One-pot synthesis of phosphorylsuccinates and triphenylphosphanylidenesuccinates containing a thioamido group

Stable substituted dialkyl phosphorylsuccinates were synthesized, as a mixture of two diastereoisomers, in high yields using one-pot reaction of dialkyl acetylenedicarboxylates, trialkyl phosphites, and thioamides in CH2Cl2 at room temperature. Using triphenylphosphine instead of phosphites, afforded stabilized triphenylphosphanylidenesuccinates. DFT calculations at B3LYP/6-31 + G(d) level indicated that among four possible conformational diastereoisomers of dimethyl 2-(dimethoxyphosphoryl)-3-ethanethioamidosuccinate, the (2R,3S) and (2S,3S) diastereomers are the most stable forms.