Bicyclic compounds derived from 4-amino-3-mercapto-1,2,4-triazoles: Facileroutes to 1,2,4-triazolo [3,4-b][1,3,4]thiadiazoles and 1,2,4-triazolo[3,4-b][1,3,4]thiadiazines

Treatment of 5-substituted-4-amino-3-mercapto-1,2,4-triazoles (1), with tri ethyl ortho-formate or acetyl chloride gave the corresponding triazolo[3,4- b]thiadiazoles (2) and 13), respectively, Reaction of (1) with phenacyl bro mide, DMAD and DEAD afforded the corresponding thiazolo[3,4-b][1,3,4] thiad iazines (4), (5) and (6), respectively. Reaction of (I) with propargyl brom ide in the presence of sodium methoxide gave the corresponding sulfide (7) which upon treatment with LiH gave the corresponding 1,2,1-triazola[3,4-b][ 1,3,3]thiadiazine (8) Reaction of (1) with 2,4-dinitrochlorobenzene gave su bstituted 5H-1,2,4-triazolo[3,4-b][1,3,4]benzothiadiazine (9).