Acylphosphonates as substrates for Wittig and Horner-Wittig reactions. Unusual stereoselectivity in the synthesis of β-phosphinoylacrylates

Abstract

Phosphorus-stabilized carbanions with additional stabilizing groups react with dialkyl acylphos- phonates (alkanoyl- and aroyl-phosphonates) to give fair to good yields of dialkyl vinylphosphonates, with some limitations imposed by competing side reactions of the acylphosphonates. β-Phosphinoyl-acrylates prepared by the Wittig reaction were almost exclusively (E)-olefins, whereas the corresponding Horner-Wittig reactions favoured (2) products. It is suggested that electronic interactions of substituents in the reaction intermediates play a role in determining this stereoselectivity.