Breathing air as oxidant: Optimization of 2-chloro-2-oxo-1,3,2-dioxaphospholane synthesis as a precursor for phosphoryl choline derivatives and cyclic phosphate monomers

Article abstract of DOI:10.1016/j.tet.2017.05.037

Phosphoryl choline derivatives are important compounds for drug development. Also other phosphoesters have received increased demand in recent years. Many of such compounds rely 2-chloro-2-oxo-1,3,2-dioxaphospholane (COP) as an intermediate. COP is available in a two-step reaction from the cyclic adduct of phosphorus chloride and ethylene glycol after oxidation. Although commercially available, in-house synthesis of COP is often required due to pricing, purity, and delivery issues. Air is a convenient and economical oxidizing agent, yet not used for synthesis of COP. While slow consumption of the P(III)-precursor 2-chloro-1,3,2-dioxaphospholane with molecular oxygen from a gas bottle, high amounts of unreacted oxygen are lavished and even may cause an explosion. Oxygen from air is a reasonable and safer alternative. Additionally, catalytic amounts of cobalt(II)chloride increase the reaction kinetics remarkably. The results presented allow a controlled and fast access to a variety of phosphoesters by optimized reaction conditions of COP and its derivatives.