Search

Abstract Catalytic asymmetric synthesis of polysubstituted chiral cyclopropane presents a significant challenge in organic synthesis due to the difficulty in enantioselective control. Here we report a rhodium-catalyzed highly chemo-, regio- and enantioselective hydroformylation of trisubstituted cyclopropenes affording chiral quaternary cyclopropanes. Importantly, the easy made sterically bulky ligand L1 can effectively suppress hydrogenation and decomposition reactions and give quaternary cyclopropanes with high regio- and enantioselectivities for both aryl and alkyl functionalized substrates. Control experiments and computational studies reveal the sterically hindered well-defined chiral pocket instead of the substrates bearing electron-withdrawing diester groups is important for controlling the enantioselectivity and regioselectivity. Scale-up reaction and follow-up diverse transformations are also presented. Density Functional theory (DFT) computations suggest that the regio- and enantio-selectivities originate from the cyclopropene insertion to the Rh-H bond. The high regioselectivity is found to benefit from the presence of more efficient noncovalent interactions (NCIs) manifesting in the form of C–H···Cl, C–H···N, and l.p(Cl)···π contacts.

Abstract Developing catalysts with both useful enantioselectivities and million turnover numbers (TONs) for asymmetric hydrogenation of ketones is attractive for industrial production of high-value bioactive chiral entities but remains a challenging. Herein, we report an ultra-efficient anionic Ir-catalyst integrated with the concept of multidentate ligation for asymmetric hydrogenation of ketones. Biocatalysis-like efficacy of up to 99% ee (enantiomeric excess), 13,425,000 TON (turnover number) and 224 s−1 TOF (turnover frequency) were documented for benchmark acetophenone. Up to 1,000,000 TON and 99% ee were achieved for challenging pyridyl alkyl ketone where at most 10,000 TONs are previously reported. The anionic Ir-catalyst showed a novel preferred ONa/MH instead of NNa/MH bifunctional mechanism. A selective industrial route to enantiopure nicotine has been established using this anionic Ir-catalyst for the key asymmetric hydrogenation step at 500 kg batch scale, providing 40 tons scale of product.

Chiral succinimides are ubiquitous in bioactive compounds. Here, authors report a stereodivergent method for accessing 3,4-disubstituted succinimides, and the origin of stereoselectivity is elucidated by experimental and theoretical investigations.

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.

The development of highly active and enantioselective ligands and catalysts for the asymmetric hydrogenation of ketone has been the goal of synthetic chemists for more than fifty years. Herein, a series of ferrocene-based tetradentate ligands were developed and applied in Ir-catalysed asymmetric hydrogenation of ketone. The hydrolytic ring-opening of the oxazoline moiety of ligand f-amphox leads to the accidental discovery of a highly efficient and enantioselective tetradentate ligand f-phamidol which showed extraordinarily high reactivity and enantioselectivity (up to 99% yield, up to >99% ee and up to 1,000,000 TON). In addition, two types of other tetradentate ligands f-phamida and f-phamide were also synthesized and evaluated.

Isomerization-linear-hydroformylation is demanding, however, not an addressed issue, for 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−1 TOF whereas 96% linear selectivity (n:i ​= ​24), 71% conversion and 948 h−1 TOF 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−1 TOF.

A practical and efficient two-step synthetic process for the preparation of (R)-(-)-denopamine has been developed. The key step asymmetric hydrogenation was conducted at mild temperature (60 ​°C) under a hydrogen pressure of 50 ​atm by using Ir/f-amphox as catalyst at low catalyst loading (S/C ​= ​20 ​000). Under the optimized condition, the desired product (R)-(-)-denopamine was obtained with 70% total yield and > 99.9% ee after crystallization. The pilot-scale experiment has been performed at 500 ​g level, showing great potential for the production of high quality active pharmaceutical ingredient (API).

Enantiomeric bridged [2,2,1] bicyclic lactone skeletons and their ring-opening products are important scaffolds widely occurring in both pharmaceutics and biology active compounds. Here the authors show an efficient method for enantioselective construction of these compounds bearing a quaternary stereocenter via Rh-catalyzed asymmetric hydroformylation/intramolecular cyclization/ pyridinium chlorochromate oxidation.

A large number of marketed drugs contains a chiral carboxylic acid scaffold. Here, the authors report the asymmetric hydrogenation of α,β-unsaturated carboxylic acids to α-chiral carboxylic acids using a cobalt catalyst bearing an electron-donating chiral diphosphine ligand.

Summary: Chiral cyclic sulfamidates are useful building blocks to construct compounds, such as chiral amines, with important applications. Often these compounds can only be generated through expensive precious metal catalysts. Here, Ni(OAc)2/(S, S)-Ph-BPE-catalyzed highly efficient asymmetric hydrogenation of cyclic sulfamidate imines was successfully developed, affording various chiral cyclic sulfamidates with high yields and excellent enantioselectivities (up to 99% yield, >99% enantiomeric excess [ee]). This Ni-catalyzed asymmetric hydrogenation on a gram scale has been achieved with only 0.1 mol% catalyst loading in 99% yield with 93% ee. Other types of N-sulfonyl ketimines were also hydrogenated well to obtain the corresponding products with >99% conversion, 96%–97% yields, and 97%–>99% ee. In addition, this asymmetric methodology could produce other enantioenriched organic molecules, such as chiral β-fluoroamine, amino ether, and phenylglycinol. Moreover, a reasonable catalytic cycle was provided according to the deuterium-labeling studies, which could reveal a possible mechanism for this Ni-catalyzed asymmetric hydrogenation. : Chemistry; Catalysis; Organic Chemistry; Stereochemistry Subject Areas: Chemistry, Catalysis, Organic Chemistry, Stereochemistry

Cycloisomerization of 1,n-allenynes allows to efficiently assembly polycyclic skeletons, however its asymmetric variant remains elusive. Here, the authors report the enantioselective Rh(I)-catalyzed cycloisomerization of 1,6-allenynes and disclose an uncommon 5-exo-dig pathway via DFT calculations.

Hydroformylation of 1,2-disubstituted alkenes usually occurs at the α position of the directing heteroatom. Here, the authors report the asymmetric rhodium-catalyzed hydroformylation of 1,2-disubstituted alkenylsilanes with excellent regioselectivity at the β position (relative to the silicon heteroatom) and enantioselectivity.

Ginkgolides are the major active component of Ginkgo biloba for inhibition of platelet activating factor receptor. An azide-alkyne Huisgen cycloaddition reaction was used to introduce a triazole nucleus into the target ginkgolide molecules. A series of ginkgolide-1,2,3-triazole conjugates with varied functional groups including benzyl, phenyl and heterocycle moieties was thus synthesized. Many of the designed derivatives showed potent antiplatelet aggregation activities with IC50 values of 5~21 nM.

The organocatalysis-based dynamic kinetic resolution (DKR) process has proved to be a powerful strategy for the construction of chiral compounds. In this feature review, we summarized recent progress on the DKR process, which was promoted by chiral bifunctional (thio)urea and squaramide catalysis via hydrogen-bonding interactions between substrates and catalysts. A wide range of asymmetric reactions involving DKR, such as asymmetric alcoholysis of azlactones, asymmetric Michael–Michael cascade reaction, and enantioselective selenocyclization, are reviewed and demonstrate the efficiency of this strategy. The (thio)urea and squaramide catalysts with dual activation would be efficient for more unmet challenges in dynamic kinetic resolution.

A water-mediated and Rh-catalysed one-pot multi-step synthesis of chiral 1,3-diarylpropan-1-ols is presented. This protocol utilizes readily available terminal alkynes and aldehydes as reaction partners, and features mild conditions, easy operation and water as the sole solvent, thus serving as an ideal means for the efficient synthesis of chiral 1,3-diarylpropan-1-ols. Control experiments suggested that the formation of chalcone intermediate followed by a double reductive process is crucial for the success of the reaction. This catalytic methodology could be easily scaled up for gram-scale synthesis with up to 10 000 S/C and the resulting products can be used to easily derive various bioactive molecules. [ABSTRACT FROM AUTHOR]