Synthesis of novel benzo-1,2,5-thiadiazines, their antimicrobial activity and isomerization into benzo-1,2,4-triazines

P. G. Department of Chemistry, Shri Shivaji Science College, Amravati-444 603, India E-mail: pradip222091 @yahoo.co.in Manuscript received 23 April 2003. revised 12 March 2004. accepted 6 April 2004 Benzo[c]-6-aryl/alkylimino-1,2,5-thiadiazines (4a-g) have been obtained by the basification of benzo[c]-6-aryl/alkylimino-1 ,2,5- thiadiazine dihydroiodides (3a-g). The latter were synthesized by the oxidative cyclisation of substituted 1-aryl/alkyl- 3-(2' -aminophenyl)thiocarbamides (2a-g) by ethanolic iodine. Compounds (4a-g) on acylation with acetic anhydride and glacial acetic acid in 1 : 2 ratio afforded 2,5-diacetyl derivatives (Sa-g), on reaction with sodium nitrite in 1 : 2 ratio in acidic medium afforded 2,5-dinitroso derivatives (6a-g) and on boiling with aqueous ethanolic sodium hydroxide solution isomerized into corresponding benzo-1,2,4-triazines (7a-g). The title compounds were assayed for their antimicrobial activity against gram-positive and gram-negative micro-organisms