Synthesis of phosphaformamidines and phosphaformamidinates.

A large-scale synthetic route to a variety of phosphaformamidines and phosphaformamidinates, a type of derivative that was not accessible by the methods previously known for preparing phosphaamidines and phosphaamidinates, is reported. Thermally stable ethyl N-arylformimidates 1 (ArN=CH(OEt), Ar = 2,4,6-(Me)3Ph or 2,6-(iPr)2Ph) readily reacted with lithium dialkyl- and diarylphosphanides to afford the corresponding N-aryl phosphaformamidines in 80 and 60% yield, respectively, whereas with lithium (aryl)(silyl)phosphanide, the N-aryl-N-silylphosphaformamidine (60% yield) was obtained. Addition of primary lithium arylphosphanides to 1 followed by addition of a stoichiometric amount of nBuLi gave rise to the respective phosphaformamidinates (70-88% yield). Methanolysis of the products afforded the N-aryl-N-hydrogenophosphaformamidines (90-95% yield). The solid-state structure of one of the phosphaformamidinates is also presented.