Greener synthesis and antimicrobial activity of some coumarin analogues

Abstract

Herein, a rapid, clean, less expensive and environmental friendly route to a novel series of coumarins bearing thiazoles or 1,3,4- H thiadiazoles was developed via grinding method. Thus, 6-bromo-3-(2-bromoacetyl)-2-chromen-2-one was treated with cyanothioacetamide to produce thiazole-2-acetonitrile derivative 2, which was then transformed to iminocoumarins by reacting with hydroxyaldehydes. Hydrolysis of iminocoumarins by Conc. HCl furnished coumarins. Furthermore, treatment of compound 2 with phenylisothiocyanate produced thioanilide. Reaction of the latter with hydrazonoyl halide and / or α-halocarbonyl compounds afforded 1, 3, 4-thiadiazole and thiophene derivative, consequently. All the newly prepared coumarins were screened against six pathogenic microorganisms. The results indicated that compounds 7 and 12 were the most effective against B. pumilis, while compound 4b was highly active against S. faecalis. Also, compound 5b was highly active against E. cloacae. Compounds 2 and 7 were higher active compared with reference drug ketoconazole against fungi S. cerevisiae.