Ruthenium Catalysts Containing Rigid Chiral Diamines and Achiral Diphosphanes for Highly Enantioselective Hydrogenation of Aromatic Ketones

Cinchona-Alkaloid-Derived NN Ligands and Achiral Phosphines for Iridium-Catalyzed Asymmetric Hydrogenation of Heteroaromatic and α-Chloroheteroaryl Ketones

A concise synthesis of cinchona-alkaloid-derived NN ligands bearing alkyl substituents on chiral nitrogen atoms was described. Iridium catalysts containing new chiral NN ligands and achiral phosphines were effective for the asymmetric hydrogenation of heteroaromatic ketones, which afforded corresponding alcohols in up to 99.9% ee. The same protocol was applicable to the asymmetric hydrogenation of α-chloroheteroaryl ketones. Most importantly, the gram-scale asymmetric hydrogenation of 2-acetylthiophene and 2-acetylfuran proceeded smoothly even under 1 MPa of H2.

Automation and Microfluidics for the Efficient, Fast, and Focused Reaction Development of Asymmetric Hydrogenation Catalysis

Automation and microfluidic tools potentially enable efficient, fast, and focused reaction development of complex chemistries, while minimizing resource- and material consumption. The introduction of automation-assisted workflows will contribute to the more sustainable development and scale-up of new and improved catalytic technologies. Herein, the application of automation and microfluidics to the development of a complex asymmetric hydrogenation reaction is described. Screening and optimization experiments were performed using an automated microfluidic platform, which enabled a drastic reduction in the material consumption compared to conventional laboratory practices. A suitable catalytic system was identified from a library of Ru^II -diamino precatalysts. In situ precatalyst activation was studied with ¹ H/³¹ P nuclear magnetic resonance (NMR), and the reaction was scaled up to multigram quantities in a batch autoclave. These reactions were monitored using an automated liquid-phase sampling system. Ultimately, in less than a week of total experimental time, multigram quantities of the target enantiopure alcohol product were provided by this automation-assisted approach.

Iridium-catalyzed enantioselective synthesis of chiral γ-amino alcohols and intermediates of (S)-duloxetine, (R)-fluoxetine, and (R)-atomoxetine

Chiral γ-amino alcohols are the prevalent structural motifs and building blocks in pharmaceuticals and bioactive molecules. Enantioselective hydrogenation of β-amino ketones provides a straightforward and powerful tool for the synthesis of chiral γ-amino alcohols, but the asymmetric transformation is synthetically challenging. Here, a series of tridentate ferrocene-based phosphine ligands bearing modular and tunable unsymmetrical vicinal diamine scaffolds were designed, synthesized, and evaluated in the iridium-catalyzed asymmetric hydrogenation of β-amino ketones. The system was greatly effective to substrates with flexible structure and functionality, and diverse β-tertiary-amino ketones and β-secondary-amino ketones were hydrogenated smoothly. The excellent reactivities and enantioselectivities were achieved in the asymmetric delivery of various chiral γ-amino alcohols with up to 99% yields, >99% ee values, and turnover number (TON) of 48,500. The gram-scale reactions with low catalyst loading showed the potential application in industrial synthesis of chiral drugs, such as (S)-duloxetine, (R)-fluoxetine, and (R)-atomoxetine.

Ruthenium-catalyzed asymmetric hydrogenation of aromatic and heteroaromatic ketones using cinchona alkaloid-derived NNP ligands

A series of cinchona alkaloid-based NNP ligands, including a new one, have been employed for the asymmetric hydrogenation of ketones. By combining ruthenium complexes, various aromatic and heteroaromatic ketones were smoothly reacted, yielding valuable chiral alcohols with extremely high 99.9% ee. Moreover, a proposed reaction mechanism was discussed and verified by NMR.

A combined experimental and computational study to decipher complexity in the asymmetric hydrogenation of imines with Ru catalysts bearing atropisomerizable ligands

RuCl₂(P–OP)(N–N) complexes containing an atropisomerizable phosphine–phosphite and a chiral diamine are effective catalyst precursors for the asymmetric hydrogenation of N-aryl imines following an outer-sphere mechanism.

The enantioselectivity in asymmetric ketone hydrogenation catalyzed by RuH2(diphosphine)(diamine) complexes: insights from a 3D-QSSR and DFT study

The 3D-QSSR method was carried out to investigate the enantioselectivity of the asymmetric ketone hydrogenation (AKH) catalyzed by RuH₂(diphosphine)(diamine) complexes integrating with DFT method, which could provide a way to design homogeneous transition-metal catalysts.

The N-H functional group in organometallic catalysis

The organometallic approach is one of the most active topics in catalysis. The application of NH functionality in organometallic catalysis has become an important and attractive concept in catalyst design. NH moieties in the modifiers of organometallic catalysts have been shown to have various beneficial functions in catalysis by molecular recognition through hydrogen bonding to give catalyst-substrate, ligand-ligand, ligand-catalyst, and catalyst-catalyst interactions. This Review summarizes recent progress in the development of the organometallic catalysts based on the concept of cooperative catalysis by focusing on the NH moiety.