New potential fungicides pyrazole-based heterocycles derived from 2-cyano-3-(1,3-diphenyl-1 <i>H</i> -pyrazol-4-yl) acryloyl isothiocyanate
Sayed K. Ramadan, Nasser A. Ibrahim, Sarah Ahmed El-Kaed, Eman A. E. El‐Helw
Abstract
New series of pyrazole-based heterocyclic systems were synthesized using 2-cyanopropenoyl isothiocyanate derivative as an intermediate through treating with some nucleophilic reagents. Therefore, derivatives of carbamothioate, acylthiourea, pyrimidinethione, benzothiazole, triazolopyrimidine, pyrimidobenzothiazine, and pyrimidothiadiazepine were obtained. Structures of the obtained compounds were elucidated according to their elemental analyses and compatible spectral data. The fungicidal activity of the title compounds was evaluated against five plant pathogens belonging to both airborne and soil-borne strains using the radial growth rate method and the pyrazole derivative 13 was the most potent one that showed better fungicidal activity against F. Solani and R. Solani soil-borne fungi than the standard fungicide and moderate activity against airborne fungi. Also, pyrazole derivative 16 displayed better activity than the two standard fungicides against B. cinerea airborne fungus. Both A. Alternata and S. Sclerotiorum airborne fungi showed more resistance to the new pyrazoles than the standard fungicides. This means, fungicidal activity of the synthesized pyrazoles is remarkably diversified and affected by the heterocyclic ring or functional group attached to the core pyrazole.