SYNTHESIS OF -TETRAHYDRO-1,2,4-4H-TRIAZOLO[3,2-B]BENZOTHIAZOLES AND THEIR 3-ARYL-[3,4-B] ISOMERS

Condensation of 3-aryl-5-thio-1,2,4-4H-trizoles (2a-i) and 2-bromodime done (3) in THF/benzene gave -hydroxy-5,5a,6,7,8,8a-hexahydro-1,2,4-4H -triazolo [3,2-b]benzothiazoles (5a-i). These were also obtained by a one step synthesis on heating a mixture of dimedone, NBS, and 2a-i in benzene containing a trace of benzoyl peroxide. Thermal dehydration of 5a-i in PPA/anhydrous ethanol yielded the corresponding -tetrahydro-1 ,2,4-4H-triazolo[3,2-b]benzothiazoles (6a-i). The formation of [3,4-b] fused isomers (4a-i) during the reaction of 2 with 3 was ruled out by an unambiguous synthesis of 8a-i. Antibacterial screening of selected compounds against Escherichia coli and Staphylococcus aureus was not encouraging.