Microwave-assisted multicomponent reaction of aryl amidines: regiospecific synthesis of new polysubstituted thiopyrano-, and pyrano[4,3-d]pyrimidines

A series of new functionalized thiopyrano-, pyrano[4,3-d]pyrimidine derivatives with benzyl group residing in 8-position of fused pyrimidine nucleus were synthesized through multicomponent reactions of aromatic aldehydes, tetrahydrothiopyran-4-one(tetrahydropyran-4-one), and aryl amidines using t-BuOK as a base under microwave heating. The procedure is facile, avoiding time-consuming and costly syntheses, tedious work-up, and purifications of precursors as well as protection/deprotection of functional groups. This method is very efficient due to short reaction times and easy work up and provides a four-component strategy for the construction of the thiopyrano-, and pyrano[4,3-d] pyrimidine skeletons.