Synthesis and fungicidal activity of aryl(arylamino)methylphosphonic acids

A series of aryl(arylamino)methylphosphonic acids were synthesized based on the previous work for the modification of alkylphosphonates. As key intermediates, α-aminophosphonates were synthesized with high yield by a three-component Kabachnik–Fields reaction under solvent-free conditions. The compounds were identified and characterized by infrared, ¹H NMR, ¹³C NMR, mass spectrum, and elemental analyses. Their fungicidal activities against typical fungi occurring in the Chinese agro-ecosystems were evaluated. The results of preliminary bioassays showed that some of the title compounds exhibited moderate fungicidal activities against tomato late blight and cucumber fusarium wilt. For example, compound 3b showed 78% inhibitory activity against tomato late blight, and compound 3h possessed 86% inhibitory activity against cucumber fusarium wilt.