Search

An efficient rhodium-catalyzed asymmetric transfer hydrogenation of β-cyano α-ketoesters via dynamic kinetic resolution has been developed. Despite the challenge posed by multiple functional groups, the reaction proceeded smoothly under mild conditions, generating versatile synthons with two adjacent stereocenters in high yields with excellent enantio- and diastereoselectivities. Furthermore, the power of this strategy is highlighted by the scale-up reaction and the follow-up synthesis of cytoxazone and paclitaxel intermediates.

The realm of application of organometallic catalysis to organic synthesis has witnessed a transformative shift in recent years, owing much to the evolution of ate complexes from mere reagents to versatile catalysts. Ate complexes, formed through the coordination of a neutral Lewis acid with an organic anionic base, have emerged as pivotal intermediates that not only facilitate organic transformations but also serve as efficient catalysts in a wide range of chemical reactions. This review presents the fascinating journey of ate complexes, highlighting their development from stoichiometric reagents to active catalysts. Historically, ate complexes were primarily regarded as stoichiometric species essential for various metal-catalyzed transformations. However, constant research has unveiled their potential as catalysts in their own right, reshaping the landscape of modern organic synthesis. In this minireview, we discuss the pivotal role of ate complexes in the evolution of organic synthesis, from their early days as reactive intermediates to their current stature as catalytic pioneers offering a glimpse into the exciting future of this dynamic field.

A sequence of f-phamidol-based tetradentate phosphine ligands have been developed and successfully used in iridium-catalyzed enantioselective hydrogenation of benzophenones to deliver chiral benzhydrols in almost quantitative yields and with excellent enantioselectivities (up to >99% yield and up to >99% ee). Moreover, the catalytic system shows a broad substrate scope and functional group tolerance. The synthetic utilities of this methodology have been showcased by gram-scale experiments and the formal synthesis of levocetirizine.

An extremely concise, scalable, and stereoselective synthesis of a privileged chiral skeleton based on 2,2′-biindolyl and commercially available chiral building blocks has been developed. This novel skeleton allows for easy access to a range of bisphosphine ligands (decagram scale, up to 58% total yield, only three steps). The synthetic method is characterized by an efficient central-to-axial chirality transfer strategy. In particular, the superior performance of the ligands has been demonstrated in diverse reactions, including several asymmetric hydrogenations, asymmetric conjugate reductions, and cycloisomerization reactions, indicating a great potential for the application of the newly developed chiral backbones in further modifications and exploration of novel chiral ligands and catalysts.

Transition metal catalysts with a million turnovers and excellent selectivity are rarely reported but are crucial for the industrial manufacture of optical pure pharmaceuticals, natural products, and fine chemicals. In this paper, we report an unprecedented aninoic Ir-f-phamidol catalyst for asymmetric hydrogenation of γ-amino ketones followed by stereoselective cyclization for construction of valuable chiral 2-aryl-pyrrolidine pharmacophores. The Ir-f-phamidol catalyst showed up to 1,000,000 TON and >99% ee, as well as excellent tolerance of substrates and protecting groups, providing various chiral amino alcohol intermediates. Upon optimization of the conditions, the stereoselective cyclization reaction was highly smooth and efficient (quantitative conversions, 92 to >99% ee). Finally, this solution was applied in the preparation of high-value chiral entities containing such chiral 2-aryl-pyrrolidine pharmacophores.

Optically active secondary alcohols are key building blocks for a variety of chiral drugs, and transition-metal-catalyzed asymmetric hydrogenation represents one of the most efficient and direct methods for the preparation of chiral secondary alcohols. We herein report a practical and efficient asymmetric hydrogenation catalyzed by a chiral iridium complex bearing (R)-O-SpiroPAP as the ligand, producing intermediates of crizotinib, ensartinib, lorlatinib, and pibrentasvir in up to 99% yield with up to 99% ee and >20:1 dr. The synthetic potential of the current catalytic system was demonstrated by experiments on the gram and kilogram scales.

Chlorohydrins and oxaheterocycles are synthetically valuable building blocks for diverse natural products and therapeutic substances. A highly efficient Ir/f-phamidol-catalyzed asymmetric hydrogenation of ω-chloroketones was successfully developed, and various chlorohydrins and oxaheterocycles were obtained divergently with excellent yields and enantioselectivities (up to >99% yield and >99% ee). Synthetic utilities of this divergent transformation were demonstrated by gram-scale synthesis of key intermediates of several enantiomerically enriched drugs via this catalytic methodology.

A new class of cobalt catalytic system for asymmetric hydrogenation of ketones was herein reported, involving the development of novel ferrocene-based secondary phosphine oxide ligands. An unusual P–O bidentate coordination pattern with cobalt was confirmed by an X-ray diffraction study. The bichelating tetrahedral cobalt(II) complexes afforded high reactivities (up to 99% yield) and good to excellent enantioselectivities (up to 92% ee) in the AH of various ortho-substituted diaryl ketones. In addition, the diferrocenyl cobalt complex was characterized with intriguing UV–vis absorption and electrochemical properties.

The ruthenium-catalyzed asymmetric reductive amination of aryl-trifluoromethyl ketones affording high value primary α-(trifluoromethyl)arylmethylamines using cheap NH4OAc as the nitrogen source and H2as the reductant is reported. This user-friendly and simple catalytic method tolerates various aromatic functions with electron-withdrawing or -donating substituents at the para- or meta-positions and as well challenging heteroaromatic functions, yielding primary α-(trifluoromethyl)arylmethylamines with excellent chemoselectivities, enantioselectivities, and useful yields (80–97% ee, 51–92% isolated yields). Finally, scalable and concise synthesis of key drug intermediates using this methodology is presented.

Synthesis of optically enriched racetam analogues was achieved via highly remote diastereocontrolled and enantiocontrolled Pd/C-catalyzed hydrogenation of α,β-unsaturated γ-lactams. Various mono- and disubstituted 2-pyrrolidones were obtained in excellent yields and stereoselectivities, and a concise and large-scale synthesis of brivaracetam was developed from inexpensive l-2-aminobutyric acid. Surprisingly, stereodivergent hydrogenation was observed by modifying remote functionalized stereocenters and additives, which would provide alternative stereochemical options of chiral racetams synthesis.

A series of novel atropisomeric diphosphine ligands termed TanPhos were designed and synthesized, which has a smaller bite angle compared with that of other ligands such as BINAP. TanPhos showed high reactivity and enantioselectivity in the rhodium-catalyzed asymmetric hydrogenation of a-dehydro amino ketones, and up 99% yield and 99% ee were obtained for a wide range of chiral α-amino ketones.

Due to their low reactivity, difficult enantiocontrol, and proneness to N–O bond cleavage, the catalytic asymmetric hydrogenation of oximes to hydroxylamines has remained a significant challenge. Herein, a Lewis and Brønsted acid cooperation strategy was established for the asymmetric hydrogenation of oximes, providing the corresponding hydroxylamines with up to 95% yield and up to 96% ee. Addition of Lewis and Brønsted acid was crucial to obtain high conversion and enantioselectivity. Mechanistic investigations indicates that the thiourea fragment of the ligand, Lewis acid (In(OTf)3or Zn(OAc)2), as well as the Brønsted acid (l-CSA) played vital roles in the control of reactivity and enantioselectivity of the reaction. In addition, the synthetic elaboration of this transformation was demonstrated by gram scale experiment with retention of the yield and enantioselectivity.

A highly efficient and enantioselective method for the asymmetric reductive amination of β-keto phosphine derivatives was disclosed, and the corresponding β-amino phosphine oxides could be obtained in high yields (up to 97% yield) and excellent enantioselectivities (up to 97% ee). Moreover, the reaction worked well on a gram scale, indicating that our protocol has potential applications in the synthesis of chiral ligands and organocatalysts.

A new series of C2-symmetrical chiral ferrocene-based diphosphino-ethane ligands termed as f-DPE were developed. Assisted by the ion pairing interaction with the ligand, a wide scope of 2-substituted acrylic acids was hydrogenated to obtain chiral propanoic acids with high yields and enantioselectivities. The well-known anti-inflammatory drugs ibuprofen, naproxen, and flurbiprofen could be synthesized efficiently. In addition, the synthetic utilities of the current method were demonstrated by gram-scale experiments.

A general base metal catalytic system for asymmetric hydrogenation of different types of carbonyl compounds has rarely been reported. Here, we describe the development of a versatile Co/BPE system for the asymmetric hydrogenation of both α-ketoamides and aryl alkyl ketones that enable fast access to various chiral α-hydroxy amides and secondary alcohols in excellent yields and enantioselectivities (up to 98% yield and 99:1 enantiomeric ratio [er]) under base- and additive-free conditions. More importantly, cobalt-catalyzed diastereo- and enantioselective hydrogenation of α-substituted β-ketoamides has been achieved for the first time under a dynamic kinetic resolution (DKR) process using the same system. The synthetic potential has been demonstrated through reaction scale-up, product derivatization, and synthesis of various key intermediates for chiral drugs. Mechanistic studies support a new Co(II) instead of a Co(II)/Co(0) catalytic cycle involving hydride transfer and H2splitting processes, in which the oxidation state of cobalt remains unchanged.

We herein report a convenient method to convert olefins to organic iodides and amines using an Ir/ZhaoPhos catalyst, molecular hydrogen, and an electrophilic iodine(I) reagent. High yields and regioselectivities were obtained under mild conditions. In addition, basic workup with potassium carbonate leads to C–N products. Control experiments and DFT calculations tentatively excluded the pathway involving the in situformation of HI. Instead, a catalytic cycle involving the hydrogenation of the haliranium ion intermediate was proposed.

Isomerization-linear-hydroformylation is demanding, however, not an addressed issue, for the production of value-added linear aldehydes by converting cheap and abundant internal alkenes available from bio- & petrochemical industry. In this paper, a dual metal catalysis system combining a Ru-isomerization catalyst and a Rh-linear-hydroformylation catalyst satisfying the “4S” criterions was reported for isomerization-linear-hydroformylation of C4 raffinate (mixed butenes) and internal olefins. The optimized dual metal catalyst system hydroformylated Raffinate II feed to valuable valeraldehyde in 98% linear selectivity (n:i ​= ​49), 80% conversion and high activity of 1069 h−1TOF whereas 96% linear selectivity (n:i ​= ​24), 71% conversion and 948 h−1TOF were observed using only the Rh-hydroformylation catalyst. Notably, valeraldehyde are produced in million tons scale annually for making non-toxic plasticizer DPHP. Various 2-olefins were also converted to linear aldehydes in > 98% linear selectivity (n:i ​> ​49), 78%–82% conversion and high activity of 802–851 h−1TOF.

The transition-metal-catalyzed asymmetric cycloisomerization of 1,7-enynes is regarded as a formidable challenge due to the poor ability of 1,7-enynes to serve as bidentate ligands to metal. In this Letter, a highly enantioselective rhodium(I)-catalyzed Alder-ene-type cycloisomerization of 1,7-enynes is disclosed, offering an efficient method for the synthesis of a wide range of fused six-membered cyclic compounds. Furthermore, a high turnover frequency experiment and deuterium-labeling experiment were performed to give insight into this transformation.

Asymmetric hydrogenation of tetrasubstituted alkenes remains a formidable challenge in asymmetric catalysis. We report herein an unprecedented Rh-catalyzed enantioselective and diastereoselective hydrogenation of easily accessed α,β-disubstituted unsaturated lactams to afford synthetically valuable chiral lactams with 1,2-consecutive stereocenters. The reaction could be performed on the gram scale, and the products could be concisely transformed to enantiomerically pure trans-3,4-disubstituted piperidines, which are prevalent structural units in medicinal agents.

Asymmetric homogeneous hydrogenation under high pressure in continuous flow was achieved with a slug flow reactor. High hydrogen pressure enabled iridium-catalyzed asymmetric hydrogenation of acetophenone with a turn-over-frequency (TOF) of up to 274,000 h−1. An operandoinfrared tool was used to provide in-situ monitoring of the reaction. The effect of gas-liquid ratio and speed of slug flow in the microchannel were studied. The multi-step flow synthesis of active pharmaceutical ingredients, in which asymmetric hydrogenation is a key step, was successfully demonstrated, with subsequent reactions carried out under longer residence times within a cascade of CSTRs.

We report an asymmetric 1,2-reduction of cyclic α,β-unsaturated ketones to access various enantiomerically enriched cyclic allylic alcohols under mild conditions, catalyzed by in situ generated copper hydride ligated with (R)-DTBM-C3*-TunePhos. α-Brominated cycloalkenones were reduced with excellent enantioselectivities of up to 98% ee, while substrates that were without α-substituents were reduced chemoselectively, with moderate enantioselectivities.

The incorporation of Brønsted acid, thiourea anion binding, and transition metal catalysis enables an efficient method to synthesize chiral indolines via hydrogenation of indoles. Catalyzed by a rhodium/ZhaoPhos complex, asymmetric hydrogenation of unprotected indoles is performed smoothly with excellent enantioselectivities (up to 99% ee, up to 400 TON). Brønsted acid HCl activates indoles to form iminium ion intermediates. Mechanistic studies support the assumption that anion binding plays a crucial role as a secondary interaction. DFT calculations reveal an outer-sphere mechanism in this chemical transformation.

A highly enantioselective iridium-catalyzed hydrogenation of α-keto amides to form α-hydroxy amides has been achieved with excellent results (up to >99% conversion and up to >99% ee, TON up to 100 000). As an example, this protocol was applied to the synthesis of (S)-4-(2-amino-1-hydroxyethyl)benzene-1,2-diol, the enantiomer of norepinephrine, which is widely used as an injectable drug for the treatment of critically low blood pressure. Density functional theory (DFT) calculations were also carried out to reveal the reaction mechanism.

The dynamic kinetic resolution (DKR) process remains a highly efficacious approach for constructing chiral amino alcohols viathe catalytic asymmetric hydrogenation of α-amino ketones. We report herein a highly efficient and enantioselective anti-selective dynamic kinetic asymmetric hydrogenation of α-amino ketones catalyzed by Ir-(S)-f-phamidol system, providing various chiral amino alcohols and chiral oxazolidin-2-ones divergently with high diastereo- and enantioselectivity (up to 99% yield, up to 99% eeand up to 99:1 dr). In addition, the reaction could be performed on the gram-scale, and the resulting chiral amino alcohols are key intermediates of norephedrine and metaraminol.

Efficient transformation of platform chemicals into key intermediates has been increasingly important for the pharmaceutical industry. The development of the catalytic reduction of abundant carboxylic acids with molecular hydrogen has been of both practical and theoretical value. We herein report the homogeneous hydrogenation of dicarboxylic acids with the strategy of desymmetrization. Using a rhodium/bisphosphine catalyst, one carboxyl group of meso-diacids was selectively reduced to yield chiral lactones with satisfactory enantioselectivity. This method provides a straightforward approach to produce chiral lactone intermediates for the manufacture of biotin, telaprevir, and other antivirus drugs. Both experimental and computational investigations were carried out, revealing a novel neighboring group coordination mechanism in the catalytic cycle.

Herein we have developed a highly practical and efficient one-step coupling protocol for the synthesis of chiral spiro diphosphine ligands, especially for the oxa-spiro diphosphine ligands O-SDP, which showed excellent reactivity and diastereoselectivity in the asymmetric hydrogenation of a key intermediate of Sacubitril. It should be noted that the one-step coupling protocol could be operated on a kilogram scale, and the resulting ruthenium catalyst of O-SDP could hydrogenate the key intermediate of Sacubitril on an industrial scale.

A general and practical carboxylation of benzyl alcohols using the air- and moisture-stable Herrmann-Beller palladacycle was developed. With this novel methodology, numerous carboxylated products were constructed and various functional groups were tolerated. More specifically, some prevailing anti-inflammatory drugs, Ibuprofen, Naproxen, Fenoprofen and Flurbiprofen were all successfully synthesized with this novel procedure. Gram scale experiments revealed the industrial potentiality of this procedure. Several interesting control experiments were performed, and the general reaction pathway was proposed.

Asymmetric hydrogenation of α-substituted ethenylphosphonic acids has been successfully achieved by Rh/ferrocenyl chiral bisphosphorus ligand (SPO-Wudaphos) through noncovalent ion-pair interaction between the substrate and catalyst under mild reaction conditions without base. A series of chiral phosphonic acids were obtained with excellent results (up to 98% ee, >99% conversion, 2000 TON). Moreover, the control experiments showed that the noncovalent ion-pair interaction was critical in this asymmetric hydrogenation.