Reactions of phosphines with aluminum carbenoids

Abstract

Metal carbenoids are known as highly reactive compounds that are often used as intermediates in the organic synthesis [1, 2]. We formerly studied the reactions with acetylenes of various structures of aluminum carbenoids obtained in situ from CH2I2 and trialkylalanes [3–5]. It was established that the structure of compounds obtained and the mechanism of their formation essentially depended on the nature of the substituent at the acetylene bond. In order to elucidate the role of the nature of the substituent at the acetylene bond we studied the transformation of organophosphorus acetylenes under the action of the aluminum carbenoids. The reaction of hex-1-yn-1-yl(diphenyl)phosphine with the obtained in situ diethyl(iodomethyl)aluminum Et2AlCH2I [6] after treating the mixture with deuterium oxide afforded 1-hexynyl-(deuteromethyl) diphenylphosphonium iodide (Iа) in a quantitative yield. The structure of the compound obtained was confi rmed by an authentic synthesis of hex-1-yn-1-yl(diphenyl) phosphonium iodide (IIa) by the reaction of hex-1-yn1-yl(diphenyl)phosphine with 1 equiv of MeI without solvent The 13C and 1H NMR spectra of thus prepared phosphonium salt and the hydrolysis product of the reaction mixture were identical. In the 13C NMR spectrum of compound Ia a doublet of triplets was observed at δ 14.00 ppm due to the coupling of carbon atom with phosphorus and deuterium nuclei. Thus it was established that the reaction of (hex-1yn-1-yl)diphenylphosphine with aluminum carbenoid Et2AlCH2I led to the formation of a phosphonium salt, and the acetylene bond was not involved into the reaction. In this case the C–I bond in the aluminum carbenoid was more reactive than the metal–carbon bond. Besides the