SYNTHESIS AND PROPERTIES OF "[1,2,3]THIADIAZOLO[4,5-D]PYRIMIDINE DERIVATIVES INCLUDING THEIR MESOIONIC COMPOUNDS - NEW CLASS OF HETEROCYCLES

Treatment of 6-hydrazino-l,3-dimethyluracil (la) with thionyi chloride gave 4, 6-dimethyl[l, 2, 3]thiadiazolo[4, 5-d]pyrimidine-5,7(4H,6H)-dione (5a), a new class of heterocycles. Reaction of 6-hydrazino-3-methyluracil (8a) with thionyi chloride afforded 6-methyl[l, 2, 3, 5]thiatriazolino[5,4-c]pyrimidine-5,7(6H)-dione 1-oxide (10a), which was subsequently converted to 6-methyl[l, 2, 3]thiadiazolo[4,5-d]pyrimidine-5,7(4H,6H)-dione (14a) by a novel 1,3-sul-fur migration. Treatment of 3-methyl-6-(l-methylhydrazino)uracil (8d) with thionyi chloride provided the mesoionic compound, anhydro-3, 6-dimethyl-5-hydroxy[1, 2, 3]thiadiazolo[4,5-d]pyrimidinium-7(6H)-one hydroxide (14d), via the 1, 3-sulfur migration of 3, 6-dimethyl[l, 2, 3, 5]thiatriazolino[5, 4-c]pyrimidine-5, 7(6H)-dione 1-oxide (10d). Several other thiadiazolo[4, 5-d]pyrimidines including their mesoionic compounds were also synthesized. Thiation of 5a with phosphorus pentasulfide in pyridine yielded 4, 6-dimethyl[l, 2, 3]thiadiazolo[4, 5-d]pyrimidin-5(4H)-one-7(6H)-thione (17). Nucleophilic displacement of 17 with hydrazines furnished the corresponding 4, 6-dimethyl[l, 2, 3]thiadiazolo[4, 5-d)pyrimidin-5(4H)-one 7(6H)-hydrazones (18a-c). The photolysis of 5a in ethanol gave l, 3-dimethyl-5-mercaptouracil disulfide (22), while the thermolysis of 5a in Dowtherm A yielded both 1, 3, 5, 7-tetramethyl[l,4]dithiino[2, 3-d;5,6-e']dipyrimidine-2, 6, 8,10(lH,3H,5H,7H)-tetrone (26) and 1, 3, 5, 7-tetramethyl-thiopheno[2,3-d;4, 5-e']dipyrimidine-2, 6, 8, 9(lH,3H,5H,7H)-tetrone (27) probably via the thiirene intermediate 25. © 1978, American Chemical Society. All rights reserved.