Catalytic Carbonyl Z-Dienylation via Multicomponent Reductive Coupling of Acetylene to Aldehydes and α-Ketoesters Mediated by Hydrogen:  Carbonyl Insertion into Cationic Rhodacyclopentadienes

Jong Rock Kong and Michael J. Krische*
Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
J. Am. Chem. Soc., 2006, 128 (50), pp 16040–16041
DOI: 10.1021/ja0664786
Publication Date (Web): November 22, 2006
Copyright © 2006 American Chemical Society
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, mkrische@mail.utexas.edu

Abstract

Abstract Image

Exposure of aldehydes or α-ketoesters to equal volumes of acetylene and hydrogen gas at ambient temperature and pressure in the presence of cationic rhodium catalysts provides products of carbonyl Z-butadienylation, which arise via multicomponent coupling of four molecules:  two molecules of acetylene, a molecule of vicinal dicarbonyl compound, and a molecule of elemental hydrogen. The collective data suggest a catalytic mechanism involving carbonyl insertion into a cationic rhodacyclopentadiene intermediate derived via oxidative dimerization of acetylene. Hydrogenolytic cleavage of the resulting oxarhodacycloheptadiene via formal σ-bond metathesis provides the product of carbonyl addition and cationic rhodium(I) to close the catalytic cycle. Studies involving the hydrogenation of 1,6-diyne 14a in the presence of α-ketoester 6a corroborate the proposed catalytic mechanism. These multicomponent couplings represent the first use of acetylene gas, a basic chemical feedstock, in metal-catalyzed reductive C−C bond formation.

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History

  • Published In Issue December 20, 2006
  • Received September 7, 2006

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