Reaction of 6-arylidenehydrazino-1,3-dimethyluracils with thionyl chloride leading to purine,thiazolo[4,5-d]pyrimidine,pyrimido[4,5-e][1,3,4]thiadiazine,pyrazolo[3,4-d]pyrimidine,and [1,2,3]thiadiazolo[4,5-d]pyrimidine derivativese

The reaction of 6-arylidenehydrazino-1,3-dimethyluracils with thionyl chloride in benzene afforded purine, thiazolo4,5-d]pyrimidine, pyrimido4,5-e]1,3,4]thiadiazine, pyrazolo3,4-d]pyrimidine, and 1,2,3]thiadiazolo4,5-d]pyrimidine derivatives, while the treatment of 6-(benzylidene-1′-methylhydrazino)-1,3-dimethyluracil with thionyl chloride in benzene gave 4-methylpyrimido4,5-e]1,3,4]thiadiazine and 1-methylpyrazolo-3,4-d]pyrimidine derivatives. Plausible mechanisms for the formation of these fused pyrimidines are also described.