Copper-Catalyzed Radical/Radical C sp 3H/PH Cross-Coupling: α-Phosphorylation of Aryl Ketone O-Acetyloximes†

TLDR: In this paper, a copper-catalyzed radical/radical C sp 3H/PH cross-coupling has been developed, which provides a radical/ radical cross coupling in a selective manner, in which aryl ketone o-acetyloximes and phosphine oxides were suitable for this transformation.

Abstract: The selective radical/radical cross-coupling of two different organic radicals is a great challenge due to the inherent activity of radicals. In this paper, a copper-catalyzed radical/radical C sp 3H/PH cross-coupling has been developed. It provides a radical/radical cross-coupling in a selective manner. This work offers a simple way toward β-ketophosphonates by oxidative coupling of aryl ketone o-acetyloximes with phosphine oxides using CuCl as catalyst and PCy3 as ligand in dioxane under N2 atmosphere at 130 °C for 5 h, and yields ranging from 47 % to 86 %. The preliminary mechanistic studies by electron paramagnetic resonance (EPR) showed that, 1) the reduction of ketone o-acetyloximes generates iminium radicals, which could isomerize to α-sp3-carbon radical species; 2) phosphorus radicals were generated from the oxidation of phosphine oxides. Various aryl ketone o-acetyloximes and phosphine oxides were suitable for this transformation.