RuPHOX-Ru Catalyzed Asymmetric Cascade Hydrogenation of 3-Substituted Chromones for the Synthesis of Corresponding Chiral Chromanols

An efficient RuPHOX-Ru catalyzed asymmetric cascade hydrogenation of 3-substituted chromones has been achieved under mild reaction conditions, affording the corresponding chiral 3-substituted chromanols in high yields with excellent enantio- and diastereoselectivities (up to 99 % yield, >99 % ee and >20 : 1 dr). Control reactions and deuterium labelling experiments revealed that a dynamic kinetic resolution process occurs during the subsequent hydrogenation of the C=O double bond, which is responsible for the high performance of the asymmetric cascade hydrogenation. The resulting products allow for several transformations and it was shown that the protocol provides a practical and alternative strategy for the synthesis of chiral 3-substituted chromanols and their derivatives.

Bimetallic Ru/Ru-Catalyzed Asymmetric One-Pot Sequential Hydrogenations for the Stereodivergent Synthesis of Chiral Lactones

Asymmetric sequential hydrogenations of α-methylene γ- or δ-keto carboxylic acids are established in one-pot using a bimetallic Ru/Ru catalyst system, achieving the stereodivergent synthesis of all four stereoisomers of both chiral γ- and δ-lactones with two non-vicinal carbon stereocenters in high yields (up to 99%) and with excellent stereoselectivities (up to >99% ee and >20:1 dr). The compatibility of the two chiral Ru catalyst systems is investigated in detail, and it is found that the basicity of the reaction system plays a key role in the sequential hydrogenation processes. The protocol can be performed on a gram-scale with a low catalyst loading (up to 11000 S/C) and the resulting products allow for many transformations, particularly for the synthesis of several key intermediates useful for the preparation of chiral drugs and natural products.

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.

RuPHOX-Ru Catalyzed Asymmetric Hydrogenation of α-Substituted Tetralones via a Dynamic Kinetic Resolution

The efficient RuPHOX-Ru catalyzed asymmetric hydrogenation of α-substituted tetralones via a dynamic kinetic resolution has been achieved for the synthesis of chiral tetrahydronaphthols. The mechanism study indicated that the hydrogenation...

Kinetic resolution of azaflavanones via a RuPHOX-Ru catalyzed asymmetric hydrogenation

The kinetic resolution of azaflavanones has been established via RuPHOX-Ru catalyzed asymmetric hydrogenation, providing chiral azaflavanones and azaflavanols in high yields with up to >20 : 1 dr and 99.7% ee.

Computational design of syntheses leading to compound libraries or isotopically labelled targets

Although computer programs for retrosynthetic planning have shown improved and in some cases quite satisfactory performance in designing routes leading to specific, individual targets, no algorithms capable of planning syntheses of entire target libraries - important in modern drug discovery - have yet been reported. This study describes how network-search routines underlying existing retrosynthetic programs can be adapted and extended to multi-target design operating on one common search graph, benefitting from the use of common intermediates and reducing the overall synthetic cost. Implementation in the Chematica platform illustrates the usefulness of such algorithms in the syntheses of either (i) all members of a user-defined library, or (ii) the most synthetically accessible members of this library. In the latter case, algorithms are also readily adapted to the identification of the most facile syntheses of isotopically labelled targets. These examples are industrially relevant in the context of hit-to-lead optimization and syntheses of isotopomers of various bioactive molecules.

Selective Asymmetric Hydrogenation of Four-Membered Exo-α,β-Unsaturated Cyclobutanones Using RuPHOX-Ru as a Catalyst

The selective asymmetric hydrogenation of four-membered exo-α,β-unsaturated cyclobutanones has been achieved for the first time using RuPHOX-Ru as a catalyst, providing four-membered exo-cyclic chiral allylic alcohols in high yields and with up to 99.9% ee. The reaction could be performed on a gram scale with a relatively low catalyst loading (up to 10000 S/C), and the resulting products can be transformed to several biologically active molecules.

Synthesis of chiral chromanols via a RuPHOX-Ru catalyzed asymmetric hydrogenation of chromones

Chiral chromanols and their derivatives have been synthesized via a RuPHOX-Ru catalyzed asymmetric hydrogenation of chromones in high yields, >20 : 1 drs and with up to 99.9% ee. Control experiments show that the reaction undergoes two sequential asymmetric hydrogenation steps of the C[double bond, length as m-dash]C and C[double bond, length as m-dash]O double bonds. The reaction could be performed on a gram-scale with a relatively low catalyst loading (up to 1000 S/C), and the resulting products can be transformed to several biologically active compounds.

Yolk-Shell-Mesostructured Silica-Supported Dual Molecular Catalyst for Enantioselective Tandem Reactions

Yolk-shell-mesostructured silica was used as a support in the development of an active-site-isolated bifunctional catalyst that can mediate a sequential organic transformation. Herein, through immobilization, the location of two catalytic species is controlled: a base functionality is anchored in the channels of the outer silica shell and a chiral ruthenium/diamine functionality is anchored on the inner silica yolk. The result is a yolk-shell-mesostructured silica-supported active-site-isolated dual molecule catalyst. Structural analysis through solid-state carbon ¹³ C NMR spectroscopy reveals its well-defined single-site dual active centers. Electron microscopy investigations disclose its uniformly distributed mesoporous nanoparticles. As envisaged, this bifunctional catalyst enables a controllable aza-Michael addition/asymmetric transfer hydrogenation catalytic sequence, where the base-catalyzed aza-Michael addition of enones and amines to aryl-substituted β -secondary amino ketones is followed by a Ru-catalyzed asymmetric transfer hydrogenation. Various aryl-substituted γ-secondary amino alcohols are obtained in high yields and enantioselectivities via this one-pot enantioselective organic transformation. Furthermore, the heterogeneous catalyst can be applied in a continuous-flow process, which was shown to be particularly attractive for the practical preparation of aryl-substituted γ-secondary amino alcohols in an environmentally friendly medium.

Boron Tetrafluoride Anion Bonding Dual Active Species Within a Large-Pore Mesoporous Silica for Two-Step Successive Organic Transformaion to Prepare Optically Pure Amino Alcohols

Development of a simple and easy handing process for preparation of multifunctional heterogenous catalysts and exploration of their applications in sequential organic transformation are of great significance in heterogeneous asymmetric catalysis. Herein, through the utilization of a BF4- anion–bonding strategy, we anchor conveniently both organic bases and chiral ruthenium complex into the nanopores of Me-FDU−12, fabricating a Lewis base/Ru bifunctional heterogeneous catalyst. As we envisaged, cyclic amine as a Lewis base promotes an intermolecular aza–Michael addition between enones and arylamines, affording γ-secondary amino ketones featuring with aryl motif, whereas ruthenium/diamine species as catalytic promoter boosts an asymmetric transfer hydrogenation of γ-secondary amino ketones to γ-secondary amino alcohols. As expected, both enhance synergistically the aza–Michael addition/asymmetric transfer hydrogenation one–pot enantioselective organic transformation, producing chiral γ-secondary amino alcohols with up to 98% enantioselectivity. Unique features, such as operationally simple one–step synthesis of heterogeneous catalyst, homo–like catalytic environment as well as green sustainable process make this heterogeneous catalyst an attracting in a practical preparation of optically pure pharmaceutical intermediates of antidepressants.

Efficient access to chiral 1,2-amino alcohols via Ir/f-amphox-catalyzed asymmetric hydrogenation of α-amino ketones

We successfully developed the iridium/f-amphox-catalyzed asymmetric hydrogenation of α-amino ketones to prepare chiral 1,2-amino alcohols with excellent results.

One-pot sequential asymmetric hydrogenation of β-aryl-β-aryloxy acroleins

A one-pot sequential asymmetric hydrogenation of β-aryl-β-aryloxy acroleins has been developed for the preparation of chiral 3-aryl-3-aryloxy alcohols.

Pd-catalyzed asymmetric allylic amination using easily accessible metallocenyl P,N-ligands

Compared to their C1-symmetric counterparts, planar chiral C2-symmetric metallocenyl P,N-ligands are efficient chiral ligands for Pd-catalyzed asymmetric allylic aminations, providing a number of amination products with high enantioselectivities. A non-C2-symmetric ferrocenyl P,N-ligand (a by-product obtained during the synthesis of the above C2-symmetric species) was also found to be an efficient ligand for asymmetric allylic aminations. A mixed ligand system consisting of both C2- and non-C2-symmetric ferrocene complexes was examined and showed high catalytic activity with the amination products being obtained with excellent enantioselectivities.

Asymmetric hydrogenation by RuCl2(R-Binap)(dmf)n encapsulated in silica-based nanoreactors

RuCl₂-(R-Binap)(dmf)_n encapsulated in silica-based nanoreactors: a solid catalyst as a whole, but a homogeneous catalyst on the nanoscale.