A Convenient One-Step, High-Yield Preparation of Methylphosphonyl Dichloride from Dimethyl Methylphosphonate

Based on a 1H and 31P nmr study of the interactions of alkyl-phosphonyl dichlorides, RP(O)Cl2, with dialkyl alkylphosphonates, RP(O)(OR)2, a method was developed for the preparation of CH3P(O)Cl2 (R [dbnd] CH3) in 98% yield. This method consists of the slow addition of the phosphonate to an excess of refluxing SOCl2, thus suppressing irreversible side reactions. For R [dbnd] C2H5, a yield of 72% was achieved; for R [dbnd] C4H9 and ClCH2CH2 pure product could not be isolated.