The copper‐catalysed oxidation of unsaturated carbonyl compounds Part III: Oxidation of α,β‐ and β,γ‐unsaturated aldehydes and ketones by oxygen in the presence of cupric complexes

Abstract

Unsaturated (α,β‐ and β,γ‐) aldehydes and ketones, capable of forming a conjugated dienol can be oxidized under mild reaction conditions in the presence of catalytic amounts of cupric‐amine complexes in alkaline methanolic solution.Specific oxidation in the γ‐position is thought to occur with formation of a γ‐hydroperoxy α,β‐unsaturated carbonyl compound as a primary intermediate. The decomposition products of the γ‐hydroperoxide depend upon the number of hydrogen atoms attached to the γ‐carbon atom. A hydroperoxide group attached to a primary carbon atom is converted into an aldehyde function; likewise a secondary and a tertiary γ‐carbon atom lead to a keto and an alcohol function, respectively.The alcohols can be isolated as such, whereas products containing an aldehyde and a keto function form either cyclization products like unsaturated lactones, polyacetals or cyclic ethers or are cleft into esters and aldehydes.The mechanism of the oxidation reaction is discussed briefly.