LETTER	Synlett 2007: 0313-0317   DOI: 10.1055/s-2007-967994
© Georg Thieme Verlag Stuttgart · New York
Lawesson's Reagent and Microwaves: A New Efficient Access to Benzoxazoles and Benzothiazoles from Carboxylic Acids under Solvent-Free Conditions
Julio A. Seijas*, M. Pilar Vázquez-Tato*, M. Raquel Carballido-Reboredo, José Crecente-Campo, Lucía Romar-López
Departamento de Química Orgánica, Universidad de Santiago de Compostela, Facultad de Ciencias, Aptdo. 280, 27080 Lugo, Spain Fax: +34(982)285872; e-Mail: qoseijas@lugo.usc.es; e-Mail: pilarvt@lugo.usc.es;
Received 10 October 2006

Abstract

Lawesson's reagent acts as an efficient promoter in the solvent-free microwave-assisted synthesis of 2-substituted benzoxazoles from carboxylic acids and 2-aminophenol, and thus, constitutes a general synthetic method for these compounds. This new application of Lawesson's reagent is valid also for benzothiazoles with very high efficiency level. A variety of aromatic, heteroaromatic and aliphatic carboxylic acids react under the conditions developed with good yields in all cases. Thiobenzoic acid is a good alternative for microwave-assisted synthesis of 2-phenylbenzoxazole and 2-phenylbenzothiazole in the absence of solvents.

Key words

benzothiazoles - benzoxazoles - Lawesson's reagent - microwaves - thiobenzoic acid