Oxidative Homologation of Aldehydes to a-Ketoaldehydes by using Iodoform, o-Iodoxybenzoic Acid, and Dimethyl Sulf-oxide

An efficient three-step synthetic route to a-ketoaldehydes starting from aryl aldehydes is reported. The aldehydes were treated with iPrMgCl and iodoform to obtain beta-diiodoalcohols, which were then oxidized with o-iodoxybenzoic acid at room temperature to the corresponding beta-diiodoketones. Subsequent reaction of the beta-diiodoketone to the a-ketoaldehyde occurred under oxygen transfer from dimethyl sulfoxide. These sensitive products were in situ cyclized with o-phenylenediamine to form the stable monosubstituted quinoxalines, which could be characterized and isolated easily.