3 research outputs found
Aldehydes and Ketones Form Intermediate π Complexes with the Gilman Reagent, Me<sub>2</sub>CuLi, at Low Temperatures in Tetrahydrofuran
Typical aldehydes
and ketones form π complexes with Me<sub>2</sub>CuLi at low
temperatures in tetrahydrofuran. They range in
stability from fleeting intermediates at −100 °C to entities
that persist up to −20 °C. Three subsequent reaction pathways
have been identified
Rapid Injection NMR Reveals η<sup>3</sup> ‘π-Allyl’ Cu<sup>III</sup> Intermediates in Addition Reactions of Organocuprate Reagents
By using rapid injection NMR, it has now been possible
to prepare
and characterize the η<sup>3</sup> ‘π-allyl’
copperÂ(III) intermediate that has been proposed for addition reactions
of organocopperÂ(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 Ï€-complexes of lithium dimethylcuprateÂ(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 η<sup>2</sup> 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<sup>III</sup> intermediates