Diversity in the Base-induced Photoreactions of Thiolane-2,4-dione and Derivatives. Reductive Ring Cleavage and Novel Rearrangements of the Carbon Skeleton

Abstract

Abstract The irradiation of thiolane-2,4-dione (thiotetronic acid) and its derivatives, 1a–1d, in methanol in the presence of bases induced the reductive ring cleavage to give β,β′-diketo esters. The base-induced reductive ring cleavage was also observed in aprotic solvents, such as acetonitrile or acetone, although the products were obtained as β,β′-diketo amides in these cases. On the other hand, the irradiation of 1a–1d in water in the presence of bases induced a rearrangement of the carbon skeleton to give succinic thioanhydrides, γ-keto amides or succinamides, along with the reduction products. When pyridine was used as a base in the photolysis in water, two 3-acetyl derivatives, 1a and 1b, gave γ-keto thiols and the corresponding disulfides, resulted from another type of rearrangement of the carbon skeleton. Conceivable reaction mechanisms were discussed.