Synthesis, Antifungal Activity, and DFT Calculation Study of Novel 1-Acyl-5-amino-1,2,4-triazole-thioether Derivatives Containing Natural gem-Dimethylcyclopropane Ring Structure

A series of novel 1-acyl-5-amino-1,2,4-triazole-thioether derivatives containing natural gem-dimethylcyclopropane ring structure were synthesized from natural biomass resource 3-carene. Their structures were confirmed by FT-IR, NMR, ESI-MS, and elemental analysis. The possible mechanism of regioselectivity for the N-acylation reaction of 5-amino-1,2,4-triazole with 2-(2,2-dimethyl-3-propylcyclopropyl) acetyl chloride was explored by DFT theoretical calculation. All the target compounds were evaluated for antifungal activity in vitro against eight plant pathogens, and some target compounds showed good inhibitory activity against the tested pathogens. For example, compounds 1-(5-Amino-3-((4-chlorobenzyl)thio)-1H-1,2,4-triazol-1-yl)-2-(2,2-dimethyl-3-propylcyclopropyl)ethan-1-one and 1-(5-Amino-3-((2,6-dichlorobenzyl)thio)-1H-1,2,4-triazol-1-yl)-2-(2,2-dimethyl-3-propylcyclopropyl)ethan-1-one exhibited inhibitory rates of 81.6 % and 80.9 % against Cercospora arachidicola and Alternaria solani, respectively, better than that of the commercial fungicide thifluzamide with corresponding inhibitory rates of 75.0 % and 78.6 %. Besides, against Gibberella zeae, most of the target compounds displayed better antifungal activity than the positive control thifluzamide.