Synthesis and Evaluation of Novel 1,2,3,4-Tetrahydroquinoxaline Derivatives as Potential Fungicidal Agents

Nitrogen-containing heterocyclic compounds play a significant role in the development of novel pesticides. To promote the discovery and development of new fungicides, a series of 1,2,3,4-tetrahydroquinoxaline derivatives were synthesized and assessed for their fungicidal activities. Bioassays demonstrated that compound <b>B1</b> exhibited significant fungicidal activity against <i>Gaeumannomyces graminis</i> var. <i>tritici</i>, <i>Botrytis cinerea</i>, and <i>Valsa mali</i>, with EC₅₀ values of 0.486, 1.83, and 3.66 mg/L, respectively. In particular, compound <b>B1</b> showed good fungicidal efficacy against <i>G</i>. <i>graminis</i> compared to the positive control <b>Tebuconazole</b> (EC₅₀ = 0.625 mg/L). <i>In vivo</i> studies revealed that at 200 mg/L, compound <b>B1</b> exhibited inhibition rates of 39.7% and 78.7% against <i>G. graminis</i> and <i>B. cinerea</i>, respectively. Mechanistic investigations indicated that compound <b>B1</b> enhanced cell membrane permeability and disrupted membrane integrity, potentially hindering normal mycelial growth. This study provides insights into the potential of 1,2,3,4-tetrahydroquinoxaline derivatives as promising agricultural fungicides.