Transformation of 6-methylthiopyrimidines. Preparation of new pyrimidine derivatives and fused pyrimidines

2,4-Diamino-6-methylthiopyrimidines 1 reacted with sodium methoxyde and benzylamine to give the corresponding 6-methoxypyrimidine and 6-benzylaminopyrimidine derivatives 2 and 4 respectively. The reaction of 1 with hydrazine hydrate, in ethanol, gave 6-hydrazino derivatives 6. However, by treating pyrimidines 1 in boiling hydrazine hydrate 3,6-diamino-4-hydrazino-1H-pyrazolo[3,4-d]pyrimidine 5 was obtained. The 6-hydrazinopyrimidines 6 could be converted into the pyrazolo[3,4-d], triazolo[4,3-c] and tetrazolo-[1,5-c]pyrimidines 7, 8 and 9 by the action of heating, trimethyl orthoformate and nitrous acid, respectively.