Efficient One-Step Synthesis of Benzazoles in Aqueous Media

Benzazoles (benzoxazoles, benzothiazoles, and benzimidazoles) were efficiently prepared by the aquatic reaction of the corresponding thioamidinium salts and 2-aminophenol, 2-aminothiophenol, and 1,2-diaminobenzene, respectively. The thioamidinium salt was successfully applied as an alternative to a carboxylic acid derivative to react smoothly with an amino precursor and in the presence of catalytic amounts of hexadecyltrimethylammonium. bromide salt to produce benzazoles in good to excellent yields. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim., Germany, 2009)