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The Effects of Phosphorus Ligands on the Stereoselectivity of the Nickel-catalyzed Dimerization of Norbornadiene

1976; Oxford University Press; Volume: 49; Issue: 4 Linguagem: Inglês

10.1246/bcsj.49.1093

1348-0634

Susumu Yoshikawa, Jitsuo Kiji, Junji Furukawa,

Cyclopropane Reaction Mechanisms

Abstract The effects of phosphorus ligands on the stereoselectivity of the nickel-catalyzed 2+2 cyclodimerization of norbornadiene have been studied. The electronic factor, νCO(A1), of Ni(CO)3L (where L is the ligand) is correlated with the ratio of the exo-trans-exo (X-t-X) to the exo-trans-endo (X-t-N) isomers of the product, but no simple correlation is apparent between the steric parameter and the selectivity. A three-coordinated Ni(0) species is proposed as the intermediate. The values of ΔHX-t-X\eweq−ΔHX-t-N\eweq and ΔSX-t-X\eweq−ΔSX-t-N\eweq are large and negative.