Electrochemical Generation of Sulfonamidyl Radicals via Anodic Oxidation of Hydrogen Bonding Complexes: Applications to Electrosynthesis of Benzosultams.

Amidyl radicals and sulfonamidyl radicals are widely used in the field of organic synthesis. In particular, the electrochemical oxidation of amides in the presence of bases is one of the most practical methods for generating amidyl radicals. However, it is often difficult to observe the "true" radical precursor, such as an amide anion and/or a hydrogen bonding complex with an amide and a base. We found that a sulfonamide and BuNOAc form a 1:1 hydrogen bonding complex by spectroscopic experiments. Cyclic voltammetry suggested that 1:1 hydrogen bonding complexes should be oxidized predominantly under the optimized conditions to afford a sulfonamidyl radical via the proton-coupled electron transfer (PCET) process by the oxidation of the complex. Thus-generated sulfonamidyl radicals could be used in the electrochemical synthesis of a variety of benzosultams.