Synthesis of some new 5‐chloro‐7‐mercapto‐1‐methyl/phenyl‐1,2,4‐triazolo[4,5‐ b ]pyrazin‐2(1 H )‐ones and 5‐chloro‐3‐thiopyrazin‐2(1 H )‐one derivatives as possible antibacterial and antifungal agents

Several new 5‐chloro‐7‐mercapto‐1‐methyl/phenyl‐1,2,4‐triazolo[4,5‐6]pyrazin‐2(1/ H )‐ones V and their disul‐phides VI, 5‐chloro‐3‐mercapto‐2(1 H )‐pyrazinonones III, 5‐chloro‐3‐( N ‐aryl‐ N ‐acetylthioureido)‐1‐methyl/‐phenyl‐2(1 H )‐pyrazinones VII, 5‐chloro‐1‐methyl/phenyl‐3‐sulphonamido‐2(1 H )‐pyrazinones X and chloro‐2‐methyl/phenyl‐(3‐methyl)‐3‐thio‐2(1 H )‐pyrazinones XI were synthesized starting from 3,5‐dichloro‐1‐methyl/phenylpyrazin‐2(1 H )‐ones I. Fifteen of these compounds were screened for their antibacterial and antifungal activity against two bacteria B. subtilis and S. aureus , and two fungi A. niger and H. oryzae. A possible structure activity relationship is given.