The oxidation of alcohols into their corresponding carbonyl compounds is one of the most fundamental transformations in organic chemistry. In our recent report, 2-azaadamantane N-oxyl (AZADO)/copper catalysis promoted the highly chemoselective aerobic oxidation of unprotected amino alcohols into amino carbonyl compounds. Herein, we investigated the extension of the promising AZADO/copper-catalyzed aerobic oxidation of alcohols to other types of alcohol. During close optimization of the reaction conditions by using various alcohols, we found that the optimum combination of nitroxyl radical, copper salt, and solution concentration was dependent on the type of substrate. Various alcohols, including highly hindered and heteroatom-rich ones, were efficiently oxidized into their corresponding carbonyl compounds under mild conditions with lower amounts of the catalysts.
The chemoselective oxidation of alcohols containing electron-rich sulfur functionalities (e.g., 1,3-dithianes and sulfides) into their corresponding carbonyl compounds with the sulfur groups can sometimes be a demanding task in modern organic chemistry. A reliable method for this transformation, which features azaadamantane-type nitroxyl radical/copper catalysis using ambient air as the terminal oxidant is reported. The superiority of the developed method was demonstrated by comparing it with various conventional alcohol oxidation methods.
Scope. -The corresponding carbonyl compounds are efficiently obtained under mild reaction conditions from various alcohols, including highly hindered and heteroatom-rich ones. It is found that the optimum combination of the nitroxyl radical, copper salt, and concentration of the solution depends on the type of the substrate. -(SASANO, Y.; KOGURE, N.; NISHIYAMA, T.; NAGASAWA, S.; IWABUCHI*, Y.; Chem. -Asian J. 10 (2015) 4, 1004-1009, http://dx.
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