Efficient transfer hydrogenation of ketones in the presence of ruthenium N-heterocyclic carbene catalysts

Novel ruthenium carbene complexes have been in situ generated and tested for the transfer hydrogenation of ketones. Applying Ru(cod)(methylallyl)2 in the presence of imidazolium salts in 2-propanol and sodium-2-propanolate as base, turnover frequencies up to 346 h−1 have been obtained for reduction of acetophenone. A comparative study involving ruthenium carbene and ruthenium phosphine complexes demonstrated the higher activity of ruthenium carbene complexes.

Graphical abstractVarious ruthenium carbene complexes have been in situ generated and tested for transfer hydrogenation of aromatic and aliphatic ketones. Turnover frequencies up to 346 h−1 were obtained for reduction of acetophenone. In addition a comparative study involving ruthenium carbene and ruthenium phosphine complexes has been performed.Figure optionsDownload full-size imageDownload as PowerPoint slide