Expansion of Substrate Scope for Nitroxyl Radical/Copper-Catalyzed Aerobic Oxidation of Primary Alcohols: A Guideline for Catalyst Selection

Four distinctive sets of optimum nitroxyl radical/copper salt/additive catalyst combinations have been identified for accommodating the aerobic oxidation of various types of primary alcohols to their corresponding aldehydes. Interestingly, less nucleophilic catalysts exhibited higher catalytic activities for the oxidation of particular primary allylic and propargylic alcohols to give alpha, beta-unsaturated aldehydes that function as competent Michael acceptors. The optimum conditions identified herein were successful in the oxidation of various types of primary alcohols, including unprotected amino alcohols and divalent-sulfur-containing alcohols in good-to-high yields. Moreover, N-protected alaninol, an inefficient substrate in the nitroxyl radical/copper-catalyzed aerobic oxidation, was oxidized in good yield. On the basis of the optimization results, a guideline for catalyst selection has been established.

Automated summary

Four distinctive sets of optimal nitroxyl radical/copper salt/additive catalyst combinations have been identified for aerobic oxidation of various primary alcohols to their corresponding aldehydes. Less nucleophilic catalysts showed higher catalytic activities for oxidation of specific primary allylic and propargylic alcohols. The identified optimum conditions successfully oxidized various primary alcohols, including unprotected amino alcohols and divalent-sulfur-containing alcohols.