Synthesis of some new pyrimidines, thienopyrimidines and thiopyranopyrimidines

Isothiocyanate 1 reacted with enaminone 2 to give thioamide 3 that cyclized by sodium hydroxide to pyrimidine 4 but cyclized by bromine to give isothiazole 5, pyrimidine 4 was transformed into thiopyranopyrimidines 7, 9 or 11 upon respective reaction with benzaldehyde, maleic acid, or maleic anhydride. Aminative cyclization of 4 yielded isothiazolopyrimidine 13. Reaction of 4 and ethyl bromoacetate or phenacyl bromides afforded thienopyrimidines 15a-b respectively. Oxidation of 4 yielded oxopyrimidine 16.