Ultrasound promoted greener synthesis of spiro[indole-3,5′-[1,3]oxathiolanes in water

An aqueous mediated novel synthesis of substituted 2′amino-4′benzoyl-2′-methyl spiroindole 3,5′-1,3]oxathiolane]-2(1H)-ones (2a–f) was carried out from the reaction of spiro indole-3,2′-oxiranes] (1a–f) with thioacetamide in the presence of LiBr as catalyst. The reaction was carried out under both microwaves and sonication and results were also compared with conventional method. In general, improvement in rate and yields observed when reaction was carried out under sonication as compared to microwave irradiation and conventional method.