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Search for "benzoxazole" in Full Text gives 34 result(s) in Beilstein Journal of Organic Chemistry.
Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis
- Darcy J. Atkinson,
- Briar J. Naysmith,
- Daniel P. Furkert and
- Margaret A. Brimble
Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226
- ], halogenated [36], acetal [37][38][39], benzoxazole [40], thiobenzoxazole [40], ester and carbonate [41] analogues were synthesised and evaluated for antibacterial activity. Only the semisynthetic derivatives possessing hydrophobic groups on the terminal sugar moiety (green) exhibited comparable antibacterial
Graphical Abstract
Figure 1: Structures of the enduracididine family of amino acids (1–6).
Figure 2: Enduracidin A (7) and B (8).
Figure 3: Minosaminomycin (9) and related antibiotic kasugamycin (10).
Figure 4: Enduracididine-containing compound 11 identified in a cytotoxic extract of Leptoclinides dubius [32].
Figure 5: Mannopeptimycins α–ε (12–16).
Figure 6: Regions of the mannopeptimycin structure investigated in structure–activity relationship investigat...
Figure 7: Teixobactin (17).
Scheme 1: Proposed biosynthesis of L-enduracididine (1) and L-β-hydroxyenduracididine (5).
Scheme 2: Synthesis of enduracididine (1) by Shiba et al.
Scheme 3: Synthesis of protected enduracididine diastereomers 31 and 32.
Scheme 4: Synthesis of the C-2 azido diastereomers 36 and 37.
Scheme 5: Synthesis of 2-azido-β-hydroxyenduracididine derivatives 38 and 39.
Scheme 6: Synthesis of protected β-hydroxyenduracididine derivatives 40 and 41.
Scheme 7: Synthesis of C-2 diastereomeric amino acids 46 and 47.
Scheme 8: Synthesis of protected β-hydroxyenduracididines 51 and 52.
Scheme 9: General transformation of alkenes to cyclic sulfonamide 54 via aziridine intermediate 53.
Scheme 10: Synthesis of (±)-enduracididine (1) and (±)-allo-enduracididine (3).
Scheme 11: Synthesis of L-allo-enduracididine (3).
Scheme 12: Synthesis of protected L-allo-enduracididine 63.
Scheme 13: Synthesis of β-hydroxyenduracididine derivative 69.
Scheme 14: Synthesis of minosaminomycin (9).
Scheme 15: Retrosynthetic analysis of mannopeptimycin aglycone (77).
Scheme 16: Synthesis of protected amino acids 87 and 88.
Scheme 17: Synthesis of mannopeptimycin aglycone (77).
Scheme 18: Synthesis of N-mannosylation model guanidine 92 and attempted synthesis of benzyl protected mannosy...
Scheme 19: Synthesis of benzyl protected mannosyl D-β-hydroxyenduracididine 97.
Scheme 20: Synthesis of L-β-hydroxyenduracididine 98.
Scheme 21: Total synthesis of mannopeptimycin α (12) and β (13).
Scheme 22: Synthesis of protected L-allo-enduracididine 102.
Scheme 23: The solid phase synthesis of teixobactin (17).
Scheme 24: Retrosynthesis of the macrocyclic core 109 of teixobactin (17).
Scheme 25: Synthesis of macrocycle 117.
On the mechanism of imine elimination from Fischer tungsten carbene complexes
- Philipp Veit,
- Christoph Förster and
- Katja Heinze
Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125
- tungsten complexes M(CO)4/5(10), (M = Mo, W) eliminate two equivalents of propene giving the imine complexes M(CO)5(11). Formation of the imine complex tungsten(benzoxazole)(pentacarbonyl) W(CO)5(13) has been reported by Tamm and Hahn during the synthesis of the carbene complex tungsten(benzoxazolin-2
Graphical Abstract
Scheme 1: Imine formation and isomerization reactions from NH carbene complexes Cr(CO)5(E-2) (a) [27], Cr(CO)5(E/Z...
Scheme 2: Synthesis of W(CO)5(E-2) from W(CO)5(1Et) [20,21] and aminoferrocene [40,41] with concomitant formation of E-1,2-...
Scheme 3: Reaction pathways 1a/1b (migration–elimination) and 2a/2b (elimination–migration) for the formation...
Scheme 4: Reaction pathways 3a/3b/3c (CO dissociation) for the formation of imine E-3 from W(CO)5(E-2).
Figure 1: DFT calculated oxidative addition/pseudorotation/reductive elimination pathway 3c from W(CO)4(E-2) ...
Figure 2: DFT calculated geometries of the two hydrido intermediates cis(N,H)-W(CO)4(H)(Z-15) and cis(C,H)-W(...
Scheme 5: Proposed reaction sequence from W(CO)5(E-2) to W(CO)5(PPh3) in the presence of triphenylphosphane.
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
- necessary for achieving high reactivity, presumably because it minimizes undesired ligation of the benzoxazole substrates or intermediates. A variety of α-substituted acrylates as well as methacrylonitrile were good substrates. The system is sensitive to sterics, an acetate additive was needed to improve
- rhodium catalyst binding to the benzoxazole nitrogen 68. Deuterium labeling studies were performed on the system and based on their results a mechanism was proposed in which the stereodetermining step is a rhodium-hydride transfer instead of protonation of an oxo-π-allylrhodium species (Scheme 17
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.
2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties
- Yury A. Sayapin,
- Inna O. Tupaeva,
- Alexandra A. Kolodina,
- Eugeny A. Gusakov,
- Vitaly N. Komissarov,
- Igor V. Dorogan,
- Nadezhda I. Makarova,
- Anatoly V. Metelitsa,
- Valery V. Tkachev,
- Sergey M. Aldoshin and
- Vladimir I. Minkin
Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236
- (4,5,6,7-tetrachloro)-1,3-tropolones with alcohols leads to the contraction of the seven-membered tropone ring with the formation of 2-(2-benzoxa(thia)zolyl)-6-alkoxycarbonylphenols. The molecular structure of 2-(2-ethoxycarbonyl-6-hydroxy-3,4,5-trichlorophenyl)benzoxazole has been determined by X-ray
- -trichloro-1,3-tropolone, 2-(benzoxazolyl)-4,5,6,7-tetrachloro-1,3-tropolone, 2-(2-ethoxycarbonyl-3,4-dichloro-6-hydroxyphenyl)benzoxazole, 2-(2-ethoxycarbonyl-6-hydroxy-3,4,5-trichlorophenyl)benzoxazole, 2-(5-chlorobenzothiazolyl)-5,6,7-trichloro-1,3-tropolone and 2-(5-chlorobenzothiazolyl)-4,5,6,7
- )benzoxazole 11b is shown in Figure 4. All atoms of the benzoxazolyl fragment of 11b are located in a single plane with the accuracy of 0.005 Å. A common plane (with the accuracy of 0.02 Å) is formed by С(1), С(2), С(3), С(4), С(5), C(7), О(2) and two chlorine atoms Cl(1) and Cl(2). The torsion angle N(1)–С(8
Graphical Abstract
Scheme 1: 1,3-Tropolones 2–4 prepared by the reaction of o-chloranil with methylene active compounds.
Scheme 2: General scheme of the synthesis of 2-(2-hetaryl)-5,6,7-trichloro-1,3-tropolones 5 and 2-(2-hetaryl)...
Scheme 3: The mechanism for the formation of 5,6,7-trichloro-1,3-tropolones 5 and 4,5,6,7-tetrachloro-1,3-tro...
Figure 1: Molecular structure of 2-(3,3-dimethylindolyl)-5,6,7-trichloro-1,3-tropolone 5g. Thermal ellipsoids...
Figure 2: Molecular structure of 2-(5-chlorobenzothiazolyl)-4,5,6,7-tetrachloro-1,3-tropolone 6e. Thermal ell...
Scheme 4:
The fast prototropic N–H···O ![[Graphic 3]](/bjoc/content/inline/1860-5397-11-236-i8.png?max-width=637&scale=1.18182)
N···H–O equilibrium in solutions of 2-hetaryl-5,6,7-trichloro- and 4,...
Scheme 5: Two reaction paths for coupling 2-hetaryl-1,3-tropolones 5 and 6 with alcohols.
Figure 3: Molecular structure of 2-(3,3-dimethylindolyl)-5,7-dichloro-6-ethoxy-1,3-tropolone 13. Selected bon...
Figure 4: Molecular structure of 2-(2-ethoxycarbonyl-6-hydroxy-3,4,5-trichlorophenyl)benzoxazole 11b. Selecte...
Figure 5: Electronic absorption (1, 2), fluorescence emission (λexc = 350 nm) (3, 4) and fluorescence excitat...
Cross-dehydrogenative coupling for the intermolecular C–O bond formation
- Igor B. Krylov,
- Vera A. Vil’ and
- Alexander O. Terent’ev
Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13
- 6 to form 7) [42], benzoxazole (acetoxylation of 8 to form 9) [43], benzimidazole (alkoxylation of 10 to form 11) [44], and triazole (acyloxylation of 12 to form 13 [45], alkoxylation of 14 to form 15 [46]) moieties were also used as directing groups for the ortho-acyloxylation and alkoxylation of
Graphical Abstract
Scheme 1: Cross-dehydrogenative coupling.
Scheme 2: Cross-dehydrogenative C–O coupling.
Scheme 3: Regioselective ortho-acetoxylation of meta-substituted arylpyridines and N-arylamides.
Scheme 4: ortho-Acyloxylation and alkoxylation of arenes directed by pyrimidine, benzoxazole, benzimidazole a...
Scheme 5: Cu(OAc)2/AgOTf/O2 oxidative system in the ortho-alkoxylation of arenes.
Scheme 6: Pd(OAc)2/persulfate oxidative system in the ortho-alkoxylation and acetoxylation of arenes with nit...
Scheme 7: ortho-Acetoxylation and methoxylation of O-methyl aryl oximes, N-phenylpyrrolidin-2-one, and (3-ben...
Scheme 8: Ruthenium-catalyzed ortho-acyloxylation of acetanilides.
Scheme 9: Acetoxylation and alkoxylation of arenes with amide directing group using Pd(OAc)2/PhI(OAc)2 oxidat...
Scheme 10: Alkoxylation of azoarenes, 2-aryloxypyridines, picolinamides, and N-(1-methyl-1-(pyridin-2-yl)ethyl...
Scheme 11: Acetoxylation of compounds containing picolinamide and quinoline-8-amine moieties using the Pd(OAc)2...
Scheme 12: (CuOH)2CO3 catalyzed oxidative ortho-etherification using air as oxidant.
Scheme 13: Copper-catalyzed aerobic alkoxylation and aryloxylation of arenes containing pyridine-N-oxide moiet...
Scheme 14: Cobalt-catalyzed aerobic alkoxylation of arenes and alkenes containing pyridine N-oxide moiety.
Scheme 15: Non-symmetric double-fold C–H ortho-acyloxylation.
Scheme 16: N-nitroso directed ortho-alkoxylation of arenes.
Scheme 17: Selective alkoxylation and acetoxylation of alkyl groups.
Scheme 18: Acetoxylation of 2-alkylpyridines and related compounds.
Scheme 19: Acyloxylation and alkoxylation of alkyl fragments of substrates containing amide or sulfoximine dir...
Scheme 20: Palladium-catalyzed double sp3 C–H alkoxylation of N-(quinolin-8-yl)amides for the synthesis of sym...
Scheme 21: Copper-catalyzed acyloxylation of methyl groups of N-(quinolin-8-yl)amides.
Scheme 22: One-pot acylation and sp3 C–H acetoxylation of oximes.
Scheme 23: Possible mechanism of oxidative esterification catalyzed by N-heterocyclic nucleophilic carbene.
Scheme 24: Oxidative esterification employing stoichiometric amounts of aldehydes and alcohols.
Scheme 25: Selective oxidative coupling of aldehydes with alcohols in the presence of amines.
Scheme 26: Iodine mediated oxidative esterification.
Scheme 27: Oxidative C–O coupling of benzyl alcohols with methylarenes under the action of Bu4NI/t-BuOOH syste...
Scheme 28: Oxidative coupling of methyl- and ethylarenes with aromatic aldehydes under the action of Bu4NI/t-B...
Scheme 29: Cross-dehydrogenative C–O coupling of aldehydes with t-BuOOH in the presence of Bu4NI.
Scheme 30: Bu4NI-catalyzed α-acyloxylation reaction of ethers and ketones with aldehydes and t-BuOOH.
Scheme 31: Oxidative coupling of aldehydes with N-hydroxyimides and hexafluoroisopropanol.
Scheme 32: Oxidative coupling of alcohols with N-hydroxyimides.
Scheme 33: Oxidative coupling of aldehydes and primary alcohols with N-hydroxyimides using (diacetoxyiodo)benz...
Scheme 34: Proposed mechanism of the oxidative coupling of aldehydes and N-hydroxysuccinimide under action of ...
Scheme 35: Oxidative coupling of aldehydes with pivalic acid (172).
Scheme 36: Oxidative C–O coupling of aldehydes with alkylarenes using the Cu(OAc)2/t-BuOOH system.
Scheme 37: Copper-catalyzed acyloxylation of C(sp3)-H bond adjacent to oxygen in ethers using benzyl alcohols.
Scheme 38: Oxidative C–O coupling of aromatic aldehydes with cycloalkanes.
Scheme 39: Ruthenium catalyzed cross-dehydrogenative coupling of primary and secondary alcohols.
Scheme 40: Cross-dehydrogenative C–O coupling reactions of β-dicarbonyl compounds with sulfonic acids, acetic ...
Scheme 41: Acyloxylation of ketones, aldehydes and β-dicarbonyl compounds using carboxylic acids and Bu4NI/t-B...
Scheme 42: Acyloxylation of ketones using Bu4NI/t-BuOOH system.
Scheme 43: Cross-dehydrogenative C–O coupling of β-dicarbonyl compounds and their heteroanalogues with N-hydro...
Scheme 44: Cross-dehydrogenative C–O coupling of β-dicarbonyl compounds and their heteroanalogues with t-BuOOH....
Scheme 45: Oxidative C–O coupling of 2,6-dialkylphenyl-β-keto esters and thioesters with tert-butyl hydroxycar...
Scheme 46: α’-Acyloxylation of α,β-unsaturated ketones using KMnO4.
Scheme 47: Possible mechanisms of the acetoxylation at the allylic position of alkenes by Pd(OAc)2.
Scheme 48: Products of the oxidation of terminal alkenes by Pd(II)/AcOH/oxidant system.
Scheme 49: Acyloxylation of terminal alkenes with carboxylic acids.
Scheme 50: Synthesis of linear E-allyl esters by cross-dehydrogenative coupling of terminal alkenes wih carbox...
Scheme 51: Pd(OAc)2-catalyzed acetoxylation of Z-vinyl(triethylsilanes).
Scheme 52: α’-Acetoxylation of α-acetoxyalkenes with copper(II) chloride in acetic acid.
Scheme 53: Oxidative acyloxylation at the allylic position of alkenes and at the benzylic position of alkylare...
Scheme 54: Copper-catalyzed alkoxylation of methylheterocyclic compounds using di-tert-butylperoxide as oxidan...
Scheme 55: Oxidative C–O coupling of methylarenes with β-dicarbonyl compounds or phenols.
Scheme 56: Copper-catalyzed esterification of methylbenzenes with cyclic ethers and cycloalkanes.
Scheme 57: Oxidative C–O coupling of carboxylic acids with toluene catalyzed by Pd(OAc)2.
Scheme 58: Oxidative acyloxylation at the allylic position of alkenes with carboxylic acids using the Bu4NI/t-...
Scheme 59: Cross-dehydrogenative C–O coupling of carboxylic acids with alkylarenes using the Bu4NI/t-BuOOH sys...
Scheme 60: Oxidative C–O cross-coupling of methylarenes with ethyl or isopropylarenes.
Scheme 61: Phosphorylation of benzyl C–H bonds using the Bu4NI/t-BuOOH oxidative system.
Scheme 62: Selective C–H acetoxylation of 2,3-disubstituted indoles.
Scheme 63: Acetoxylation of benzylic position of alkylarenes using DDQ as oxidant.
Scheme 64: C–H acyloxylation of diarylmethanes, 3-phenyl-2-propen-1-yl acetate and dimethoxyarene using DDQ.
Scheme 65: Cross-dehydrogenative C–O coupling of 1,3-diarylpropylenes and 1,3-diarylpropynes with alcohols.
Scheme 66: One-pot azidation and C–H acyloxylation of 3-chloro-1-arylpropynes.
Scheme 67: Cross-dehydrogenative C–O coupling of 1,3-diarylpropylenes, (E)-1-phenyl-2-isopropylethylene and is...
Scheme 68: Cross-dehydrogenative C–O coupling of alkylarenes and related compounds with N-hydroxyphthalimide.
Scheme 69: Acetoxylation at the benzylic position of alkylarenes mediated by N-hydroxyphthalimide.
Scheme 70: C–O coupling of methylarenes with aromatic carboxylic acids employing the NaBrO3/NaHSO3 system.
Scheme 71: tert-Butyl peroxidation of allyl, propargyl and benzyl ethers catalyzed by Fe(acac)3.
Scheme 72: Cross-dehydrogenative C–O coupling of ethers with carboxylic acids mediated by Bu4NI/t-BuOOH system....
Scheme 73: Oxidative acyloxylation of dimethylamides and dioxane with 2-aryl-2-oxoacetic acids accompanied by ...
Scheme 74: tert-Butyl peroxidation of N-benzylamides and N-allylbenzamide using the Bu4NI/t-BuOOH system.
Scheme 75: Cross-dehydrogenative C–O coupling of aromatic carboxylic acids with ethers using Fe(acac)3 as cata...
Scheme 76: Cross-dehydrogenative C–O coupling of cyclic ethers with 2-hydroxybenzaldehydes using iron carbonyl...
Scheme 77: Cross-dehydrogenative C–O coupling of ethers with β-dicarbonyl compounds and phenols using copper c...
Scheme 78: Cross-dehydrogenative C–O coupling of 2-hydroxybenzaldehyde with dioxane catalyzed by Cu2(BPDC)2(BP...
Scheme 79: Ruthenium chloride-catalyzed acyloxylation of β-lactams.
Scheme 80: Ruthenium-catalyzed tert-butyl peroxydation amides and acetoxylation of β-lactams.
Scheme 81: PhI(OAc)2-mediated α,β-diacetoxylation of tertiary amines.
Scheme 82: Electrochemical oxidative methoxylation of tertiary amines.
Scheme 83: Cross-dehydrogenative C–O coupling of ketene dithioacetals with carboxylic acids in the presence of...
Scheme 84: Cross-dehydrogenative C–O coupling of enamides with carboxylic acids using iodosobenzene as oxidant....
Scheme 85: Oxidative alkoxylation, acetoxylation, and tosyloxylation of acylanilides using PhI(O(O)CCF3)2 in t...
Scheme 86: Proposed mechanism of the oxidative C–O coupling of actetanilide with O-nucleophiles in the presenc...
Scheme 87: Three-component coupling of aldehydes, anilines and alcohols involving oxidative intermolecular C–O...
Scheme 88: Oxidative coupling of phenols with alcohols.
Scheme 89: 2-Acyloxylation of quinoline N-oxides with arylaldehydes in the presence of the CuOTf/t-BuOOH syste...
Scheme 90: Cross-dehydrogenative C–O coupling of azoles with primary alcohols.
Scheme 91: Oxidation of dipyrroles to dipyrrins and subsequent oxidative alkoxylation in the presence of Na3Co...
Scheme 92: Oxidative dehydrogenative carboxylation of alkanes and cycloalkanes to allylic esters.
Scheme 93: Pd-catalyzed acetoxylation of benzene.
Palladium-catalyzed 2,5-diheteroarylation of 2,5-dibromothiophene derivatives
- Fatma Belkessam,
- Aidene Mohand,
- Jean-François Soulé,
- Abdelhamid Elias and
- Henri Doucet
Beilstein J. Org. Chem. 2014, 10, 2912–2919, doi:10.3762/bjoc.10.309
- et al. reported the Pd-catalyzed coupling of 2,5-dibromothiophene with 3-methoxythiophene to afford the corresponding terthiophene in 29% yield [37]. From 2,5-diiodothiophene and benzoxazole, using 5 mol % Pd(phen)2(PF6)2 catalyst, the 2,5-diheteroarylated thiophene was obtained in 89% yield by Murai
Graphical Abstract
Figure 1: 2,2':5',2"-Terthiophene.
Scheme 1: Palladium-catalyzed direct arylation using 2,5-dibromothiophene and 2-ethyl-4-methylthiazole as cou...
Scheme 2: Reactivity of 2,5-dibromothiophene with different heteroarenes.
Scheme 3: Reactivity of 2,5-dibromo-3-methylthiophene with different heteroarenes.
Scheme 4: Sequential diheteroarylation of 2,5-dibromothiophene.
Scheme 5: Sequential diheteroarylation of 2,5-dibromothiophene.
Scheme 6: Heteroarylation of 2-bromothiophene.
Scheme 7: Reactivity of 4,7-dibromobenzothiadiazole.
Amyloid-β probes: Review of structure–activity and brain-kinetics relationships
- Todd J. Eckroat,
- Abdelrahman S. Mayhoub and
- Sylvie Garneau-Tsodikova
Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116
- (9) and diphenyl-1,3,4-oxadiazole (10); and thioflavin-T analogues such as benzothiazole (11), benzoxazole (12), benzofuran (13), imidazopyridine (14), and benzimidazole (15); as well as quinoline (16) and naphthalene (17) derivatives (Figure 1B). In this review, we provide an overview of these AD
- . Benzoxazoles Replacement of the sulfur of the benzothiazole backbone by oxygen affords the benzoxazole backbone. Compounds 94, 95a–n, and 96–99 (Figure 3) have also been successfully employed for radioimaging of Aβ plaques. The isosteric replacement of the sulfur of [125I]TZDM (58a) with an oxygen was designed
- target compound. SAR analysis of the compounds indicates that the benzamide moiety is favored at position 5 rather than 6 of the benzoxazole core in terms of binding affinity for Aβ plaques in vitro (Table 9). The best compound was 95e, which had a Ki value of 9.3 nM, but [123I]95e was unable to cross
Graphical Abstract
Figure 1: Structures of A. dyes originally used to stain Aβ and B. newer scaffolds explored for the developme...
Scheme 1: General synthetic strategies (Gs) used to introduce A. 18F, B. 11C, C. 99mTc/Re, and D. 123I and 125...
Scheme 2: A. Structures of radiolabeled chalcone analogues discussed. B.–D. Synthetic schemes for the prepara...
Scheme 3: A. Structures of the radiolabeled flavone and aurone analogues discussed. B. Synthetic scheme for t...
Scheme 4: A. Structures of the radiolabeled stilbene analogues discussed. B. Synthetic scheme for the prepara...
Scheme 5: A. Structures of the diphenyl-1,3,4- and diphenyl-1,2,4-oxadiazoles discussed. B.,C. Synthetic sche...
Figure 2: Structures of the radiolabeled benzothiazole analogues discussed.
Scheme 6: A.–F. Synthetic schemes for the preparation of [11C]56b, [11C]56c, 57, 58a,b, 61, and [18F]65a–d.
Scheme 7: A. Structures of the [Re]- and [99mTc]-labeled benzothiazole analogues discussed. B.,C. Synthetic s...
Figure 3: Structures of the radiolabeled benzoxazole analogues discussed.
Scheme 8: A.–E. Synthetic schemes for the preparation of 94, [123I]95e, 96–98.
Figure 4: Structures of the radiolabeled benzofuran analogues discussed.
Scheme 9: A.–E. Synthetic schemes for the preparation of 121, [125I]122a, 123a,b, 125a,b, and 126.
Scheme 10: A. Structures of the radiolabeled imidazopyridine analogues discussed. B. Synthetic scheme for the ...
Scheme 11: Synthetic scheme for the preparation of the benzimidazole 146.
Figure 5: Structures of the quinolines discussed.
Scheme 12: Synthetic scheme for the preparation of the naphthalene analogues 152 and 160a,b.
Scheme 13: A. Structures of the radiolabeled analogues resulting from the combination of various scaffolds. B.,...
Scheme 14: A.–C. Synthetic schemes for the preparation of radiolabeled probes with unique scaffolds.
Scheme 15: A. Structures of the oxazine-derived fluorescence probes discussed. B. Synthetic scheme for the pre...
Figure 6: Structure of THK-265 (190).
Scheme 16: Synthetic scheme for the preparation of quinoxaline analogue 191.
Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series
- Cécile Verrier,
- Pierrik Lassalas,
- Laure Théveau,
- Guy Quéguiner,
- François Trécourt,
- Francis Marsais and
- Christophe Hoarau
Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187
- the reactivity at the C2 position significantly. Tamagnan further reported the first example of Pd(0)/Cu(I)-catalyzed direct arylation of benzoxazole (Scheme 7) [41]. Interestingly, Bellina and Rossi reported the Pd(0)/Cu(I)-catalyzed direct arylation of indoles, imidazoles, oxazoles and thiazoles
- , which was highly effective in the direct arylation of oxazoles with various arylbromides (Scheme 7) [44]. In his initial study, Miura observed a substantial amount of C2-arylation of azoles, including benzoxazole, using Cu(I) alone as catalyst (Scheme 8) [40]. In 2007, this methodology was judiciously
- achieve Pd(0)-catalyzed direct arylation of various electron-rich heterocycles, including benzoxazole with aryl chlorides (Scheme 12) [54]. Bhanage proposed the use of 2,2,6,6-tetramethyl-3,5-heptanedione ligand (TMHD) to achieve regioselective, Pd(0)-catalyzed, direct arylation of N-methylindole
Graphical Abstract
Scheme 1: Stoichiometric and catalytic direct (hetero)arylation of arenes.
Scheme 2: Stille and Negishi cross-coupling methodologies in oxazole series [28,30,31,33,34].
Scheme 3: Stoichiometric direct (hetero)arylation of (benz)oxazole with magnesate bases [35].
Scheme 4: Ohta's pioneering catalytic direct C5-selective pyrazinylation of oxazole [36,37].
Scheme 5: Preparation of pharmaceutical compounds by following the pioneering Ohta protocol [38,39].
Scheme 6: Miura’s pioneering catalytic direct arylations of (benz)oxazoles [40]. aIsolated yield.
Scheme 7: Pd(0)- and Cu(I)-catalyzed direct C2-selective arylation of (benz)oxazoles [41-44].
Scheme 8: Cu(I)-catalyzed direct C2-selective arylations of (benz)oxazoles [40,45-47].
Scheme 9: Copper-free Pd(0)-catalyzed direct C5- and C2-selective arylation of oxazole-4-carboxylate esters [48-50,52].
Scheme 10: Iterative synthesis of bis- and trioxazoles [51].
Scheme 11: Preparation of DPO- and POPOP-analogues [53].
Scheme 12: Pd(0)-catalyzed direct arylation of benzoxazole with aryl chlorides [54].
Scheme 13: Pd(0)-catalyzed direct C2-selective arylation of (benz)oxazoles with bromides and chlorides using b...
Scheme 14: Palladium-catalyzed direct arylation of oxazoles under green conditions; (a) Zhuralev direct arylat...
Scheme 15: Pd(0)-catalyzed C2- and C5-selective (hetero)arylation of oxazole [63].
Scheme 16: Pd(0)-catalyzed C2- and C5-selective (hetero)arylation of ethyl oxazole-4-carboxylate [64].
Scheme 17: Pd(0)-catalyzed direct C4-phenylation of oxazoles; (a) Miura’s procedure [65]; (b) Fagnou’s procedure [66].
Scheme 18: Catalytic cycles for Cu(I)-catalyzed (routeA) and Pd(0)/Cu(I)-catalyzed (route B) direct arylation ...
Scheme 19: Base-assisted, Pd(0)-catalyzed, C2-selective, direct arylation of benzoxazole proposed by Zhuralev [58]...
Scheme 20: Electrophilic substitution-type mechanism proposed by Hoarau [64].
Scheme 21: CMD-proceeding C5-selective direct arylation of oxazole proposed by Strotman and Chobabian [63].
Scheme 22: DFT calculations on methyl oxazole-4-carboxylate and consequently developed methodologies for the P...
Scheme 23: Pd(0)-catalyzed direct arylation of (benz)oxazoles with tosylates and mesylates [71].
Scheme 24: Pd(0)-catalyzed direct arylation of oxazoles with sulfamates [72].
Scheme 25: Pd(II)- and Cu(II)-catalyzed decarboxylative direct C–H coupling of oxazoles with 4- and 5-carboxyo...
Scheme 26: Pd(II)- and Ag(II)-catalyzed decarboxylative direct arylation of (benzo)oxazoles [74]; (a) procedure; (...
Scheme 27: Pd(II)- and Cu(II)-catalyzed direct arylation of benzoxazole with arylboronic acids [76]; (a) procedure...
Scheme 28: Ni(II)-catalyzed direct arylation of benzoxazoles with arylboronic acids under O2 [76]; (a) procedure; ...
Scheme 29: Rhodium-catalyzed direct arylation of benzoxazole [78,79].
Scheme 30: Ni(II)-catalyzed direct arylation of (benz)oxazoles with aryl halides; (a) Itami's procedure [80]; (b) ...
Scheme 31: Dehydrogenative cross-coupling of (benz)oxazoles; (a) Pd(II)- and Cu(II)-catalyzed cross-coupling o...
Mitomycins syntheses: a recent update
- Jean-Christophe Andrez
Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33
- oxidation and an intramolecular Heck reaction [149]. Exposure of the quinone 207 to sunlight triggered the formation of benzoxazole 208, which cleaved to form an intermediate iminium salt. Subsequent proton transfer gave the vinylogous carbamate 209 (Scheme 57). After oxidation of the hydroquinone to the
Graphical Abstract
Scheme 1: Aziridine containing natural products.
Scheme 2: Mitomycin structures and nomenclature.
Scheme 3: Base catalysed epimerization of mitomycin B.
Scheme 4: Biosynthesis of mitomycin C (MMC) 7.
Scheme 5: Mode of action of mitomycin C.
Scheme 6: The N–C3–C9a disconnection.
Scheme 7: Danishefsky’s Retrosynthesis of mitomycin K.
Scheme 8: Hetero Diels–Alder reaction en route to mitomycins.
Scheme 9: Nitroso Diels–Alder cycloaddition.
Scheme 10: Frank azide cycloadddition.
Scheme 11: Final steps of mitomycin K synthesis. aPDC, DCM; bPhSCH2N3, PhH, 80 °C; cL-selectride, THF, −78 °C; ...
Scheme 12: Naruta–Maruyama retrosynthesis.
Scheme 13: Synthesis of a leucoaziridinomitosane by nitrene cycloaddition. aAlCl3-Et2O; bNaH, ClCH2OMe; cn-BuL...
Scheme 14: Thermal decomposition of azidoquinone 51.
Scheme 15: Diastereoselectivity during the cycloaddition.
Scheme 16: Oxidation with iodo-azide.
Scheme 17: Williams’ approach towards mitomycins.aDEIPSCl, Imidazole, DCM; bPd/C, HCO2NH4, MeOH; cAllocCl, NaH...
Scheme 18: Synthesis of pyrrolidones by homoconjugate addition.
Scheme 19: Homoconjugate addition on the fully functionalized substrate.
Scheme 20: Introduction of the olefin.
Scheme 21: Retrosynthesis of N–C9a, N–C3 bond formation.
Scheme 22: Synthesis of the pyrrolo[1,2]indole 82 using N-PSP activation.aAc2O, Py; bAc2O, Hg(OAc)2, AcOH, 90%...
Scheme 23: Synthesis of an aziridinomitosane. am-CPBA, DCM then iPr2NH, CCl4 reflux; bK2CO3, MeOH; cBnBr, KH; d...
Scheme 24: Oxidation products of a leucoaziridinomitosane obtained from a Polonovski oxidation.
Scheme 25: Polonovski oxidation of an aziridinomitosane. am-CPBA; bPd/C, H2; cDimethoxypropane, PPTS.
Scheme 26: The C1–C9a disconnection.
Scheme 27: Ziegler synthesis of desmethoxymitomycin A.aIm2C=O, THF; bNH3; cTMSOTf, 2,6-di-tert-butylpyridine, ...
Scheme 28: Transformation of sodium erythorbate.aTBDMSCl; bNaN3; cPPh3; d(Boc)2O, DMAP; eTBAF; fTf2O, Pyr.
Scheme 29: Formation of C9,C10-unsaturation in the mitomycins. am-CPBA, DCM; bO3, MeOH; cMe2S; dKHMDS, (EtO)3P...
Scheme 30: Fragmentation mechanism.
Scheme 31: Michael addition-cyclisation.
Scheme 32: SmI2 8-endo-dig cyclisation.
Scheme 33: Synthesis of pyrrolo[1,2-a]indole by 5-exo-dig radical cyclization.
Scheme 34: The C9–C9a disconnection.
Scheme 35: Intramolecular nitrile oxide cycloaddition.
Scheme 36: Regioselectivity of the INOC.
Scheme 37: Fukuyama’s INOC strategy.
Scheme 38: Synthesis of a mitosane core by rearrangement of a 1-(1-pyrrolidinyl)-1,3-butadiene.
Scheme 39: Sulikowski synthesis of an aziridinomitosene. aPd(Tol3P)2Cl2, Bu3SnF, 140; bH2, Pd/C; cTFAA, Et3N; d...
Scheme 40: Enantioselective carbene insertion.
Scheme 41: Parson’s radical cyclization.
Scheme 42: Cha’s mitomycin B core synthesis.
Scheme 43: The N-aromatic disconnection.
Scheme 44: Kishi retrosynthesis.
Scheme 45: Kishi synthesis of a starting material. aallyl bromide, K2CO3, acetone, reflux; bN,N-Dimethylanilin...
Scheme 46: Kishi synthesis of MMC 7. aLDA, THF, −78 °C then PhSeBr, THF, −78 °C; bH2O2, THF-EtOAc; cDIBAL, DCM...
Scheme 47: Acid catalyzed degradation of MMC 7.
Scheme 48: In vivo formation of apomitomycin B.
Scheme 49: Advanced intermediate for apomitomycin B synthesis.
Scheme 50: Remers synthesis of a functionalized mitosene. aTMSCl, Et3N, ZnCl2 then NBS; bAcOK; cNH2OH; dPd/C, H...
Scheme 51: Coleman synthesis of desmethoxymitomycin A. aSnCl2, PhSH, Et3N, CH3CN; bClCO2Bn, Et3N; cPPh3, DIAD,...
Scheme 52: Transition state and pyrrolidine synthesis.
Scheme 53: Air oxidation of mitosanes and aziridinomitosanes.
Scheme 54: The C9-aromatic disconnection.
Scheme 55: Synthesis of the aziridine precursor. aLHMDS, THF; bNaOH; c(s)-α-Me-BnNH2, DCC, HOBT; dDIBAL; eK2CO3...
Scheme 56: Synthesis of 206 via enamine conjugate addition.
Scheme 57: Rapoport synthesis of an aziridinomitosene.
Scheme 58: One pot synthesis of a mitomycin analog.
Scheme 59: Synthesis of compound 218 via intramolecular Heck coupling. aEtMgCl, THF, then 220; bMsCl, Et3N; cN...
Scheme 60: Elaboration of indole 223. aEt3N, Ac2O; bAcOH; cSOCl2, Et3N; dNaN3, DMF; eH2SO4, THF; fK2CO3, MeOH; ...
Scheme 61: C9-C9a functionalization from indole.
Scheme 62: Synthesis of mitomycin K. a2 equiv. MoO5.HMPA, MeOH; bPPh3, Et3N, THF-H2O; cMeOTf, Py, DCM; dMe3SiCH...
Scheme 63: Configurational stability of mitomycin K derivatives.
Scheme 64: Epimerization of carbon C9a in compound 227b.
Scheme 65: Corey–Chaykovsky synthesis of indol 235.
Scheme 66: Cory intramolecular aza-Darzens reaction for the formation of aziridinomitosene 239.
Scheme 67: Jimenez synthesis of aziridinomitosene 242.
Scheme 68: Von Braun opening of indoline 244.
Scheme 69: C9a oxidation of an aziridinomitosane with DDQ/OsO4.
Scheme 70: Synthesis of epi-mitomycin K. aNaH, Me2SO4; bH2, Pd/C; cMitscher reagent [165]; d[(trimethylsilyl)methyl...
Scheme 71: Mitomycins rearrangement.
Scheme 72: Fukuyama’s retrosynthesis.
Scheme 73: [2+3] Cycloaddition en route to isomitomycin A. aToluene, 110 °C; bDIBAL, THF, −78 °C; cAc2O, Py.; d...
Scheme 74: Final steps of Fukuyama’s synthesis.
Scheme 75: “Crisscross annulation”.
Scheme 76: Synthesis of 274; the 8-membered ring 274 was made using a crisscross annulation. a20% Pd(OH)2/C, H2...
Scheme 77: Conformational analysis of compound 273 and 275.
Scheme 78: Synthesis of a mitomycin analog. aNa2S2O4, H2O, DCM; bBnBr (10 equiv), K2CO3, 18-crown-6 (cat.), TH...
Scheme 79: Vedejs retrosynthesis.
Scheme 80: Formation of the azomethine ylide.
Scheme 81: Vedejs second synthesis of an aziridinomitosene. aDIBAL; bTPAP, NMO; c287; dTBSCl, imidazole.
Scheme 82: Trityl deprotection and new aziridine protecting group 300.
Scheme 83: Ene reaction towards benzazocinones.
Scheme 84: Benzazocenols via homo-Brook rearrangement.
Scheme 85: Pt-catalyzed [3+2] cycloaddition.
Scheme 86: Carbonylative lactamization entry to benzazocenols. aZn(OTf)2, (+)-N-methylephedrine, Et3N, TMS-ace...
Scheme 87: 8 membered ring formation by RCM. aBOC2O, NaHCO3; bTBSCl, Imidazole, DMF; callyl bromide, NaH, DMF; ...
Scheme 88: Aziridinomitosene synthesis. aTMSN3; bTFA; cPOCl3, DMF; dNaClO2, NaH2PO4, 2-methyl-2-butene; eMeI, ...
Scheme 89: Metathesis from an indole.
Scheme 90: Synthesis of early biosynthetic intermediates of mitomycins.
