New Preparation of Diethyl Methylformyl-2-phosphonate Dimethylhydrazone: A Reagent for Aldehyde Homologation

The phosphonate reagent diethyl methylformyl-2-phosphonate dimethylhydrazone contains a protected aldehyde group instead of the usual ester group. It can be used for the two-carbon homologation of aldehydes to α, -unsaturated aldehydes. The reagent can be prepared in good overall yield (82%) and purity by deprotection of commercially available diethyl-2,2-(diethoxy)ethylphosphonate with p-toluenesulfonic acid in 1.5% aqueous acetone to give diethyl formylmethyl-2-phosphonate, followed by a simple preparation of the dimethylhydrazone derivative with N,N-dimethylhydrazine.