1019-90-5Relevant articles and documents
Iron-Catalyzed Sulfur-Promoted Decyanative Redox Condensation of o-Nitrophenols and Arylacetonitriles: An Unprecedented Route to 2-Arylbenzoxazoles
Nguyen, Thanh Binh,Lung, Jerome Cheung
, p. 5815 - 5818 (2018)
Elemental sulfur in the presence of a catalytic amount of FeCl2·4H2O was found to be highly efficient for the promotion of decyanative redox condensation reactions of o-nitrophenols with arylacetonitriles, to give a wide range of 2-arylbenzoxazoles. The utility of elemental sulfur was highlighted by its role as cyanide scavenger and external reducing agent.
Mechanistic exploration of the palladium-catalyzed process for the synthesis of benzoxazoles and benzothiazoles
Bochatay, Valentin N.,Boissarie, Patrick J.,Murphy, John A.,Suckling, Colin J.,Lang, Stuart
, p. 1471 - 1477 (2013)
A convenient one-pot palladium-catalyzed cascade process for the preparation of both benzoxazoles and benzothiazoles has been developed. While these reactions proceed to give similar compounds the mechanisms governing the processes are different as are the experimental conditions employed.
Iron-catalyzed 2-arylbenzoxazole formation from o-nitrophenols and benzylic alcohols
Wu, Mingyue,Hu, Xiong,Liu, Juan,Liao, Yunfeng,Deng, Guo-Jun
, p. 2722 - 2725 (2012)
The iron-catalyzed 2-arylbenzoxazole formation from o-nitrophenols and benzylic alcohols using hydrogen transfer is described. Various 2-arylbenzoxazoles were selectively obtained in good to excellent yields. The reaction tolerated a wide range of functionalities. The alcohol oxidation, nitro reduction, condensation, and dehydrogenation were realized in a cascade without external reducing reagent and oxidant.
Mechanistic evidence for a ring-opening pathway in the Pd-catalyzed direct arylation of benzoxazoles
Sanchez, Rafael S.,Zhuravlev, Fedor A.
, p. 5824 - 5825 (2007)
The direct Pd-catalyzed arylation of 5-substituted benzoxazoles, used as a mechanistic model for 1,3-azoles, was investigated experimentally and computationally. The results of the primary deuterium kinetic isotope effect, Hammett studies, and H/D exchange were shown to be inconsistent with the rate-limiting electrophilic or concerted palladation. A mechanism, proposed on the basis of kinetic and computational studies, includes generation of isocyanophenolate as the key step. The DFT calculations suggest that the overall catalytic cycle is facile and is largely controlled by the C-H acidity of the substrate. Copyright
Cyanide as a powerful catalyst for facile preparation of 2-substituted benzoxazoles via aerobic oxidation
Cho, Yeon Ho,Lee, Chun-Young,Ha, Deok-Chan,Cheon, Cheol-Hong
, p. 2992 - 2996 (2012)
A cyanide-catalyzed synthesis of 2-substituted benzoxazoles from Schiff bases via aerobic oxidation has been developed. The products from various Schiff bases were obtained in high yields in an open flask under ambient conditions without other external oxidants. We have also developed a simple one-step protocol for the synthesis of benzoxazoles from aminophenol and the corresponding aldehydes in the presence of cyanide without isolation of imine intermediates. Copyright
Straightforward synthesis of benzoxazoles and benzothiazoles via photocatalytic radical cyclization of 2-substituted anilines with aldehydes
Le, Hao Anh Nguyen,Nguyen, Long Hoang,Nguyen, Quynh Nhu Ba,Nguyen, Hai Truong,Nguyen, Khang Quoc,Tran, Phuong Hoang
, (2020)
Eosin Y-catalyzed one-pot coupling and cyclization of o-substituted anilines with aldehydes to form benzoxazoles and benzothiazoles under mild condition has been developed. The reaction scope was broadly tolerant of various 2-substituted anilines and aldehydes. The desired products were obtained in high yields with the use of eosin Y as a photocatalyst under a substantial refinement of reaction conditions in comparison with previous literature. Based on the experimental results observed, a plausible mechanism involving a radical process has been proposed.
Oxidative NHC Catalysis for the Generation of Imidoyl Azoliums: Synthesis of Benzoxazoles
Patra, Atanu,James, Anjima,Das, Tamal Kanti,Biju, Akkattu T.
, p. 14820 - 14826 (2018)
N-Heterocyclic carbene (NHC)-catalyzed intramolecular cyclization of aldimines generated from 2-amino phenols and aromatic aldehydes leading to the synthesis of 2-arylbenzoxazoles under mild conditions is presented. The reaction proceeds via the generation of the aza-Breslow intermediates from imines and NHC, which under oxidative conditions form the key imidoyl azoliums and a subsequent intramolecular cyclization furnishes the product. The reaction tolerates a broad range of functional groups, and the products are formed in generally good yields.
Biomimetic oxidative coupling of benzylamines and 2-aminophenols: Synthesis of benzoxazoles
Endo, Yoshinori,B?ckvall, Jan-E.
, p. 13609 - 13613 (2012)
Aerobic oxidation: In a biomimetic approach, a mixture of redox catalysts forms couples that effect the aerobic oxidation of a mixture of benzylamine and 2-aminophenol derivatives to give the corresponding benzoxazoles (see scheme). This biomimetic oxidation proceeds smoothly under mild conditions and the protocol can also be used for preparing benzimidazoles and benzothiazoles. Copyright
TEMPO-mediated aerobic oxidative synthesis of 2-aryl benzoxazoles via ring-opening of benzoxazoles with benzylamines
Rao, Mugada Sugunakara,Hussain, Sahid
, p. 2684 - 2694 (2021)
A simple and efficient TEMPO-mediated system for aerobic oxidative synthesis of 2-aryl benzoxazoles from readily available benzoxazoles and primary benzylic and hetero benzylic amines is presented in one pot. The reaction proceeds through the ring-opening of benzoxazoles and is followed by oxidative condensation with benzylamines. These metal-free, straightforward reactions worked well with a wide range of substrates, yielding moderate to good yields under mild conditions using air as an external green oxidant.
A domino copper-catalyzed C-N and C-O cross-coupling for the conversion of primary amides into benzoxazoles
Altenhoff, Gereon,Glorius, Frank
, p. 1661 - 1664 (2004)
Benzoxazoles can be efficiently prepared in a single step and in good yield from primary amides and o-dihalobenzenes using Cu catalysis. Starting from substituted o-bromochlorobenzenes this unusual domino reaction allows the regioselective formation of benzoxazoles.
Heteropolyacid as a new, green and recyclable catalyst for the synthesis of 2-aryl benzoxazole under solvent-free conditions
Heravi, Majid M.,Javanmardi, Najme,Oskooie, Hossein A.,Baghernejad, Bita,Heidari, Maryam,Bamoharram, Fatemeh F.
, p. 589 - 593 (2009)
A simple, convenient and general method has been developed for the synthesis of 2-arylbenzoxazole via condensation of o-aminophenols and benzoyl chloride derivatives under solvent-free conditions in the presence of a catalytic amount of heteropolyacids in good yields.
Synthesis of benzoxazoles catalyzed by MCM-41, a green and reusable catalyst
Shoar, Rahim Hekmat,Heidary, Maryam,Farzaneh, Maryam,Malakouti, Reihaneh
, p. 1742 - 1751 (2009)
Benzoxazoles can be rapidly and efficiently synthesized from acyl chloride with 2-aminophenols in one simple step, which provided a practical and efficient method for high-throughput synthesis of this important class of heterocyclic compounds. Copyright Taylor & Francis Group, LLC.
A simple and efficient one step synthesis of benzoxazoles and benzimidazoles from carboxylic acids
Wang, Ying,Sarris, Kathy,Sauer, Daryl R.,Djuric, Stevan W.
, p. 4823 - 4826 (2006)
Benzoxazoles or benzimidazoles can be rapidly and efficiently synthesized from a variety of carboxylic acids with 2-aminophenols or 1,2-phenylenediamines in one simple step, respectively. The use of commercially available PS-PPh3 resin combined with microwave heating delivered a variety of benzoxazoles and benzimidazoles in high yields and purities.
Iron(III) Chloride Mediated para-Selective C-H Functionalization: Access to C5-Chloro and C5,C7-Dichloro/Dianisyl Substituted 2-Arylbenzoxazoles
Sahoo, Kanchanbala,Panda, Niranjan
, p. 1023 - 1030 (2022/02/03)
Iron(III) chloride mediated para-selective C?H chlorination and subsequent annulation of 2-amidophenol to synthesize C5- and C5, C7-chlorinated benzoxazoles was developed. Further, the oxidative cross-dehydrogenative coupling of amidophenol with anisole b
Stable Pd(0) Complexes with Ferrocene Bisphosphanes Bearing Phosphatrioxaadamantyl Substituents Efficiently Catalyze Selective C-H Arylation of Benzoxazoles by Aryl Chlorides
Horky, Filip,Císa?ová, Ivana,?těpni?ka, Petr
, p. 4848 - 4856 (2021/10/12)
Versatile applications and unique performance of 1,1’-bis(diphenylphosphanyl)ferrocene (dppf) in coordination chemistry and catalysis prompted the search for its analogs. This contribution describes the synthesis of the first donor-unsymmetric dppf congeners bearing bulky and rigid 1,3,5,7-tetramethyl-2,4,6-trioxa-8-phosphaadamantyl (CgP) donor groups, viz. Ph2PfcPCg (1) and Ph2PfcCH2PCg (2; fc=ferrocene-1,1’-diyl). Bis-phosphanes 1 and 2 were converted into air-stable Pd(0) complexes, [Pd(ma)(L^L)] (L^L=1 and 2; ma=maleic anhydride). Together with [Pd(ma)(dppf)], these complexes were applied as catalysts in Pd-catalyzed C?H arylation of benzoxazoles with aryl chlorides in n-butanol as an environmentally benign solvent. Among all catalysts tested in this study, complex [Pd(ma)(2)] performed the best, providing a high-yield and selective synthesis of 2-arylbenzoxazoles from a range of the generally less reactive chloroarenes at low catalyst loading (typically 1 mol.%). Under similar conditions, the structurally related heterocycles (e. g., 1-methylbenzimidazole and benzothiazole) did not react.