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 ...