Cu(III)‐CF3 Compound‐Activated DMSO: An Efficient Oxidizing Reagent to Convert Alcohols to Ketones

In this study high-valent Cu(III) trifluoromethyl compounds in combination with DMSO is shown to be an efficient and mild oxidizing system for the conversion of alcohols to ketones (aldehydes as well). Trifluoromethoxylated sulfonium species is proposed to be initially formed that engages in crucial steps of alkoxy replacement at sulfonium center and deprotonative collapse of the resulting alkoxysulfonium intermediate in the presence of a base. This reaction is highly selective without over-oxidation, and can tolerate a broad range of functional groups owing to mild oxidizing ability of the Cu(III)-CF3/DMSO system and the inert N2 conditions. This method can be applied to the synthesis and functionalization of commercial drug compounds. This study illustrates an unusual reactivity property of high-valent Cu(III) trifluoromethyl compounds beyond the conventional CF3 group transfer reactivity, and opens up new opportunities for developing novel reactions of Cu(III)-CF3 compounds. The combined use of high-valent Cu(III)-CF3 compound and DMSO is anticipated to find more applications to develop other novel and useful oxidation reactions.