An Electrocatalytic Cascade Reaction for the Synthesis of Ketones Using CO2 as a CO Surrogate

Abstract

AbstractThe construction of carbonyl compounds via carbonylation reactions using safe CO sources remains a long‐standing challenge to synthetic chemists. Herein, we propose a catalyst cascade Scheme in which CO2 is used as a CO surrogate in the carbonylation of benzyl chlorides. Our approach is based on the cooperation between two coexisting catalytic cycles: the CO2‐to‐CO electroreduction cycle promoted by [Fe(TPP)Cl] (TPP=meso‐tetraphenylporphyrin) and an electrochemical carbonylation cycle catalyzed by [Ni(bpy)Br2] (2,2′‐bipyridine). As a proof of concept, this protocol allows for the synthesis of symmetric ketones from good to excellent yields in an undivided cell with non‐sacrificial electrodes. The reaction can be directly scaled up to gram‐scale and operates effectively at a CO2 concentration of 10 %, demonstrating its robustness. Our mechanistic studies based on cyclic voltammetry, IR spectroelectrochemistry and Density Functional Theory calculations suggest a synergistic effect between the two catalysts. The CO produced from CO2 reduction is key in the formation of the [Ni(bpy)(CO)2], which is proposed as the catalytic intermediate responsible for the C−C bond formation in the carbonylation steps.