Transition metal promoted reactions of unsaturated hydrocarbons : II. Insertion of bicyclic olefins into allylic-palladium and -platinum bonds |
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Authors: | Russell P Hughes John Powell |
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Institution: | ]Lash Miller Chemical Laboratories, University of Toronto, Toronto 181, Ontario Canada |
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Abstract: | Addition of strained olefins, based on norbornene, norbornadiene,benzonorbornadiene or bicyclo 2.2.2] octene skeletons to π-allylic(hexafluoroacetylacetonato) palladium(II) complexes (π-All)Pd(Hfacac)], gives “enyl” products derived from “insertion” of the olefin into the least substituted terminal allylicpalladium bond. The reaction involves an initial rapid and reversible formation of (gs-allyl)(π-olefin)Pd(Hfacac). The rate-determining step involves migration of a σ-allylic carbon atom from Pd to the coordinated olefin in a concerted cis—exo addition of PdC across the double bond. Remote electronegative substituents on the olefin do not affect the coordinative ability of the olefin towards Pd. They do however inhibit the migration of the σ-allylic ligand to the coordinated olefin. This observation is interpreted in terms of a small degree of polarization of the π-olefin—Pd bond in the transition state for the σ-allyl migration. |
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Keywords: | Address correspondence to this author |
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