Rediscovering copper-based catalysts for intramolecular carbon-hydrogen bond functionalization by carbene insertion.

A series of Tp(x)Cu complexes (Tp(x) = hydrotrispyrazolylborate ligand) have been tested as catalysts for the decomposition of several diazoacetates and N,N-disubstituted diazoacetamides and the subsequent formation of lactones and lactams, respectively. The complexes containing the ligands Tp(Br3) or Tp(Ms) have provided activities and selectivities for these transformations comparable with or, in some cases, better than the well-known rhodium catalyst Rh(2)(OAc)(4).