A simple synthesis of stable phosphorus ylides containing cyano groups, from the reaction between triphenylphosphine and acetylenic esters in the presence of CH- acid compounds
Malek Taher Maghsoodlou,* Hamid Reza Shaterian, Ghasem Marandi, Fahimeh Shahraki Poor, and Jaber Salehzadeh
Department of Chemistry, The University of Sistan & Balouchestan, P. O. Box 98135-674, Zahedan, Iran
E-mail:
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Abstract
Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, in the presence of strong CH- acids such as malononitrile or ethyl cyanoacetate. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon–carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group.
Keywords: Acetylenic ester, CH- acids, stable phosphorus ylides, triphenylphosphine, geometrical isomer
Introduction
The synthesis of phosphorus ylides is important in organic chemistry because of their applications in the synthesis of organic products,1 especially the synthesis of naturally-occurring products with potentially useful biological and pharmacological properties.2 Phosphorus ylides are reactive intermediates, which take part in many valuable reactions in organic synthesis,3–5 and several methods have been developed for their preparation. These ylides are usually prepared by treatment of a phosphonium salt with a base, and phosphonium salts are usually prepared from the phosphine and an alkyl halide.1,6–10 Among other methods, phosphonium salts are also prepared by Michael addition of phosphorus nucleophiles to activated olefins.6–21 We report here an efficient synthetic route for the generation of stable phosphoranes bearing cyano groups via the reaction of triphenylphosphine with dialkyl acetylenedicarboxylates (1) in the presence of
