Polarised ketene dithioacetals. Part 32. Studies on base-catalysed rearrangements of 2-bis(methylthio)methyleneindan-1-one, 2-bis(methylthio)methylene-1-tetralone, and 3-bis(methylthio)methylene-2,3-dihydro-1-benzothiopyran-4-one

Abstract

The ketene dithioacetal (7) derived from indan-1-one gave a dimeric product (8) on treatment with sodium hydride in dimethylformamide under nitrogen. The dithioacetal (15) derived from 1-tetralone on prolonged treatment with sodium hydride under identical conditions yielded the corresponding methyl β-oxodithioester (16) and the S-methyl β-oxothioester (17). Under similar conditions, the dithioacetal (28) derived from 2,3-dihydro-1-benzothiopyran-4-one gave the expected rearranged product (29) formed by a 1,3-methylthio shift. The structural assignments of the products (8), (16), (17), and (29) and the probable mechanism for the formation of (8), (16), and (17) are described.