Synthesis of Spiro Thiazolo(3,2-a)pyrimidine Compounds by 1,3-Dipolar Cycloaddition Reaction

A new class of spiro thiazolo(3,2-a)pyrimidine compounds 2a~2j were synthesized by the 1,3-dipolar cycloaddition reaction of 2-arylmethylidene-6,7-dihydro-5H-thiazolo(3,2-a)pyrimidin-3-one (1a~1j) with azomethine ylide (generated in situ by the reaction of isatin with sarcosine). The structures of the products 2a~2j were determined and characterized thoroughly by NMR, MS, IR techniques, elemental analysis, and X-ray crystallographic analysis. The results of experiment indicated that this 1,3-dipolar cycloaddition proceeded with high stereoselectivity and regioselectivity.