Insensitivity to steric hindrance of a nucleophilic, neighbouring-group substitution at pentavalent phosphorus

Abstract

The reactions of ethyl α-hydroxyimino-p-nitro-benzyl alkylphosphonates (III; R = Me, Et, Bu^t), and the α-hydroxyimino-p-nitrobenzyl esters of 1-hydroxy-2,2,3,4,4-pentamethyl- and -2,2,3-trimethyl-1-oxo-phosphetans [I, II; X = C(:NOH)·C₆H₄·NO₂-p] at pH 8–9 proceed at rates independent of steric factors to give p-nitroaniline and the corresponding phosphonic or phosphinic acid, in marked contrast to the corresponding alkyl esters.