Fused Pyrimidines. V. Synthesis of 2-Aminopyrimido [4, 5-e]-1, 3, 4-thiadiazine and Some Related Compounds from 6-Thiosemicarbazidouracils

Oxidation of 1, 3-dialkyl-6-(4-substituted-thiosemicarbazido)-uracils (II) with N-chlorosuccinimide in chloroform at room temperature furnished 5, 7-dialkyl-2-substituted-amino-4H-pyrimido [4, 5-e]-1, 3, 4-thiadiazine-6, 8 (5H, 7H)-diones (III) in good yields. Heating of III resulted in ring contraction to afford 3-substituted-aminopyrazolo [3, 4-d]-pyrimidine-4, 6 (5H, 7H)-diones (IV). Treatment of II with bromine gave 4, 6-dialkyl-1, 2, 3-thiadiazolo [4, 5-d] pyrimidine-5, 7 (4H, 6H)-diones (IX) or N, N'-dialkyl-1, 3, 9, 11-tetramethyl-dipyrimido [4, 5-e : 4', 5'-k] [1, 7, 3, 4, 9, 10] dithiatetraazacyclododecine-2, 4, 6, 10, 12, 14 (1H, 3H, 9H, 11H)-hexanone-6, 14-diimines (VIII), depending on the reaction conditions employed. Compounds IX were also obtained either by treatment of 1, 3-dialkyl-6-hydrazinouracils (I) with thionyl chloride or by treatment of III with bromine.