Ligand‐Tailored Divergence of Copper‐Catalyzed Aerobic Oxidation of Cyclopropanols. Application to the Practical Synthesis of β‐Aminoketones and β‐Enaminones

Abstract

The aerobic ring‐opening oxidation of cyclopropanols catalyzed by copper complexes was systematically investigated, with a focus on the effect of nitrogen ligands on the distribution of oxidation products. This study led to the development of a new synthesis of β‐aminoketones and β‐enaminones from cyclopropanols, where product specificity is tuned through ligand and solvent selection. β‐Aminoketones were prepared in 34–99% yields by copper(II) acetate‐catalyzed aerobic oxidation of cyclopropanols in the presence of nucleophilic secondary aliphatic amines. In contrast, bipyridine‐ligated copper catalysts resulted in the generation of β‐enaminones in 36–86% yields, presumably via the Kornblum‐DeLaMare rearrangement of intermediate 1,2‐dioxolanes