Selective Formation of Phosphonium Ylide or Iminophosphorane by Electroreduction of Alkylaminophosphonium Salt

Abstract

Electroreduction of alkylaminophosphonium salt has been utilized for the simple and safe preparation of the iminophosphorane without the use of the organic azide or dihalophosphorus compounds. An equimolar amount of electricity was applied to give one electron reduction products, from which hydrogen atom at alpha position was cleaved giving iminophosphorane and phosphonium ylide. Under the presence of aldehyde in this system, the reaction products were isolated and identified to elucidate the reaction paths involved. The onium salt with electron donating methyl group it gave only iminophosphorane quantitatively. On the other hand, the onium salt with electron withdrawing groups such as carbonyl groups yielded only phosphonium ylide quantitatively. In case of the onium salt with benzyl group, the mixed products from both Wittig and Aza-Wittig reactions were obtained.