Enantioselective fluorination of β-ketoesters using tartrate derived bidentate bioxazoline-Cu(II) complexes

Enantioselective fluorination of aliphatic cyclic and acyclic β-ketoesters was achieved in excellent yield (up to 98%) with moderate to good enantioselectivities (up to 86% ee) using tartrate derived bidentate bioxazoline-Cu(II) complexes. This is the first report of a bioxazoline which forms a 5-membered chelate inducing enantioselectivity in the asymmetric fluorination of β-ketoesters.     

Stepwise Metal–Ligand Cooperation by a Reversible Aromatization/Deconjugation Sequence in Ruthenium Complexes with a Tetradentate Phenanthroline‐Based Ligand

The synthesis and reactivity of ruthenium complexes containing the tetradentate phenanthroline‐based phosphine ligand 2,9‐bis((di‐tert‐butylphosphino)methyl)‐1,10‐phenanthroline (PPhenP) is described. The hydrido chloro complex [RuHCl(PPhenP)] ( 2 ) undergoes facile dearomatization upon deprotonation of the benzylic position, to give [RuH(PPhenP‐H)] ( 4 ). Addition of dihydrogen to 4 causes rearomatization of the phenanthroline moiety to trans‐[Ru(H)₂(PPhenP)] ( 5 ), followed by hydrogenation of an aromatic heterocycle in the ligand backbone, to give a new dearomatized and deconjugated complex [RuH(PPhenP*‐H)] ( 6 ). These aromatization/deconjugation steps of the coordinated ligand were demonstrated to be reversible and operative in the dehydrogenation of primary alcohols without the need for a hydrogen acceptor. This aromatization/deconjugation sequence constitutes an unprecedented mode of a stepwise cooperation between the metal center and the coordinated ligand.     

Efficient hydrogenation of biomass-derived cyclic di-esters to 1,2-diols

The unprecedented homogeneous hydrogenation of cyclic di-esters, in particular biomass-derived glycolide and lactide, to the corresponding 1,2-diols is catalyzed by Ru(II) PNN (1) and Ru(II) CNN (2) pincer complexes under mild hydrogen pressure and (in the case of 1) neutral conditions. No racemization was observed when a chiral di-ester was used.