NewC2- andC1-Symmetric Phosphorus Ligands Based on Carbohydrate Scaffolds and Their Use in the Iridium-Catalysed Hydrogenation of Ketimines

Carbohydrate-derived 1,3-diphosphite ligands as chiral nanoparticle stabilizers: promising catalytic systems for asymmetric hydrogenation

Metallic Ru, Rh, and Ir nanoparticles were prepared by the decomposition of organometallic precursors under H(2) pressure in the presence of 1,3-diphosphite ligands, derived from carbohydrates, as stabilizing agents. Structural modifications to the diphosphite backbone were found to influence the nanoparticles' size, dispersion, and catalytic activity. In the hydrogenation of o- and m-methylanisole, the Rh nanoparticles showed higher catalytic activity than the corresponding Ru nanoparticles. The Ir nanoparticles presented the lowest catalytic activity of the series. In all cases, the hydrogenation of o-methylanisole gave total selectivity for the cis-product, however, the ee of the product was always less than 6 %. A maximum of 81 % cis-selectivity was obtained for the hydrogenation of m-methylanisole, however, no asymmetric induction was observed. These results show that the catalytic activity is affected by a combination of influences from the substrate, the diphosphite ligands, and the metallic nanoparticles.

New P,N-Ferrocenyl Ligands for the Asymmetric Ir-Catalyzed Hydrogenation of Imines

The Ir-catalyzed enantioselective hydrogenation of various N-(3,5-dimethyl-4-methoxy)phenylimines was performed under mild conditions in the presence of new P,N-ferrocenyl iridium complexes leading to (R)-N-(3,5-dimethyl-4-methoxy)phenylamines in high yields and enantioselectivities (up to 99%). These chiral aryl amines can be readily deprotected using Ce(NH4)2(NO3)6.