Ruthenacycles and Iridacycles as Catalysts for Asymmetric Transfer Hydrogenation and Racemisation

Ruthenacycles, which are easily prepared in a single step by reaction between enantiopure aromatic amines and [Ru(arene)Cl2]2 in the presence of NaOH and KPF6, are very good asymmetric transfer hydrogenation catalysts. A range of aromatic ketones were reduced using isopropanol in good yields with ee’s up to 98%. Iridacycles, which are prepared in similar fashion from [IrCp*Cl2]2 are excellent catalysts for the racemisation of secondary alcohols and chlorohydrins at room temperature. This allowed the development of a new dynamic kinetic resolution of chlorohydrins to the enantiopure epoxides in up to 90% yield and 98% enantiomeric excess (ee) using a mutant of the enzyme Haloalcohol dehalogenase C and an iridacycle as racemisation catalyst.

Synthesis of enantiopure chloroalcohols by enzymatic kinetic resolution

3-Alkenyl and heteroaryl chloroalcohols have been obtained in excellent enantiomeric excess (>99%) by enzymatic kinetic resolution using the haloalcohol dehalogenase HheC. Yields were close to the theoretical maximum for all substrates employed. Furthermore, the applicability of this methodology on multigram scale has been established.

CCDC 605888: Experimental Crystal Structure Determination

Related Article: R.M.Haak, C.Tarabiono, D.B.Janssen, A.J.Minnaard, J.G.de Vries, B.L.Feringa|2007|Org.Biomol.Chem.|5|318|doi:10.1039/b613937j,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Dynamic Kinetic Resolution of Racemic β-Haloalcohols: Direct Access to Enantioenriched Epoxides

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