Remote anodic oxidation of carboxylic acids in fluorosulphuric acid: a synthesis of lactones and unsaturated cyclic ketones

Abstract

The oxidation of octanoic, heptanoic, 4-methylpentanoic, and 5-methylhexanoic acids at a smooth platinum anode in fluorosulphuric acid containing potassium fluorosulphate (1M) at 273 K is described. Oxidation leads to cleavage of a C–H bond and formation of a cationic centre at a place in the carbon skeleton remote from the functional group. The final products isolated are 5- and 6-membered ring compounds, lactones, and unsaturated cyclic ketones, and the ratio of products depends on the length of time the anolyte solution is left prior to work-up. A mechanism which explains the formation of all products is suggested.