Mechanistic Insights into the Copper‐Catalyzed Cross‐Dehydrogenative Allylic Alkynylation Reaction

Abstract

Allylic functionalization reactions are an important tool for constructing many organic compounds, as they allow for the insertion of the versatile allyl group. Numerous catalytic processes have been developed, primarily utilizing noble metals such as palladium and pre‐functionalized substrates. Conversely, the copper‐catalyzed oxidative C‐H derivatization route, whether thermal or photocatalyzed, remains relatively underdeveloped. This is mostly due to the lack of a general concept and corresponding mechanistic understanding. Here we present a comprehensive analysis of the mechanism of this transformation. We utilized a range of spectroscopic techniques, including UV‐Vis, NMR, and EPR, single crystal x‐ray diffraction, as well as cyclovoltammetry, and DFT calculations. We propose that there are no free organic radicals involved in this cross‐dehydrogenative coupling, and that the reaction pathway is analogous to the well‐known Karash‐Sosnovsky reaction