Rapid Catalysis for Aerobic Oxidation of Alcohols Based on Nitroxyl-Radical-Free Copper(II) under Ambient Conditions

Aerobic oxidation of alcohols is one of the most important methods for the production of aldehydes. In this work, a scalable, continuous flow synthesis method for the aerobic oxidation of alcohols using a copper catalyst with redox-active ligand and molecular oxygen (O-2, air) was developed. The yield of benzaldehyde could reach 93.4% by optimizing the following conditions, such as copper content, solvent, O-2 flow rate, and temperature. This synthesis method exhibited excellent functional group compatibility for various alcohols with excellent reactivity and reusability, avoiding the use of some nitroxyl radicals (TEMPO, ABNO) or base additives. In the microchannel reactor, the total reaction time could be reduced from 24 h to 40 min, and a simplified kinetic model was established.

Automated summary

A scalable, continuous flow synthesis method for the aerobic oxidation of alcohols using a copper catalyst and molecular oxygen was developed, showing high yield of benzaldehyde by optimizing conditions. The method demonstrated fast reaction kinetics and a simplified kinetic model in a microchannel reactor.