Rapid Injection NMR Reveals η³ ‘π-Allyl’ Cu^III Intermediates in Addition Reactions of Organocuprate Reagents

By using rapid injection NMR, it has now been possible to prepare and characterize the η³ ‘π-allyl’ copper­(III) intermediate that has been proposed for addition reactions of organocopper­(I) reagents and α,β-unsaturated carbonyl compounds

Complexes of the Gilman Reagent with Double Bonds across the π–σ Continuum

By using rapid injection NMR at low temperatures, a variety of π-complexes of lithium dimethylcuprate­(I) with C–C, C–N, and C–S double bonds have been prepared and characterized. Complexation is generally accompanied by large upfield changes in chemical shift for the substrate carbon atoms bonded to copper. In the case of α,β-unsaturated carbonyl compounds, the changes for the carbonyl carbons are much smaller in magnitude, which is consistent with the usual η² representation of these structures. It is possible for one ligand to displace another, and in this way an order of stability can be elucidated. Treatment of selected π-complexes with chlorosilanes or cyanosilanes gives Cu^III intermediates