Ruthenium and osmium complexes in CC bond-forming reactions by borrowing hydrogen catalysis

Abstract This review deals with the application of ruthenium and osmium complexes in C C bond-forming reactions by borrowing hydrogen (BH) or hydrogen autotransfer (HA) catalysis, describing the considerable progress made over the years by these metal-complexes in the α-alkylation of ketones, β-alkylation of secondary alcohols, C-alkylation of relatively inactivated substrates bearing fewer acidic α-hydrogens (acetonitriles, acetamides, esters, etc.) with alcohols, and in the formation of other C C bonds using alcohols as substrates (or reactants). The results obtained in a process based on ruthenium- and osmium-catalysed alcohol-unsaturate transfer hydrogenative C C couplings are also included. Moreover, mechanistic aspects related to these reactions are discussed.