An efficient and organo-catalyzed method has been developed for the synthesis of 5- arylidenethiazolidine-2, 4-diones and 5-arylidene-2-thioxothiazolidin-4-ones via Knoevenagel condensation of arylaldehydes 1 and 2, 4-thiazolidinedione 2a/2- thioxothiazolidin-4-one 2b under mild conditions. Urea-adduct 4 and azomethine 5 also afford arylidene-products 3 by reacting with 2a–b via addition–elimination reaction. This ...