Mild and efficient oxidation of catecholboron ketone enolates is performed by reaction with the persistent TEMPO radical. Catecholboron enolates are readily prepared via 1,4-reduction of α,β-unsaturated ketones, via "transmetallation" of silyl enol ethers and zinc enolates.
Enolate formation and oxidation can be performed as a one pot process with high regio- and stereoselectivity. This reaction demonstrates that enolyl radicals can be generated directly from boron enolate via a radical substitution process.

This work was carried out in the group of Prof. Philippe Renaud.

References:

• M. Pouliot, P. Renaud, K. Schenk, A. Studer and T. Vogler;
  "Oxidation of Catecholboron Enolates with TEMPO"
  Angew. Chem. Int. Ed., 48, 6037-6040, (2009); doi:10.1002/anie.200902242.