Design, synthesis, DFT study and antifungal activity of the derivatives of pyrazolecarboxamide containing thiazole or oxazole ring.

Pyrazolecarboxamide fungicides are one of the most important classes of agricultural fungicides, which belong to succinodehydrogenase inhibitors (SDHIS). To discover new pyrazolecarboxamide analogues with broad spectrum and high activity, a class of new compounds of pyrazole carboxamide derivatives containing thiazole or oxazole ring were designed by scaffold hopping and bioisosterism, and 36 pyrazole carboxamide derivatives with antifungal activity were synthesized. Those compounds were evaluated against five phytopathogenic fungi, Gibberella zeae, Phytophythora capsici, Sclerotonia sclerotiorum, Erysiphe graminis and Puccinia sorghi. The results indicated that most of the compounds displayed good fungicidal activities, especially against E. graminis. Theoretical calculations were carried out at the B3LYP/6-31G (d, p) level and the full geometry optimization was carried out using the 6-31G (d, p) basis set, and the frontier orbital energy, atomic net charges, molecular docking were discussed, and the structure-activity relationships were also studied.