Cleavage of alkenes by anodic oxidation

Abstract

Oxidative cleavage of olefinic double bonds to carboxylic acids, aldehydes or ketones is one of the important reactions in organic synthesis. Ozonolysis is mostly applied for this purpose, however, high costs for safety precautions in technical scale conversions demand alternatives. For this purpose different electrochemical methods are investigated. In the direct oxidation of cyclohexene at a platinum or graphite anode no cleavage occurs, but substituted and rearranged products are obtained. At the boron doped diamond electrode (BDDE) aliphatic olefins with high oxidation potential are not converted. Electrochemical ozonolysis by oxidation of water to ozone at the lead dioxide electrode leads to carboxylic acids as cleavage products in high material yield but low current yield. Anodic bromo-formyloxylation followed by an anodic cleavage provides a two step conversion of cyclohexene to hexane-1,6-dial derivatives. Thereby anodic discharge of bromide in formic acid leads to (2-bromocyclohexyl)-formate, which is converted to cyclohexane-1,2-diol and the major part of potassium bromide is recovered for the next cycle. This electrochemical conversion appears to be an attractive alternative to chemical oxidations with oxygen and catalysts or with hydrogen peroxide. The diol is cleaved in high yield to hexane-1,6-dial or its acetal either directly or indirectly with periodate as mediator.

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

“…Additionally, Shäfer has also reported an electrochemical method to generate ozone using a lead oxide anode—ozonolysis of olefins could be accomplished in good yields, albeit in modest current efficiencies. 500 …”

“…The use of a lead oxide/titanium composite electrode was found to be optimal for this process. Additionally, Shäfer has also reported an electrochemical method to generate ozone using a lead oxide anodeozonolysis of olefins could be accomplished in good yields, albeit in modest current efficiencies …”

Benzils: A Review on their Synthesis

“…In addition, the electrochemical method also often suffers from over oxidation. For example, anodic oxidation of alkenes [114a–b] and of 1,2‐diols [114c] and their derivatives often leads to carbon‐carbon bond cleavage. The present electrochemical method overcomes this unusual problem by integrating with an extremely mild chemical method such as DMSO oxidation.…”

Oxidative Alkene Cleavage by Chemical and Enzymatic Methods

“…The oxidation pathway apparently involved the corresponding 1,2‐diols, which were converted to the aldehydes in high yield under the same conditions. In another approach anodic bromo‐formyloxylation, followed by an anodic 1,2‐diol cleavage, resulted in overall double bond cleavage of cyclohexene to hexane‐1,6‐dial or its acetals 34…”