Synthesis of Bisfurazanobenzo-2,1,3-thiadiazole and Related Compounds

Abstract

Nitration of 4,7-dibromobenzo-2,1,3-thiadiazole (I) with fuming nitric acid afforded 4,7-dibromo-5,6-dinitrobenzo-2,1,3-thiadiazole (II) and, unexpectedly, the tribromo derivative: C6Br3N8O2S (III). Compound II was readily converted by treatment with sodium azide into bisfuroxanobenzo-2,1,3-thiadiazole (IV), which was reduced with triethylphosphite to give bisfurazanobenzo-2,1,3-thiadiazole (VII). Compound VII was also synthesized starting from 4-bromo-6,7-(2′,1′,3′-oxadiazole)benzo-2,1,3-thiadiazole (VIII). Reduction of VII with sodium hydrosulfite gave 4,5-diamino-6,7-(2′,1′,3′-oxadiazole)-benzo-2,1,3-thiadiazole (XI), which was cyclized to 4,5-(2′,1′,3′-oxadiazole)benzo[1,2-c: 3,4-c′]bis[1,2,5]thiadiazole (XII) by treatment with N-sulfinylaniline. The transformation of XII to benzo[1,2-c: 3,4-c′: 5,6-c″]tris[1,2,5]thiadiazole (XIV), via 4,5-diaminobenzo-[1,2-c: 3,4-c′]bis[1,2,5]thiadiazole (XIII), is also described. © 1980, The Pharmaceutical Society of Japan. All rights reserved.