(Arylsulfonyl)acetonitriles were shown to react with mercaptoacetic acid in refluxing pyridine yielding 2-[(arylsulfonyl)methylidene]thiazolidin-4-ones. The latter underwent alkylation with α-bromoketones in the presence of K2CO3 selectively at the nitrogen atom. Further formylation of the resulting phenacyl derivatives with excess DMF·POCl3 complex afforded 5-aroyl-7-arylsulfonyl-2-[(dimethylamino)methylidene]pyrrolo[2,1-b]thiazol-3(2H)-ones.
alkylations - nitriles - pyrrolo[2,1-b]thiazoles - sulfones - Vilsmeier complex