Studies on organophosphorous compounds: IX. C-Phosphorylation of compounds bearing an active methylene group

Abstract

The formation of P-C bond is one of the important problems in synthetic organophosphorous chemistry. This paper describes the study of the formation of P-C linkage via phosphorylation of carbon atom containing active hydrogen.p-Substituted phenylacetonitrile possessing an active methylene group undergoes stepwise C-phosphorylation smoothly with diethyl phosphoryl chloride in the presence of naphthalene-sodium. Phosphonyl chloride reacts analogously. Being a deprotonizing agent naphthalene-sodium is distinguished by its availability, effectiveness and mild reaction conditions. The presence of an electron-withdrawing group in the benzene ring reduces the yield of phosphorylation seriously. The chemical shift of ~31P NMR of the resulted α-cyano-benzylphosphonates (1) correlates linearly with the Hammett σ constants of the substituents. As indicated by ~1H NMR studies the protons in the ester ethyl groups are magnetically nonequivalent. Compound 1 can be alkylated with alkyl halide or condensed with aromatic aldehyde by Hornor-Wittig type reaction due to the presence of active hydrogen atom. The structure-reactivity studies of diethyl phosphoryl chloride on reacting with various β-diketones and β-keto esters (5) as regiospecific reaction were reported. The influences of metal ions in the enolates on the reactivity of the latter were examined and discussed. Only vinyl phosphates with predominantly Z configuration have been isolated exclusively. The 0 atom with an active hydrogen in the β-diketones investigated is inert to phosphorylation. These experimental results are well supported by reaction selectivity in terms of E_(q_o)/E_(CO_c) based on EHMO calculation.