Synthesis, Characterization and Evaluation of Biological Activity of Novel Cyclic Imides Containing Heterocycles Based on 2,5-disubstituted-1,3,4-thiadiazoles

Starting from 2-amino-5-mercapto-1,3,4-thiadiazole a variety of new cyclic imides linked to 1,3,4-thiadiazole moiety were synthesized via following different methods. The first method involved synthesis of a series of amic acids containing 1,3,4- thiadiazole ring via reaction of different cyclic anhydrides with 2-amino-5-mercapto- 1,3,4-thiadiazole, then the resulted amic acids were dehydrated by using acetic anhydride and anhydrous sodium acetate as dehydrating agent to produce the corresponding cyclic imides. The strategy used in performing the second method involved reaction of 2-amino-5-mercapto-1,3,4-thiadiazole with (bis naphthalic anhydride, 2,3-pyridinic anhydride and 1,8-naphthalic anhydride) in the presence of glacial acetic acid. The present work involved also synthesis of six new cyclic imides linked to 1,3,4-thiadizole ring and containing six-membered (phthalazine, 4-methyl pyridazine, pyridazine and tetrahydropyridazine)-3,6-dione moiety. Synthesis of four of these imides based on introducing 2-amino-5-hydrazino-1,3,4-thiadiazole on reaction with different cyclic anhydrides producing the corresponding bis amic acids which were subsequently introduced in dehydration reaction producing the desirable new compounds while the other two imides were prepared via direct reaction of 2-(Nmaleimidyl)- 5-hydrazino-1,3,4-thiadiazole with cyclic anhydride in glacial acetic acid under reflux conditions. The synthesized compounds were screened for their antimicrobial activity and were found to exhibit good to moderate antimicrobial activity against the tested organisms.