Synthetic and mechanistic aspects on the competition between C-H insertion and hydride transfer in copper-mediated transformations of α-diazo-β- keto sulfones

Competition between C-H insertion and hydride transfer is reported for the copper-catalysed reactions of a range of phenyl-substituted α-diazo- β-keto sulfones. Control of chemoselectivity is possible by alteration of the electronic properties of the diazo substrate. The production of enantioenriched cyclopentanones (up to 89% ee), formed via C-H insertion, and alkylidene tetrahydrofurans (up to 43% ee), produced via hydride transfer, is described. The isolation of products derived from hydride transfer provides mechanistic insight into the copper-mediated C-H insertion of α-diazoÂcarbonyl compounds.