Catalytic Functionalization of Indoles by Copper‐Mediated Carbene Transfer. Issue 7 (24th June 2014) - Delgado‐Rebollo, Manuela
Abstract The complex [TpBr3Cu(NCMe)] (TpBr3=hydrotris(3, 4, 5‐tribromo)pyrazolylborate) efficiently catalyzes the CH functionalization of indole derivatives at C3 by carbene transfer from different diazoesters in a high‐yield transformation involving low catalyst loadings and short reaction times. This system has shown that the previously proposed dichotomy of carbene addition (to the double bond) vs carbene insertion (to the CH bond) corresponds to two consecutive reaction steps: the cyclopropane intermediates, observed in the reaction mixtures, are the precursors of the final CH functionalization derivatives in a ring‐opening process involving acid catalysis. Those in situ generated cyclopropanes undergo nucleophilic ring opening with Me2CuLi to afford both C2 and C3 functionalized indoles.