Synthesis of novel N-heterocyclic carbene-Rh complexes derived from L-proline and their catalysis in the addition of arylboronic acids to aldehydes

Novel chiral imidazolium salts and a stable N-heterocyclic carbene-Rh complex derived from L-proline have been synthesized. The N-heterocyclic carbene-Rh complexes either generated in situ or pre-synthesized are active catalysts for the addition reaction of arylboronic acids to aldehydes affording the corresponding secondary alcohols in excellent yields.