New route to pyrimido[4,5-e][1,3,4]thiadiazine derivatives

5-Bromo-2-chloro-4-methyl-6-(1-methylhydrazino)pyrimidine is readily obtained from the recently reported 5-bromo-2,4-dichloro-6-methylpyrimidine by treatment with methylhydrazine in chloroform. Treatment of this compound with carbon disulfide and several alkyl halides gave an intermediate which was successfully converted to its corresponding 3-(alkylsulfanyl)-7-chloro-1,5-dimethyl-1H-pyrimido[4,5e][1,3,4]thiadiazine derivatives in basic acetonitrile. The latter compounds were reacted with secondary amines in boiling ethanol to afford the related 7-amino derivatives.