Design, synthesis and biological evaluation of thiazole and imidazo[1,2-a]pyridine derivatives containing a hydrazone substructure as potential agrochemicals

Agricultural chemicals with multifunctional applications in crop protection have attracted increasing attention. Herein, two new series of thiazole and imidazo[1,2-a]pyridine derivatives containing a hydrazone substructure were designed and synthesized via a concise synthesis route. Bioassay results showed that most of the thiazole derivatives exhibited broad-spectrum fungistatic activities, which were exemplified by compounds 1c, 1e, 1g, 1h and 1j. In particular, compound 1e displayed excellent in vitro inhibitory effects with the EC₅₀ values of 5.00, 18.24, 6.94, and 3.03 μg/mL against the fungi Botrytis cinerea, Cytospora sp, Fusarium graminearum, and Fusarium solani, respectively. Detached fruit experiments against tomato gray mold (caused by B. cinerea) in vivo revealed that the control efficiency of compound 1e at 10, 20 and 40 μg/mL for 5 days was 35.05%, 54.14% and 81.83%, respectively, which was comparable and even superior to that of the fungicide carbendazim. Additionally, the title compounds also showed remarkable larvicidal activity against M. separata and some compounds exhibited good aphicidal activity. In a word, the bioassay indicated that a certain number of title compounds had multiple biological activities. Given their excellent antifungal and larvicidal characteristics, these interesting derivatives based on the title compounds could be served as new scaffolds for the development of pesticide with multifunctional applications.