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Catalytic cyclopropanation of olefins using copper(I) diphosphinoamines

Ahuja, R and Samuelson, AG (2009) Catalytic cyclopropanation of olefins using copper(I) diphosphinoamines. In: Journal of Organometallic Chemistry, 694 (7-8). 1153 -1160.

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Abstract

Catalytic cyclopropanation reactions of olefins with ethyl diazoacetate were carried out using copper(I) diphosphinoamine (PPh2)(2)N(R) (R = Pr-i, H, Ph and -CH2-C6H4-CH=CH2) complexes at 40 degrees C in chloroform. High yields of the cyclopropanes were obtained in all cases. The rate of the reaction was influenced by the nuclearity of the complex and the binding mode of the ligand which was either bridging or chelating. Comparison of isostructural complexes shows that the rate follows the order R = Pr-i > H > Ph, where R is the substituent on the N. However, cyclopropane formation versus dimerization of the carbene, and trans to cis ratios of cyclopropane was similar in all cases. The nearly identical selectivity for different products formed was indicative of a common catalytic intermediate. A labile "copper-olefin" complex which does not involve the phosphine or the counterion is the most likely candidate. The differences in the reaction rates for different complexes are attributed to differences in the concentration of the catalytically active species which are in equilibrium with the catalytically inactive copper-phosphinoamine complex. To test the hypothesis a diphosphinoamine polymer complexed to copper(I) was used as a heterogeneous catalyst. Leaching of copper(I) and deactivation of the catalyst confirmed the proposed mechanism. (C) 2008 Elsevier B. V. All rights reserved.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier Science.
Keywords: Catalysis; Copper(I); Cyclopropanation; Diphosphinoamine; Ethyl diazoacetate; Olefin
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Depositing User: Users 920 not found.
Date Deposited: 05 Mar 2010 08:05
Last Modified: 19 Sep 2010 05:56
URI: http://eprints.iisc.ac.in/id/eprint/25953

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