Synthesis and evaluation of a new class of ruthenium-based catalytic systems for atom transfer radical addition and enol ester synthesis

We now report the synthesis and characterization of a new class of N-heterocyclic carbene (NHC) and Schiff base containing ruthenium complexes and their performance as catalysts in atom transfer radical addition and enol ester synthesis reactions. The ruthenium Schiff base complexes 3a–f mediated the atom transfer radical addition (ATRA) of carbon tetrachloride across olefins in excellent yields which markedly depended on the catalyst and the substrate used. Furthermore, dependant on the catalytic system and the reaction conditions used, enol esters or enynes can be obtained in excellent yields with very high selectivities.