Synthesis and molluscicidal evaluation of some new pyrazole, isoxazole, pyridine, pyrimidine, 1,4-thiazine and 1,3,4-thiadiazine derivatives incorporating benzofuran moiety

Chalcone derivative 3 was synthesized via the base catalyzed Claisen–Schmidt condensation and was used as a precursor for synthesizing pyrazoline 11, isoxazoline 12, pyrazoline carbothioamide 13, 5,6-dihydropyrimidine-2-(1H)-thione 14 and aminopyridinecarbonitrile derivative 15. Bromination of 3 afforded the dibromo derivative 4. Monobromo derivative 5 obtained by boiling 4 in dry benzene in the presence of triethylamine. Fused thiadiazines 9a,b and 1,4-thiazine 9c derivatives were synthesized upon treatment of α-bromopropenone derivative 5 with 4-amino-4H-1,2,4-triazole-3-thiol (6) or 1-amino-2-mercapto-5-methylpyrimidin-4(1H)-one (7) or with 2-aminothiophenol (8) in ethanolic potassium hydroxide solution. The newly synthesized compounds were screened for their molluscicidal activities, whereas compounds 3, 4, 9a, 11 and 15 exhibited promising molluscicidal activities. On the other hand compounds 5, 9b, 9c, 12, 13 and 14 showed a moderate effect as compared to the standard molluscicidal agent (Bayluscide).

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