Alkyl di-t-butylphosphinites. Exceptionally halogenophilic phosphinites in Arbuzov reactions

Abstract

Methyl and ethyl di-t-butylphosphinite have been prepared and reactions of the latter with a number of alkyl halides investigated. Normal Arbuzov products, Bu^t₂RPO, are the predominant or sole products for RX = Mel, Etl, PhCH₂Br, Br(CH₂)₃Br, BrCH₂CH₂OPh, ClCH₂COOEt, and ClCH₂CONH₂. For RX = ClCH₂CN, CH₂I₂ and BrCH₂CH₂Br the main products are Bu^t₂P(O)X, and for RX = ClCH₂COCH₃ and ClCH₂P(O)Ph₂ both products are formed. The reaction mixtures have been analysed mostly by ¹H n.m.r. spectroscopy, and major products have been isolated and characterized and plausible reaction pathways outlined. It is shown that Bu^t₂P(O)X arises from attack of Bu^t₂POEt on the halogen of RX, the pronounced halogenophilicity of Bu^t₂POEt being ascribed to steric hindrance from the t-butyl groups.