Liquid-phase synthesis of 2-substituted benzimidazoles, benzoxazoles and benzothiazoles

A novel acid fluoride for use in the liquid-phase synthesis of substituted benzimidazoles, benzoxazoles and benzothiazoles was developed. Its synthetic utility is exemplified by a structurally diverse set of aromatic heterocycles. Final cleavage is achieved by treatment with sodium methoxide in methanol for 12 h. The corresponding benzimidazoles, benzoxazoles and benzothiazoles were obtained in good isolated yields (22-62%, four steps).     

A convenient synthesis of 2-acyl benzothiazoles/thiazoles from benzothiazole/thiazole and N,N'-carbonyldiimidazole activated carboxylic acids

A convenient and efficient strategy for the synthesis of 2-acyl benzothiazoles/thiazoles has been developed. The treatment of benzothiazole/thiazole with allylic Grignard reagents readily generates the corresponding 2-Grignard reagents, which is followed by a reaction with N,N'-carbonyldiimidazole activated carboxylic acids to afford various 2-acyl benzothiazoles/thiazoles products. The synthetic method is applicable to a wide array of carboxylic acids and allows easy access to 2-acyl benzothiazoles/thiazoles with considerable yields under mild reaction conditions.     

Reaction of N,N-dichlorosulfonamides with aryl isothiocyanates

The reaction of aryl isothiocyanates with the N,N-dichloroamides of arenesulfonic acids and with the morpholide of sulfamic acid has been studied. Instead of the expected products of the oxidative imination of the aryl isothiocyanates, 2-(arylsulfonylamino)benzothiazoles and 2-(morpholinosulfonylamino)benzothiazoles, respectively, were obtained.     

Heterocyclic Quinones in the Nenitzescu Reaction. Synthesis of Furo- and Pyrrolobenzothiazoles from 2-Methyl-4,7-dioxobenzothiazole

Treatment of the enamines of acetylacetone and benzoylacetone with 2-methyl-4,7-dioxobenzothiazole under Nenitzescu reaction conditions gave furo[2,3-e]benzothiazoles (in acetic acid) and pyrrolo[2,3-e]benzothiazoles (in nitromethane). Using enamines of acetoacetic ester gave exclusively pyrrolo[2,3-e]benzothiazoles.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 252–258, February, 2005.     

Synthesis of 2- and 2,5-substituted benzoxazoles and benzothiazoles

A number of 2- and 2,5-perfluoroalkyl and perfluoroalkylether substituted benzoxazoles and benzothiazoles have been prepared. Their relative hydrolytic stability has been examined. In all cases the benzothiazoles were more stable that the benzoxazoles. Substituents in the 2-position offering steric hindrance improve hydrolytic stability.     

Iron-Catalyzed Highly Efficient Aerobic Oxidative Synthesis of Benzimidazoles,Benzoxazoles, and Benzothiazoles Directly from Aromatic Primary Amines Under Solvent-Free Conditions in the Open Air

Solvent-free oxidative synthesis of benzimidazoles, benzoxazoles, and benzothiazoles from aromatic primary amines and o-phenylenediamine, o-aminophenol, and o-aminothiophenol has been achieved by using Fe(NO₃)₃ and TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl). This reaction can use air as an economical and green oxidant, and a wide variety of derivatives were obtained in good to excellent yields. The reaction mechanism was proposed and this method provides a direct, practical, and efficient approach for the preparation of substituted benzimidazoles, benzoxazoles, and benzothiazoles.     

Synthesis of 2-N-substituted benzothiazoles via domino condensation-hetero cyclization process,mediated by copper oxide nanoparticles under ligand-free conditions

A simple and highly practical method for the synthesis of 2-N-substituted benzothiazoles has been developed by using nanocopper oxide as a recyclable catalyst. The present tandem process allows to get access to a wide range of 2-N-substituted benzothiazoles in good to excellent yields by the reaction of 2-iodo aniline with carbon disulfide and piperidine in presence of KOH as a base and DMSO as a solvent under ligand-free conditions.     

Iridium‐Catalyzed Intramolecular Asymmetric Allylic Dearomatization Reaction of Benzoxazoles,Benzothiazoles, and Benzimidazoles

An iridium‐catalyzed intramolecular asymmetric allylic dearomatization reaction of benzoxazoles, benzothiazoles, and benzimidazoles was developed. The reaction was found to be compatible with a wide range of five‐membered‐ring electron‐deficient heteroaromatic compounds and furnished the corresponding dearomatized heterocycles in high yield with excellent enantioselectivity.     

Base-catalyzed hydrogen-deuterium exchange in some 5-substituted benzothiazoles and in thiazolo-[4,5-c]pyridine. effect of substituents and polar effects of the aza group

The rates of base-catalyzed hydrogen-deuterium exchange at C-2 in some 5-substituted benzothiazoles and in thiazolo[4,5-c]pyridine were studied. Transmission through the thiazole ring of the effects of substituents in the benzothiazoles and of the polar effects of the aza group in the thiazolopyridine, was assessed from these data.     

Synthesis and biological activity of novel benzoazoles,benzoazines and other analogs functionalized by 2,4-dihydroxyphenyl moiety

Research on Chemical Intermediates - Novel benzoazoles, benzoazines, benzothiazoles, benzothiazines and other related compounds possessing a 2,4-dihydroxyphenyl moiety were prepared. The compounds...     

Peroxide-mediated oxidative coupling of primary alcohols and disulfides: Synthesis of 2-substituted benzothiazoles

A peroxide-mediated protocol for the synthesis of 2-substituted benzothiazoles was developed, starting from bis(o-aminophenyl) disulfides and primary alcohols. Eleven differently 2-substituted benzothiazoles were prepared in moderate to excellent yields using di-tert-butyl peroxide (DTBP) as an oxidant.     

Nano ceria catalyzed synthesis of substituted benzimidazole,benzothiazole, and benzoxazole in aqueous media

A series of substituted benzimidazoles, benzothiazoles, and benzoxazoles was synthesized by combining 1,2-phenylenediamine, 2-aminothiophenol, or 2-aminophenol with aryl, heteroaryl, aliphatic, α,β-unsaturated aldehydes in the presence of nano ceria (CeO₂) as an efficient heterogeneous catalyst.     

Iridium‐Catalyzed Intramolecular Asymmetric Allylic Dearomatization Reaction of Benzoxazoles,Benzothiazoles, and Benzimidazoles

An iridium‐catalyzed intramolecular asymmetric allylic dearomatization reaction of benzoxazoles, benzothiazoles, and benzimidazoles was developed. The reaction was found to be compatible with a wide range of five‐membered‐ring electron‐deficient heteroaromatic compounds and furnished the corresponding dearomatized heterocycles in high yield with excellent enantioselectivity.     

Yttrium-catalyzed heterocyclic formation via aerobic oxygenation: A green approach to benzothiazoles

The YCl₃-catalyzed aerobic oxidative cyclization reaction for the synthesis of benzothiazoles has been developed.This method provides a practical,effective and green synthetic approach to benzothiazoles which are important units in many biologically active compounds.     

Synthesis of benzothiazoles via ipso substitution of ortho-methoxythiobenzamides

An efficient route to the synthesis of benzothiazoles from ortho-methoxythiobenzamides via the ipso substitution of an aromatic methoxy group is presented, and the mechanism of the Jacobson synthesis of benzothiazoles is further investigated.     

Indion 190 resin: efficient,environmentally friendly,and reusable catalyst for synthesis of benzimidazoles,benzoxazoles, and benzothiazoles

Abstract

An efficient and mild protocol has been developed for the preparation of benzimidazoles, benzoxazoles, and benzothiazoles from reactions of aldehydes with o-substituted aminoaromatics in the presence of catalytic amount of Indion 190 resin. Short reaction time, ambient conditions, simple work-up procedure, high yield, easy availability, reusability, and use of an eco-friendly catalyst are some of the striking features of the present protocol.     

Ru(III)-catalyzed oxidative reaction in ionic liquid: an efficient and practical route to 2-substituted benzothiazoles and their hybrids with pyrimidine nucleoside

An efficient, practical and environmentally benign synthesis of 2-substituted benzothiazoles was developed through RuCl₃-catalyzed oxidative condensation of 2-aminothiophenol with aldehyde in ionic liquid by using air as the oxidant. With this procedure, a series of 2-substituted benzothiazoles and benzothiazole/pyrimidine nucleoside hybrids with antimicrobial activities were efficiently prepared from easily accessible starting materials.     

水相铜催化α-酮酸与邻氨基苯硫酚合成苯并噻唑化合物

发展了一种新颖的水相α-酮酸与邻氨基苯硫酚合成苯并噻唑化合物的方法。在CuCl₂•2H₂O的催化下,通过该反应顺利合成了2-取代苯并噻唑化合物,产率较高,底物适应性较好。      

Green and Highly Efficient Synthesis of Mono‐ and Bis‐Benzothiazoles in the Presence of Fe(SD)3 under Ultrasound Irradiation

A convenient, practical, green, and environmentally friendly method was developed for the synthesis of benzothiazoles from 2‐aminothiophenol and various aldehydes. Bis‐benzothiazoles were synthesized in high yield under mild reaction conditions. Products were obtained in the presence of in situ prepared Fe(SD )₃ [iron(III ) dodecyl sulfate] as a combined Lewis acid–surfactant catalyst (LASC ) in water under ultrasound irradiation.     

Synthesis of some substituted imidazo [5, 1-b] benzothiazoles

Cyclization of formylated and acetylated -substituted 2-aminomethylbenzothiazoles with phosphorus oxychloride gives 3-substituted imidazo [5, 1-b] benzothiazoles, and 3-substituted 1-methylimidazo [5, 1-b] benzothiazoles. Treatment of 2-benzothiazolyl-4-pyridylaminomethane with formic acid gives 3-(4-pyridyl) imidazo [5, 1-b] benzothiazole. 1-Mercapto-3-phenylimidazo [5, 1-b] benzothiazole is converted into 3-phenylimidazo [5, 1-b] benzothiazole by elimination of the mercapto group.