Stereodivergent assembly of tetrahydro-γ-carbolines via synergistic catalytic asymmetric cascade reaction

Asymmetric synthesis of quinolinone-based polycyclic indoles through [1,3]-rearrangement/cyclization reaction

We have developed an enantioselective [1,3]-rearrangement/cyclization reaction that provides efficient access to quinolinone-based polycyclic indole derivatives. This catalytic system exhibits broad substrate scope, enabling the stereocontrolled synthesis of two valuable scaffolds: 3,4-dihydroquinolin-2-ones and cyclopenta[b]indoles with excellent stereoselectivity (>40 examples, 83-99% ee, >19 : 1 dr). Notably, the obtained products demonstrate promising anticancer activity.

Ternary Aldehyde-Copper-Iridium Catalysis Enables Stereodivergent Allylation via α-C-H Functionalization of Primary Amines

α-Chiral primary amines are recognized as one of the most valuable and versatile synthetic intermediates, widely utilized in the construction of diverse amine-containing natural products, pharmaceuticals, and agrochemicals. The direct asymmetric α-C-H functionalization of unprotected primary amines is the most straightforward method for creating these motifs. However, this transformation remains underdeveloped, particularly in stereodivergent synthesis of primary amines with multiple stereocenters. Herein, we report an aldehyde/copper/iridium ternary catalytic system, which was successfully employed for the direct enantio- and diastereodivergent α-allylation of primary α-amino-chromanone without requiring additional protection or activation of the NH2 group. A wide range of α-tertiary primary amines bearing vicinal stereocenters were prepared in high yields with excellent enantio- and diastereoselectivities (generally >20:1 dr and >99% ee). Notably, all four stereoisomers of the α-tertiary amines can be readily prepared by simply switching the configuration combinations of the two chiral metal catalysts. Furthermore, the asymmetric induction model for the α-C-H functionalization of primary amines was meticulously elucidated through comprehensive density functional theory (DFT) calculations.

The stereo-divergent functionalization of alkynes: a comprehensive review

Alkynes are central in crafting pharmaceuticals, agrochemicals, and materials owing to their reactivity and linear geometry. This review unveils cutting-edge advancements in the stereo-divergent functionalization of alkynes, transforming them into invaluable tools for synthesizing stereochemically defined alkenes and alkanes. The review highlights ground-breaking methodologies that achieve exceptional E- and Z-selectivity using innovative catalysts like cobalt, nickel, and palladium through hydrogenation, hydroboration, and hydrosilylation. Recent breakthroughs such as dual-catalytic systems and energy transfer catalysis enable unprecedented stereocontrol. Sustainable strategies including water as a hydrogen source and recyclable catalysts align with green chemistry principles, paving the way for eco-friendly synthesis. This synthesis of cutting-edge techniques and their applications inspire new avenues in synthetic chemistry, offering transformative tools for creating complex molecular architectures with precision and sustainability.

Cascade Reaction Enables Heterointerfaces-Enriched Nanoarrays for Ampere-Level Hydrogen Production

Designing high-performance electrocatalysts with superior catalytic activity and stability is essential for large-scale hydrogen production via water electrolysis. Heterostructure nanoarrays are promising candidates, though achieving both high activity and stability simultaneously, especially under high current densities, remains challenging. To this end, we have developed a cascade reaction process that constructs a series of heterostructure nanoarrays with rich heterointerfaces. This process involves treating nickel foam (NF) with molten KSCN and transition metal salts. Initially, NF reacts with KSCN to form Ni9S8 nanoarrays and S2- ions, which are subsequently captured by transition metal ions to form sulfides that are directly integrated onto the nanoarrays, resulting in abundant heterointerfaces. Both experimental and theoretical results indicate that these rich heterointerfaces significantly enhance the interfacial interaction between Ni9S8 and RuS2 within the nanoarrays (termed RH-Ni9S8/RuS2), markedly improving both the intrinsic activity and stability for the hydrogen evolution reaction (HER). Impressively, the RH-Ni9S8/RuS2 demonstrates exceptional HER performance, achieving a low overpotential of just 180 mV at 1000 mA cm-2 and maintaining stability for up to 500 h under such high-current-density conditions. This innovative approach paves the way for the interfacial design and synthesis of high-performance catalysts for ampere-level hydrogen production.

Pd/Cu Catalyzed Asymmetric Allylation for Stereodivergent Synthesis of Glutamic Acid Derivatives

A synergistic Pd/Cu catalyst system has been developed for stereodivergent transformation of Morita-Baylis-Hillman (MBH) carbonates and Schiff bases derived from simple amino acids to afford a series of optically active β-branched γ-methyleneglutamic acid derivatives with adjacent tertiary/tertiary and quaternary/tertiary stereocenters in high yields (up to 96 %) with excellent diastereo- and enantioselectivities (>20/1 dr and >99 % ee in most cases) under mild conditions. The use of SKP ligand is disclosed to be crucial for the success of the transformation, and in particular allowing the reaction to proceed at low catalyst loading (0.02 mol % for Pd and 0.08 mol % for Cu). The high efficiency of the catalysis was attributed to the formation of intimate ion pair complex A1, composed of Pd-phosphonium cation and a t-butoxide anion, which would facilitate the subsequent deprotonation and C-C coupling events. All four stereoisomers of the β-branched glutamic acid derivatives were readily prepared by permutation of the catalyst enantiomers. Synthetic utility of the methodology was exemplified by efficient synthesis of a fused pyrrolooxazolidinone with three contiguous chiral centers, highlighting the power of synergistic Pd/Cu catalysis for asymmetric allylic alkylation with MBH carbonates.

Stereodivergent assembly of δ-valerolactones with an azaarene-containing quaternary stereocenter enabled by Cu/Ru relay catalysis

Developing methodologies for the expedient construction of biologically important δ-valerolactones bearing a privileged azaarene moiety and a sterically congested all-carbon quaternary stereocenter is important and full of challenges. We present herein a novel multicatalytic strategy for the stereodivergent synthesis of highly functionalized chiral δ-valerolactones bearing 1,4-nonadjacent quaternary/tertiary stereocenters by orthogonally merging borrowing hydrogen and Michael addition between α-azaaryl acetates and allylic alcohols followed by lactonization in a one-pot manner. Enabled by Cu/Ru relay catalysis, this cascade protocol offers the advantages of atom/step economy, redox-neutrality, mild reaction conditions, and broad substrate tolerance. Scale-up experiments and synthetic transformations further demonstrated the potential for synthetic applications. Mechanistic experiments support the envisioned bimetallic relay catalytic mechanism, and the key role of Cs2CO3 in promoting lactonization was also revealed.

Rational Design and Stereodivergent Construction of Enantioenriched Tetrahydro-β-Carbolines Containing Multistereogenic Centers

Chiral tetrahydro-β-carbolines, as one of the most intriguing subtypes of indole alkaloids, have emerged as the privileged units in plenty of natural products and biologically active molecules with an impressive range of bioactive properties. However, the stereodivergent construction of these valuable skeletons containing multistereogenic centers from readily available starting materials remains very challenging, especially, in view of the introduction of an axial chirality. Herein, we developed an efficient method toward enantioenriched tetrahydro-β-carbolines with readily available tryptophan-derived aldimine esters and allylic carbonates under mild reaction conditions. The reaction proceeds in a sequential fashion involving synergistic Cu/Ir-catalyzed stereodivergent allylation and the Brønsted acid-promoted stereospecific Pictet-Spengler reaction, affording a wide range of chiral tetrahydro-β-carbolines bearing up to four stereogenic centers in good yields with excellent stereoselectivity control. When N-aryl-substituted tryptophan-derived aldimine esters were utilized, notably, a unique C-N heterobiaryl axis could be simultaneously constructed with the formation of the third point stereogenic center in the last cyclization step through dynamic kinetic resolution (DKR). Computational mechanistic studies established a plausible synergistic mechanism for dual Cu/Ir-catalyzed asymmetric allylation and the succeeding protonation-assisted Pictet-Spengler cyclization to complete the annulation. Structure-activity relationship analyses unveil the origins of stereochemistry for the building of one axis and three point stereogenic centers.

Pd/Cu-Cocatalyzed Enantio- and Diastereodivergent Wacker-Type Dicarbofunctionalization of Unactivated Alkenes

The Wacker and Wacker-type reactions are some of the most fundamental and powerful transformations in organic chemistry for their ability to efficiently produce valuable chemicals. Remarkable progress has been achieved in asymmetric oxy/aza-Wacker-type reactions; however, asymmetric Wacker-type dicarbofunctionalization remains underdeveloped, especially for the concurrent construction of two stereocenters. Herein, we report a Pd/Cu-cocatalyzed enantio- and diastereodivergent Wacker-type dicarbofunctionalization of alkene-tethered aryl triflates with imino esters. A series of 2-indanyl motifs bearing adjacent carbon stereocenters could be easily synthesized in moderate to excellent yields and with good to excellent diastereo- and enantioselectivities (up to >20:1 dr and >99% ee). Density functional theory calculations revealed that the origin of diastereoselectivity in this Pd/Cu synergistic catalytic system is jointly determined by both the intermolecular anti-carbopalladation of alkenes and the reductive elimination processes, in accordance with the Curtin-Hammett principle.

Ni/Cu Dual-Catalyzed Propargylation for the Stereodivergent Synthesis of Methohexital

The development of efficient methodologies for the controlled manufacture of specific stereoisomers bearing quaternary stereocenters has prompted advances in a variety of scientific disciplines including pharmaceutical chemistry, materials science, and chemical biology. However, complete control of the absolute and relative stereochemical configurations of alkyne derivatives remains an unmet synthetic challenge. Herein, a Ni/Cu dual-catalyzed asymmetric propargylic substitution reaction is presented to produce propargylated products with all-carbon quaternary stereocenters in high yields with significant diastereo- and enantioselectivities (up to >20:1 dr, >99% ee). The synthesis of all stereochemical variants of methohexital, a widely used sedative-hypnotic drug, exemplifies the efficacy of dual-catalyzed stereodivergent propargylation.

Stereodivergent Construction of 1,5/1,7-Nonadjacent Tetrasubstituted Stereocenters Enabled by Pd/Cu-Cocatalyzed Asymmetric Heck Cascade Reaction

The construction of chiral motifs containing nonadjacent stereocenters in an enantio- and diastereoselective manner has long been a challenging task in synthetic chemistry, especially with respect to their stereodivergent synthesis. Herein, we describe a protocol that enables the enantio- and diastereoselective construction of 1,5/1,7-nonadjacent tetrasubstituted stereocenters through a Pd/Cu-cocatalyzed Heck cascade reaction. Notably, a C=C bond relay strategy involving the shift of the π-allyl palladium intermediate was successfully applied in the asymmetric construction of 1,7-nonadjacent stereocenters. The current method allows for the efficient preparation of chiral molecules bearing two privileged scaffolds, oxindoles and non-natural α-amino acids, with good functional group tolerance. The full complement of the four stereoisomers of products bearing 1,5/1,7-nonadjacent stereocenters could be readily accessed by a simple combination of two chiral metal catalysts with different enantiomers.

Enal-azomethine ylides: application in the synthesis of functionalized pyrroles

Rhodium-catalyzed [3 + 2] annulation of diazoenals and N-alkyl imines resulted in N-alkyl-pyrrole-3-carbaldehyde derivatives. The reaction involves thermal 6π-electrocyclization and aromatization of a new class of enal-azomethine ylides (EAYs). The EAYs derived from dihydroisoquinoline and 2H-azirine gave fused-pyrrole and pyridine derivatives, respectively. The synthetic importance of pyrrole products has been demonstrated by one-step synthesis of the biologically relevant pyrrolo[3,2-c]quinoline scaffold as well as pyrrolo[2,1-a]isoquinoline which is a core structure of lamellarin alkaloids.

Copper/ruthenium relay catalysis enables 1,6-double chiral inductions with stereodivergence

The dual catalysis strategy is an efficient and powerful tool to fulfill the stereodivergent synthesis of stereoisomeric products from the same set of starting materials. Great attention has been given to the construction of chiral compounds with two contiguous stereocenters. However, the synthesis of two remote noncontiguous stereocenters is more challenging and is less developed, despite the high demand for synthetic tactics. We herein developed an unprecedented example of the stereodivergent preparation of synthetically useful and biologically important chiral ζ-hydroxy amino ester derivatives containing remote 1,6-noncontiguous stereocenters and a unique β,γ-unsaturation moiety. This cascade dehydrogenation/1,6-Michael addition/hydrogenation protocol between readily-available ketoimine esters and racemic branched dienyl carbinols was rationally realized with bimetallic copper/ruthenium relay catalysis. The key features of the process were atom economy, step economy, and redox-neutrality. All four stereoisomers of chiral ζ-hydroxy amino ester derivatives were easily achieved by the orthogonal permutations of a chiral copper catalyst and chiral ruthenium catalyst. Importantly, a much more challenging stereodivergent synthesis of all eight stereoisomers of chiral peptide products containing three remote stereocenters was accomplished with excellent results through the cooperation of two chiral catalyst pairs and substrate enantiomers.

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.

Synthesis of Pyridazino[4,5-b]indoles by [3+3] Annulation of 2-Alkenylindoles and Hydrazonyl Chlorides

A novel [3+3] annulation reaction of 2-alkenylindoles with hydrazonyl chlorides in the presence of base for the formation of pyridazino[4,5-b]indoles was developed. This approach provided a convenient and efficient way to synthesize a series of functionalized pyridazino[4,5-b]indoles derivatives. The method exhibited a broad substrate scope and provided the corresponding pyridazino[4,5-b]indoles products with excellent yields.

Diastereo-divergent synthesis of chiral hindered ethers via a synergistic calcium(II)/gold(I) catalyzed cascade hydration/1,4-addition reaction

Hindered ethers are ubiquitous in natural products and bioactive molecules. However, developing an efficient method for the stereocontrolled synthesis of all stereoisomers of chiral hindered ethers is highly desirable but challenging. Here we show a strategy that utilizes in situ-generated water as a nucleophile in an asymmetric cascade reaction involving two highly reactive intermediates, 3-furyl methyl cations and ortho-quinone methides (o-QMs), to synthesize chiral hindered ethers. The Ca(II)/Au(I) synergistic catalytic system enables the control of diastereoselectivity and enantioselectivity by selecting suitable chiral phosphine ligands in this cascade hydration/1,4-addition reaction, affording all four stereoisomers of a diverse range of chiral tetra-aryl substituted ethers with high diastereoselectivities (up to >20/1) and enantioselectivities (up to 95% ee). This work provides an example of chiral Ca(II)/Au(I) bimetallic catalytic system controlling two stereogenic centers via a cascade reaction in a single operation.

Synthesis of S(IV)-Stereogenic Chiral Thio-Oxazolidinones via Palladium-Catalyzed Asymmetric [3+2] Annulations

Organic molecules bearing chiral sulfur stereocenters exert a great impact on asymmetric catalysis and synthesis, chiral drugs, and chiral materials. Compared with acyclic ones, the catalytic asymmetric synthesis of thio-heterocycles has largely lagged behind due to the lack of efficient synthetic strategies. Here we establish the first modular platform to access chiral thio-oxazolidinones via Pd-catalyzed asymmetric [3+2] annulations of vinylethylene carbonates with sulfinylanilines. This protocol is featured by readily available starting materials, and high enantio- and diastereoselectivity. In particular, an unusual effect of a non-chiral supporting ligand on the diastereoselectivity was observed. Possible reaction mechanisms and stereocontrol models were proposed.

Asymmetric Construction of Carbon-Fluorine Quaternary Stereogenic Centers via Synergistic Pd/Cu Catalysis

We developed an asymmetric decarboxylative allylic alkylation of vinylethylene carbonates with α-fluoro pyridinyl acetates through a synergistic palladium/copper catalysis. This protocol provides chiral allylic alcohol with carbon-fluorine quaternary stereogenic centers in good yield with good enantioselectivities and excellent regioselectivities. The utility of this approach was further demonstrated via a gram-scale experiment and derivatizations of the product.

Copper/Ruthenium Relay Catalysis for Stereodivergent Access to δ-Hydroxy α-Amino Acids and Small Peptides

An atom- and step-economical and redox-neutral cascade reaction enabled by asymmetric bimetallic relay catalysis by merging a ruthenium-catalyzed asymmetric borrowing-hydrogen reaction with copper-catalyzed asymmetric Michael addition has been realized. A variety of highly functionalized 2-amino-5-hydroxyvaleric acid esters or peptides bearing 1,4-non-adjacent stereogenic centers have been prepared in high yields with excellent enantio- and diastereoselectivity. Judicious selection and rational modification of the Ru catalysts with careful tuning of the reaction conditions played a pivotal role in stereoselectivity control as well as attenuating undesired α-epimerization, thus enabling a full complement of all four stereoisomers that were otherwise inaccessible in previous work. Concise asymmetric stereodivergent synthesis of the key intermediates for biologically important chiral molecules further showcases the synthetic utility of this methodology.

Dual-Catalyzed Stereodivergent Electrooxidative Homocoupling of Benzoxazolyl Acetate

The development of a reliable strategy for stereodivergent radical reactions that allows convenient access to all stereoisomers of homocoupling adducts with multiple stereogenic centers remains an unmet goal in organic synthesis. Herein, we describe a dual-catalyzed electrooxidative C(sp3)-H/C(sp3)-H homocoupling with complete absolute and relative stereocontrol for the synthesis of molecules with contiguous quaternary stereocenters in a general and predictable manner. The stereodivergent electrooxidative homocoupling reaction is achieved by synergistically utilizing two distinct chiral catalysts that convert identical racemic substrates into inherently distinctive reactive chiral intermediates, dictate enantioselective radical addition, and allow access to the full complement of stereoisomeric products via simple catalyst permutation. The successful execution of the dual-electrocatalytic strategy programmed via electrooxidative activation provides a significant conceptual advantage and will serve as a useful foundation for further research into cooperative stereocontrolled radical transformations and diversity-oriented synthesis.

Modular access to chiral bridged piperidine-γ-butyrolactones via catalytic asymmetric allylation/aza-Prins cyclization/lactonization sequences

Chiral functionalized piperidine and lactone heterocycles are widely spread in natural products and drug candidates with promising pharmacological properties. However, there remains no general asymmetric methodologies that enable rapid assemble both critical biologically important units into one three-dimensional chiral molecule. Herein, we describe a straightforward relay strategy for the construction of enantioenriched bridged piperidine-γ-butyrolactone skeletons incorporating three skipped stereocenters via asymmetric allylic alkylation and aza-Prins cyclization/lactonization sequences. The excellent enantioselectivity control in asymmetric allylation with the simplest allylic precursor is enabled by the synergistic Cu/Ir-catalyzed protocol; the success of aza-Prins cyclization/lactonization can be attributed to the pivotal role of the ester substituent, which acts as a preferential intramolecular nucleophile to terminate the aza-Prins intermediacy of piperid-4-yl cation species. The resulting chiral piperidine-γ-butyrolactone bridged-heterocyclic products show impressive preliminary biological activities against a panel of cancer cell lines.

Stereodivergent synthesis of α-fluoro α-azaaryl γ-butyrolactones via cooperative copper and iridium catalysis

The development of stereodivergent synthetic methods to access all four stereoisomers of biologically important α-fluoro γ-butyrolactones containing vicinal stereocenters is of great importance and poses a formidable challenge owing to ring strain and steric hindrance. Herein, a novel asymmetric [3+2] annulation of α-fluoro α-azaaryl acetates with vinylethylene carbonate was successfully developed through Cu/Ir-catalyzed cascade allylic alkylation/lactonization, affording a variety of enantioenriched α-fluoro γ-butyrolactones bearing vicinal stereogenic centers with high reaction efficiency and excellent levels of both stereoselectivity and regioselectivity (up to 98% yield, generally >20:1 dr and >99% ee). Notably, all four stereoisomers of these pharmaceutically valuable molecules could be accessed individually via simple permutations of two enantiomeric catalysts. In addition, other azaaryl acetates bearing α-methyl, α-chlorine or α-phenyl group were tolerated well in this transformation. Reaction mechanistic investigations were conducted to explore the process of this bimetallic catalysis based on the results of reaction intermediates, isotopic labelling experiments, and kinetic studies.

Enantio- and Diastereodivergent N-Heterocyclic Carbene/Nickel Dual-Catalyzed Umpolung Propargylic Substitutions of Enals

The creation of full stereoisomers of an organic compound comprising multiple contiguous stereocenters with simultaneous control over both relative and absolute configurations remains a significant challenge in synthetic chemistry. Using a cooperative catalysis strategy, we established an N-heterocyclic carbene/nickel-catalyzed enantio- and diastereodivergent propargylation reaction to access 3,3'-disubstituted oxindoles, enabling the incorporation of internal alkyne functionality and the introduction of a single quaternary or vicinal quaternary/tertiary stereogenic center. By selecting the appropriate combination of catalyst chirality, all four potential stereoisomers of α-quaternary propargylated oxindoles were synthesized in a predictable and precise way with remarkable yields, diastereoselectivities, and enantioselectivities from identical starting materials. The synthetic utility of this method was demonstrated in the concise asymmetric total synthesis of (-)-debromoflustramine B and (-)-C(β-Me)-debromoflustramine B.

From Conventional to Sustainable Catalytic Approaches for Heterocycles Synthesis

Synthesis of heterocyclic compounds is fundamental for all the research area in chemistry, from drug synthesis to material science. In this framework, catalysed synthetic methods are of great interest to effective reach such important building blocks. In this review, we will report on some selected examples from the last five years, of the major improvement in the field, focusing on the most important conventional catalytic systems, such as transition metals, organocatalysts, to more sustainable ones such as photocatalysts, iodine-catalysed reaction, electrochemical reactions and green innovative methods.

Asymmetric Synthesis of Chiral 1,2-Bis(Boronic) Esters Featuring Acyclic, Non-Adjacent 1,3-Stereocenters

The construction of acyclic, non-adjacent 1,3-stereogenic centers, prevalent motifs in drugs and bioactive molecules, has been a long-standing synthetic challenge due to acyclic nucleophiles being distant from the chiral environment. In this study, we successfully synthesized highly valuable 1,2-bis(boronic) esters featuring acyclic and nonadjacent 1,3-stereocenters. Notably, this reaction selectively produces migratory coupling products rather than alternative deborylative allylation or direct allylation byproducts. This approach introduces a new activation mode for selective transformations of gem-diborylmethane in asymmetric catalysis. Additionally, we found that other gem-diborylalkanes, previously challenging due to steric hindrance, also successfully participated in this reaction. The incorporation of 1,2-bis(boryl)alkenes facilitated the diversification of the alkenyl and two boron moieties in our target compounds, thereby enabling access to a broad array of versatile molecules. DFT calculations were performed to elucidate the reaction mechanism and shed light on the factors responsible for the observed excellent enantioselectivity and diastereoselectivity. These were determined to arise from ligand-substrate steric repulsions in the syn-addition transition state.

Dispersion Interactions in Asymmetric Induction for Constructing Vicinal Stereogenic Centers

ConspectusVicinal stereogenic centers are prevalent structural motifs of primary functional relevance in natural products and bioactive molecules. The quest for the rapid and controllable construction of vicinal stereogenic centers stands as a frontier endeavor in asymmetric organic synthesis. Over the past decade, stereodivergent synthesis has been intensely researched within the realm of bimetallic catalysis, aiming at establishing novel transition-metal dual-catalytic reactions that efficiently generate all stereochemical combinations of multichiral molecules from identical starting materials, thus offering new opportunities toward rapid complexity building and diversity-oriented chiral compound library generation. In this Account, we summarize our recent advancements in computational investigations of stereodivergent asymmetric allylic alkylation, an important reaction class heavily studied for the purpose of constructing vicinal stereogenic centers. Our discussions focus on synergistic bimetallic catalysis for the syntheses of α,α-disubstituted α-amino acids and cascade allylation/cyclization toward enantiomerically enriched indole-containing heterocycles. We describe our series of studies that converge in establishing the molecular mechanism of asymmetric induction for chiral copper-azomethine ylide, a nucleophile that holds widespread utility and is characterized by a distinctive, sterically biased surrounding enveloping the prochiral center. Notably, our studies revealed that attacks at the prochiral site by allylmetal species are significantly favored by dispersion attraction from one face (-PPh2) but blocked by steric repulsion and associated structural distortions on the opposite face (oxazoline), therefore building up a multimodal and highly robust face-selective stereoinduction. We showcase how a suite of systematic computational analyses generates precise atomistic insights into a number of systems of relevance. We also discuss how the same methodologies can be applied to chiral intermediates with shared interaction patterns, including the rhodium-Josiphos catalyst in asymmetric hydrogenation to create two continuous stereocenters. In the selectivity-controlling migratory insertion step, our computational models unveiled that the reaction is favored by ligand-substrate dispersion attraction on the -PPh2 side and hindered by steric repulsion on the opposite -PtBu2 side. These noncovalent interactions along with the distal ligand-auxiliary structural distortions enable strictly oriented three-dimensional stereoinduction. Our analysis of ligand-substrate dispersion interactions and steric effects in competing pathways highlights certain interaction-level similarities between PHOX-type and Josiphos-type ligands in asymmetric induction. In summary, this Account underscores the foundational significance and broad applicability of nonbonded dispersion interactions in asymmetric inductions for the construction of vicinal stereogenic centers. We envisage that the computational methodologies employed in these studies will shift toward a paradigm of interaction-based rational molecular and reaction design.

Enantioconvergent iso-Pictet-Spengler Reactions: Organocatalytic Synthesis of Chiral Tetrahydro-γ-carbolines

Enantioconvergent iso-Pictet-Spengler reactions of chiral racemic ß-formyl esters and a ß-keto ester are reported, providing complex tetrahydro-γ-carbolines containing two contiguous stereocenters. The reactions are catalyzed by a chiral thiourea and benzoic acid cocatalytic system and constitute rare cases of nonhydrogenative stereoconvergent additions to racemic α-stereogenic-ß-dicarbonyls. Elaboration of the products to chiral aminoalcohols and carbamates is demonstrated.

Electron-rich benzofulvenes as effective dipolarophiles in copper(i)-catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides

A series of benzofulvenes without any electron-withdrawing substituents were employed as 2π-type dipolarophiles for the first time to participate in Cu(i)-catalyzed asymmetric 1,3-dipolar cycloaddition (1,3-DC) reactions of azomethine ylides. An intrinsic non-benzenoid aromatic characteristic from benzofulvenes serves as a key driving force for activation of the electron-rich benzofulvenes. Utilizing the current methodology, a wide range of multi-substituted chiral spiro-pyrrolidine derivatives containing two contiguous all-carbon quaternary centers were formed in good yield with exclusive chemo-/regioselectivity and high to excellent stereoselectivity. Computational mechanistic studies elucidate the origin of the stereochemical outcome and the chemoselectivity, in which the thermostability of these cycloaddition products is the major factor.

Synergistic Li/Li Bimetallic System for the Asymmetric Synthesis of Antituberculosis Drug TBAJ-587

TBAJ-587, an analogue of the antituberculosis drug bedaquiline (BDQ), bearing a diarylquinoline skeleton retains the high bacterial potency, is less toxic, and has a better pharmacokinetic profile than the parent molecule, which has entered phase I clinical trials. In contrast to its fascinating bioactivity, however, the highly efficient synthesis of this molecule is still an unsolved challenge. Herein, the first asymmetric synthesis of TBAJ-587 based on a synergistic Li/Li bimetallic system is reported. The product could be obtained in an excellent yield of 90% and an enantiomeric ratio (er) of 80:20. Furthermore, the reaction could be conducted on a 5 g scale, and the product was obtained with 99.9:0.1 er after a simple recrystallization. The realization of this protocol will greatly aid the demand for clinical drug production.

Enantio- and diastereodivergent synthesis of fused indolizines enabled by synergistic Cu/Ir catalysis

Highly diastereo-/enantioselective assembly of 2,3-fused indolizine derivatives could be easily available through a cascade allylation/Friedel-Crafts type reaction enabled by a synergistic Cu/Ir catalysis. This designed protocol provides an unprecedented and facile route to enantioenriched indolizines bearing three stereogenic centers in moderate to high yields with excellent stereoselective control, which also featured broad substrate generality. Remarkably, four stereoisomers of the 2,3-fused indolizine products could be efficiently constructed in a predictable manner through the pairwise combination of copper and iridium catalysts. The synthetic utility of this method was readily elaborated by a gram-scale reaction, and synthetic transformations to other important chiral indolizine derivatives. Quantum mechanical explorations constructed a plausible synergetic catalytic cycle, revealed the origins of stereodivergence, and rationalized the protonation-stimulated stereoselective Friedel-Crafts type cyclization to form the indolizine products.

Stereodivergent Construction of 1,3-Chiral Centers via Tandem Asymmetric Conjugate Addition and Allylic Substitution Reaction

Herein, we report a synthesis of cyclohexanones bearing multi-continuous stereocenters by combining copper-catalyzed asymmetric conjugate addition of dialkylzinc reagents to cyclic enones with iridium-catalyzed asymmetric allylic substitution reaction. Good to excellent yields, diastereoselectivity and enantioselectivity can be obtained. Unlike the stereodivergent construction of adjacent stereocenters (1,2-position) reported in the literature, the current reaction can achieve the stereodivergent construction of nonadjacent stereocenters (1,3-position) by a proper combination of two chiral catalysts with different enantiomers.

Metal-Catalyzed Cascade Reactions between Alkynoic Acids and Dinucleophiles: A Review

Cascade reactions provide a straightforward access to many valuable compounds and reduce considerably the number of steps of a synthetic sequence. Among the domino and multicomponent processes that involve alkynes, the cascade reaction between alkynoic acids and C-, N-, O- and S-aminonucleophiles stands out as a particularly powerful tool for the one-pot construction of libraries of nitrogen-containing heterocyclic compounds with scaffold diversity and molecular complexity. This reaction, based on an initial metal-catalyzed cycloisomerization that generates an alkylidene lactone intermediate, was originally catalyzed by gold(I) catalysts, along with silver salts or Brönsted acid additives, but other alternative metal catalysts have emerged in the last decade as well as different reaction media. This review examines the existing literature on the topic of metal-catalyzed cascade reactions of acetylenic acids and dinucleophiles and discusses aspects concerning substrate/catalyst ratio for every catalyst system, nature of the aminonucleophile involved and substrate scope. In addition, alternative solvents are also considered, and an insight into the pathway of the reaction and possible intermediates is also provided.

Iridium-Catalyzed Intramolecular Asymmetric Allylation of Vinyl Benzoxazinones for the Synthesis of Chiral 4H-3,1-Benzoxazines via Kinetic Resolution

Chiral benzoxazinones and 4H-3,1-benzoxazines as important motifs are widely found in abundant pharmaceuticals and biological molecules. We herein successfully developed the first kinetic resolution (KR) process of racemic benzoxazinones through Ir-catalyzed asymmetric intramolecular allylation, furnishing a wide range of chiral benzoxazinones and 4H-3,1-benzoxazines with excellent results via outstanding KR performances (with the s factor up to 170). This protocol exhibited broad substrate scope generality and good functional group tolerance, and the chiral 4H-3,1-benzoxazine products could be readily transformed to other useful optically active heterocycles.

Stereodivergent Synthesis of Allenes with α,β-Adjacent Central Chiralities Empowered by Synergistic Pd/Cu Catalysis

The stereodivergent synthesis of allene compounds bearing α,β-adjacent central chiralities has been realized via the Pd/Cu-catalyzed dynamic kinetic asymmetric alkylation of racemic allenylic esters. The matched reactivity of bimetallic catalytic system enables the challenging reaction of racemic aryl-substituted allenylic acetates with sterically crowded aldimine esters smoothly under mild reaction conditions. Various chiral non-natural amino acids bearing a terminal allenyl group are easily synthesized in high yields and with excellent diastereo- and enantioselectivities (up to >20 : 1 dr, >99 % ee). Importantly, all four stereoisomers of the product can be readily accessed by switching the configurations of the two chiral metal catalysts. Furthermore, the easy interconversion between the uncommon η³ -butadienyl palladium intermediate featuring a weak C=C/Pd coordination bond and a stable Csp² -Pd bond is beneficial for the dynamic kinetic asymmetric transformation process (DyKAT).

Diastereodivergent Desymmetric Annulation to Access Spirooxindoles: Chemical Probes for Mitosis

Spirooxindoles have emerged as promising architectures for engineering biologically active compounds. The diastereodivergent construction of unique scaffolds of this type with full control of continuous chiral centers including an all-carbon quaternary stereogenic center is yet to be developed. Here, we report an unprecedented diastereodivergent desymmetric [3 + 3] annulation of oxabicyclic alkenes with enals enabled by N-heterocyclic carbene (NHC)/Rh cooperative catalysis, leading to a series of enantiomerically enriched spirooxindole lactones with excellent enantioselectivities (up to >99% ee) and diastereoselectivities (up to >95:5 dr). The combined catalyst system comprises a rhodium complex that controls the configuration at the electrophilic carbon and an NHC catalyst that controls the configuration at the nucleophilic oxindole-containing carbon; thus, four stereoisomers of the spirooxindole products can be readily obtained simply by switching the configurations of the two chiral catalysts. Transformations of the chiral spirooxindoles delivered synthetically useful compounds. Importantly, those chiral spirooxindoles arrested mammalian cells in mitosis and exhibited potent antiproliferative activities against HeLa cells. Significantly, both absolute and relative configurations exert prominent effects on the bioactivities, underscoring great importance of catalytic asymmetric diastereodivergent synthesis beyond creating useful tools for the exploration of structure-activity relationships.

Arylsulfonylation-Triggered Cyclization of 3-Alkenyl Indoles Enabling Synthesis of Tetrahydro-γ-carboline

A visible-light promoted cyclization reaction of 3-alkenyl indole derivatives with arylsulfonyl chlorides as coupling partners has been developed, which afforded functionalized tetrahydro-γ-carbolines in good chemical yields. The reaction used 3-alkenyl indoles as radical acceptors and proceeded via the sequence of sulfonylation and intramolecular cyclization. The reaction was carried out under mild conditions and tolerated a wide range of substrates, which provides an efficient strategy for the synthesis of tetrahydro-γ-carboline derivatives.

Stereodivergent Synthesis of Enantioenriched α-Deuterated α-Amino Acids via Cascade Cu(I)-Catalyzed H-D Exchange and Dual Cu- and Ir-Catalyzed Allylation

A one-pot Cu-mediated H-D exchange with inexpensive heavy water as the deuterium source, followed by Cu- and Ir-catalyzed stereodivergent allylic alkylation, has been developed, providing efficient access to enantioenriched α-deuterium-labeled α-amino acids from readily available glycine imine esters in a high yield with excellent stereoselectivity. High deuterium enrichment, exquisite regioselectivity, precise stereoselectivity control, and operationally convenient procedures make this protocol appealing for the preparation of highly synthetically useful α-deuterated α-amino acids.

Enantioselective Synthesis of Spiroketals and Spiroaminals via Gold and Iridium Sequential Catalysis

The enantioselective cascade reaction between racemic 2-(1-hydroxyallyl)phenols and alkynols/alkynamides was realized by using a gold and iridium sequential catalytic system. In this procedure, the in situ generated exocyclic vinyl ethers or enamides undergo the asymmetric allylation/spiroketalization with π-ally-Ir amphiphilic species, which provides an efficient and straightforward access to spiroketals and spiroaminals with excellent enantioselectivities. Moreover, racemic 2-(1-hydroxyallyl)anilines were also suitable in this reaction along with a kinetic resolution process, affording enantioenriched spiroaminals and 2-(1-hydroxyallyl)anilines in good yields. The synthetic utility of this method has been demonstrated by efficient enantioselective synthesis of the analogue of Paecilospirone.

Iridium-Catalyzed Asymmetric Allylic Substitution of Methyl Azaarenes

Herein, an Ir-catalyzed asymmetric allylic substitution reaction of methyl azaarenes is described. Azaarenes such as (benzo)thiazole, oxazole, benzoimidazole, pyridine, and (iso)quinoline are all tolerated. The corresponding chiral azaarene derivatives are obtained in good yields with high enantioselectivity (up to 96 % yield and 99 % ee). The utilization of the Knochel reagent TMPZnBr⋅LiBr warrants the in situ formation of benzylic nucleophiles without additional activating reagents. ¹ H NMR studies suggested a two-fold function of the Knochel reagent in this reaction. The synthetic utility of this method has been showcased by a concise enantioselective synthesis of an allosteric protein kinase modulator.

Stereodivergent synthesis of enantioenriched azepino[3,4,5-cd]-indoles via cooperative Cu/Ir-catalyzed asymmetric allylic alkylation and intramolecular Friedel-Crafts reaction

The development of enantioselective annulation reactions using readily available substrates for the construction of structurally and stereochemically diverse heterocycles is a compelling topic in diversity-oriented synthesis. Herein, we report efficient catalytic asymmetric formal 1,3-dipolar (3 + 4) cycloadditions of azomethine ylides with 4-indolyl allylic carbonates for the construction of azepino[3,4,5-cd]-indoles fused with a challenging seven-membered N-heterocycle, a frequently occurring tricyclic indole scaffold in bioactive compounds and pharmaceuticals. Through cooperative Cu/Ir-catalyzed asymmetric allylic alkylation followed by intramolecular Friedel-Crafts reaction, an array of azepino[3,4,5-cd]-indoles were obtained in good yields with excellent diastereo-/enantioselective control. More importantly, the full stereodivergence of this transformation was established via synergistic catalysis followed by acid-promoted epimerization, and up to eight stereoisomers of the cycloadducts bearing three stereogenic centers could be predictably achieved from the same set of starting materials for the first time. Quantum mechanical computations established a plausible mechanism for the synergistic Cu/Ir catalysis to stereodivergently introduce two vicinal stereocenters whose stereochemical information is remotely delivered across the fused azepine ring to control the third chiral center. Epimerization of the last center involves protonation-enabled reversal of the thermodynamically controlled relative configuration.