Copper‐Catalyzed Radical/Radical CH/PH Cross‐Coupling: α‐Phosphorylation of Aryl Ketone O‐Acetyloximes

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 3)-H/P-H 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-sp(3) -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.

Iodine‐Promoted Semmler–Wolff Reactions: Step‐Economic Access to meta‐Substituted Primary Anilines via Aromatization

“…Lei and co‐workers proved that the conjugated radical intermediates were possibly produced from ketone oxime derivatives under heating . The trap of a radical by TEMPO will lead to the quench of radicals (Scheme a) .…”

“…Therefore, our observations are preliminarily in agreement with a radical mechanism (Scheme c). The I 2 ‐mediated homolysis of N−O bond in oxime A gives imine radical B , which may quickly isomerize to α‐carbon radical C via 1,3‐H shift . Radical C undergoes two possible paths.…”

Silver‐Catalyzed Oxidative C(sp3)−P Bond Formation through C−C and P−H Bond Cleavage

“…[3] In particular, silver-triggered radical-type reactions,i ncluding oxidation, addition, coupling, and cyclization, have sprung up rapidly and become acuttingedge research area in organic chemistry in recent years. Herein, we disclose the development of an ovel silver-catalyzed tandem transformation of a1 ,3-dicarbonyl compound with an H-phosphonate involving oxidative C(sp 3 )ÀPb ond formation [5] followed by selective C(sp 3 )ÀC(CO) bond cleavage (Scheme 1d). Herein, we disclose the development of an ovel silver-catalyzed tandem transformation of a1 ,3-dicarbonyl compound with an H-phosphonate involving oxidative C(sp 3 )ÀPb ond formation [5] followed by selective C(sp 3 )ÀC(CO) bond cleavage (Scheme 1d).…”

Silver‐Catalyzed Aerobic Oxidative Decarboxylative Coupling of Arylpropiolic Acids with H‐Phosphine Oxides: Mild and Facile Synthesis of β‐Oxophosphine Oxides

“…[20] Very recently, Lei fulfilled a radical/radical C sp 3-H/P-H cross-coupling reaction leading to β-oxophosphine oxides with the assistance of CuCl and tricyclohexylphosphine (PCy 3 ; Scheme 1g). [21] …”