Montmorillonite Ksf Catalyzed Facile Synthesis of Novel Spiro Heterocycles under Microwave Irradiation

The arylidienes of spiro thiazolidines (5) containing α,β-unsaturated function have been used as component of Micheal addition with equimolar amount of 2-aminopyridine (6a) to give novel spiro [indole-3,2′-pyrido[1,2-a]thiazolo[5,4-e]pyrimidines] (7) in a single step under microwaves in presence of montmorillonite KSF as solid support. The new improved synthetic method for spiro [indole-3, 2′-thiazolo[4,5-d]pyrimidines] (8) has also been developed involving the reaction of (5) with thiourea under microwaves. Comparison with conventional synthesis indicated the enhanced yield with faster reactions under microwaves.