Stereodivergent Synthesis of Enantioenriched γ-Butyrolactones Bearing Two Vicinal Stereocenters Enabled by Synergistic Copper and Iridium Catalysis

Direct Enantioselective Allylic Alkylation of α-Amino Esters to Quaternary Glutamates via Strategic Pyridoxal Catalyst Design

The difficulty for N-unprotected α-substituted glycinates as α-C nucleophiles originates from both competing N nucleophilic interference and steric hindrance of the α substituent, which makes direct asymmetric α-C alkylation of N-unprotected α-substituted glycinates with Morita-Baylis-Hillman (MBH) adducts especially challenging. Given the wide utilization of α-quaternary chiral glutamic acid derivatives in therapeutic studies, we took advantage of biomimetic carbonyl catalysis to achieve their efficient synthesis. A bifunctional centrally chiral pyridoxal, featured with an expanded catalytic cavity and reduced steric hindrance around the aldehyde group, was designed and synthesized. In this work, we describe the novel centrally chiral pyridoxal enabled direct asymmetric α-C alkylation of N-unprotected α-substituted glycinates with MBH acetates. A broad range of α-quaternary chiral glutamic acid derivatives with multiple modifications were produced with high reactivity and excellent stereocontrol.

Synthesis of chiral β-hydroxy allylic sulfides via iridium-catalyzed asymmetric cascade allylation/acyl transfer rearrangement

Iridium-catalyzed asymmetric allylation/acyl transfer rearrangement of thioesters and vinyl ethylene carbonate (VEC) has been developed. A wide range of structurally important chiral β-hydroxy allylic sulfide derivatives could be prepared in good yields with excellent enantioselectivity.

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.

Structure-Dependent, Switchable Alder-Ene/[2π + 2σ] Cycloadditions of Vinyl Bicyclo[1.1.0]butanes with α-Ketoesters Enabled by Palladium Catalysis

A structure-dependent, palladium-catalyzed switchable alder-ene/[2π + 2σ] cycloaddition of VBCBs with α-ketoesters has been reported. A variety of cyclobutenes and 2-oxabicyclo[2.1.1]hexanes have been efficiently achieved in good to excellent yields through strain-release-driven alder-ene reactions and [2π + 2σ] cycloadditions, respectively. The potential of this method is illustrated by the scale-up reaction and diverse postsynthetic transformations of the obtained cyclic scaffolds. Additionally, the reaction mechanism and origins of the chemoselectivity have been probed by computational studies.

Asymmetric Formal [5 + 2] Annulation of 3-Hydroxyquinolinones and Vinylethylene Carbonates through Pd/Cu Tandem Catalysis

The asymmetric [5 + 2] cycloaddition of VECs remains to be comparatively rare. Herein, we reported an enantioselective formal [5 + 2] annulation of 3-hydroxyquinolinones and vinylethylene carbonates (VECs) through Pd- and Cu-catalyzed tandem allylation/asymmetric [1,3]-rearrangement/hemiketalization sequences. The strategy exhibits good substrate tolerance, affording a wide range of tricyclic quinolinones bearing two adjacent quaternary stereocenters in moderate to good yields with excellent enantioselectivities.

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.

Direct Enantioselective α-C-H Conjugate Addition of Propargylamines to α,β-Unsaturated Ketones via Carbonyl Catalysis

Direct asymmetric α-C-H conjugate addition of propargylamines to α,β-unsaturated ketones remains a great challenge due to the low α-amino C-H acidity of propargylamines and the nucleophilic interference of the NH2 group. Utilizing a new type of pyridoxals featuring a benzene-pyridine biaryl skeleton and a bulky amide side chain as carbonyl catalyst, we have accomplished direct asymmetric α-C-H conjugate addition of NH2-unprotected propargylamines to α,β-unsaturated ketones. The adducts undergo subsequent in situ intramolecular cyclization, delivering a wide range of chiral polysubstituted 1-pyrrolines in high yields (up to 92%) with excellent diastereo- and enatioelectivities (up to >20:1 dr and 99% ee). This work has demonstrated a straightforward approach to access pharmaceutically important chiral 1-pyrrolines, and it has also provided an impressive instance of direct asymmetric functionalization of inert C-H bonds enabled by biomimetic organocatalysts.

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.

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.

Enantioselective Tsuji-Trost α-Fluoroallylation of Amino Acid Esters with Gem-Difluorinated Cyclopropanes

A novel enantioselective Tsuji-Trost-type cross coupling reaction between gem-difluorinated cyclopropanes and N-unprotected amino acid esters enabled by synergistic Pd/Ni/chiral aldehyde catalysis is presented herein. This transformation streamlined the diversity-oriented synthesis (DOS) of optically active α-quaternary α-amino acid esters bearing a linear 2-fluoroallylic motif, which served as an appealing platform for the construction of other valuable enantioenriched compounds. The key intermediates were confirmed by HRMS detection, while DFT calculations revealed that the excellent enantioselectivity was attributed to the stabilizing non-covalent interactions between the Pd(II)-π-fluoroallyl species and the Ni(II)-Schiff base complex.

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.

Stereodivergent Synthesis of Spiroaminals via Chiral Bifunctional Hydrogen Bonding Organocatalysis

Spiroaminals represent novel structural motifs prevalent in diverse natural products and biologically active molecules. Achieving their enantioselective synthesis is a highly desirable and challenging task in synthetic endeavors due to their intricate molecular frameworks. Herein, we accomplished the first stereodivergent construction of spiroaminals using chiral bifunctional organocatalyzed intramolecular 1,2-addition followed by an oxa-Michael addition cascade in a high atom and step economical pathway. A proper modulation of the cinchona-derived squaramide catalysts efficiently provided access to all the possible stereoisomers with high yield, diastereoselectivity, and excellent enantioselectivity while displaying a broad substrate tolerance. Additionally, we validated the scalability of the reaction and demonstrated the synthesis of variable spiroaminal scaffolds, confirming the viability of our protocol.

Synergistic Palladium/Copper-Catalyzed 1,4-Difunctionalization of 1,3-Dienes for Stereodivergent Construction of 1,5-Nonadjacent Stereocenters

The construction of two distal stereocenters through a single catalytic process is of great interest in organic synthesis. While there are some successful reports regarding stereodivergent preparation of 1,3- or 1,4-stereocenters, the more challenged 1,5-nonadjacent stereocenters have never been achieved in a stereodivergent fashion. Herein we describe a synergistic palladium/copper catalysis for 1,4-difunctionalization reactions of 1,3-dienes, providing access to 1,5-nonadjacent quaternary stereocenters. Because each of the two catalysts separately controlled one of the newly formed stereocenters, stereodivergent synthesis of all four diastereomers of the products could readily be achieved simply by choosing an appropriate combination of chiral catalysts. Experimental and computational studies supported a mechanism involving a Heck/Tsuji-Trost cascade reaction, and the origins of the stereoselectivity were elucidated.

The Catalytic Asymmetric Allylic Alkylation of Acyclic Enolates for the Construction of Quaternary and Tetrasubstituted Stereogenic Centres

To facilitate the discovery and development of new pharmaceuticals, the demand for novel stereofunctionalised building blocks has never been greater. Whilst molecules bearing quaternary and tetrasubstituted stereogenic centres are ideally suited to explore untapped areas of chemical space, the asymmetric construction ofsterically congested carbon centres remains a longstanding challenge in organic synthesis. The enantioselective assembly of acyclic stereogenic centres is even more demanding due to the need to restrict a much wider range of geometries and conformations of the intermediates involved. In this context, the catalytic asymmetric allylicalkylation (AAA) of acyclic prochiral nucleophiles, namely enolates, has become an indispensable tool to access a range of linearα-quaternary andα-tetrasubstituted carbonyl compounds. However, unlike the AAA of cyclic enolates with a fixed enolate geometry, to achieve high levels of stereocontrol in the AAA of acyclic enolates, the stereoselectivity of enolisation must be considered. The aim of this review is to offer acomprehensivediscussion of catalytic AAA reactions of acyclic prochiral enolates and their analogues to generate congested quaternary and tetrasubstituted chiral centres using metal, non-metal and dual catalysis, with particular focus given to the control of enolate geometry and its impact on the stereochemical outcome of the reaction.

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.

Rhodium-Catalyzed Tandem Asymmetric Allylic Decarboxylative Addition and Cyclization of Vinylethylene Carbonates with N-Nosylimines

A enantioselective tandem transformation, concerning asymmetric allylic decarboxylative addition and cyclization of N-nosylimines with vinylethylene carbonates (VECs), in the presence of [Rh(C2H4)2Cl]2, chiral sulfoxide-N-olefin tridentate ligand has been developed. The reaction of VECs with various substituted N-nosylimines proceeded smoothly under mild conditions, providing highly functionalized oxazolidine frameworks in good to high yields with good to excellent enantioselectivity.

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.

Iridium/Acid Dual-Catalyzed Enantioselective Aza-ene-type Allylic Alkylation of Nitro Ketene Aminals with Racemic Allylic Alcohols

The enantioselective allylic alkylation of nitro ketene aminals with racemic allylic alcohols was realized by iridium/acid dual catalysis. An allyl group was installed on the α-position of nitro ketene aminals in a branched-selective manner in high efficiency with excellent enantioselectivities (93-99% ee). The protocol was applied to the late-stage modification of neonicotinoid insecticides, which directly furnished a novel neonicotinoid analogue with good insecticidal activity against Aphis craccivora (LC50 = 6.40 mg/L). On the basis of the control experiment, an aza-ene-type allylic alkylation reaction mechanism was proposed.

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.

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.

Palladium-catalyzed decarboxylative α-allylation of thiazolidinones and azlactones with sulfonamido-substituted acyclic allylic carbonates

A palladium-catalyzed decarboxylative α-allylation of thiazolidinones and azlactones with aza-π-allylpalladium zwitterionic intermediates, in situ generated from sulfonamido-substituted allylic carbonates, is successfully developed. This method allows the formation of a series of structurally diverse 5-alkylated thiazolidinones and 2-piperidones under mild conditions in moderate to high yields (up to 99% yield).

Palladium-Catalyzed Asymmetric (3 + 2) Cycloaddition of 5-Allenyloxazolidine-2,4-Diones with Barbiturate-Derived Alkenes: Synthesis of Spirobarbiturate-γ-Lactams

The 5-allenyloxazolidine-2,4-diones had been synthesized as novel precursors of π-allyl palladium zwitterion and were applied in a palladium-catalyzed enantioselective (3 + 2) annulation by using barbiturate-derived alkenes as the reaction partner in the presence of an axially chiral phosphoramidite ligand. This reaction proceeded smoothly under mild reaction conditions, affording highly functionalized spirobarbiturate-γ-lactam derivatives in excellent yields along with high diastereo- and enantioselectivities. The scale-up reaction and further transformation of the product were also successful.

Synergistic Ni/Pd Catalysis for Asymmetric Allylic Alkylation of 2-Acyl Imidazoles

The asymmetric α-allylation of α-aryl-substituted 2-acetyl imidazoles synergistically catalyzed by Ni/Pd catalysts has been developed. In this process, the nickel-bisoxazoline complex activates the enolate of an acetyl imidazole, which then reacts with a π-allyl palladium electrophile generated from an allyl alcohol derivative by a palladium-based catalyst. A broad scope of substrates was suitable for this reaction. The utility of this method was demonstrated by a gram-scale reaction and subsequent elaboration of the allylation products.

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.

Enantioselective Synthesis of Ten-Membered Lactones via Palladium-Catalyzed [5 + 5] Annulation

Ten-membered lactones are the core units of many biologically active natural products but with a great synthetic challenge. Based on the principle of vinylogy, novel types of cyclic vinylogous anhydrides have been designed as five-carbon carbonyl synthons, further applied in [5 + 5] annulation with vinylethylene carbonates under chiral palladium catalysis. This strategy features excellent regioselectivity, mild conditions, and broad substrate scope, affording a range of spiro ten-membered lactones bearing oxindole and pyrrolidinone motif in excellent yield (up to 99%) with moderate to high enantioselectivity (up to 89% ee).

Stereodivergent Access to [6.7]-Fused N-Heterocycles Bearing 1,3-Nonadjacent Stereogenic Centers by Pd-Catalyzed [4 + 2] Annulations

We describe a highly efficient stereodivergent [4 + 2] annulation reaction of vinyl benzoxazinaones and seven-membered cyclic N-sulfonyl aldimines for the synthesis of a wide array of N-heterocycles with 1,3-nonadjacent stereogenic centers via palladium catalysis. The polarity of solvents was found to play a key role in the switch of diastereoselectivity. Furthermore, good enantioselectivities of these reactions were achieved by the employment of commercially available Wingphos as the chiral ligand.

Fungicide-inspired precursors of π-allylpalladium intermediates for palladium-catalyzed decarboxylative cycloadditions

Inspired by a fungicide, we designed 5-vinyloxazolidine-2,4-diones as new precursors of π-allylpalladium zwitterionic intermediates and developed palladium-catalyzed asymmetric (5 + 3) cycloaddition with azomethine imines and (3 + 2) cycloaddition with 1,1-dicyanoalkenes. Both reactions proceeded smoothly under mild reaction conditions to produce various chiral heterocyclic compounds in high yields with excellent enantioselectivities. These results revealed that 5-vinyloxazolidine-2,4-diones were a type of suitable precursor for palladium catalysis and will find extensive applications in Pd-catalyzed reactions such as cycloaddition and allylic alkylation.

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.

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.

Chiral Silver Complex-Catalyzed Asymmetric Conjugate Addition of 1-Pyrroline-5-Carbonitrile to α-Enones

The conjugated addition reaction of 1-pyrroline-5-carbonitrile to α-enones was effectively catalyzed by AgF/ThioClickFerrophos (TCF) in diethyl ether in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and nearly single diastereomers of adducts with good enantiomeric excesses (up to 97% ee) were obtained in high yields. The reduction of the nitrile group with H₂/Raney Ni in ethanol successfully transformed the conjugate adduct to the corresponding spirocyclic piperidine (60% yield) as a single stereoisomer.

Ir-Catalyzed Asymmetric Cascade Allylation/Spiroketalization Reaction for Stereoselective Synthesis of Oxazoline-Spiroketals

An asymmetric cascade allylation/spiroketalization reaction between 2-(1-hydroxyallyl)phenols and 5-methyleneoxazolines is accomplished by using a chiral Ir(I) catalyst derived from commercially available iridium precursor and the Carreira ligand. This protocol furnishes a class of structurally novel and unique oxazoline-spiroketals in up to 86% yield, >99% ee and >20:1 dr. Moreover, control experiments reveal that 4,4-disubstitution on 5-methyleneoxazolines is necessary to avoid the aromatization and for the spiroketalization to occur. On the basis of this, a plausible reaction mechanism is illustrated.

Stereodivergent Construction of Csp3 -Csp3 Bonds Bearing Vicinal Stereocenters by Synergistic Palladium and Phase-Transfer Catalysis

Synergistic catalysis has emerged as one of the most powerful tools for stereodivergent formation of Csp³ -Csp³ bonds bearing vicinal stereocenters. Despite the many successes that have been achieved in this field, stereodivergent Csp³ -Csp³ coupling reactions involving stabilized nucleophiles remain challenging because of the competing single-catalysis pathway. Herein, we report a synergistic palladium/phase-transfer catalyst system that enables diastereodivergent Csp³ -Csp³ coupling reactions of 1,3-dienes with stabilized nucleophile oxindoles. Both the syn and anti coupling products, bearing quaternary and tertiary vicinal stereocenters, could be selectively produced in good yields with high enantio- and diastereoselectivities. Non-covalent activation of the stabilized nucleophile via chiral ion pair in a biphasic system is a crucial success factor in achieving diastereodivergence.

Iridium-Catalyzed Asymmetric Cascade Allylation/Retro-Claisen Reaction

An enantiomerically enriched 3-hydroxymethyl pentenal unit is one of the key structural cores in plenty of natural products and drug candidates with significant biological activities. However, very few synthetic methodologies for the facile construction of the related skeletons have been reported to date. Herein, an elegant iridium-catalyzed asymmetric cascade allylation/retro-Claisen reaction of readily available β-diketones with VEC was successfully developed, and a wide range of functionalized chiral 3-hydroxymethyl pentenal derivatives could be prepared in good yields with excellent enantioselectivities. Various 1,3-diketones and functionalized ketones containing different electron-withdrawing groups on the β-position were well tolerated as outstanding partners with high reactivity and excellent regio-/chemo-/enantioselectivity. The synthetic utility of product chiral 3-hydroxymethyl pentenal derivatives was well shown through gram-scale transformation, hydrogenation, cyclopropanation, hydroboration, and olefin metathesis. Moreover, this elegant protocol demonstrated synthetic applications in the concise synthesis of synthetically useful chiral building block (S)-Taniguchi lactone and the formal synthesis of natural product cytisine. A rational reaction pathway was proposed based on the experimental results and control experiments.

Enantioselective Synthesis of Functionalized Tetrahydropyridines through Iridium-Catalyzed Formal [5+1] Annulation

An efficient iridium-catalyzed asymmetric formal [5+1] annulation by in situ generation of enamines as N-nucleophiles for the synthesis of tetrahydropyridine derivatives is disclosed. The methodology offers direct access to a wide variety of chiral tetrahydropyridine derivatives in moderate to good yields and excellent enantioselectivity.

Ir and NHC Dual Chiral Synergetic Catalysis: Mechanism and Stereoselectivity in γ-Butyrolactone Formation

Cooperative dual catalysis is a powerful strategy for achieving unique reactivity by combining catalysts with orthogonal modes of action. This approach allows for independent control of the absolute and relative stereochemistry of the product. Despite its potential utility, the combination of N-heterocyclic carbene (NHC) organocatalysis and transition metal catalysis has remained a formidable challenge as NHCs readily coordinate metal centers. This characteristic also makes it difficult to rationalize or predict the stereochemical outcomes of these reactions. Herein, we use quantum mechanical calculations to investigate formation of γ-butyrolactones from aldehydes and allyl cyclic carbonates by means of an NHC organocatalyst and an iridium catalyst. Stereoconvergent activation of the racemic allyl cyclic carbonate forms an Ir-π-allyl intermediate and activation of an unsaturated aldehyde forms an NHC enolate, the latter of which is rate-limiting. Union of the two fragments leads to stereodetermining C-C bond formation and ultimately ring closure to generate the product lactone. Notably, CO2 loss occurs after formation of the C-C bond and Et3NH+ plays a key role in stabilizing carboxylate intermediates and in facilitating proton transfer to form the NHC enolate. The computed pathways agree with the experimental findings in terms of the absolute configuration, the enantiomer excess, and the different diastereomers seen with the (R)- and (S)-spiro-phosphoramidite combined with the NHC catalyst. Calculations reveal the lowest energy pathway includes both an NHC ligand and a phosphoramidite ligand on the iridium center. However, the stereochemical features of this Ir-bound NHC were found to not contribute to the selectivity of the process.