Synthesis and antifungal activity of novel analogs of boscalid

A series of novel 2-chloro-nicotinamides (3a-3h,5a-5n) were designed and synthesized based on the lead compound boscalid. The structures were characterized by 1H NMR, 13C NMR and HRMS. The preliminary results showed that most of the compounds possessed some fungicidal activity to seven phytopathogenic fungi at 50 μg/mL. Notably, compound 3h showed similar fungicidal activity and the broadest spectrum as boscalid. It exhibited the inhibition rate of 94.1% and 95.6% to the Colletotrichum orbiculare and Botrytis cinerea, respectively and the EC50 value against Rhizoctonia solani, C. orbiculare and Phytophthora infestans was 4.56,14.35 and 58.86 μg/mL, respectively.