Dimeric Anhydro Bases from Benzothiazole Derivatives

In order to develop a novel strategy for the synthesis of aminothiol derivatives, the cycloadducts obtained from the reaction of 4-alkenylthiazoles with N-substituted maleimides and similar products where the central ring is totally oxidized, were used as starting materials in the sequence N-methylation, reduction and hydrolytic cleavage of the thiazole ring. However, instead of the expected aminothiol derivative, a dimeric anhydro base was isolated in the last step. The mechanism implies the formation of a thiazolium cation which evolves to the dimeric anhydro base under the basic conditions.