-ket...
Scheme 3: The general accepted Ugi-mechanism.
Scheme 4: Three commonly applied Ugi/cyclization approaches. a) UDC-process, b) UAC-sequence, c) UDAC-combina...
Scheme 5: Ugi reaction that involves the condensation of Armstrong’s convertible isocyanide.
Scheme 6: Mechanism of the U-4C-3CR towards bicyclic β-lactams.
Scheme 7: The Ugi 4C-3CR towards oxabicyclo β-lactams.
Scheme 8: Ugi MCR between an enantiopure monoterpene based β-amino acid, aldehyde and isocyanide resulting in...
Scheme 9: General MCR for β-lactams in water.
Scheme 10: a) Ugi reaction for β-lactam-linked peptidomimetics. b) Varying the β-amino acid resulted in β-lact...
Scheme 11: Ugi-4CR followed by a Pd-catalyzed Sn2 cyclization.
Scheme 12: Ugi-3CR of dipeptide mimics from 2-substituted pyrrolines.
Scheme 13: Joullié–Ugi reaction towards 2,5-disubstituted pyrrolidines.
Scheme 14: Further elaboration of the Ugi-scaffold towards bicyclic systems.
Scheme 15: Dihydroxyproline derivatives from an Ugi reaction.
Scheme 16: Diastereoselective Ugi reaction described by Banfi and co-workers.
Scheme 17: Similar Ugi reaction as in Scheme 16 but with different acids and two chiral isocyanides.
Scheme 18: Highly diastereoselective synthesis of pyrrolidine-dipeptoids via a MAO-N/MCR-procedure.
Scheme 19: MAO-N/MCR-approach towards the hepatitis C drug telaprevir.
Scheme 20: Enantioselective MAO-U-3CR procedure starting from chiral pyrroline 64.
Scheme 21: Synthesis of γ-lactams via an UDC-sequence.
Scheme 22: Utilizing bifunctional groups to provide bicyclic γ-lactam-ketopiperazines.
Scheme 23: The Ugi reaction provided both γ- as δ-lactams depending on which inputs were used.
Scheme 24: The sequential Ugi/RCM with olefinic substrates provided bicyclic lactams.
Scheme 25: a) The structural and dipole similarities of the triazole unit with the amide bond. b) The copper-c...
Scheme 26: The Ugi/Click sequence provided triazole based peptidomimetics.
Scheme 27: The Ugi/Click reaction as described by Nanajdenko.
Scheme 28: The Ugi/Click-approach by Pramitha and Bahulayan.
Scheme 29: The Ugi/Click-combination by Niu et al.
Scheme 30: Triazole linked peptidomimetics obtained from two separate MCRs and a sequential Click reaction.
Scheme 31: Copper-free synthesis of triazoles via two MCRs in one-pot.
Scheme 32: The sequential Ugi/Paal–Knorr reaction to afford pyrazoles.
Scheme 33: An intramolecular Paal–Knorr condensation provided under basic conditions pyrazolones.
Scheme 34: Similar cyclization performed under acidic conditions provided pyrazolones without the trifluoroace...
Scheme 35: The Ugi-4CR towards 2,4-disubstituted thiazoles.
Scheme 36: Solid phase approach towards thiazoles.
Scheme 37: Reaction mechanism of formation of thiazole peptidomimetics containing an additional β-lactam moiet...
Scheme 38: The synthesis of the trisubstituted thiazoles could be either performed via an Ugi reaction with pr...
Scheme 39: Performing the Ugi reaction with DMB-protected isocyanide gave access to either oxazoles or thiazol...
Scheme 40: Ugi/cyclization-approach towards 2,5-disubstituted thiazoles. The Ugi reaction was performed with d...
Scheme 41: Further derivatization of the thiazole scaffold.
Scheme 42: Three-step procedure towards the natural product bacillamide C.
Scheme 43: Ugi-4CR to oxazoles reported by Zhu and co-workers.
Scheme 44: Ugi-based synthesis of oxazole-containing peptidomimetics.
Scheme 45: TMNS3 based Ugi reaction for peptidomimics containing a tetrazole.
Scheme 46: Catalytic cycle of the enantioselective Passerini reaction towards tetrazole-based peptidomimetics.
Scheme 47: Tetrazole-based peptidomimetics via an Ugi reaction and a subsequent sigmatropic rearrangement.
Scheme 48: Resin-bound Ugi-approach towards tetrazole-based peptidomimetics.
Scheme 49: Ugi/cyclization approach towards γ/δ/ε-lactam tetrazoles.
Scheme 50: Ugi-3CR to pipecolic acid-based peptidomimetics.
Scheme 51: Staudinger–Aza-Wittig/Ugi-approach towards pipecolic acid peptidomimetics.
Figure 1: The three structural isomers of diketopiperazines. The 2,5-DKP isomer is most common.
Scheme 52: UDC-approach to obtain 2,5-DKPs, either using Armstrong’s isocyanide or via ethylglyoxalate.
Scheme 53: a) Ugi reaction in water gave either 2,5-DKP structures or spiro compounds. b) The Ugi reaction in ...
Scheme 54: Solid-phase approach towards diketopiperazines.
Scheme 55: UDAC-approach towards DKPs.
Scheme 56: The intermediate amide is activated as leaving group by acid and microwave assisted organic synthes...
Scheme 57: UDC-procedure towards active oxytocin inhibitors.
Scheme 58: An improved stereoselective MCR-approach towards the oxytocin inhibitor.
Scheme 59: The less common Ugi reaction towards DKPs, involving a Sn2-substitution.
Figure 2: Spatial similarities between a natural β-turn conformation and a DKP based β-turn mimetic [158].
Scheme 60: Ugi-based syntheses of bicyclic DKPs. The amine component is derived from a coupling between (R)-N-...
Scheme 61: Ugi-based synthesis of β-turn and γ-turn mimetics.
Figure 3: Isocyanide substituted 3,4-dihydropyridin-2-ones, dihydropyridines and the Freidinger lactams. Bio-...
Scheme 62: The mechanism of the 4-CR towards 3,4-dihydropyridine-2-ones 212.
Scheme 63: a) Multiple MCR-approach to provide DHP-peptidomimetic in two-steps. b) A one-pot 6-CR providing th...
Scheme 64: The MCR–alkylation–MCR procedure to obtain either tetrapeptoids or depsipeptides.
Scheme 65: U-3CR/cyclization employing semicarbazone as imine component gave triazine based peptidomimetics.
Scheme 66: 4CR towards triazinane-diones.
Scheme 67: The MCR–alkylation–IMCR-sequence described by our group towards triazinane dione-based peptidomimet...
Scheme 68: Ugi-4CR approaches followed by a cyclization to thiomorpholin-ones (a) and pyrrolidines (b).
Scheme 69: UDC-approach for benzodiazepinones.
Scheme 70: Ugi/Mitsunobu sequence to BDPs.
Scheme 71: A UDAC-approach to BDPs with convertible isocyanides. The corresponding amide is cleaved by microwa...
Scheme 72: microwave assisted post condensation Ugi reaction.
Scheme 73: Benzodiazepinones synthesized via the post-condensation Ugi/ Staudinger–Aza-Wittig cyclization.
Scheme 74: Two Ugi/cyclization approaches utilizing chiral carboxylic acids. Reaction (a) provided the product...
Scheme 75: The mechanism of the Gewald-3CR includes three base-catalysed steps involving first a Knoevnagel–Co...
Scheme 76: Two structural 1,4-thienodiazepine-2,5-dione isomers by U-4CR/cyclization.
Scheme 77: Tetrazole-based diazepinones by UDC-procedure.
Scheme 78: Tetrazole-based BDPs via a sequential Ugi/hydrolysis/coupling.
Scheme 79: MCR synthesis of three different tricyclic BPDs.
Scheme 80: Two similar approaches both involving an Ugi reaction and a Mitsunobu cyclization.
Scheme 81: Mitsunobu–Ugi-approach towards dihydro-1,4-benzoxazepines.
Scheme 82: Ugi reaction towards hetero-aryl fused 5-oxo-1,4-oxazepines.
Scheme 83: a) Ugi/RCM-approach towards nine-membered peptidomimetics b) Sequential peptide-coupling, deprotect...
Scheme 84: Ugi-based synthesis towards cyclic RGD-pentapeptides.
Scheme 85: Ugi/MCR-approach towards 12–15 membered macrocycles.
Scheme 86: Stereoselective Ugi/RCM approach towards 16-membered macrocycles.
Scheme 87: Passerini/RCM-sequence to 22-membered macrocycles.
Scheme 88: UDAC-approach towards 12–18-membered depsipeptides.
Figure 4: Enopeptin A with its more active derivative ADEP-4.
Scheme 89: a) The Joullié–Ugi-approach towards ADEP-4 derivatives b) Ugi-approach for the α,α-dimethylated der...
Scheme 90: Ugi–Click-strategy for 15-membered macrocyclic glyco-peptidomimetics.
Scheme 91: Ugi/Click combinations provided macrocycles containing both a triazole and an oxazole moiety.
Scheme 92: a) A solution-phase procedure towards macrocycles. b) Alternative solid-phase synthesis as was repo...
Scheme 93: Ugi/cyclization towards cyclophane based macrocycles.
Scheme 94: PADAM-strategy towards eurystatin A.
Scheme 95: PADAM-approach for cyclotheanamide.
Scheme 96: A triple MCR-approach affording RGD-pentapeptoids.
Scheme 97: Ugi-MiBs-approach towards peptoid macrocycles.
Scheme 98: Passerini-based MiB approaches towards macrocycles 345 and 346.
Scheme 99: Macrocyclic peptide formation by the use of amphoteric aziridine-based aldehydes.
On the control of secondary carbanion structure utilising ligand effects during directed metallation
- Andrew E. H. Wheatley,
- Jonathan Clayden,
- Ian H. Hillier,
- Alison Campbell Smith,
- Mark A. Vincent,
- Laurence J. Taylor and
- Joanna Haywood
Beilstein J. Org. Chem. 2012, 8, 50–60, doi:10.3762/bjoc.8.5
- single ortho substituent [25]. At ambient temperature, amides with this substitution pattern are conformationally mobile about their aryl–CO bond [26] on a timescale of seconds or less, and hence, inseparable into atropisomers [27]. However, at the temperatures commonly used to effect lithiation
- reactions, they should exist as chiral, racemic atropisomers. The stepwise lateral ethylation/ortho methylation of 3-H and lateral methylation/ortho methylation of 6-H [17] prior to warming returned conformationally rigid but oppositely configured amides with diastereomeric ratios >9:1; establishing that
Graphical Abstract
Scheme 1: Molecular structures of 1/2-H and their corresponding ortho-lithiates [21].
Scheme 2: Molecular structures of 3/4-H and their corresponding lateral lithiates [23,24].
Scheme 3: Conversion of kinetic ortho-lithiate into the thermodynamic lateral lithiate under the influence of...
Scheme 4: Molecular structure of 5-H and its lateral and ortho-lithiates [20].
Scheme 5: Lateral metallation of 6-H using t-BuLi in the presence of Lewis base L.
Figure 1: Molecular structure of 6-Lil·PMDTA; H-atoms (excl. H8) omitted for clarity. Selected bond lengths (...
Scheme 6: Comparison of aromatic and aryl–(α-C) bond distances in 5-Lil·L [20] and 6-Lil·L (L = PMDTA).
Figure 2: Molecular structure of 6-Lil·DGME; H-atoms omitted. Selected bond lengths (Å) and angles (°): O1–Li...
Figure 3: Computed minimum energy conformers (B3LYP density functional/6-311++G(2d,2p) basis set; H-atoms omi...
Carbamate-directed benzylic lithiation for the diastereo- and enantioselective synthesis of diaryl ether atropisomers
- Abigail Page and
- Jonathan Clayden
Beilstein J. Org. Chem. 2011, 7, 1327–1333, doi:10.3762/bjoc.7.156
- for the synthesis of “nonstandard” atropisomer structures containing rigid fragments joined by a hindered single bond, but which are different from the typically well-studied biaryl compounds [4][5]. These non-biaryl atropisomers have included aromatic amides [6][7][8], ureas [9], ethers [10][11][12
- rotation [19]. Several of the classes of atropisomers we have studied contain functional groups which are excellent directors of lithiation [20], and indeed our original interest in lithiation stemmed from the need to build these atropisomeric structures rapidly and efficiently [21]. We recently reported
- obtained, suggested that they are insufficiently hindered to exist as stable atropisomers and they interconvert on a relatively short timescale, of seconds to minutes, at room temperature. In order to enhance the ease of metallation of the substrates (6 gives low yield at −78 °C unless sparteine is present
Graphical Abstract
Scheme 1: Desymmetrising metallation for the enantioselective synthesis of atropisomers.
Scheme 2: Benzylic lithiation of a diaryl ether.
Scheme 3: Benzylic metallation of a diaryl ether α to a carbamate.
Scheme 4: Diastereo- and enantioselective synthesis of atropisomeric ethers by benzylic lithiation.
Scheme 5: Atroposelective stannylation.
Scheme 6: Stereospecific tin–lithium exchange/quench reactions.
Scheme 7: Proposed stereochemical pathway.
Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes
- Yu-Hsuan Wang,
- Joshua F. Bailey,
- Jeffrey L. Petersen and
- Kung K. Wang
Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58
- sensitive to the steric requirement of the substituent at the alkynyl terminus. The benzannulated enediyne 1b with a sterically demanding 2,6-dibromophenyl substituent was also smoothly converted to 3b [6]. With 1c having a 1,1'-binaphthyl substituent, a 1:1 mixture of the syn and the anti atropisomers of
Graphical Abstract
Scheme 1: Synthesis of 5-aryl-11H-benzo[b]fluorenes via benzannulated enyne–allenes.
Scheme 2: Synthesis of 1,1'-binaphthyl-substituted 11H-benzo[b]fluorene 3c.
Scheme 3: Synthesis of 5-(2-methoxyphenyl)- and 5-[2-(methoxymethyl)phenyl]-11H-benzo[b]fluorene 13a and 13b.
Scheme 4: Synthesis of 5-(1-naphthyl)- and 5-(2-methoxy-1-naphthyl)-11H-benzo[b]fluorene 20a and 20b.
Scheme 5: Synthesis of 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene 20c.
Scheme 6: Demethylation of 22b to form 5-(2-hydroxy-1-naphthyl)-11H-benzo[b]fluorene 24.
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...
Asymmetric synthesis of biaryl atropisomers by dynamic resolution on condensation of biaryl aldehydes with (−)-ephedrine or a proline- derived diamine
- Ann Bracegirdle,
- Jonathan Clayden and
- Lai Wah Lai
Beilstein J. Org. Chem. 2008, 4, No. 47, doi:10.3762/bjoc.4.47
- ][8][9]. In view of the thermal instability inherent in a stereogenic bond (rather than a centre) dynamic methods appear particularly suited to the stereoselective synthesis of atropisomers [10][11]. In connection with our work on non-biaryl atropisomers such as amides [12][13][14][15][16], ethers [17
Graphical Abstract
Scheme 1: Synthesis of racemic aldehydes.
Scheme 2: Diastereoisomeric imidazolidines and oxazolidines from biaryl aldehydes.
Figure 1: X-ray crystal structure of 9a. X-ray data has been deposited with the Cambridge Crystallographic Da...
Figure 2: X-ray crystal structure of 10a. X-ray data has been deposited with the Cambridge Crystallographic D...
Scheme 3: Atropisomeric alcohols by hydrolysis and reduction.
Scheme 4: Mechanistic rationalisation of the dynamic resolution in the formation of 9.
