One-pot synthesis of 1-ethynylcyclohexyl vinyl ether from cyclohexanone and acetylene

Abstract

Vinyl ether derived from tertiary acetylenic alcohols have not been reported so far. The reason is that such alcohols are unstable on heating in the presence of bases (classical retro-Favorskii reaction) [1–3]. Nevertheless, insofar as the Favorskii reaction is reversible, we can presume that O-vinylation of a tertiary acetylenic alcohol present in the reaction mixture even at a small concentration should eventually lead to expected vinyl ether due to continuous displacement of the equilibrium (Scheme 1). Therefore, vinyl ethers of tertiary acetylenic alcohols could be obtained in one step by heating ketones with acetylene in the presence of a base. Screening of the reaction conditions and superbasic catalytic systems, as well as of ketones and acetylenic compounds used as reactants, has shown that 1-ethynylcyclohexyl vinyl ether (III) is indeed formed upon treatment of cyclohexanone (I) with acetylene in the presence of a base. In the reaction performed in a suspension of KOH in DMSO (molar ratio I–KOH 1 : 1) at 90°C under acetylene pressure the yield of vinyl ether III reached 40% (Scheme 2). An important condition is acetylene pressure which ensures its high concentration in the liquid phase and favors displacement of equilibrium toward formation of 1-ethynylcyclohexan-1-ol (II) which then undergoes vinylation (Scheme 2). ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 6, pp. 858–859. © Pleiades Publishing, Ltd., 2012. Original Russian Text © B.A. Trofimov, E.Yu. Shmidt, I.A. Bidusenko, E.V. Ivanova, N.V. Zorina, A.I. Mikhaleva, 2012, published in Zhurnal Organicheskoi Khimii, 2012, Vol. 48, No. 6, pp. 860–861.