Phosphonylation of 3-Substituted 2H-Benzo[b][1,4]oxazin-2-ones and Quinoxalin-2(1H)‑ones with Dialkylphosphites Under mild Conditions: Access to Diverse Heterocyclic α-Aminophosphonates

An efficient protocol for the phosphonylation of 3-substituted quinoxalin-2(1H)‑ones and 2H-benzo[b][1,4]oxazin-2-ones with dialkylphosphites has been developed. This method provides a novel and more sustainable approach to access structurally diverse quaternary heterocyclic α-aminophosphonates in good yields under solvent and metal-free conditions. Additionally, we report the phosphonylation of 3,4-dihydroquinoxalin-2(1H)-one via the corresponding N-acyl iminium ion, providing efficient access to (1,2,3,4-tetrahydroquinoxalin-2-yl)phosphonate in good yield.