A Fresh Look at the Staudinger Reaction on Azido Esters: Formation of 2H‑1,2,3-Triazol-4-ols from α‑Azido Esters Using Trialkyl Phosphines

Phenyl esters of α-azido acids react with trialkylphosphines in THF/H2O to give 5-substituted 2H-1,2,3-triazol-4-ols in good to excellent yields. In contrast, their reaction with PPh3 in THF/H2O give the amino esters as the major product and no triazoles. Reaction between an α-azido phenyl ester and P­(OEt)3 provided the corresponding phosphoramidate in excellent yield, but no triazole was formed.