Catalytic oxidation of internal epoxides by bismuth derivatives under molecular oxygen in DMSO affords the corresponding alpha-diketones. The influence of several parameters such as of the nature of the catalyst, Bi-(III) salts or Bi-(0), the solvent, the presence of additives and other oxidants has been examined. The preparation of a series of linear and cyclic, aliphatic and aromatic alpha-diketones is reported in 31-77% yields. (C) 2003 Elsevier B.V. All rights reserved.