Synthesis and molluscicidal activity of some new thiophene, thiadiazole and pyrazole derivatives

The base-catalyzed reaction of benzoyl acetone 1 with phenyl isothiocyanate yields the non-isolable intermediate 2. Treatment of 2 with dilute HCl afforded the corresponding thiocarbamoyl derivative 3. Reaction of the intermediate 2 with phenacyl bromide, ethyl bromoacetate, chloroacetonitrile, chloroacetyl chloride, bromodiethyl malonate and chloroacetone afforded the corresponding thiophene derivatives 5, 8, 15 and 17. The thiocarbamoyl derivative 3 reacts with arylazophenacyl bromide and/or hydrazine hydrate to afford the corresponding thiadiazole and pyrazole derivatives 20a-c and 22, respectively. These new synthesized compounds show generally a moderate molluscicidal activity to Biomphalaria alexandrina snails. (C) 2008 Elsevier Masson SAS. All rights reserved.