Chapter 5 - Reductive Bond Cleavage Processes-II

Abstract

The carbon-heteroatom bonds in saturated alkyl alcohols, ethers, sulphides, and amines cannot be cleaved by electrochemical reduction. This situation is modified substantially by the presence of an adjacent unsaturated group. Reaction can be initiated by addition of an electron to the π-antibonding orbital leading to an overall two-electron cleavage of a carbon-heteroatom bond. Aliphatic alcohols are not reducible under electrochemical conditions. Conversion to a suitable anionic leaving group, however, does allow a carbon-oxygen bond cleavage. Thus, methanesulphonates are reduced at a lead electrode under constant current conditions, and this affords an overall two-step process for the conversion of alcohols to alkanes. Deoxygenation of alcohols by this route has been applied successfully in the presence of other functional groups, which are difficult to reduce such as alkene, epoxide, ester, and nitrile. Carbon-oxygen bonds adjacent to an aromatic ring or an alkene function can be cleaved by reduction at very negative potentials. The process is often followed by reduction of the activating group.