Synthesis and Evaluation of Antimicrobial Activity of Some Novel Heterocyclic Compounds from 5-Bromosalicylaldehyde

A novel series of coumarins, thiadiazoles, thiazoles, and pyridines were synthesized via reaction of 5-bromosalicylaldehyde with different reagents. Thus, 5-bromosalicylaldehyde 1 was reacted with compounds 2a-d affording iminocoumarins 3a-d, which on hydrolysis with 10% hydrochloric acid, afforded coumarins 4a-d, respectively. On the other hand, reaction of 1 with benzylhydrazinecarbodithioate 5 afforded derivative 6, which reacted with hydrazonoyl halides 7a-f, afforded 1,3,4-thiadiazoles 11a-f, respectively. Moreover, thiazoles 15 and 16 were obtained via reaction of 1 with thiocarbohydrazide 13 and hydrazonoyl halides. However, condensation of 2-acetyl-5-bromobenzofuran 17 with benzaldehyde afforded chalcone 18, which reacted with pyridiniumbromides 19a-c, afforded pyridines 20a-c, respectively. Furthermore, pyridines 21-24 were synthesized from the reaction of chalcone 18 with different active methylene compounds. Reaction of 24 with ethylchloroacetate, chloroacetone, and chloroacetonitrile afforded thienopyridines 26a-c, respectively. The structures of the newly synthesized compounds were established based on their spectral data and elemental analyses. Also, selected newly synthesized compounds were screened for their antimicrobial activity against various microorganisms by disk diffusion method.