IMPROVED ONE-POT SYNTHESIS OF 3-SPIRO INDOLINES UNDER MICROWAVE IRRADIATION

Abstract

The potential of the domestic microwave oven has been utilized to accelerate the one-pot synthesis of spiro[indole-thiazolidine]diones and spiro[indole-benzothiazine]diones by condensation of substituted indole-2.3-diones (1) and appropriate anilines (2) with mercaptopropionic acid (4a/b) and o-mercaptobenzoic acid (5) in open borosilicate vessels, using ethanol as energy transfer medium. The reaction rate was 400–500 times faster than the reaction rate in the conventional way. Excellent isolated yields with easier workup than classical heating were the main advantages observed.