Highly efficient and enantioselective synthesis of β-heteroaryl amino alcohols via Ru-catalyzed asymmetric hydrogenation

We herein report a highly enantioselective hydrogenation of α-N-heteroaryl ketones catalyzed by chiral ruthenium catalysts, furnishing β-heteroaryl amino alcohols in superb yields and enantioselectivities (up to 99% yield and up to 99% ee).

Asymmetric hydrogenation of 1,4-diketones: facile synthesis of enantiopure 1,4-diarylbutane-1,4-diols

Owing to the biological significance and great synthetic value of 1,4-diarylbutane-1,4-diols and their derivatives, increasingly considerable attention has been paid to developing effective synthetic methods for chiral 1,4-diarylbutane-1,4-diols. We herein report an efficient asymmetric hydrogenation of 1,4-diaryldiketones catalyzed by a chiral iridium complex bearing f-amphox as ligand, furnishing a series of 1,4-diarylbutane-1,4-diols in excellent yields (up to >99%) with exceptional enantioselectivities (up to >99.9% ee) and diastereoselectivities (up to >100 : 1 dr).

Cinchona-Alkaloid-Derived NNP Ligand for Iridium-Catalyzed Asymmetric Hydrogenation of Ketones

Most ligands applied for asymmetric hydrogenation are synthesized via multistep reactions with expensive chemical reagents. Herein, a series of novel and easily accessed cinchona-alkaloid-based NNP ligands have been developed in two steps. By combining [Ir(COD)Cl]₂, 39 ketones including aromatic, heteroaryl, and alkyl ketones have been hydrogenated, all affording valuable chiral alcohols with 96.0-99.9% ee. A plausible reaction mechanism was discussed by NMR, HRMS, and DFT, and an activating model involving trihydride was verified.

Chiral Tridentate Ligands in Transition Metal-Catalyzed Asymmetric Hydrogenation

Asymmetric hydrogenation (AH) of double bonds has been one of the most effective methods for the preparation of chiral molecules and for the synthesis of important chiral building blocks. In the past 60 years, noble metals with bidentate ligands have shown marvelous reactivity and enantioselectivity in asymmetric hydrogenation of a series of prochiral substrates. In recent years, developing chiral tridentate ligands has played an increasingly important role in AH. With modular frameworks and a variety of functionalities on the side arms, chiral tridentate ligand complexes enable both reactivities and stereoselectivities. Although great achievements have been made for noble metal catalysts with chiral tridentate ligands since the 1990s, the design of chiral tridentate ligands for earth abundant metal catalysts has still been in high demand. This review summarizes the development of chiral tridentate ligands for homogeneous asymmetric hydrogenation. The philosophy of ligand design and the reaction mechanisms are highlighted and discussed as well.

Biocatalytic asymmetric synthesis of (R)-1-tetralol using Lactobacillus paracasei BD101

Asymmetric bioreduction of ketones is a fundamental process in the production of organic molecules. Compounds containing tetralone rings are found in the structure of many biologically active and pharmaceutical molecules. Biocatalytic reduction of ketones is one of the most promising and significant routes to prepare optically active alcohols. In this study, the reductive capacity of Lactobacillus paracasei BD101 was investigated as whole-cell biocatalyst in the enantioselective reduction of 1-tetralone (1). In biocatalytic reduction reactions, the conversion of the substrate and the enantiomeric excess (ee) of the product are significantly affected by optimization parameters such as temperature, agitation rate, pH, and incubation time. Effects of these parameters on ee and conversion were investigated comprehensively. (R)-1-tetralol ((R)-2), which can be used to treat disorder such as obsessive compulsive, post-traumatic stress, premenstrual dysphoric, and social anxiety, was manufactured in enantiopure form, high yield and gram-scale, using whole-cell biocatalysts of L. paracasei BD101. The 7.04 g of (R)-2 was obtained in optically pure form with 95% yield. Also, to our knowledge, this is the first report on production of (R)-2 using whole-cell biocatalyst in excellent yield, conversion, enantiopure form and gram scale. This is a clean, eco-friendly and cheap method for the synthesis of (R)-2 compared with chemical catalyst.

Iridium-catalyzed asymmetric hydrogenation of N-phosphinoylimine

On catalysis with an iridium tridentate catalyst, prochiral N-phosphinoylimines were hydrogenated with high enantioselectivity and reactivity. An outer-sphere reaction model was proposed in this hydrogenation of CN bonds.

Highly chemoselective hydrogenation of cyclic imides to ω-hydroxylactams or ω-hydroxyamides catalyzed by iridium catalysts

Several novel ferrocene-based PNN ligands were prepared, which were found to be highly effective catalysts (TON up to 50 000) for the homogeneous hydrogenation of cyclic imides with iridium.

Collado I, Aleu J. Biocatalytic Preparation of Chloroindanol Derivatives. Antifungal Activity and Detoxification by the Phytopathogenic Fungus Botrytis cinerea

Indanols are a family of chemical compounds that have been widely studied due to their broad range of biological activity. They are also important intermediates used as synthetic precursors to other products with important applications in pharmacology. Enantiomerically pure chloroindanol derivatives exhibiting antifungal activity against the phytopathogenic fungus Botrytis cinerea were prepared using biocatalytic methods. As a result of the biotransformation of racemic 6-chloroindanol (1) and 5-chloroindanol (2) by the fungus B. cinerea, the compounds anti-(+)-6-chloroindan-1,2-diol (anti-(+)-7), anti-(+)-5-chloroindan-1,3-diol (anti-(+)-8), syn-(+)-5-chloroindan-1,3-diol (syn-(+)-8), syn-(-)-5-chloroindan-1,3-diol (syn-(-)-8), and anti-(+)-5-chloroindan-1,2-diol (anti-(+)-9) were isolated for the first time. These products were characterized by spectroscopic techniques and their enantiomeric excesses studied by chromatographic techniques. The results obtained in the biotransformation seem to suggest that the fungus B. cinerea uses oxidation reactions as a detoxification mechanism.

Recent Progress and Applications of Transition-Metal-Catalyzed Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones and Imines through Dynamic Kinetic Resolution

Based on the ever-increasing demand for enantiomerically pure compounds, the development of efficient, atom-economical, and sustainable methods to produce chiral alcohols and amines is a major concern. Homogeneous asymmetric catalysis with transition-metal complexes including asymmetric hydrogenation (AH) and transfer hydrogenation (ATH) of ketones and imines through dynamic kinetic resolution (DKR) allowing the construction of up to three stereogenic centers is the main focus of the present short review, emphasizing the development of new catalytic systems combined to new classes of substrates and their applications as well.

1 Introduction

2 Asymmetric Hydrogenation via Dynamic Kinetic Resolution

2.1 α-Substituted Ketones

2.2 α-Substituted β-Keto Esters and Amides

2.3 α-Substituted Esters

2.4 Imine Derivatives

3 Asymmetric Transfer Hydrogenation via Dynamic Kinetic Resolution

3.1 α-Substituted Ketones

3.2 α-Substituted β-Keto Esters, Amides, and Sulfonamides

3.3 α,β-Disubstituted Cyclic Ketones

3.4 β-Substituted Ketones

3.5 Imine Derivatives

4. Conclusion

Design of Ru(II)-NHC-Diamine Precatalysts Directed by Ligand Cooperation: Applications and Mechanistic Investigations for Asymmetric Hydrogenation

A modular synthesis of Ru(II)-NHC-diamine complexes from readily available chiral N-heterocyclic carbenes (NHCs) and chiral diamines is disclosed for the first time. The well-defined Ru(II)-NHC-diamine complexes show unique structure and coordination chemistry including an unusual tridentate coordination effect of 1,2-diphenylethylenediamine. The isolated air- and moisture-stable Ru(II)-NHC-diamine complexes act as versatile precatalysts for the asymmetric hydrogenation of isocoumarines, benzothiophene 1,1-dioxides, and ketones. Moreover, on the basis of the identification of reaction intermediates by stoichiometric reactions and NMR experiments, together with the DFT calculations, a possible catalytic cycle was proposed.

Efficient synthesis of chiral β-hydroxy sulfones via iridium-catalyzed hydrogenation

A highly efficient Ir-catalyzed asymmetric hydrogenation of prochiral β-keto sulfones was successfully developed, affording a series of chiral β-hydroxy sulfones with excellent results (up to >99% conversion, 99% yield, >99% ee, and 20 000 TON).