NMR Spectroscopic Evidence for π-Complexation and the Formation of a Yinylcopper Intermediate in the Reaction between Methyl phenylpropiolate and ~tBuCu(CN)Li

摘要

Organocuprates have proved to be versatile tools in organic synthesis. The applicability of the organocuprate reactions could be even more powerful if the mechanisms were fully understood. The mechanistic model often used for the addition to enones and enoates assumes a nucleophilic addition of the cuprate to the π-bond. A transient square-planar intermediate, the controversial Cu(III) species, is believed to precede the formation of the carbon-carbon bond. Alternatively, the reaction can be seen as an addition across the π-bond leading to an α-cuprio carbonyl compound.