Direct Phosphate Triester Synthesis via Condensation of Phosphoric Acid with Alcohols and Unsymmetrical Phosphate Triester Synthesis via Esterification of Diaryl Phosphates

Phosphorus is a critical element for agriculture and industrial applications, but it is finite and geographically localized. This study addresses the challenge of phosphorus resource depletion by developing a direct triesterification method for ubiquitously available phosphoric acid, thereby bypassing the use of white phosphorus. We demonstrate that phosphoric acid can be directly converted into phosphate triesters using alcohols and N,N-dimethylformamide. The reaction exhibited a substrate scope for primary saturated and unsaturated aliphatic alcohols in isolated yields of 39–94%, whereas secondary alcohols, low-boiling alcohols, phenol, and benzyl alcohol showed limitations. This approach was further extended to the synthesis of unsymmetrical phosphate triesters from diaryl phosphate diesters, and monoalkyl diaryl phosphates were obtained in isolated yields of 23–58%. Overall, this study offers a practical and resource-conscious alternative for the direct synthesis of industrially valuable phosphate triesters from phosphoric acid, thereby reducing the reliance on phosphate rock or white phosphorus.