[(Bisphosphine) Ru(II) diamine] complexes in asymmetric hydrogenation: expanding the scope of the diamine ligand.

[(Bisphosphine) RuCl 2 (1,2-diamine)] complexes are powerful catalysts in the asymmetric hydrogenation of unfunctionalized ketones. We sought to expand the scope and applicability of these complexes by exploring changes to the diamine structural motif. Via introduction of 1,3- and 1,4-diamines, the catalytic activity was significantly altered such that new classes of ketones could be considered for [(bisphosphine) RuCl 2 (diamine)] asymmetric hydrogenation.

Carbohydrate-derived amino-alcohol ligands for asymmetric alkynylation of aldehydes.

[reaction: see text] Conformationally restricted amino alcohols based on carbohydrate scaffolds provide flexible and fine-tuneable libraries that greatly expand the range of ligands available in the Zn(OTf)(2)-mediated addition of alkynes to aldehydes, in some cases with very high stereoselectivities.

Asymmetric hydrogenation of isobutyrophenone using a [(Diphosphine) RuCl2 (1,4-diamine)] catalyst.

[reaction: see text] The use of three chiral 1,4-diamines in the [(diphosphine) RuCl(2) (diamine)] catalyst system is demonstrated in the hydrogenation of acetophenone. The use of a 1,4-diamine offers unique properties that allow tuning of the catalyst system. These include the first example of the use of a racemic diamine in combination with a chiral phosphine, which gives 95% ee in the hydrogenation of isobutyrophenone.

Asymmetric hydrogenation using chiral Rh complexes immobilised with a new ion-exchange strategy.

Rh diphosphine complexes using DuPhos and JosiPhos as chiral ligands have been immobilised by ion exchange into the mesoporous material MCM-41. When used as catalysts for the enantioselective hydrogenation of dimethyl itaconate and methyl-2-acetamidoacrylate, these heterogeneous catalysts give catalytic performance in terms of yield and enantioselection that are comparable to the corresponding homogeneous catalysts. Furthermore, the heterogeneous catalysts can be readily recovered and reused without loss of catalyst performance. A second immobilisation strategy is described in which [Rh(COD)2]+BF4- is initially immobilised by ion exchange and subsequently modified by the chiral diphosphine and this give comparable catalyst performance. This immobilisation strategy opens up the possibility of easy ligand-screening for parallel synthesis and libraries.

Precise structure activity relationships in asymmetric catalysis using carbohydrate scaffolds to allow ready fine tuning: dialkylzinc-aldehyde additions.

The ready construction of 24 stereochemically and functionally diverse carbohydrate ligand structures from a core D-glucosamine scaffold has allowed the evaluation of broad ranging structure activity relationships in ligand accelerated zincate additions to aldehydes, with variations in deltadeltaG+/+(R-S) of up to 5650 J mol(-1) that create opposing senses of asymmetric induction and that are consistent with models based on several ligand X-ray structures and molecular mechanics analysis. Factorial analysis of enantioselectivity using key dihedral angles and steric volume on N-2 also highlight the potential for the use of factorial design in ligand construction.