Design, Synthesis and Fungicidal Activity of N -(thiophen-2-yl) Nicotinamide Derivatives.

Based on the modification of natural products and the active substructure splicing method, a series of new -(thiophen-2-yl) nicotinamide derivatives were designed and synthesized by splicing the nitrogen-containing heterocycle natural molecule nicotinic acid and the sulfur-containing heterocycle thiophene. The structures of the target compounds were identified through H NMR, C NMR and HRMS spectra. The in vivo bioassay results of all the compounds against cucumber downy mildew (CDM, (Berk.et Curt.) Rostov.) in a greenhouse indicated that compounds (EC = 4.69 mg/L) and (EC = 1.96 mg/L) exhibited excellent fungicidal activities which were higher than both diflumetorim (EC = 21.44 mg/L) and flumorph (EC = 7.55 mg/L). The bioassay results of the field trial against CDM demonstrated that the 10% EC formulation of compound displayed excellent efficacies (70% and 79% control efficacies, respectively, each at 100 mg/L and 200 mg/L) which were superior to those of the two commercial fungicides flumorph (56% control efficacy at 200 mg/L) and mancozeb (76% control efficacy at 1000 mg/L). -(thiophen-2-yl) nicotinamide derivatives are significant lead compounds that can be used for further structural optimization, and compound is also a promising fungicide candidate against CDM that can be used for further development.