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Search for "benzothiazole" in Full Text gives 59 result(s) in Beilstein Journal of Organic Chemistry.
Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations
- Rafia Siddiqui and
- Rashid Ali
Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26
- substituents (Scheme 5), and (v) the rate-determining step (i.e., breaking of the C–H bond) was suggested to follow a first-order kinetic isotope effect (KH/KD = 5). As such, a library of benzothiazole derivatives was reported using this methodology, and a plausible mechanism is shown in Figure 9. Synthesis of
Graphical Abstract
Figure 1: List of photoredox catalysts used for C–H bond functionalizations.
Figure 2: List of metal-based photoredox catalysts used in this review article.
Figure 3: Jablonski diagram.
Figure 4: Photoredox catalysis via reductive or oxidative pathways. D = donor, A = acceptor, S = substrate, P...
Figure 5: Schematic representation of the combination of photoredox catalysis and transition metal catalysis.
Scheme 1: Weinreb amide C–H olefination.
Figure 6: Mechanism for the formation of 21 from 19 using photoredox catalyst 11.
Scheme 2: C–H olefination of phenolic ethers.
Scheme 3: Decarboxylative acylation of acetanilides.
Figure 7: Mechanism for the formation of 30 from acetanilide derivatives.
Scheme 4: Synthesis of fluorenone derivatives by intramolecular deoxygenative acylation of biaryl carboxylic ...
Figure 8: Mechanism for the photoredox-catalyzed synthesis of fluorenone derivatives.
Scheme 5: Synthesis of benzothiazoles via aerobic C–H thiolation.
Figure 9: Plausible mechanism for the construction of benzothiazoles from benzothioamides.
Scheme 6: Synthesis of benzothiazoles via oxidant-free C–H thiolation.
Figure 10: Mechanism involved in the synthesis of benzothiazoles via oxidant-free C–H thiolation.
Scheme 7: Synthesis of indoles via C–H cyclization of anilides with alkynes.
Scheme 8: Preparation of 3-trifluoromethylcoumarins via C–H cyclization of arylpropiolate esters.
Figure 11: Mechanistic pathway for the synthesis of coumarin derivatives via C–H cyclization.
Scheme 9: Monobenzoyloxylation without chelation assistance.
Figure 12: Plausible mechanism for the formation of 71 from 70.
Scheme 10: Aryl-substituted arenes prepared by inorganic photoredox catalysis using 12a.
Figure 13: Proposed mechanism for C–H arylations in the presence of 12a and a Pd catalyst.
Scheme 11: Arylation of purines via dual photoredox catalysis.
Scheme 12: Arylation of substituted arenes with an organic photoredox catalyst.
Scheme 13: C–H trifluoromethylation.
Figure 14: Proposed mechanism for the trifluoromethylation of 88.
Scheme 14: Synthesis of benzo-3,4-coumarin derivatives.
Figure 15: Plausible mechanism for the synthesis of substituted coumarins.
Scheme 15: Oxidant-free oxidative phosphonylation.
Figure 16: Mechanism proposed for the phosphonylation reaction of 100.
Scheme 16: Nitration of anilines.
Figure 17: Plausible mechanism for the nitration of aniline derivatives via photoredox catalysis.
Scheme 17: Synthesis of carbazoles via intramolecular amination.
Figure 18: Proposed mechanism for the formation of carbazoles from biaryl derivatives.
Scheme 18: Synthesis of substituted phenols using QuCN.
Figure 19: Mechanism for the synthesis of phenol derivatives with photoredox catalyst 8.
Scheme 19: Synthesis of substituted phenols with DDQ (5).
Figure 20: Possible mechanism for the generation of phenols with the aid of photoredox catalyst 5.
Scheme 20: Aerobic bromination of arenes using an acridinium-based photocatalyst.
Scheme 21: Aerobic bromination of arenes with anthraquinone.
Figure 21: Proposed mechanism for the synthesis of monobrominated compounds.
Scheme 22: Chlorination of benzene derivatives with Mes-Acr-MeClO4 (2).
Figure 22: Mechanism for the synthesis of 131 from 132.
Scheme 23: Chlorination of arenes with 4CzIPN (5a).
Figure 23: Plausible mechanism for the oxidative photocatalytic monochlorination using 5a.
Scheme 24: Monofluorination using QuCN-ClO4 (8).
Scheme 25: Fluorination with fluorine-18.
Scheme 26: Aerobic amination with acridinium catalyst 3a.
Figure 24: Plausible mechanism for the aerobic amination using acridinium catalyst 3a.
Scheme 27: Aerobic aminations with semiconductor photoredox catalyst 18.
Scheme 28: Perfluoroalkylation of arenes.
Scheme 29: Synthesis of benzonitriles in the presence of 3a.
Figure 25: Plausible mechanism for the synthesis of substituted benzonitrile derivatives in the presence of 3a....
Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation
- Andreas Boelke,
- Yulia A. Vlasenko,
- Mekhman S. Yusubov,
- Boris J. Nachtsheim and
- Pavel S. Postnikov
Beilstein J. Org. Chem. 2019, 15, 2311–2318, doi:10.3762/bjoc.15.223
- , benzothiazole- and pyrazole-substituted hydroxy(phenyl)-λ3-iodanes (12 and 6–8) show an excellent relation between thermal stability and reactivity, in particular in direct comparison with well-known benziodoxolones. We can also conclude that the pseudocyclic forms of aryl(phenyl)-λ3-iodanes should be the
Graphical Abstract
Figure 1: General structure of aryl-λ3-iodanes.
Figure 2: Tpeak and ΔHdec-values for a range of N- and O-substituted iodanes.
Figure 3: TGA/DSC curves of (a) benziodoxolone 1, (b) triazole 2 and (c) pyrazole 6.
Figure 4: Decomposition enthalpy (ΔHdec) scale for pseudocyclic tosylates 1–15 and cyclic iodoso species 16 a...
Figure 5: Correlation between the relative reactivity for pseudocyclic NHIs based on the reaction time in the...
Figure 6: Tpeak and ΔHdec values for a range of N- and O-substituted iodanes.
Figure 7: Decomposition enthalpy (ΔHdec) scale for (pseudo)cyclic mesitylen(phenyl)- λ3-iodanes 18–33.
Figure 8: TGA/DSC curves for the benzimidazole based diaryliodonium salt 25.
Figure 9: TGA/DSC curves for the cyclic triazole 32.
Scheme 1: The thermal decomposition of (pseudo)cyclic N-heterocycle-stabilized mesityl(aryl)-λ3-iodanes 25 an...
Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage
- Gagandeep Kour Reen,
- Ashok Kumar and
- Pratibha Sharma
Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165
Graphical Abstract
Figure 1: Various drugs having IP nucleus.
Figure 2: Participation percentage of various TMs for the syntheses of IPs.
Scheme 1: CuI–NaHSO4·SiO2-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 2: Experimental examination of reaction conditions.
Scheme 3: One-pot tandem reaction for the synthesis of 2-haloimidazopyridines.
Scheme 4: Mechanistic scheme for the synthesis of 2-haloimidazopyridine.
Scheme 5: Copper-MOF-catalyzed three-component reaction (3-CR) for imidazo[1,2-a]pyridines.
Scheme 6: Mechanism for copper-MOF-driven synthesis.
Scheme 7: Heterogeneous synthesis via titania-supported CuCl2.
Scheme 8: Mechanism involving oxidative C–H functionalization.
Scheme 9: Heterogeneous synthesis of IPs.
Scheme 10: One-pot regiospecific synthesis of imidazo[1,2-a]pyridines.
Scheme 11: Vinyl azide as an unprecedented substrate for imidazo[1,2-a]pyridines.
Scheme 12: Radical pathway.
Scheme 13: Cu(I)-catalyzed transannulation approach for imidazo[1,5-a]pyridines.
Scheme 14: Plausible radical pathway for the synthesis of imidazo[1,5-a]pyridines.
Scheme 15: A solvent-free domino reaction for imidazo[1,2-a]pyridines.
Scheme 16: Cu-NPs-mediated synthesis of imidazo[1,2-a]pyridines.
Scheme 17: CuI-catalyzed synthesis of isoxazolylimidazo[1,2-a]pyridines.
Scheme 18: Functionalization of 4-bromo derivative via Sonogashira coupling reaction.
Scheme 19: A plausible reaction pathway.
Scheme 20: Cu(I)-catalyzed intramolecular oxidative C–H amidation reaction.
Scheme 21: One-pot synthetic reaction for imidazo[1,2-a]pyridine.
Scheme 22: Plausible reaction mechanism.
Scheme 23: Cu(OAc)2-promoted synthesis of imidazo[1,2-a]pyridines.
Scheme 24: Mechanism for aminomethylation/cycloisomerization of propiolates with imines.
Scheme 25: Three-component synthesis of imidazo[1,2-a]pyridines.
Figure 3: Scope of pyridin-2(1H)-ones and acetophenones.
Scheme 26: CuO NPS-promoted A3 coupling reaction.
Scheme 27: Cu(II)-catalyzed C–N bond formation reaction.
Scheme 28: Mechanism involving Chan–Lam/Ullmann coupling.
Scheme 29: Synthesis of formyl-substituted imidazo[1,2-a]pyridines.
Scheme 30: A tandem sp3 C–H amination reaction.
Scheme 31: Probable mechanistic approach.
Scheme 32: Dual catalytic system for imidazo[1,2-a]pyridines.
Scheme 33: Tentative mechanism.
Scheme 34: CuO/CuAl2O4/ᴅ-glucose-promoted 3-CCR.
Scheme 35: A tandem CuOx/OMS-2-based synthetic strategy.
Figure 4: Biomimetic catalytic oxidation in the presence of electron-transfer mediators (ETMs).
Scheme 36: Control experiment.
Scheme 37: Copper-catalyzed C(sp3)–H aminatin reaction.
Scheme 38: Reaction of secondary amines.
Scheme 39: Probable mechanistic pathway.
Scheme 40: Coupling reaction of α-azidoketones.
Scheme 41: Probable pathway.
Scheme 42: Probable mechanism with free energy calculations.
Scheme 43: MCR for cyanated IP synthesis.
Scheme 44: Substrate scope for the reaction.
Scheme 45: Reaction mechanism.
Scheme 46: Probable mechanistic pathway for Cu/ZnAl2O4-catalyzed reaction.
Scheme 47: Copper-catalyzed double oxidative C–H amination reaction.
Scheme 48: Application towards different coupling reactions.
Scheme 49: Reaction mechanism.
Scheme 50: Condensation–cyclization approach for the synthesis of 1,3-diarylated imidazo[1,5-a]pyridines.
Scheme 51: Optimized reaction conditions.
Scheme 52: One-pot 2-CR.
Scheme 53: One-pot 3-CR without the isolation of chalcone.
Scheme 54: Copper–Pybox-catalyzed cyclization reaction.
Scheme 55: Mechanistic pathway catalyzed by Cu–Pybox complex.
Scheme 56: Cu(II)-promoted C(sp3)-H amination reaction.
Scheme 57: Wider substrate applicability for the reaction.
Scheme 58: Plausible reaction mechanism.
Scheme 59: CuI assisted C–N cross-coupling reaction.
Scheme 60: Probable reaction mechanism involving sp3 C–H amination.
Scheme 61: One-pot MCR-catalyzed by CoFe2O4/CNT-Cu.
Scheme 62: Mechanistic pathway.
Scheme 63: Synthetic scheme for 3-nitroimidazo[1,2-a]pyridines.
Scheme 64: Plausible mechanism for CuBr-catalyzed reaction.
Scheme 65: Regioselective synthesis of halo-substituted imidazo[1,2-a]pyridines.
Scheme 66: Synthesis of 2-phenylimidazo[1,2-a]pyridines.
Scheme 67: Synthesis of diarylated compounds.
Scheme 68: CuBr2-mediated one-pot two-component oxidative coupling reaction.
Scheme 69: Decarboxylative cyclization route to synthesize 1,3-diarylimidazo[1,5-a]pyridines.
Scheme 70: Mechanistic pathway.
Scheme 71: C–H functionalization reaction of enamines to produce diversified heterocycles.
Scheme 72: A plausible mechanism.
Scheme 73: CuI-promoted aerobic oxidative cyclization reaction of ketoxime acetates and pyridines.
Scheme 74: CuI-catalyzed pathway for the formation of imidazo[1,2-a]pyridine.
Scheme 75: Mechanistic pathway.
Scheme 76: Mechanistic rationale for the synthesis of products.
Scheme 77: Copper-catalyzed synthesis of vinyloxy-IP.
Scheme 78: Regioselective product formation with propiolates.
Scheme 79: Proposed mechanism for vinyloxy-IP formation.
Scheme 80: Regioselective synthesis of 3-hetero-substituted imidazo[1,2-a]pyridines with different reaction su...
Scheme 81: Mechanistic pathway.
Scheme 82: CuI-mediated synthesis of 3-formylimidazo[1,2-a]pyridines.
Scheme 83: Radical pathway for 3-formylated IP synthesis.
Scheme 84: Pd-catalyzed urea-cyclization reaction for IPs.
Scheme 85: Pd-catalyzed one-pot-tandem amination and intramolecular amidation reaction.
Figure 5: Scope of aniline nucleophiles.
Scheme 86: Pd–Cu-catalyzed Sonogashira coupling reaction.
Scheme 87: One-pot amide coupling reaction for the synthesis of imidazo[4,5-b]pyridines.
Scheme 88: Urea cyclization reaction for the synthesis of two series of pyridines.
Scheme 89: Amidation reaction for the synthesis of imidazo[4,5-b]pyridines.
Figure 6: Amide scope.
Scheme 90: Pd NPs-catalyzed 3-component reaction for the synthesis of 2,3-diarylated IPs.
Scheme 91: Plausible mechanistic pathway for Pd NPs-catalyzed MCR.
Scheme 92: Synthesis of chromenoannulated imidazo[1,2-a]pyridines.
Scheme 93: Mechanism for the synthesis of chromeno-annulated IPs.
Scheme 94: Zinc oxide NRs-catalyzed synthesis of imidazo[1,2-a]azines/diazines.
Scheme 95: Zinc oxide-catalyzed isocyanide based GBB reaction.
Scheme 96: Reaction pathway for ZnO-catalyzed GBB reaction.
Scheme 97: Mechanistic pathway.
Scheme 98: ZnO NRs-catalyzed MCR for the synthesis of imidazo[1,2-a]azines.
Scheme 99: Ugi type GBB three-component reaction.
Scheme 100: Magnetic NPs-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 101: Regioselective synthesis of 2-alkoxyimidazo[1,2-a]pyridines catalyzed by Fe-SBA-15.
Scheme 102: Plausible mechanistic pathway for the synthesis of 2-alkoxyimidazopyridine.
Scheme 103: Iron-catalyzed synthetic approach.
Scheme 104: Iron-catalyzed aminooxygenation reaction.
Scheme 105: Mechanistic pathway.
Scheme 106: Rh(III)-catalyzed double C–H activation of 2-substituted imidazoles and alkynes.
Scheme 107: Plausible reaction mechanism.
Scheme 108: Rh(III)-catalyzed non-aromatic C(sp2)–H bond activation–functionalization for the synthesis of imid...
Scheme 109: Reactivity and selectivity of different substrates.
Scheme 110: Rh-catalyzed direct C–H alkynylation by Li et al.
Scheme 111: Suggested radical mechanism.
Scheme 112: Scandium(III)triflate-catalyzed one-pot reaction and its mechanism for the synthesis of benzimidazo...
Scheme 113: RuCl3-assisted Ugi-type Groebke–Blackburn condensation reaction.
Scheme 114: C-3 aroylation via Ru-catalyzed two-component reaction.
Scheme 115: Regioselective synthetic mechanism.
Scheme 116: La(III)-catalyzed one-pot GBB reaction.
Scheme 117: Mechanistic approach for the synthesis of imidazo[1,2-a]pyridines.
Scheme 118: Synthesis of imidazo[1,2-a]pyridine using LaMnO3 NPs under neat conditions.
Scheme 119: Mechanistic approach.
Scheme 120: One-pot 3-CR for regioselective synthesis of 2-alkoxy-3-arylimidazo[1,2-a]pyridines.
Scheme 121: Formation of two possible products under optimization of the catalysts.
Scheme 122: Mechanistic strategy for NiFe2O4-catalyzed reaction.
Scheme 123: Two-component reaction for synthesizing imidazodipyridiniums.
Scheme 124: Mechanistic scheme for the synthesis of imidazodipyridiniums.
Scheme 125: CuI-catalyzed arylation of imidazo[1,2-a]pyridines.
Scheme 126: Mechanism for arylation reaction.
Scheme 127: Cupric acetate-catalyzed double carbonylation approach.
Scheme 128: Radical mechanism for double carbonylation of IP.
Scheme 129: C–S bond formation reaction catalyzed by cupric acetate.
Scheme 130: Cupric acetate-catalyzed C-3 formylation approach.
Scheme 131: Control experiments for signifying the role of DMSO and oxygen.
Scheme 132: Mechanism pathway.
Scheme 133: Copper bromide-catalyzed CDC reaction.
Scheme 134: Extension of the substrate scope.
Scheme 135: Plausible radical pathway.
Scheme 136: Transannulation reaction for the synthesis of imidazo[1,5-a]pyridines.
Scheme 137: Plausible reaction pathway for denitrogenative transannulation.
Scheme 138: Cupric acetate-catalyzed C-3 carbonylation reaction.
Scheme 139: Plausible mechanism for regioselective C-3 carbonylation.
Scheme 140: Alkynylation reaction at C-2 of 3H-imidazo[4,5-b]pyridines.
Scheme 141: Two-way mechanism for C-2 alkynylation of 3H-imidazo[4,5-b]pyridines.
Scheme 142: Palladium-catalyzed SCCR approach.
Scheme 143: Palladium-catalyzed Suzuki coupling reaction.
Scheme 144: Reaction mechanism.
Scheme 145: A phosphine free palladium-catalyzed synthesis of C-3 arylated imidazopyridines.
Scheme 146: Palladium-mediated Buchwald–Hartwig cross-coupling reaction.
Figure 7: Structure of the ligands optimized.
Scheme 147: Palladium acetate-catalyzed direct arylation of imidazo[1,2-a]pyridines.
Scheme 148: Palladium acetate-catalyzed mechanistic pathway.
Scheme 149: Palladium acetate-catalyzed regioselective arylation reported by Liu and Zhan.
Scheme 150: Mechanism for selective C-3 arylation of IP.
Scheme 151: Pd(II)-catalyzed alkenylation reaction with styrenes.
Scheme 152: Pd(II)-catalyzed alkenylation reaction with acrylates.
Scheme 153: A two way mechanism.
Scheme 154: Double C–H activation reaction catalyzed by Pd(OAc)2.
Scheme 155: Probable mechanism.
Scheme 156: Palladium-catalyzed decarboxylative coupling.
Scheme 157: Mechanistic cycle for decarboxylative arylation reaction.
Scheme 158: Ligand-free approach for arylation of imidazo[1,2-a]pyridine-3-carboxylic acids.
Scheme 159: Mechanism for ligandless arylation reaction.
Scheme 160: NHC-Pd(II) complex assisted arylation reaction.
Scheme 161: C-3 arylation of imidazo[1,2-a]pyridines with aryl bromides catalyzed by Pd(OAc)2.
Scheme 162: Pd(II)-catalyzed C-3 arylations with aryl tosylates and mesylates.
Scheme 163: CDC reaction for the synthesis of imidazo[1,2-a]pyridines.
Scheme 164: Plausible reaction mechanism for Pd(OAc)2-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 165: Pd-catalyzed C–H amination reaction.
Scheme 166: Mechanism for C–H amination reaction.
Scheme 167: One-pot synthesis for 3,6-di- or 2,3,6-tri(hetero)arylimidazo[1,2-a]pyridines.
Scheme 168: C–H/C–H cross-coupling reaction of IPs and azoles catalyzed by Pd(II).
Scheme 169: Mechanistic cycle.
Scheme 170: Rh-catalyzed C–H arylation reaction.
Scheme 171: Mechanistic pathway for C–H arylation of imidazo[1,2-a]pyridine.
Scheme 172: Rh(III)-catalyzed double C–H activation of 2-phenylimidazo[1,2-a]pyridines and alkynes.
Scheme 173: Rh(III)-catalyzed mechanistic pathway.
Scheme 174: Rh(III)-mediated oxidative coupling reaction.
Scheme 175: Reactions showing functionalization of the product obtained by the group of Kotla.
Scheme 176: Mechanism for Rh(III)-catalyzed oxidative coupling reaction.
Scheme 177: Rh(III)-catalyzed C–H activation reaction.
Scheme 178: Mechanistic cycle.
Scheme 179: Annulation reactions of 2-arylimidazo[1,2-a]pyridines and alkynes.
Scheme 180: Two-way reaction mechanism for annulations reaction.
Scheme 181: [RuCl2(p-cymene)]2-catalyzed C–C bond formation reaction.
Scheme 182: Reported reaction mechanism.
Scheme 183: Fe(III) catalyzed C-3 formylation approach.
Scheme 184: SET mechanism-catalyzed by Fe(III).
Scheme 185: Ni(dpp)Cl2-catalyzed KTC coupling.
Scheme 186: Pd-catalyzed SM coupling.
Scheme 187: Vanadium-catalyzed coupling of IP and NMO.
Scheme 188: Mechanistic cycle.
Scheme 189: Selective C3/C5–H bond functionalizations by mono and bimetallic systems.
Scheme 190: rGO-Ni@Pd-catalyzed C–H bond arylation of imidazo[1,2-a]pyridine.
Scheme 191: Mechanistic pathway for heterogeneously catalyzed arylation reaction.
Scheme 192: Zinc triflate-catalyzed coupling reaction of substituted propargyl alcohols.
Precious metal-free molecular machines for solar thermal energy storage
- Meglena I. Kandinska,
- Snejana M. Kitova,
- Vladimira S. Videva,
- Stanimir S. Stoyanov,
- Stanislava B. Yordanova,
- Stanislav B. Baluschev,
- Silvia E. Angelova and
- Aleksey A. Vasilev
Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106
- Abstract Four benzothiazolium crown ether-containing styryl dyes were prepared through an optimized synthetic procedure. Two of the dyes (4b and 4d) having substituents in the 5-position of the benzothiazole ring are newly synthesized compounds. They demonstrated a higher degree of trans–cis
- aggregated much faster than its methyl-substituted analogue 4b. From another hand the substituent in the 5-position of the benzothiazole heterocycle sterically hinders the rotation of the alkylsulfo-anchoring group and thus plays the role of a controller with regard to its direction towards the crown ether
- . This finding is a resemblance to the results from reference [24] where the 5-methoxy-substituted benzothiazole styryl-crown ethers demonstrated higher quantum yields of trans-to-cis photoisomerization. Insight from electronic structure calculations To rationalize the experimental findings, we performed
Graphical Abstract
Scheme 1: Quaternization of 2-methylbenzothiazoles with alkane sultones.
Scheme 2: Synthesis of 4-(aza-15-crown-5)benzocarbaldehyde (3) [22].
Scheme 3: Synthesis of dyes 4a–d.
Figure 1: a–c) Dependence of the absorption spectra of the dyes 4b, 4c and 4d, respectively (cL = 1.0 × 10−5 ...
Figure 2: Dependence of the fluorescence of 4b on the concentration of the Ba2+ ions. Excitation wavelength λ...
Figure 3: a) Dependence of absorption spectra of dye 4b (cL = 1.0 × 10−4 M) with Ba2+ (cM = 1 M) on the irrad...
Figure 4: UV–vis absorption spectra of dye 4b (1.0 × 10−4 M) free and in complex with Ba2+ (1 M) before and a...
Figure 5: Optimized structures of the cis and trans isomers of dyes 4a–d.
Figure 6: Optimized structures of the Ba2+-complexes of cis and trans isomer of 4b.
Figure 7: Simulated spectra with spectral lifetime broadening TDPBE0 spectra in ACN for dye 4b and its Ba2+ c...
Metal-free C–H mercaptalization of benzothiazoles and benzoxazoles using 1,3-propanedithiol as thiol source
- Yan Xiao,
- Bing Jing,
- Xiaoxia Liu,
- Hongyu Xue and
- Yajun Liu
Beilstein J. Org. Chem. 2019, 15, 279–284, doi:10.3762/bjoc.15.24
- potassium hydroxide and DMSO. This novel protocol is featured by direct C–H mercaptalization of heteroarenes and a simple reaction system. Keywords: benzothiazole; benzoxazole; C–H functionalization; mercaptalization; 1,3-propanedithiol; Introduction Both 2-mercaptobenzothiazoles and 2
- -catalyzed C–H thiolation of benzothiazole or benzoxazole with a disulfide and a thiol provides easy access to the corresponding sulfides [26][27][28][29][30][31][32][33][34]. However, the examples using C–H functionalization for preparing 2-mercaptobenzoxazoles or 2-mercaptobenzothiazoles are still rare. In
- ]. Therefore, we envisioned that aliphatic dithiol may be able to work as thiol source in the C–H mercaptalization of benzothiazole and benzoxazole as well, leading to the formation of 2-mercaptobenzothiazole and 2-mercaptobenzoxazole, respectively. We tested our hypothesis using benzothiazole (1a) as model
Graphical Abstract
Figure 1: Representative examples of biologically active 2-mercaptobenzoxazoles and 2-mercaptobenzothiazoles.
Scheme 1: Strategies for the synthesis of 2-mercaptobenzothiazole and 2-mercaptobenzoxazole (X = O, S).
Figure 2: Substrate scope of the developed C–H mercaptalization strategy. Reaction conditions: benzothiazole ...
Scheme 2: Control experiments.
Scheme 3: Proposed reaction pathway.
Fluorogenic PNA probes
- Tirayut Vilaivan
Beilstein J. Org. Chem. 2018, 14, 253–281, doi:10.3762/bjoc.14.17
Graphical Abstract
Figure 1: The design of classical DNA molecular beacons.
Figure 2: Structures of DNA and selected PNA systems.
Figure 3: Various binding modes of PNA to double stranded DNA including triplex formation, triplex invasion, ...
Figure 4: The design and working principle of the PNA beacons according to (A) Ortiz et al. [41] and (B) Armitage...
Figure 5: The design of "stemless" PNA beacons.
Figure 6: The applications of PNA openers to facilitate the binding of PNA beacons to double stranded DNA [40,47].
Figure 7: The working principle of snap-to-it probes that employed metal chelation to bring the dyes in close...
Figure 8: Examples of pre-formed dye-labeled PNA monomers and functionalizable PNA monomers.
Figure 9: Dual-labeled PNA beacons with end-stacking or intercalating quencher.
Figure 10: The working principle of hybrid PNA-peptide beacons for detection of (A) proteins [80] and (B) protease...
Figure 11: The working principle of binary probes.
Figure 12: The working principle of nucleic acid templated fluorogenic reactions leading to a (A) ligated prod...
Figure 13: Catalytic cycles in fluorogenic nucleic acid templated reactions [90].
Figure 14: The working principle of strand displacement probes.
Figure 15: (A) Examples of CPP successfully used with labeled PNA probes. (B) The use of single-labeled PNA pr...
Figure 16: The concept of PNA–GO platform for DNA/RNA sensing.
Figure 17: Single-labeled fluorogenic PNA probes.
Figure 18: Examples of environment sensitive fluorescent labels that have been incorporated into PNA probes as...
Figure 19: The mechanism of fluorescence change in TO dye.
Figure 20: Fluorescent nucleobases capable of hydrogen bonding that have been incorporated into PNA probes.
Figure 21: Comparison of the designs of the (A) light-up PNA probe and (B) FIT PNA probe.
Figure 22: The structures of TO and its analogues that have successfully been used in FIT PNA probes.
Figure 23: The working principle of dual-labeled FIT PNA probes [222,223].
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
- . Rearomatization via hydrogen atom abstraction by the former generated superoxide radical anion leads to the desired 2-substituted benzothiazole. The authors observed a green colour of the reaction mixture indicating the formation of [Ru(bpy)3]3+. Therefore, they suggest an oxidative quenching cycle, but an
- photoexcited [Ru(bpy)3]2+* leading to [Ru(bpy)3]+ and a thiyl radical intermediate. Radical addition to the aromatic anilide moiety, single-electron oxidation and further deprotonation forms the desired 2-substituted benzothiazole by rearomatization. Both the regeneration of the [Ru(bpy)3]2+ by single-electron
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.
Halogen-containing thiazole orange analogues – new fluorogenic DNA stains
- Aleksey A. Vasilev,
- Meglena I. Kandinska,
- Stanimir S. Stoyanov,
- Stanislava B. Yordanova,
- David Sucunza,
- Juan J. Vaquero,
- Obis D. Castaño,
- Stanislav Baluschev and
- Silvia E. Angelova
Beilstein J. Org. Chem. 2017, 13, 2902–2914, doi:10.3762/bjoc.13.283
- also noteworthy that the presence of the Br substituent in the C-5 position of the benzothiazole system does not influence the positions of the absorption maxima (cf. 5a vs 5c and 5b vs 5d) but does lead to a decrease in the molar absorptivity (up to 20% from 5b to 5d). The addition of dsDNA to the dye
- for deactivation of the excited state [43]. The replacement of the hydrogen atom at the C-5 position in the benzothiazole side of the molecules with a bromo substituent does not have any significant influence on the fluorescence of dyes 5c and 5d, which is similar to its effect on the absorption
- spectra and is in contrast to the by Armitage et al. observed influence of the replacement of hydrogen with fluorine atom in the benzothiazole ring [43]. Photostability The photostability of all dyes in the series was evaluated in acetonitrile with irradiation at 254 nm with a mercury lamp in equal
Graphical Abstract
Scheme 1: Chemical structures of TO and SYBR Green I – commercial monomethine fluorescent dsDNA binders.
Scheme 2: Synthesis of the monofluoro-substituted dye TO-1F. Reagents, conditions and yields: (i) sodium meth...
Scheme 3: Synthesis of new halogen-containing analogues of TO. Reagents, conditions and yields: (i) DMS, 100 ...
Figure 1: Absorption spectra of the studied compounds in MeOH (c = 1 × 10−5 M).
Figure 2: Absorption spectra of dye 5b (c = 5 × 10−7 M) in TE buffer, in the absence and presence of dsDNA (c...
Figure 3: Fluorescence spectra of dye 5a (c = 5 × 10–7 M) in TE buffer and in the presence of increasing conc...
Figure 4: Photostability of dyes TO-7Cl and 5a–d in acetonitrile in the concentration range of 1 × 10−5 M.
Figure 5: B3LYP optimized structures.
Figure 6: Graphical representation of the frontier orbitals (isodensity plot, isovalue = 0.02 a.u.).
Figure 7: Simulated TDPBE0 spectra in methanol.
Figure 8: Electron density (isovalue = 0.002) mapped with electrostatic potential (color scheme: green for ne...
Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides
- Irwan Iskandar Roslan,
- Kian-Hong Ng,
- Gaik-Khuan Chuah and
- Stephan Jaenicke
Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270
- •CCl3 radicals are quenched to CHCl3 via HAT [93]. The proposed catalytic cycle for the synthesis of benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones is as follows. The Lewis acidic InIII metal center coordinates to the more nucleophilic benzothiazole N atom, forming an adduct A [98]. This activates the N–H
Graphical Abstract
Scheme 1: Two different intermolecular cyclization pathways controlled by reagents used.
Scheme 2: Scope of reaction. Reaction conditions: 1 (1.2 mmol), 2 (1.0 mmol), KOt-Bu (2 mmol), in 3 mL CBrCl3...
Scheme 3: Scope of the reaction. Reaction conditions: 1 (1.0 mmol), 2 (1.5 mmol), In(OTf)3 (0.1 mmol), in 1.5...
Scheme 4: Control experiments.
Figure 1: Proposed mechanism (benzo[d]imidazo[2,1-b]thiazoles).
Figure 2: Proposed mechanism (benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones).
Mechanochemical synthesis of small organic molecules
- Tapas Kumar Achar,
- Anima Bose and
- Prasenjit Mal
Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186
- ]. Jang and co-workers reported a mechanochemical synthesis of benzimidazoles [143][144], benzoxazole [145] and benzothiazole derivatives in presence of ZnO nano particles as catalyst [146]. Using 0.5 mol % of ZnO nano particles which were grown on aromatic imine D as capping agent, resulted in the best
- synthesis under mechanochemical conditions. Phosphonylation of benzothiazole and thiazole derivatives were done with organophosphorus compounds using 3 equiv of Mn(OAc)3·2H2O in a mixer mill for 1.5 h. Benzothiazole or thiazole rings having electron-donating or -withdrawing groups worked efficiently under
- [120]. Mechanochemical Hantzsch pyrrole synthesis [121]. Mechanochemical Biginelli reaction by subcomponent synthesis approach [133]. Mechanochemical asymmetric multicomponent reaction[134]. Mechanochemical Paal–Knorr pyrrole synthesis [142]. Mechanochemical synthesis of benzothiazole using ZnO nano
Graphical Abstract
Scheme 1: Mechanochemical aldol condensation reactions [48].
Scheme 2: Enantioselective organocatalyzed aldol reactions under mechanomilling. a) Based on binam-(S)-prolin...
Scheme 3: Mechanochemical Michael reaction [51].
Scheme 4: Mechanochemical organocatalytic asymmetric Michael reaction [52].
Scheme 5: Mechanochemical Morita–Baylis–Hillman (MBH) reaction [53].
Scheme 6: Mechanochemical Wittig reactions [55].
Scheme 7: Mechanochemical Suzuki reaction [56].
Scheme 8: Mechanochemical Suzuki–Miyaura coupling by LAG [57].
Scheme 9: Mechanochemical Heck reaction [59].
Scheme 10: a) Sonogashira coupling under milling conditions. b) The representative example of a double Sonogas...
Scheme 11: Copper-catalyzed CDC reaction under mechanomilling [67].
Scheme 12: Asymmetric alkynylation of prochiral sp3 C–H bonds via CDC [68].
Scheme 13: Fe(III)-catalyzed CDC coupling of 3-benzylindoles [69].
Scheme 14: Mechanochemical synthesis of 3-vinylindoles and β,β-diindolylpropionates [70].
Scheme 15: Mechanochemical C–N bond construction using anilines and arylboronic acids [78].
Scheme 16: Mechanochemical amidation reaction from aromatic aldehydes and N-chloramine [79].
Scheme 17: Mechanochemical CDC between benzaldehydes and benzyl amines [81].
Scheme 18: Mechanochemical protection of -NH2 and -COOH group of amino acids [85].
Scheme 19: Mechanochemical Ritter reaction [87].
Scheme 20: Mechanochemical synthesis of dialkyl carbonates [90].
Scheme 21: Mechanochemical transesterification reaction using basic Al2O3 [91].
Scheme 22: Mechanochemical carbamate synthesis [92].
Scheme 23: Mechanochemical bromination reaction using NaBr and oxone [96].
Scheme 24: Mechanochemical aryl halogenation reactions using NaX and oxone [97].
Scheme 25: Mechanochemical halogenation reaction of electron-rich arenes [88,98].
Scheme 26: Mechanochemical aryl halogenation reaction using trihaloisocyanuric acids [100].
Scheme 27: Mechanochemical fluorination reaction by LAG method [102].
Scheme 28: Mechanochemical Ugi reaction [116].
Scheme 29: Mechanochemical Passerine reaction [116].
Scheme 30: Mechanochemical synthesis of α-aminonitriles [120].
Scheme 31: Mechanochemical Hantzsch pyrrole synthesis [121].
Scheme 32: Mechanochemical Biginelli reaction by subcomponent synthesis approach [133].
Scheme 33: Mechanochemical asymmetric multicomponent reaction[134].
Scheme 34: Mechanochemical Paal–Knorr pyrrole synthesis [142].
Scheme 35: Mechanochemical synthesis of benzothiazole using ZnO nano particles [146].
Scheme 36: Mechanochemical synthesis of 1,2-di-substituted benzimidazoles [149].
Scheme 37: Mechanochemical click reaction using an alumina-supported Cu-catalyst [152].
Scheme 38: Mechanochemical click reaction using copper vial [155].
Scheme 39: Mechanochemical indole synthesis [157].
Scheme 40: Mechanochemical synthesis of chromene [158].
Scheme 41: Mechanochemical synthesis of azacenes [169].
Scheme 42: Mechanochemical oxidative C-P bond formation [170].
Scheme 43: Mechanochemical C–chalcogen bond formation [171].
Scheme 44: Solvent-free synthesis of an organometallic complex.
Scheme 45: Selective examples of mechano-synthesis of organometallic complexes. a) Halogenation reaction of Re...
Scheme 46: Mechanochemical activation of C–H bond of unsymmetrical azobenzene [178].
Scheme 47: Mechanochemical synthesis of organometallic pincer complex [179].
Scheme 48: Mechanochemical synthesis of tris(allyl)aluminum complex [180].
Scheme 49: Mechanochemical Ru-catalyzed olefin metathesis reaction [181].
Scheme 50: Rhodium(III)-catalyzed C–H bond functionalization under mechanochemical conditions [182].
Scheme 51: Mechanochemical Csp2–H bond amidation using Ir(III) catalyst [183].
Scheme 52: Mechanochemical Rh-catalyzed Csp2–X bond formation [184].
Scheme 53: Mechanochemical Pd-catalyzed C–H activation [185].
Scheme 54: Mechanochemical Csp2–H bond amidation using Rh catalyst.
Scheme 55: Mechanochemical synthesis of indoles using Rh catalyst [187].
Scheme 56: Mizoroki–Heck reaction of aminoacrylates with aryl halide in a ball-mill [58].
Scheme 57: IBX under mechanomilling conditions [8].
Scheme 58: Thiocarbamoylation of anilines; trapping of reactive aryl-N-thiocarbamoylbenzotriazole intermediate...
The chemistry and biology of mycolactones
- Matthias Gehringer and
- Karl-Heinz Altmann
Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159
Graphical Abstract
Figure 1: Initial proposal for the core macrolactone structure (left) and the established complete structure ...
Figure 2: Mycolactone congeners and their origins.
Figure 3: Misassigned mycolactone E structure according to Small et al. [50] (11) and the correct structure (6) f...
Figure 4: Schematic illustration of Kishi’s improved mycolactone TLC detection method exploiting derivatizati...
Figure 5: Fluorescent probes derived from natural mycolactone A/B (1a,b) or its synthetic 8-desmethyl analogs...
Figure 6: Tool compounds used by Pluschke and co-workers for elucidating the molecular targets of mycolactone...
Figure 7: Synthetic strategies towards the extended mycolactone core. A) General strategies. B) Kishi’s appro...
Scheme 1: Kishi’s 1st generation approach towards the extended core structure of mycolactones. Reagents and c...
Scheme 2: Kishi’s 2nd generation approach towards the extended core structure of mycolactones. Reagents and c...
Scheme 3: Kishi’s 3rd generation approach towards the extended core structure of mycolactones. Reagents and c...
Scheme 4: Negishi’s synthesis of the extended core structure of mycolactones. Reagents and conditions: a) (i) ...
Scheme 5: Burkart’s (incomplete) 1st generation approach towards the extended core structure of mycolactones....
Scheme 6: Burkart’s (incomplete) 1st, 2nd and 3rd generation approach towards the extended mycolactone core s...
Scheme 7: Altmann’s synthesis of alkyl iodide 91. Reagents and conditions: a) (i) PMB-trichloroacetimidate, T...
Scheme 8: Final steps of Altmann’s synthesis of the extended core structure of mycolactones. Reagents and con...
Scheme 9: Basic principles of the Aggarwal lithiation–borylation homologation process [185,186].
Scheme 10: Aggarwal’s synthesis of the C1–C11 fragment of the mycolactone core. Reagents and conditions: a) Cl...
Scheme 11: Aggarwal’s synthesis of the linear C1–C20 fragment of the mycolactone core. Reagents and conditions...
Figure 8: Synthetic strategies towards the mycolactone A/B lower side chain.
Scheme 12: Gurjar and Cherian’s synthesis of the C1’–C8’ fragment of the mycolactone A/B pentaenoate side chai...
Scheme 13: Gurjar and Cherian’s synthesis of the benzyl-protected mycolactone A/B pentaenoate side chain. Reag...
Scheme 14: Kishi’s synthesis of model compounds for elucidating the stereochemistry of the C7’–C16’ fragment o...
Scheme 15: Kishi’s synthesis of the mycolactone A/B pentaenoate side chain. (a) (i) NaH, (EtO)2P(O)CH2CO2Et, T...
Scheme 16: Feringa and Minnaard's incomplete synthesis of mycolactone A/B pentaenoate side chain. Reagents and...
Scheme 17: Altmann’s approach towards the mycolactone A/B pentaenoate side chain. Reagents and conditions: a) ...
Scheme 18: Negishi’s access to the C1’–C7’ fragment of mycolactone A. Reagents and conditions: a) (i) n-BuLi, ...
Scheme 19: Negishi’s approach to the C1’–C7’ fragment of mycolactone B. Reagents and conditions: a) (i) DIBAL-...
Scheme 20: Negishi’s synthesis of the C8’–C16’ fragment of mycolactone A/B. Reagents and conditions: a) 142, BF...
Scheme 21: Negishi’s assembly of the mycolactone A and B pentaenoate side chains. Reagents and conditions: a) ...
Scheme 22: Blanchard’s approach to the mycolactone A/B pentaenoate side chain. a) (i) Ph3P=C(Me)COOEt, CH2Cl2,...
Scheme 23: Kishi’s approach to the mycolactone C pentaenoate side chain exemplified for the 13’R,15’S-isomer 1...
Scheme 24: Altmann’s (unpublished) synthesis of the mycolactone C pentaenoate side chain. Reagents and conditi...
Scheme 25: Blanchard’s synthesis of the mycolactone C pentaenoate side chain. Reagents and conditions: a) (i) ...
Scheme 26: Kishi’s synthesis of the tetraenoate side chain of mycolactone F exemplified by enantiomer 165. Rea...
Scheme 27: Kishi’s synthesis of the mycolactone E tetraenoate side chain. Reagents and conditions: a) (i) CH2=...
Scheme 28: Wang and Dai’s synthesis of the mycolactone E tetraenoate side chain. Reagents and conditions: a) (...
Scheme 29: Kishi’s synthesis of the dithiane-protected tetraenoate side chain of the minor oxo-metabolite of m...
Scheme 30: Kishi’s synthesis of the mycolactone S1 and S2 pentaenoate side chains. Reagents and conditions: a)...
Scheme 31: Kishi’s 1st generation and Altmann’s total synthesis of mycolactone A/B (1a,b) and Negishi’s select...
Scheme 32: Kishi’s 2nd generation total synthesis of mycolactone A/B (1a,b). Reagents and conditions: a) 2,4,6...
Scheme 33: Blanchard’s synthesis of the 8-desmethylmycolactone core. Reagents and conditions: a) (i) TsCl, TEA...
Scheme 34: Altmann’s (partially unpublished) synthesis of the C20-hydroxylated mycolactone core. Reagents and ...
Scheme 35: Altmann’s and Blanchard’s approaches towards the 11-isopropyl-8-desmethylmycolactone core. Reagents...
Scheme 36: Blanchard’s synthesis of the saturated variant of the C11-isopropyl-8-desmethylmycolactone core. Re...
Scheme 37: Structure elucidation of photo-mycolactones generated from tetraenoate 224.
Scheme 38: Kishi’s synthesis of the linear precursor of the photo-mycolactone B1 lower side chain. Reagents an...
Scheme 39: Kishi’s synthesis of the photo-mycolactone B1 lower side chain. Reagents and conditions: a) LiTMP, ...
Scheme 40: Kishi’s synthesis of a stabilized lower mycolactone side chain. Reagents and conditions: a) (i) TBD...
Scheme 41: Blanchard’s variation of the C12’,C13’,C15’ stereocluster. Reagents and conditions: a) (i) DIBAL-H,...
Scheme 42: Blanchard’s synthesis of aromatic mycolactone polyenoate side chain analogs. Reagents and condition...
Scheme 43: Small’s partial synthesis of a BODIPY-labeled mycolactone derivative and Demangel’s partial synthes...
Scheme 44: Blanchard’s synthesis of the BODIPY-labeled 8-desmethylmycolactones. Reagents and conditions: a) (i...
Scheme 45: Altmann’s synthesis of biotinylated mycolactones. Reagents and conditions: a) (i) CDI, THF, rt, 2 d...
Figure 9: Kishi’s elongated n-butyl carbamoyl mycolactone A/B analog.
Direct catalytic arylation of heteroarenes with meso-bromophenyl-substituted porphyrins
- Alexei N. Kiselev,
- Olga K. Grigorova,
- Alexei D. Averin,
- Sergei A. Syrbu,
- Oskar I. Koifman and
- Irina P. Beletskaya
Beilstein J. Org. Chem. 2017, 13, 1524–1532, doi:10.3762/bjoc.13.152
- , benzothiazole and N-methylimidazole was studied in the presence of three alternative catalytic systems: Pd(dba)2/DavePhos/Cs2CO3, Pd(PPh3)4/PivOH/K2CO3 and Pd(OAc)2/Cu(OAc)2/PPh3/K2CO3. The first catalytic system was found to be successful in the reaction with benzoxazole, the second one was less efficient for
- 24.4), benzothiazole (pKa 27.3), and N-methylbenzimidazole (pKa 32.5) [30]. Starting mono- and di(p-bromophenyl)-substituted porphyrins 1 and 11 were synthesized according to a described procedure [31], their analogues 2, 10, 12 were obtained using essentially the same approach. Results and Discussion
- Zinc meso-(4-bromophenyl)porphyrinate (1) was chosen as a model substrate for the investigation of the conditions of the catalytic arylation. The reaction with benzothiazole was first catalyzed with Pd(OAc)2/DavePhos (2-dicyclohexylphosphino-2’-dimethylaminobiphenyl) (20:20 mol %) and carried out in
Graphical Abstract
Scheme 1: Arylation of zinc meso-(bromophenyl)porphyrinates 1, 2 with benzothiazole and benzoxazole.
Scheme 2: Attempts of the arylation of zinc meso-(bromophenyl)porphyrinates 1 and 2 with benzoxazole and benz...
Scheme 3: Arylation of zinc meso-(bromophenyl)porphyrinates 1, 2 with benzothiazole, benzoxazole, N-methylben...
Scheme 4: Plausible action of palladium and copper catalysts with transmetalation step.
Scheme 5: Dirylation of zinc di-meso-(bromophenyl)porphyrinates 10–12 with benzothiazole, benzoxazole and N-m...
Scheme 6: Polyarylation of zinc tetrakis-meso-(bromophenyl)porphyrinate 18 with benzoxazole.
A self-assembled cyclodextrin nanocarrier for photoreactive squaraine
- Ulrike Kauscher and
- Bart Jan Ravoo
Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248
- promising component of PDT [22][23]. Whether squaraines follow the type I or type II mechanism is discussed controversially in the literature. Santos et al. [19][20], Salice et al. [24] and Rapozzi et al. [25] investigated how benzothiazole-squaraines, which are also pursued in this project, cause
- irradiation of benzothiazole-squaraines results in a photodegradation process. Rapozzi et al. assume that oxidation probably involves through formation of a π-complex between the electron-rich enamine double bond and molecular oxygen. In comparison to the photo-oxidation of enaminon or other electron-rich
- enhance the potential of the nanocarrier. Results and Discussion Adamantane-substituted squaraine (AdSq) was synthesized in a three step synthesis. Benzothiazole rings were introduced to enlarge the π-system. The sulfur atoms of these moieties increase the intersystem crossing due to the heavy atom effect
Graphical Abstract
Figure 1: Schematic representation of adamantane-substituted squaraine (AdSq) binding as a divalent guest to ...
Figure 2: Absorption spectra of AdSq in acetonitrile. [AdSq] = 7.5 µM. Top: Absorption at different time poin...
Figure 3: Top: Emission spectra (ex: 630 nm) of AdSq immobilized at CDV. [CDV] = 0–100 µM; [AdSq] = 5 µM. Bot...
Figure 4: Confocal fluorescence microscopy of giant unilamellar vesicles (GUVs) of amphiphilic cyclodextrins ...
Figure 5: Top: Absorption spectra at different time points during irradiation of a CDV solution with AdSq imm...
Figure 6: Synthesis of AdSq (I) NaH, DMF, 1,6-dibromohexane, 24 h, rt. (II) benzothiazole, acetonitrile, 12 h...
Selective and eco-friendly procedures for the synthesis of benzimidazole derivatives. The role of the Er(OTf)3 catalyst in the reaction selectivity
- Natividad Herrera Cano,
- Jorge G. Uranga,
- Mónica Nardi,
- Antonio Procopio,
- Daniel A. Wunderlin and
- Ana N. Santiago
Beilstein J. Org. Chem. 2016, 12, 2410–2419, doi:10.3762/bjoc.12.235
- ][7] or benzothiazole [8][9] rings in numerous compounds is an important structural element for their biological and medical applications. For example benzimidazoles are widely spread in antiulcer, antihypertensive, antiviral, antifungal, anticancer, and antihistaminic medicines, among others [10][11
Graphical Abstract
Scheme 1: Formation of the benzimidazole core.
Scheme 2: Proposed mechanism for the formation of 1,2-disubstituted benzimidazoles b and 2-substituted benzim...
Figure 1: ESP maps and charge density on carbonylic oxygen atoms for the studied aldehydes obtained at the BP...
Economical and scalable synthesis of 6-amino-2-cyanobenzothiazole
- Jacob R. Hauser,
- Hester A. Beard,
- Mary E. Bayana,
- Katherine E. Jolley,
- Stuart L. Warriner and
- Robin S. Bon
Beilstein J. Org. Chem. 2016, 12, 2019–2025, doi:10.3762/bjoc.12.189
- ) connected to a 20 mL disposable syringe with an 8 inch, 16 gauge Luer fitting syringe needle. Reaction procedures 2-Chloro-6-nitro-1,3-benzothiazole (6) [15][20] 2-Chloro-1,3-benzothiazole (16, 10.0 g, 58.95 mmol) was added portion wise to concentrated H2SO4 (60 mL) in a cooled round-bottomed flask (ice
- –194 °C (EtOH); 1H NMR (500 MHz, CDCl3) δ 8.75 (d, J = 2.3 Hz, 1H, CH-7), 8.38 (dd, J = 9.0, 2.3 Hz, 1H, CH-5), 8.07 (d, J = 9.0 Hz, 1H, CH-4); 13C NMR (125 MHz, CDCl3) δ 158.9 (C-2), 154.9 (C-6), 145.6 (C-7a), 136.6 (C-3a), 123.5 (CH-4), 122.4 (CH-5), 117.8 (CH-7). 6-Nitro-1,3-benzothiazole-2
- -carbonitrile (13) [19] A solution of NaCN (2.40 g, 48.97 mmol) in H2O (100 mL) was added slowly to a stirred solution of 2-chloro-6-nitro-1,3-benzothiazole (6, 10.0 g, 46.59 mmol) and DABCO (748 mg, 6.99 mmol) in MeCN (1000 mL). The reaction mixture was stirred at room temperature for 24 h. Excess cyanide was
Graphical Abstract
Scheme 1: Functionalised CBTs 1 can be used for the synthesis of luciferins 3 and for bioorthogonal ligations...
Scheme 2: Reported synthetic routes to ACBT 8: A) Original route reported by Takakura et al. [14] and Wang et al. ...
Figure 1: Calorimeter traces for the addition of aqueous NaCN (A) or water (B) to a solution of 6 and DABCO i...
Scheme 3: Scale-up of ACBT synthesis.
Amidofluorene-appended lower rim 1,3-diconjugate of calix[4]arene: synthesis, characterization and highly selective sensor for Cu2+
- Rahman Hosseinzadeh,
- Mohammad Nemati,
- Reza Zadmard and
- Maryam Mohadjerani
Beilstein J. Org. Chem. 2016, 12, 1749–1757, doi:10.3762/bjoc.12.163
- ]arene bearing anthraceneisoxazolymethyl [3], quinolone [28], 5-nitrosalicylaldehyde [29], 3-alkoxy-2-naphthoic acid [30], coumarine [31] and benzothiazole [10][15] groups. In continuation of our studies on developing novel chemosensors containing fluorenyl moieties as fluorogenic group [32][33][34], we
Graphical Abstract
Scheme 1: Fluorene appended 1,3-diconjugate of calix[4]arene.
Scheme 2: Synthesis route of fluorene-appended amido-linked 1,3-diconjugate of calix[4]arene L.
Figure 1: Absorption spectra of L (1.0 × 10−5 M) and its complexes with different metals (10 equiv) in MeCN.
Figure 2: Color changes of receptor L upon addition of 10 equiv of various metal ions as their perchlorate sa...
Figure 3: Influence of the addition of increasing amounts (0–100 equiv) of Cu2+ on the absorption spectra of L...
Figure 4: Fluorescence spectra of L (1.0 × 10−5 M) in MeCN upon addition of different metal ions (10 equiv) w...
Figure 5: (a) Fluorescence spectra (1.0 × 10−5 M) of L recorded upon the addition of copper ion (0–5 equiv) i...
Figure 6: Fluorescence intensity of L (1.0 × 10−5 M) upon the addition of 10 equiv Cu2+ in the presence of 10...
Figure 7: 1 H NMR (400 MHz, CD3CN) spectra of L upon addition of (a) 0.0 equiv, (b) 0.2 equiv, (c) 0.4 equiv,...
Scheme 3: A proposed binding mode between L and Cu2+.
Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates
- Mohammad Haji
Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121
- 1,2-dihydropyridine-3-phosphonate 259. Yavari et al. have described the phosphorylation of benzothiazole (263) and isoquinoline (246) through a one-pot three-component reaction with activated acetylenes 260 and diphenyl phosphonate (261) under solvent-free conditions at room temperature (Scheme 54
- -phosphonates and 2-acyl-1,2-dihydroisoquinoline-1-phosphonates. Three-component reaction of pyridine derivatives with ethyl propiolate and dialkyl phosphonates. Three-component reactions for the phosphorylation of benzothiazole and isoquinoline. Three-component synthesis of diphenyl [2-(aminocarbonyl)- or [2
Graphical Abstract
Scheme 1: The Biginelli condensation.
Scheme 2: The Biginelli reaction of β-ketophosphonates catalyzed by ytterbium triflate.
Scheme 3: Trimethylchlorosilane-mediated Biginelli reaction of diethyl (3,3,3-trifluoropropyl-2-oxo)phosphona...
Scheme 4: Biginelli reaction of dialkyl (3,3,3-trifluoropropyl-2-oxo)phosphonate with trialkyl orthoformates ...
Scheme 5: p-Toluenesulfonic acid-promoted Biginelli reaction of β-ketophosphonates, aryl aldehydes and urea.
Scheme 6: General Kabachnik–Fields reaction for the synthesis of α-aminophosphonates.
Scheme 7: Phthalocyanine–AlCl catalyzed Kabachnik–Fields reaction of N-Boc-piperidin-4-one with diethyl phosp...
Scheme 8: Kabachnik–Fields reaction of isatin with diethyl phosphite and benzylamine.
Scheme 9: Magnetic Fe3O4 nanoparticle-supported phosphotungstic acid-catalyzed Kabachnik–Fields reaction of i...
Scheme 10: The Mg(ClO4)2-catalyzed Kabachnik–Fields reaction of 1-tosylpiperidine-4-one.
Scheme 11: An asymmetric version of the Kabachnik–Fields reaction for the synthesis of α-amino-3-piperidinylph...
Scheme 12: A classical Kabachnik–Fields reaction followed by an intramolecular ring-closing reaction for the s...
Scheme 13: Synthesis of (S)-piperidin-2-phosphonic acid through an asymmetric Kabachnik–Fields reaction.
Scheme 14: A modified diastereoselective Kabachnik–Fields reaction for the synthesis of isoindolin-1-one-3-pho...
Scheme 15: A microwave-assisted Kabachnik–Fields reaction toward isoindolin-1-ones.
Scheme 16: The synthesis of 3-arylmethyleneisoindolin-1-ones through a Horner–Wadsworth–Emmons reaction of Kab...
Scheme 17: An efficient one-pot method for the synthesis of ethyl (2-alkyl- and 2-aryl-3-oxoisoindolin-1-yl)ph...
Scheme 18: FeCl3 and PdCl2 co-catalyzed three-component reaction of 2-alkynylbenzaldehydes, anilines, and diet...
Scheme 19: Three-component reaction of 6-methyl-3-formylchromone (75) with hydrazine derivatives or hydroxylam...
Scheme 20: Three-component reaction of 6-methyl-3-formylchromone (75) with thiourea, guanidinium carbonate or ...
Scheme 21: Three-component reaction of 6-methyl-3-formylchromone (75) with 1,4-bi-nucleophiles in the presence...
Scheme 22: One-pot three-component reaction of 2-alkynylbenzaldehydes, amines, and diethyl phosphonate.
Scheme 23: Lewis acid–surfactant combined catalysts for the one-pot three-component reaction of 2-alkynylbenza...
Scheme 24: Lewis acid catalyzed cyclization of different Kabachnik–Fields adducts.
Scheme 25: Three-component synthesis of N-arylisoquinolone-1-phosphonates 119.
Scheme 26: CuI-catalyzed three-component tandem reaction of 2-(2-formylphenyl)ethanones with aromatic amines a...
Scheme 27: Synthesis of 1,5-benzodiazepin-2-ylphosphonates via ytterbium chloride-catalyzed three-component re...
Scheme 28: FeCl3-catalyzed four-component reaction for the synthesis of 1,5-benzodiazepin-2-ylphosphonates.
Scheme 29: Synthesis of indole bisphosphonates through a modified Kabachnik–Fields reaction.
Scheme 30: Synthesis of heterocyclic bisphosphonates via Kabachnik–Fields reaction of triethyl orthoformate.
Scheme 31: A domino Knoevenagel/phospha-Michael process for the synthesis of 2-oxoindolin-3-ylphosphonates.
Scheme 32: Intramolecular cyclization of phospha-Michael adducts to give dihydropyridinylphosphonates.
Scheme 33: Synthesis of fused phosphonylpyrans via intramolecular cyclization of phospha-Michael adducts.
Scheme 34: InCl3-catalyzed three-component synthesis of (2-amino-3-cyano-4H-chromen-4-yl)phosphonates.
Scheme 35: Synthesis of phosphonodihydropyrans via a domino Knoevenagel/hetero-Diels–Alder process.
Scheme 36: Multicomponent synthesis of phosphonodihydrothiopyrans via a domino Knoevenagel/hetero-Diels–Alder ...
Scheme 37: One-pot four-component synthesis of 1,2-dihydroisoquinolin-1-ylphosphonates under multicatalytic co...
Scheme 38: CuI-catalyzed four-component reactions of methyleneaziridines towards alkylphosphonates.
Scheme 39: Ruthenium–porphyrin complex-catalyzed three-component synthesis of aziridinylphosphonates and its p...
Scheme 40: Copper(I)-catalyzed three-component reaction towards 1,2,3-triazolyl-5-phosphonates.
Scheme 41: Three-component reaction of acylphosphonates, isocyanides and dialkyl acetylenedicarboxylate to aff...
Scheme 42: Synthesis of (4-imino-3,4-dihydroquinazolin-2-yl)phosphonates via an isocyanide-based three-compone...
Scheme 43: Silver-catalyzed three-component synthesis of (2-imidazolin-4-yl)phosphonates.
Scheme 44: Three-component synthesis of phosphonylpyrazoles.
Scheme 45: One-pot three-component synthesis of 3-carbo-5-phosphonylpyrazoles.
Scheme 46: A one-pot two-step method for the synthesis of phosphonylpyrazoles.
Scheme 47: A one-pot method for the synthesis of (5-vinylpyrazolyl)phosphonates.
Scheme 48: Synthesis of 1H-pyrrol-2-ylphosphonates via the [3 + 2] cycloaddition of phosphonate azomethine yli...
Scheme 49: Three-component synthesis of 1H-pyrrol-2-ylphosphonates.
Scheme 50: The classical Reissert reaction.
Scheme 51: One-pot three-component synthesis of N-phosphorylated isoquinolines.
Scheme 52: One-pot three-component synthesis of 1-acyl-1,2-dihydroquinoline-2-phosphonates and 2-acyl-1,2-dihy...
Scheme 53: Three-component reaction of pyridine derivatives with ethyl propiolate and dialkyl phosphonates.
Scheme 54: Three-component reactions for the phosphorylation of benzothiazole and isoquinoline.
Scheme 55: Three-component synthesis of diphenyl [2-(aminocarbonyl)- or [2-(aminothioxomethyl)-1,2-dihydroisoq...
Scheme 56: Three-component stereoselective synthesis of 1,2-dihydroquinolin-2-ylphosphonates and 1,2-dihydrois...
Scheme 57: Diphosphorylation of diazaheterocyclic compounds via a tandem 1,4–1,2 addition of dimethyl trimethy...
Scheme 58: Multicomponent reaction of alkanedials, acetamide and acetyl chloride in the presence of PCl3 and a...
Scheme 59: An oxidative domino three-component synthesis of polyfunctionalized pyridines.
Scheme 60: A sequential one-pot three-component synthesis of polysubstituted pyrroles.
Scheme 61: Three-component decarboxylative coupling of proline with aldehydes and dialkyl phosphites for the s...
Scheme 62: Three-component domino aza-Wittig/phospha-Mannich sequence for the phosphorylation of isatin deriva...
Scheme 63: Stereoselective synthesis of phosphorylated trans-1,5-benzodiazepines via a one-pot three-component...
Scheme 64: One-pot three-component synthesis of phosphorylated 2,6-dioxohexahydropyrimidines.
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
- significantly higher than those displayed by the parent 2-(2-hydroxyphenyl)benzoxazole (0.02) and 2-(2-hydroxyphenyl)benzothiazole (0.005) [34]. Conclusion The ring expansion of the 3,4,5,6-tetrachloro-1,2-benzoquinones occuring under coupling with 2-methylbenzoxazoles, 2-methylbenzothiazoles and 2,3,3
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...
C–H bond halogenation catalyzed or mediated by copper: an overview
- Wenyan Hao and
- Yunyun Liu
Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230
- ). The catalytic iodination of electron deficient 1,3-azoles was recently realized by Zhao et al. Under the catalytic conditions consisting of LiOt-Bu, 1,10-phenanthroline and CuBr2, a class of different conventional azoles 17, including benzoxazoles, benzothiazole, N-methylbenzimidazole, 5-phenyloxazole
Graphical Abstract
Scheme 1: Copper-catalyzed C–H bond halogenation of 2-arylpyridine.
Scheme 2: ortho-Chlorination of 2-arylpridines with acyl chlorides.
Scheme 3: Copper-catalyzed chlorination of 2-arylpyridines using LiCl.
Scheme 4: Copper-catalyzed C–H halogenation of 2-arylpyridines using LiX.
Scheme 5: Copper-mediated selective C–H halogenations of 2-arylpyridine.
Scheme 6: Copper-catalyzed C–H o-halogenation using removable DG.
Scheme 7: Copper-catalyzed C–H halogenations using PIP as DG.
Scheme 8: Copper-catalyzed quinoline C–H chlorination.
Scheme 9: Copper-catalyzed arene C–H fluorination of benzamides.
Scheme 10: Copper-catalyzed arene C–H iodination of 1,3-azoles.
Scheme 11: Copper-catalyzed C–H halogenations of phenols.
Scheme 12: Proposed mechanism for the C–H halogenation of phenols.
Scheme 13: Copper-catalyzed halogenation of electron enriched arenes.
Scheme 14: Copper-catalyzed C–H bromination of arenes.
Scheme 15: CuI-mediated synthesis of iododibenzo[b,d]furans via C–H functionalization.
Scheme 16: Cu-Mn spinel oxide-catalyzed phenol and heteroarene halogenation.
Scheme 17: Copper-catalyzed halogenations of 2-amino-1,3thiazoles.
Scheme 18: Copper-mediated chlorination and bromination of indolizines.
Scheme 19: Copper-catalyzed three-component synthesis of bromoindolizines.
Scheme 20: Copper-mediated C–H halogenation of azacalix[1]arene[3]pyridines.
Scheme 21: Copper-mediated cascade synthesis of halogenated pyrrolones.
Scheme 22: Copper-mediated alkene C–H chlorination in spirothienooxindole.
Scheme 23: Copper-catalyzed remote C–H chlorination of alkyl hydroperoxides.
Scheme 24: Copper-catalyzed C–H fluorination of alkanes.
Scheme 25: Copper-catalyzed or mediated C–H halogenations of active C(sp3)-bonds.
Highly selective palladium–benzothiazole carbene-catalyzed allylation of active methylene compounds under neutral conditions
- Antonio Monopoli,
- Pietro Cotugno,
- Carlo G. Zambonin,
- Francesco Ciminale and
- Angelo Nacci
Beilstein J. Org. Chem. 2015, 11, 994–999, doi:10.3762/bjoc.11.111
- from Pd2dba3 and 3-methylbenzothiazolium salt V as precursors. A comparison of the performance of benzothiazole carbene with phosphanes and an analogous imidazolium carbene ligand is also proposed. Keywords: active methylene compounds; allylic carbonates; Pd–benzothiazol-2-ylidene complex; Tsuji–Trost
- , catalyst loading, temperature and solvents (Table 1). With regard to the influence of ligands, the efficiency of benzothiazole–carbene was compared with that of sulfides II and III, both in the presence and in the absence of PPh3, as it is well known that also chelating N-heterocyclic ligands bearing
- Herrmann et al. [40], prepared in situ from 1,3-dimethylimidazolium iodide (VI). The reaction carried out under the protocol conditions afforded in 2 h the monoallylated compound 1 in a low yield (16%) confirming the superior efficiency of benzothiazole–carbene (Table 1, entry 16). A possible explanation
Graphical Abstract
Figure 1: Complexes and ligands employed.
Scheme 1: Pd-catalyzed α-allylation of active methylene compounds.
A small azide-modified thiazole-based reporter molecule for fluorescence and mass spectrometric detection
- Stefanie Wolfram,
- Hendryk Würfel,
- Stefanie H. Habenicht,
- Christine Lembke,
- Phillipp Richter,
- Eckhard Birckner,
- Rainer Beckert and
- Georg Pohnert
Beilstein J. Org. Chem. 2014, 10, 2470–2479, doi:10.3762/bjoc.10.258
- also used for probing in life science comprises the heterocyclic thiazoles. This structural element can be found in commercial products, such as thiazole orange, SYBR® Green I or TOTO®, which are, e.g., used for DNA labeling. In these compounds the thiazole ring is part of a benzothiazole. We set out
Graphical Abstract
Figure 1: Structure of the reporter molecule BPT (1).
Scheme 1: Synthesis of the azide-bearing 4-hydroxythiazole derivative 1.
Figure 2: Structure of the tested azide-modified standard fluorophores DNS (8) and NBD (9) and the bromine mo...
Figure 3: UV–vis spectra of 20 µM solutions of the azide modified fluorophores BPT (1), DNS (8), NBD (9) and ...
Figure 4: Normalized absorbance and fluorescence of BPT (1) in 20% THF/80% water (v/v), excitation at 374 nm.
Figure 5: Peak area of 100 pmol BPT (1), DNS (8), NBD (9) and BNS (6) measured with (A) C18-UPLC coupled to a...
Figure 6: Procedure of the model reaction between L-lysine and DDY (10) to form an imine (only one of two pos...
Figure 7: Mass spectra of labeled L-lysine/DDY (10)/fluorophore conjugates 11 (containing BPT), 12 (containin...
Figure 8: Fluorescent labeling of catalase treated with DDY (10) followed by CuAAC with all four reporter mol...
One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines
- Christian Muschelknautz,
- Robin Visse,
- Jan Nordmann and
- Thomas J. J. Müller
Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51
- of the most stable isomers of these novel triene merocyanines was assigned to be 2E,4Z,6Z for both the Fischer’s base derivatives 10a–g (X = CMe2) and the benzothiazole derivative 10h (X = S) (Figure 3). Since the stereoconvergent-product formation (only single sets of signals are obtained in the NMR
Graphical Abstract
Figure 1: Linear push–pull solid-state diene lumophores with conformationally flexible and fixed acceptor moi...
Scheme 1: Three-component synthesis of 1-styryleth-2-enylideneindolones 8.
Figure 2: DFT-computed energy differences of the stereoisomers of 2Z,4Z-8a and 2Z,4E-8a.
Scheme 2: Three-component synthesis of 4-(1,3,3-trimethylindolin-2-ylidene)but-2-en-1-ylideneindolones 10.
Figure 3: DFT-computed energy differences of the stereoisomers of 10a and 10h.
Scheme 3: Mechanistic rationale of the three-component sequence furnishing the 1-styryleth-2-enylideneindolon...
Figure 4: DFT-computed (B3LYP functional, 6-31G* basis set) HOMO (left) and LUMO (right) of merocyanine 8a.
Figure 5: Absorption and emission spectrum of the dropcasted film of compound 8a (recorded at room temperatur...
Figure 6: Absorption spectrum of the dropcasted film of compound 10d (recorded at room temperature, normalize...
Figure 7: Absorption spectra of compound 10h in dichloromethane (right trace) and of the dropcasted film (lef...
Figure 8: DFT-computed (B3LYP functional, 6-311G(d,p) basis set) FMOs (HOMO, bottom; LUMO (center), and LUMO+...
Four-component reaction of cyclic amines, 2-aminobenzothiazole, aromatic aldehydes and acetylenedicarboxylate
- Hong Gao,
- Jing Sun and
- Chao-Guo Yan
Beilstein J. Org. Chem. 2013, 9, 2934–2939, doi:10.3762/bjoc.9.330
- : benzothiazole; domino reaction; electron-deficient alkyne; multicomponent reaction; pyrrolidinone; Introduction Over fifty years ago, Huisgen firstly described the addition reactions of nitrogen-containing heterocycles to electron-deficient alkynes to form 1,4-dipolar intermediates, which can reacted
- preparation of the mixed heterocyclic compounds containing units of benzothiazole, piperidine and 2-pyrrolidinone in satisfactory yields. The range of substrates and the reaction mechanism for this reaction were briefly discussed. This convenient synthetic reaction might be potentially used for complex
Graphical Abstract
Figure 1: Molecular structure of compound 1f.
Figure 2: Molecular structure of compound 2a.
Figure 3: Molecular structure of compound 2h.
Scheme 1: The proposed reaction mechanism for the four-component reaction.
Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition
- Regina Berg and
- Bernd F. Straub
Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308
- is present in the ligand, the others can be replaced by benzothiazole rings. The rate of reaction in the CuAAC test reaction increases in the order (Bth)3 << (Bth)(BimH)2 < (BimH)3 << (Bth)2(BimH) [80][83]. With carboxylic acid or ester groups attached to the benzimidazole rings via alkyl chains (CH2
Graphical Abstract
Scheme 1: Exemplary 1,3-dipolar cycloaddition of phenylacetylene with phenyl azide [6].
Scheme 2: CuAAC reaction of benzyl azide with (prop-2-yn-1-yloxy)benzene [12].
Scheme 3: Bioconjugation reaction of capsid-bound azide groups with alkynyl-functionalized dye molecules (cow...
Figure 1: Tris(triazolylmethyl)amine ligands for CuAAC applications in bioorganic chemistry: TBTA = tris[(1-b...
Figure 2: Derivatives of 2,2’-bipyridine and 1,10-phenanthroline, commonly used ligands in CuAAC reactions un...
Scheme 4: CuAAC reaction with copper(II) precursor salt and rate-accelerating monodentate phosphoramidite lig...
Scheme 5: Synthesis of 1-(adamant-1-yl)-1H-1,2,3-triazol-4-ylcarbonyl-Phe-Gly-OH by solid-supported Click cat...
Scheme 6: CuAAC reaction with re-usable copper(I)-tren catalyst [129].
Scheme 7: CuAAC test reaction with chlorido[tris(1-benzyl-1H-1,2,3-triazol-4-yl)methanol-κ3N3]copper(I) and a...
Scheme 8: CuAAC model reaction with [Cu2(μ-TBTA-κ4N2,N3,N3’,N3’’)2][BF4]2 [131].
Scheme 9: Application of a (2-aminoarenethiolato)copper(I) complex as homogeneous catalyst for the CuAAC test...
Scheme 10: Application of [CuBr(PPh3)3] as homogeneous catalyst for the CuAAC test reaction of benzyl azide wi...
Figure 3: Phosphinite and phosphonite copper(I) complexes presented by Díez-González [144].
Scheme 11: Effect of additives on the CuAAC test reaction with [(SIMes)CuCl] [149].
Scheme 12: Initiation of the catalytic cycle by formation of the copper acetylide intermediate from [(ICy)2Cu]...
Scheme 13: Early mechanistic proposal by Sharpless [12,42].
Scheme 14: Chemoselective synthesis of a 5-iodo-1,4-disubstituted 1,2,3-triazole [156].
Scheme 15: Mechanistic proposals for the copper-catalyzed azide–iodoalkyne cycloaddition [156].
Scheme 16: 1,3-Dipolar cycloaddition of 3-hexyne catalyzed by [(SIMes)CuBr] [146].
Scheme 17: Mechanistic picture for the cycloaddition of internal alkynes catalyzed by NHC-copper(I) complexes ...
Scheme 18: Catalytic cycle of the CuAAC reaction on the basis of the proposed mechanistic scheme by Fokin and ...
Figure 4: Schematic representation of the single crystal X-ray structures of copper(I) acetylide complexes [Cu...
Figure 5: Acetylide-bridged dicopper complexes with tris(heteroarylmethyl)amine ligand(s) as key intermediate...
Scheme 19: Off-cycle equilibrium between unreactive polymeric copper(I) acetylide species (right) and reactive...
Figure 6: Categories of tris(heteroarylmethyl)amine ligands regarding their binding ability to copper(I) ions ...
Scheme 20: Mechanistic scheme for ligand-accelerated catalysis with tripodal tris(heteroarylmethyl)amine ligan...
Scheme 21: Synthesis of supposed intermediates in the CuAAC’s catalytic cycle [164,187].
Figure 7: Tetranuclear copper acetylide complexes as reported by Weiss (left) [176] and Tasker (middle) [185] and model...
Figure 8: Gibbs free energy diagram for the computed mechanistic pathway of the CuAAC reaction starting from ...
Figure 9: Energy diagram by Ahlquist and Fokin [125].
Scheme 22: Mechanistic proposal for the CuAAC reaction based on DFT calculations by Fokin [125] and our group [186] ([Cu...
Figure 10: ORTEP plot [202,203] of the X-ray powder diffraction crystal structure of (phenylethynyl)copper(I) [(PhC≡CCu)...
Scheme 23: Synthesis of [(PhC≡CCu)2]n as co-product in the Glaser coupling of phenylacetylene in the presence ...
Scheme 24: Mechanistic explanation for the isotopic enrichment in the product triazolide in the presence of th...
Scheme 25: Homogeneous CuAAC catalysis with a bistriazolylidene dicopper complex (0.5 mol %) and comparison wi...
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
- : BTA = 2-(4'-methylaminophenyl)benzothiazole, Figure 2), was prepared by methylation of 4-(6-methyl-2-benzothiazolyl)aniline using [11C]methyl iodide [49]. Compared to 4, 56a showed greatly increased lipophilicity and improved binding affinity for Aβ1-40 (Ki = 890 nM for 4 and Ki = 20.2 for 56a). In
- amide 69, which was subsequently converted to the thioamide by using Lawesson’s reagent and cyclized to form the benzothiazole core 70 (Scheme 6B). Demethylation with BBr3 and protection of the resulting hydroxy moiety as the methoxymethyl (MOM) ether gave 71. Reduction of the nitro group to 72
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.
