Brønsted Acid-Catalyzed Atroposelective Coupling of Carboxylic Acids with Amines and Alcohols via Ynamide Mediation

Carboxylic acids are readily available chemicals with broad applications in chemistry-related areas, and their coupling with amines and alcohols is a fundamental transformation in organic synthesis. However, the catalytic enantioselective coupling of carboxylic acids remains elusive, especially for the atroposelective reaction. Here we report a chiral Brønsted acid (CBA)-catalyzed atroposelective coupling of carboxylic acids with amines and alcohols using ynamides as coupling reagents. The novel enantiocontrol involving CBA-catalyzed ester addition enables the straightforward construction of axially chiral amides and planar-chiral esters with high enantioselectivities through atroposelective intermolecular amidation and intramolecular macrolactonization. Diverse medicinally relevant carboxylic acids can undergo direct late-stage modification by this method. Importantly, this reaction represents the first atroposelective coupling of carboxylic acids with amines, as well as the first chemocatalytic atroposelective coupling of carboxylic acids with alcohols. The resulting atropisomeric skeletons can be readily derivatized to chiral ligands and catalysts for asymmetric catalysis.

Regioselective Oxyamination of Biaryls Using Nitroarenes

Biaryl frameworks are pivotal in natural products, pharmaceuticals, agrochemicals, and materials, with the 2'-amino-2'-hydroxy-1,1'-biaryl motif being especially valuable for catalysis and bioactivity. However, synthesizing these non-C2-symmetric biaryls efficiently and regioselectively remains challenging due to limitations in current methods, such as prefunctionalization and structural constraints. Herein, we report a regioselective oxyamination of cyclometalated biaryl lanthanum reagents using nitroarenes. This lanthanum-based approach uniquely utilizes the oxophilicity and nucleophilicity of organolanthanum intermediates, enabling dual incorporation of oxygen and nitrogen into biaryl skeletons. A proposed 8-membered metallacycle intermediate avoids undesired nitrosoarene formation, delivering 2'-amino-2'-hydroxy-1,1'-biaryls with high efficiency. This one-pot, step-economical and transition-metal-free method achieves exceptional regioselectivity and a broad substrate scope, addressing longstanding challenges in biaryl functionalization and providing significant implications for catalysis, drug development, and materials science.

Asymmetric Olefin Isomerization via Phase-Transfer-Catalyzed [1,3]-Hydrogen Transfer for Access to Axially Chiral Furan-Benzimidazoles

An efficient catalytic asymmetric olefin isomerization of axially chiral methylene dihydrofuran-benzimidazoles via kinetic resolution is reported. Under mild phase-transfer catalysis, axially chiral furan-benzimidazole compounds and recovered methylene dihydrofuran-benzimidazoles were obtained in high ee. The combination of the kinetic resolution and TBD-catalyzed isomerization of recovered dihydrofuran-benzimidazoles provided access to both enantiomers of furan-benzimidazoles. Deuterium-labeling experiments reveal intramolecular [1,3]-H transfer mechanism. The utility of this method was demonstrated by scale-up synthesis and functionalization of the products.

Catalytic Atroposelective aza-Grob Fragmentation: An Approach toward Axially Chiral Biarylnitriles

Grob fragmentation is a powerful synthetic tool for cleaving C-C bonds, which was particularly useful in the construction of seven- to nine-membered carbocycles or heterocycles. This reaction typically breaks one C-C bond and one C-X bond and forms two unsaturated functional groups. As no stereogenic centers are generated, catalytic asymmetric Grob fragmentation has remained unexplored. In this study, we have successfully developed a catalytic asymmetric aza-Grob fragmentation of α-keto oxime esters, achieving atroposelective C-C bond cleavage to construct axially chiral biarylnitriles. Single-crystal X-ray diffraction analysis of oxime esters elucidated the structure-reactivity relationship, highlighting the role of torsional strain. These studies also revealed the unique role of the 2-phenyl benzoyl group in controlling the substrate conformation, tuning reactivity, and stereoselectivity. The 1H NMR titration experiments provided brief insights into the activation mode of the catalyst with the substrate, suggesting a multi-hydrogen-bonding interaction model.

Catalytic Asymmetric Construction of Nonadjacent Stereoelements

Nonadjacent chiral scaffolds are privileged motifs in bioactive molecules and medicines, which have stimulated chemists' ingenuity in achieving the asymmetric construction of non-contiguous chiral elements directly. Current strategies include bifunctional catalysis, synergistic catalysis, cascade catalysis and others, enabling the production of a wide range of enantiomerically enriched compounds featuring different combinations of nonadjacent chirality, including multiple elements of central chirality, central and allenyl axial chirality, and central and biaryl axial chirality. As compared to the patterns of multiple nonadjacent elements of central chirality, the latter two are less frequently reported. This minireview aims to summarize the key developments in reaction design, mechanistic studies, and synthetic applications, with the goal of stimulating further exploration in this important area of asymmetric catalysis.

Chemoenzymatic Dynamic Kinetic Resolution of Atropoisomeric 2-(Quinolin-8-yl)benzylalcohols

The chemoenzymatic dynamic kinetic resolution of 2-(quinolin-8-yl)benzylalcohols using a combination of lipases and ruthenium catalysts is described. While CalB lipase performs highly selective enzymatic kinetic resolution, the combination with Shvo's or Bäckvall's catalysts promotes atropisomerization of the substrate via the reversible formation of configurationally labile aldehydes, thereby enabling a dynamic kinetic resolution. This synergistic approach was applied to the synthesis of a variety of heterobiaryl acetates in excellent yields and enantioselectivities.

Enantioselective Desymmetrization of Biaryls via Cooperative Photoredox/Brønsted Acid Catalysis and Its Application to the Total Synthesis of Ancistrobrevolines

Photoredox catalysis has emerged as a powerful tool for forming and breaking chemical bonds, further taking hold with its integration with asymmetric catalysis. While the dual-catalytic approach has led to successful examples of the control of stereogenic centers, the control of stereogenic axes has remained underexplored. In this study, an acylimine intermediate was generated through photoredox catalysis, and a symmetric substrate, 2-arylresorcinol, was desymmetrized with the aid of chiral phosphoric acid catalysis. Using this approach, a stereogenic center and stereogenic axis were successfully controlled to provide a natural-product-driven compound. The origins of enantioselectivity and diastereoselectivity were investigated through a density functional theory study of four possible enantiodetermining transition states. Consequently, the first total syntheses of the ring-contracted naphthylisoquinoline alkaloid ancistrobrevolines A and B were accomplished concisely. This approach provides not only a novel methodology and strategy to synthesize naphthylisoquinoline alkaloids but also a direction to advance catalytic research and total synthesis studies.

Enhanced Pyridine-Oxazoline Ligand-Enabled Pd(II)-Catalyzed Aminoacetoxylation of Alkenes for the Asymmetric Synthesis of Biaryl-Bridged 7-Membered N-Heterocycles and Atropisomers

A new class of binaphthyl unit-enhanced pyridine-oxazoline ligands was developed to promote the Pd-catalyzed enantioselective intramolecular 7-exo aminoacetoxylation of unactivated biaryl alkenes. Biaryl-bridged 7-membered N-heterocycles bearing a chiral center were obtained in good yields with excellent enantioselectivities (up to 99:1 er). Computational investigations on a series of biaryl-bridged 7-membered rings provided insights into the rotational barrier of the potentially chiral biaryl unit by the substituent effect including the heteroatom, the protecting group, and the chiral center. The kinetic resolution of racemic axially chiral biaryls via intramolecular enantioselective aminoacetoxylation of alkenes has also been achieved, affording previously inaccessible biaryl-bridged 7-membered N-heterocycles bearing both a chiral center and a chiral axis, as well as axially chiral biaryl amino alcohols.

Simultaneous Construction of Axial and Central Stereogenicity by Cobalt-Catalyzed Stereoconvergent Reductive Coupling of Heterobiaryl Triflates and Aldehydes

Catalytic stereoconvergent coupling of racemic heterobiaryl triflates and aldehydes promoted by a readily available chiral cobalt complex is presented. Such processes represent an unprecedented reaction pathway for cobalt catalysis that enable simultaneous construction of axial and central stereogenicity through diastereo- and enantioselective dynamic kinetic transformations and introduction of a chiral fragment onto the heterobiaryl cores without the requirement of preforming stoichiometric amounts of organometallic reagents, affording densely functionalized secondary alcohols in up to 96 % yield, >98 : 2 dr and >99.5:0.5 er. Preliminary investigations on the application of the products demonstrate their potential for serving as a new class of chiral catalysts and ligands. Mechanistic studies suggest that a dynamic kinetic stereoselective process induced by chiral cobalt catalysis is involved.

Observation of the solvent enantio-isotope effect in asymmetric ring-opening of cyclic diaryliodoniums with selenocyanate

A Cu-catalyzed asymmetric coupling reaction between cyclic diaryliodoniums and the ambident nucleophile KSeCN was reported. Utilizing water as a co-solvent (CH2Cl2/H2O) achieves high chemoselectivity by forming a nitrogen-hydrogen-bond, thereby blocking the N-site of ambident NCSe- species, thus realizing efficient C-Se coupling. In contrast to the well-known kinetic isotope effect used to evaluate whether the C-H/D bond cleavage is rate-determining, the influence of deuterium-containing solvents on enantioselectivity remained largely unexplored. In this reaction, we observed a notable enhancement in enantioselectivity upon replacing H2O with D2O.

Design, Synthesis and Application of Chiral Spirocyclic Bisindoles

While modifications of the privileged catalyst backbones, such as 1,1'-spirobiindane-7,7'-diol (SPINOL), have led to the development of diverse useful chiral catalysts, the incorporation of heteroarenes in such chiral spirocyclic structures has limitedly known. Herein we report the design of a type of chiral spirocyclic bisindole skeletons where the electronically distinct heteroarenes serve as direct anchor for functional sites. Separate approaches for the synthesis of two different families of such skeletons have been developed via chiral phosphoric acid and rhodium catalysis, respectively. Both strategies provided expedient access to the highly enantioenriched spiro-bisindoles, owing to not only the high nucleophilicity of the indole ring, but also the robust asymmetric control. These new skeletons have been demonstrated as backbones of effective chiral catalysts for both transition metal catalysis and organocatalysis.

Rhodium-Catalyzed Atroposelective Synthesis of Axially Chiral 1-Aryl Isoquinolines via De Novo Isoquinoline Formation

Axially chiral heterobiaryl moieties serve as core skeletons for bioactive molecules, chiral ligands, and organocatalysts. Enantioselective de novo formation of the heteroaromatic ring is one of the most straightforward approaches to access enantioenriched heterobiaryls. Herein, an enantioselective de novo construction of isoquinolines by rhodium-catalyzed C─H activation/annulation of aromatic imines with alkynes is disclosed. This approach is operationally simple, allowing for rapid access to a variety of axially chiral 1-aryl isoquinolines in excellent yields and enantioselectivity (up to 98% yield and 99:1 er). The synthetic application of the current method was demonstrated by functional group transformations and suitability for millimolar-scale reactions. Detailed experimental and theoretical studies revealed the turnover-limiting step and provided insight into the origin of the enantioselectivity for this reaction.

Changing the absolute configuration of atropisomeric bisnaphthols (BINOLs)

Bisnaphthol (BINOL) is a ubiquitous core skeleton in versatile chiral catalysts and ligands for transition metals, and this representative atropisomeric structure also serves as a building block in various optically active natural products. Due to the high rotational barrier (∼40 kcal mol-1) in the neutral form of BINOL, it displays stable atropisomerism. Asymmetric catalysis using racemic BINOL substrates generally exhibits a kinetic resolution process, with reaction yields having to be below 50%. Dynamic kinetic resolution (DKR) combines kinetic resolution with a racemization process to push the ideal yield to 100%. A changing of the absolute configuration of BINOL has been observed since Brussee et al. did so in 1985, but its mechanism remains unknown. Recently, racemization strategies and a mechanism based on single-electron oxidation, producing a released radical-anion species as the key intermediate, have been clearly disclosed. In particular, deracemization of BINOLs achieved by using stochiometric amounts of a chiral amine or ammonium salt, and dynamic kinetic resolution in cooperation with biocatalysis, have been well established for accessing enantioenriched BINOL derivatives, as summarized and discussed in this review.

Nickel-Catalyzed Dynamic Kinetic Asymmetric Reductive Arylation of Aldehydes with Heterobiaryl Triflates

In this context, we report a nickel-catalyzed dynamic kinetic asymmetric reductive arylation of aldehydes with racemic heterobiaryl triflates, offering a series of axially chiral heterobiaryls bearing a centrally chiral secondary alcohol moiety in a highly diastereo- and enantioselective manner. The simultaneous control of both axial and central stereogenic elements of the products lies in the stereoselective nucleophilic addition of the configurationally labile hetereobiaryl nickel complex to the formyl group of aldehydes.

Organocatalytic Asymmetric Construction and Application of Axially Chiral Spiro-bisindoles

Spiro skeletons have emerged as a privileged class of chiral carriers across various research fields, including asymmetric catalysis and functional materials, due to their remarkable configurational rigidity. However, limited structural diversity of spiro frameworks significantly restricts the expansion of their applications. Here we present a new class of axially chiral spiro-bisindole frameworks and report their first enantioselective construction via a chiral phosphoric acid-catalyzed intramolecular dehydrative cyclization reaction. Unlike the classical SPINOL backbone, incorporation of indole moieties in place of phenol enhances the nucleophilicity of ketone substrates, thereby eliminating the need for a tedious pre-activation process. By leveraging the retained active sites of indole, the resulting highly enantioenriched spiro-bisindoles can be rapidly transformed into other valuable structures. More importantly, axially chiral fluorescent molecules with good asymmetry factors and quantum fluorescence efficiency are readily accessed, opening a new avenue for developing chiral fluorescent materials. Control experiments demonstrate the pivotal role of both unmasked N-H bonds in achieving good efficiency and enantiocontrol.

Atroposelective biocatalysis employing alcohol dehydrogenases

The biocatalytic synthesis of axially chiral heterobiaryl compounds is an area of great interest. A particularly valuable approach involves the atroposelective transformation of achiral, configurationally labile, or racemic heterobiaryl molecules using biocatalysis. By judicious designing the structure of the starting material, Dynamic Kinetic Resolutions (DKR) have been developed to produce higablehly enantioenriched atropisomers with excellent yields and selectivities. Thus, indole- and quinoline-based aldehydes with a precise structure have been prepared. The non-covalent Lewis interaction between the carbonyl group and a nitrogen atom is responsible for the atropoisomerization (dynamization) of the stereogenic axis. The employment of commercially available alcohol dehydrogenases (ADHs) led to the enantiodivergent synthesis of a variety of heterobiaryl alcohols with high yields and excellent enantiomeric excesses. For the substrate in which the DKR led to optical purities lower than 90 %, solvent engineering was performed, thus being possible to obtain both atropoisomers of the final alcohol with high enantiomeric excesses by using methyl tert-butyl ether or tetrahydrofuran as cosolvents.

Catalytic Atroposelective Electrophilic Amination to Access Axially Chiral Diaryl Phenols

An enantioselective synthesis of axially chiral diaryl phenols containing sulfonamide groups has been achieved involving an electrophilic amination of 1,1'-biaryl-2,6-diols with N-sulfonyl quinone diimines, catalyzed by a chiral phosphoric acid. This atroposelective reaction offers a modular approach to enantiopure diaryl phenols, with good-to-excellent yields.

Copper-catalysed dynamic kinetic asymmetric C-O cross-coupling to access chiral aryl oxime ethers and diaryl ethers

Dynamic kinetic resolution (DKR) has emerged as an elegant and powerful tool for enantioselective synthesis, enabling the transformation of racemic compounds into enantiomerically enriched products with theoretically quantitative yields. Despite its widespread success, the dynamic kinetic asymmetric C-O cross-coupling has presented significant challenges and remains unexplored. In this study, we report a dynamic kinetic asymmetric C-O cross-coupling of oximes and phenols via copper/BOX-catalysed enantioselective O-arylation with diaryliodonium salts. This method efficiently produces a wide range of inherently chiral oxime ethers, as well as axially chiral styrenes, with high yields and excellent regio- and enantioselectivities. Through controlled experiments and Density Functional Theory (DFT) studies, we have elucidated the dynamic kinetic resolution process and gained insights into the origins of regio- and enantioselectivity.

Enantioselective construction of inherently chiral pillar[5]arenes via palladium-catalysed Suzuki-Miyaura cross-coupling

Pillar[n]arenes have broad applications in biological medicine, materials science, and supramolecular gels. Notably, enantiopure pillar[5]arenes are valued for their roles in enantioselective host-guest recognition, chiral sensing, asymmetric catalysis, and related fields. Current methods for obtaining chiral pillar[n]arenes rely heavily on resolution agents or chiral HPLC resolution. However, the synthesis of these compounds via asymmetric catalysis remains challenging. In this study, we develop an asymmetric extended side-arm Suzuki-Miyaura cross-coupling strategy to construct inherently chiral pillar[5]arenes with excellent yields and high enantioselectivities using a palladium catalyst and a Sadphos ligand. The reaction scope extends beyond arylboronic acids to encompass 2-arylvinylboronic acids and other multi-OTf-substituted substrates, all efficiently producing the desired products. Further exploration of the synthetic applications, along with photophysical and chiroptical analyses, confirm the potential of these chiral pillar[5]arenes for diverse applications across multiple disciplines.

Structures and Properties of Axially Chiral (2E,4E,6Z,8Z)-Nona-2,4,6,8-Tetraenoate Derivatives Highly Substituted by Aryl Groups

Unprecedented (2E,4E,6Z,8Z)-nona-2,4,6,8-tetraenoate derivatives highly substituted by aryl groups have been synthesized by the reaction of rhodium complexes having aryl-substituted hexa-1,3,5-trienyl ligands with acrylates. These compounds have potential axial chirality, and their enantiomers are isolable by the chiral HPLC technique. Although the racemization barrier of isolated enantiomers was not high, it was found that a cyclic dimer synthesized by head-to-tail transesterification of a modified analog has quite a stable axial chirality even at a high temperature. From a structural analogy with tetraphenylethene, those compounds are emissive in the solid state, and the chiral cyclic dimer exhibits solid-state circularly polarized luminescence (CPL) activity.

Synthesis of Biaryl Atropisomers via Site-Selective C-H Functionalization

We describe an approach to form conformationally rigid atropisomers with a variety of nucleophiles not commonly applicable to transition-metal-catalyzed methods. The use of organic photoredox catalysis renders this method operationally simple, as direct substrate oxidation followed by nucleophilic attack may furnish the products via site-selective C-H functionalization in moderate to quantitative yields. Density functional theory (DFT) computations estimated the rotational barriers and half-lives of the products.

Bioinspired Copper/Amine Cooperative Catalysis Enables Asymmetric Radical Azidation

Asymmetric radical transformations (ARTs) are vital for constructing chiral drugs and materials, while the highly reactive nature of radicals often imposes a challenge in selectivity control of these processes. Inspired by the principles of enzyme-cofactor cooperation to enhance stereochemical induction in enantioselective radical transformations, we developed an enantioselective asymmetric radical azidation via cooperative organo- and transition metal catalysis. This approach enables the efficient synthesis of heavily functionalized tertiary azides from readily available aldehydes. The key to this enantioselective process is the use of both chiral organocatalysts to transiently convert aldehydes to the corresponding chiral radical cationic species upon oxidation along with a detailed screening of chiral metal-azide catalysts to cooperatively enhance stereoinduction in carbon-azide bond formation. DFT studies suggest a favorable stereocontrol model and validate the crucial roles of chirality pairing of both catalytic schemes. We envision that this copper/amine cooperative catalysis could offer a useful strategy of constructing tetrasubstituted stereogenic carbon in asymmetric radical transformation development.

Biocatalytic Desymmetrization for the Atroposelective Synthesis of Axially Chiral Biaryls Using an Engineered Imine Reductase

The enzymatic atroposelective synthesis of biaryl compounds is relatively rare, despite considerable attention received by biocatalysis in the academic and industrial sectors. Imine reductases (IREDs) are an important class of enzymes that have been applied in the asymmetric synthesis of chiral amine building blocks. In this study, two IREDs (IR140 and IR189) were identified to catalyze the efficient desymmetrization of biaryls utilizing various amine donors. Further protein engineering enabled the identification of variants (IR189 M8-M9 and IR189 M13-M14) that are able to catalyze the formation of both (R) and (S) atropisomers in excellent yields and atroposelectivities (24 examples, up to 99 % ee and yield). The absolute configuration and rotational barriers were confirmed, and the reactions were readily scaled up to allow isolation of the atropisomeric product in 99 % ee and 82 % yield. The optically pure biaryl amines were further derivatized into various synthetically useful atropisomers. To shed light on the molecular recognition mechanisms, molecular dynamics (MD) simulations were performed, offering plausible explanations for the improved atroposelectivity and enzymatic activity. The current strategy expands the scope of the IRED-catalyzed synthesis of axially chiral biaryl amines, contributing significantly to the field of atroposelective biocatalysis.

Organocatalytic Atroposelective Synthesis of Axially Chiral Indolyl Ketosulfoxonium Ylides

Despite recent advancements in the catalytic generation of axial chirality, reports on non-biaryl atropisomers remain limited because of the stringent steric requirements necessary to establish effective rotational brakes. Herein, we present a novel class of monoaryl atropisomers, indolyl ketosulfoxonium ylides, and describe an organocatalytic protocol for their synthesis. We discovered that a chiral phosphoric acid (CPA) serves as an effective catalyst for the highly enantioselective iodination of ortho-aminophenylethynyl sulfoxonium ylides. Under the optimized reaction conditions, a strong preference for the intended iodination process over the competing protonation was observed. Subsequently, intramolecular amide cyclization enabled the formation of sterically congested indole fragments. Furthermore, the synthetic utility of the products was demonstrated by showcasing versatile transformations into other chiral scaffolds with complete retention of optical purity.

Asymmetric Counteranion-Directed Electrocatalysis for Enantioselective Control of Radical Cation

The control of enantioselectivity in radical cation reactions presents long-standing challenges, despite a few successful examples. We introduce a novel strategy of asymmetric counteranion-directed electrocatalysis to address enantioselectivity in radical cation chemistry. This concept has been successfully demonstrated in two reactions: an asymmetric dehydrogenative indole-phenol [3+2] coupling and an atroposelective C-H/N-H dehydrogenative coupling. These reactions have enabled the synthesis of benzofuroindolines and C-N axially chiral indoles with high yields and excellent enantiomeric excesses. Detailed mechanistic studies confirmed a radical-radical coupling mechanism. Moreover, density functional theory (DFT) calculations supported the indole radical cation as the pivotal intermediate, rather than a neutral indolyl radical, shedding new light on the underlying processes driving these reactions.

Asymmetric synthesis of atropisomers featuring cyclobutane boronic esters facilitated by ring-strained B-ate complexes

The strain-release-driven reactions of bicyclo[1.1.0]butanes (BCBs) have received significant attention from chemists. Notably, 1,2-migratory reactions enabled by BCB-derived B-ate complexes effectively complement the reactions initiated by common BCBs. The desired products are particularly valuable for late-stage transformations due to the presence of the C-B bond. However, asymmetric reactions mediated by BCB-derived boronate complexes have progressed slowly. In this study, we develop an asymmetric synthesis of atropisomers featuring cis-cyclobutane boronic esters facilitated by 1,2-carbon or boron migration of ring-strained B-ate complexes, achieving high enantioselectivity. The reaction is compatible with various aryl, alkenyl, alkyl boronic esters and B2pin2, and shows good compatibility with natural product derivatives. Mechanistic studies are conducted to understand stereoselective control in the dynamic kinetic asymmetric transformations (DYKATs). The target products can undergo a series of transformations, further demonstrating the practicality of this methodology.

Copper-Catalyzed Enantioselective Dehydro-Diels-Alder Reaction: Atom-Economical Synthesis of Axially Chiral Carbazoles

The dehydro-Diels-Alder (DDA) reaction is a powerful method for the construction of aromatic compounds. However, the enantioselective DDA reaction has been rarely developed, probably due to the competitive thermal reaction. Herein, we report a copper-catalyzed enantioselective DDA reaction through vinyl cation pathway. The reaction leads to the atom-economical synthesis of axially chiral phenyl and indolyl carbazoles in generally excellent yields with good to excellent atroposelectivities. This methodology represents the first example of non-noble metal-catalyzed enantioselective DDA reaction. Notably, new chiral ligand and organocatalyst derived from the constructed axially chiral carbazole are demonstrated to be useful in asymmetric catalysis.

Atroposelective synthesis of axially chiral indolizinylpyrroles by catalytic asymmetric Paal-Knorr reaction

We present herein a highly efficient atroposelective synthesis of five/five-membered N-indolizinylpyrrole through the chiral phosphoric acid (CPA) catalyzed Paal-Knorr reaction of 3-aminoindolizines and 1,4-diketones. The reaction features mild reaction conditions, broad substrate scope and excellent enantioselectivity. Moreover, this method provides a facile approach to a novel axially chiral indolizine-pyrrole framework.

Pd(ii)-catalyzed enantioselective C-H olefination and photoregulation of sterically hindered diarylethenes

Sterically hindered diarylethenes with intrinsic chirality have shown great potential in chiral signal regulation, light-controlled liquid crystals (LCs), etc. Their unique enantiospecific phototransformation between axial chirality of ring-open isomers and central chirality of ring-closed isomers can break through the bottleneck of interference between multiple chiral centers in traditional chiral diarylethenes. However, these intrinsic chiral diarylethenes require necessary chiral resolution through preparative chiral HPLC, typically resulting in limited separation efficiency and production scale. Here, we present an enantioselective olefination strategy to directly construct intrinsic chiral diarylethenes from a prochiral sterically hindered diarylethene, achieving high yields and enantioselectivity. The resulting isomers can be further decorated by incorporating mesogenic units, and the derivatives enable the successful reversible photoregulation of blue, green, and red reflection colors of LCs with excellent thermal stability, fatigue resistance, and little texture disorderliness, demonstrating the practical application potential of direct enantioselective olefination in photoregulation with intrinsic chiral diarylethenes.

N-Heterocyclic Carbene Enabled Copper Catalyzed Asymmetric Synthesis of Pyrimidinyl Phosphine with both Axial and P-Stereogenicity

P-stereogenic phosphines, renowned for their utility as ligands and catalysts, have been instrumental in the field of asymmetric catalysis. However, the catalytic asymmetric synthesis of chiral ligands possessing both axial and phosphine chirality remains a significant challenge. Here, we present the successful demonstration of a Cu-catalyzed asymmetric C-P construction using in situ generated secondary phosphine and heteroaryl chloride. By introducing a chiral NHC ligand and an achiral diphosphine auxiliary ligand, we effectively alleviated the poisoning effect caused by phosphine(III) compounds and suppressed the nonenantioselective background reaction. The reaction exhibited excellent enantioselectivity, with up to 96 % ee, and good diastereoselectivity, with up to 14 : 1 dr, when employing less sterically hindered secondary phosphines. This particular substrate poses a significant challenge due to its strong poisoning effect in copper catalysis.

Construction of Axially Chiral 4-Aminoquinolines by Cycloaddition and Central-to-Axial Chirality Conversion

A two-step strategy has been established for the enantioselective synthesis of 4-aminoquinolines possessing axial chirality. This approach involves a chiral phosphoric acid-catalyzed cycloaddition, followed by a DDQ oxidation step. The method offers efficient access to a variety of 1,1'-biaryl-2,2'-amino alcohol derivatives in excellent yields and enantioselectivities (up to 98% yield and 93% ee). Furthermore, the synthetic transformation of the products was also investigated.

Construction of axially chiral 2-arylpyrroles using catalytic asymmetric Suzuki-Miyaura cross-coupling: an efficient approach to esaxerenone

A general and efficient method has been developed to access axially chiral 2-arylpyrroles using catalytic asymmetric Suzuki-Miyaura cross-coupling. A wide range of axially chiral arylpyrroles were obtained in high yields with good to excellent enantioselectivities. The key to success is the use of a combined catalytic system involving a palladium catalyst and chiral ferrocene diphosphine ligand for achieving effective enantiocontrol. More importantly, this axially chiral CF3-substituted 2-arylpyrrole serves as a key intermediate in the preparation of the anti-hypertensive and diabetic nephropathy drug esaxerenone. It was directly asymmetrically synthesized with high enantioselectivity (92% ee). Thus, a new strategy is provided for the catalytic asymmetric synthesis of esaxerenone.

Synthesis of Alkene Atropisomers with Multiple Stereogenic Elements via Catalytic Asymmetric Rearrangement of 3-Indolylmethanols

Catalytic enantioselective preparation of alkene atropisomers with multiple stereogenic elements and discovery of their applications have become significant but challenging issues in the scientific community due to the unique structures of this class of atropisomers. We herein report the first catalytic atroposelective preparation of cyclopentenyl[b]indoles, a new kind of alkene atropisomers, with stereogenic point and axial chirality via an unusual rearrangement reaction of 3-indolylmethanols under asymmetric organocatalysis. Notably, this novel type of alkene atropisomers have promising applications in developing chiral ligands or organocatalysts, discovering antitumor drug candidates and fluorescence imaging materials. Moreover, the theoretical calculations have elucidated the possible reaction mechanism and the non-covalent interactions to control the enantioselectivity. This approach offers a new synthetic strategy for alkene atropisomers with multiple stereogenic elements, and represents the first catalytic enantioselective rearrangement reaction of 3-indolylmethanols, which will advance the chemistry of atropisomers and chiral indole chemistry.

Palladium-Catalyzed Asymmetric Larock Isoquinoline Synthesis to Access Axially Chiral 3,4-Disubstituted Isoquinolines

Larock isoquinoline synthesis is one of the most efficient and straightforward approaches to the construction of 3,4-disubstituted isoquinolines. However, there have been no asymmetric versions for the synthesis of axially chiral isoquinolines since their initial report in 2001. Herein, we documented the first example of an asymmetric Larock isoquinoline synthesis by employing Pd(OAc)2/Walphos SL-W002-1 as the catalyst, affording the axially chiral 3,4-disubstituted isoquinolines with up to 97.5:2.5 er and 98% yield. Density Functional Theory (DFT) calculations clearly clarified the catalytic mechanism and the origin of the experimentally observed enantioselectivity.

Atroposelective Synthesis of Axial Biaryls by Dynamic Kinetic Resolution Using Engineered Imine Reductases

Axially chiral biaryl compounds are ubiquitous scaffolds in natural products, bioactive molecules, chiral ligands and catalysts, but biocatalytic methods for their asymmetric synthesis are limited. Herein, we report a highly efficient biocatalytic route for the atroposelective synthesis of biaryls by dynamic kinetic resolution (DKR). This DKR approach features a transient six-membered aza-acetal-bridge-promoted racemization followed by an imine reductase (IRED)-catalyzed stereoselective reduction to construct the axial chirality under ambient conditions. Directed evolution of an IRED from Streptomyces sp. GF3546 provided a variant (S-IRED-Ss-M11) capable of catalyzing the DKR process to access a variety of biaryl aminoalcohols in high yields and excellent enantioselectivities (up to 98 % yield and >99 : 1 enantiomeric ratio). Molecular dynamics simulation studies on the S-IRED-Ss-M11 variant revealed the origin of its improved activity and atroposelectivity. By exploiting the substrate promiscuity of IREDs and the power of directed evolution, our work further extends the biocatalysts' toolbox to construct challenging axially chiral molecules.

Enantio- and Diastereoselective Desymmetrization of 1,1'-Biaryl-2,6-Dicarbaldehydes by Copper-Catalyzed 1,2-Addition of Silicon Nucleophiles

A desymmetrizing 1,2-addition of silicon nucleophiles to biaryl derivatives containing an 2,6-dicarbaldehyde-1-yl unit is reported. The reaction is catalyzed by copper with a triazolium-ion-derived N-heterocyclic carbene as the chiral ligand and makes use of an Si-B reagent as the silicon pronucleophile. The practical methodology furnishes axially chiral aromatic carbaldehydes decorated with a centrally chiral α-hydroxysilane moiety in moderate to good yields and with high enantio- as well as excellent diastereoselectivities. The silicon nucleophile always attacks at the diastereotopic face of either carbonyl group away from the ortho substituent on the phenyl ring at C1 of the 2,6-dicarbaldehyde-1-yl fragment. The resulting axially and centrally chiral products can be further converted into valuable biaryl compounds with hardly any erosion of the enantiomeric excess.

Isothiourea-Catalysed Acylative Dynamic Kinetic Resolution of Tetra-substituted Morpholinone and Benzoxazinone Lactols

The development of methods to allow the selective acylative dynamic kinetic resolution (DKR) of tetra-substituted lactols is a recognised synthetic challenge. In this manuscript, a highly enantioselective isothiourea-catalysed acylative DKR of tetra-substituted morpholinone and benzoxazinone-derived lactols is reported. The scope and limitations of this methodology have been developed, with high enantioselectivity and good to excellent yields (up to 89 %, 99 : 1 er) observed across a broad range of substrate derivatives incorporating substitution at N(4) and C(2), di- and spirocyclic substitution at C(5) and C(6), as well as benzannulation (>35 examples in total). The DKR process is amenable to scale-up on a 1 g laboratory scale. The factors leading to high selectivity in this DKR process have been probed through computation, with an N-C=O⋅⋅⋅isothiouronium interaction identified as key to producing ester products in highly enantioenriched form.

Catalytic Atroposelective Synthesis of N-N Axially Chiral Indolylamides

The catalytic atroposelective synthesis of N-N axially chiral indolylamides was established via dynamic kinetic resolution, which makes use of chiral Lewis base-catalyzed asymmetric acylation of N-acylaminoindoles as a new type of platform molecule with anhydrides. By this strategy, a series of N-N axially chiral indolylamides were synthesized in overall good yields (up to 98%) with excellent enantioselectivities (up to 99% ee). Moreover, some of these N-N axially chiral indolylamides display some extent of anticancer activity, which demonstrates their potential application in medicinal chemistry. Therefore, this work has not only provided a new strategy for the synthesis of N-N axially chiral monoaryl indoles but also offered a new member of N-N axially chiral monoaryl indoles with configurational stability and promising application, thereby solving the challenges in atroposelective synthesis and application of N-N axially chiral monoaryl indoles.

Bridged Biaryl Atropisomers by Organocatalyzed Kinetic Asymmetric Alcoholysis

We disclose herein an asymmetric synthesis of axially chiral oxazepine-containing bridged biaryls via CPA-catalyzed kinetic asymmetric alcoholysis. Control experiments showed that this CPA-catalyzed alcoholysis was reversible, and lowering the reaction temperature could almost suppress the reversible reaction, thus providing a series of axially chiral oxazepine-containing bridged biaryl compounds in good to excellent enantioselectivities. The gram-scale reactions and facile derivatizations of the enantioenriched products demonstrate the practical utility of this reaction.

Enantioconvergent synthesis of axially chiral amides enabled by Pd-catalyzed dynamic kinetic asymmetric aminocarbonylation

Atropisomeric biaryls bearing carbonyl groups have attracted increasing attention due to their prevalence in diverse bioactive molecules and crucial role as efficient organo-catalysts or ligands in asymmetric transformations. However, their preparation often involves tedious multiple steps, and the direct synthesis via asymmetric carbonylation has scarcely been investigated. Herein, we report an efficient palladium-catalyzed enantioconvergent aminocarbonylation of racemic heterobiaryl triflates with amines via dynamic kinetic asymmetric transformation (DyKAT). This protocol features a broad substrate scope and excellent compatibility for rapid construction of axially chiral amides in good to high yields with excellent enantioselectivities. Detailed mechanistic investigations discover that the base can impede the intramolecular hydrogen bond-assisted axis rotation of the products, thus allowing for the success to achieve high enantioselectivity. Moreover, the achieved axially chiral heterobiaryl amides can be directly utilized as N,N,N-pincer ligands in copper-catalyzed enantioselective formation of C(sp3)-N and C(sp3)-P bonds.

Atroposelective Construction of Axially Chiral 2-Aryl-Pyrroloquinolones

A two-step protocol including an enantioselective organocatalyzed synthesis of pyrroloquinolines followed by an oxidation reaction allowed the formation of axially chiral 2-aryl-pyrroloquinolones. Thorough optimization of the experimental conditions for the second step allowed the oxygenation reaction to take place and ensured, in most cases, a central-to-axial chirality conversion with complete retention of the enantiomeric excess.

Enantioselective Construction of Anthracenylidene-Based Axial Chirality by Asymmetric Heck Reaction

Anthracenylidene is an intriguing structural unit with potential in various fields. The study presents a novel approach to introducing axial chirality into this all-carbon core skeleton through a remotely controlled desymmetrization strategy. A palladium-catalyzed enantioselective Heck arylation of exocyclic double bond of anthracene with two distinct substituents at the C10 position is harnessed to realize such a transformation. The judicious identification of the P-centrally chiral ligand is pivotal to ensure the competitive competence in reactivity and stereocontrol when the heteroatom handle is absent from the anthracenylidene skeleton. Both C10 mono- and disubstituted substrates were compatible for the established catalytic system, and structurally diverse anthracenylidene-based frameworks were forged with good-to-high enantiocontrol. The subsequent derivatization of the obtained products yielded a valuable array of centrally and axially chiral molecules, thus emphasizing the practicality of this chemistry. DFT calculations shed light on the catalytic mechanism and provided insights into the origin of the experimentally observed enantioselectivity for this reaction.

Nickel-Catalyzed Chemoselective Carbomagnesiation for Atroposelective Ring-Opening Difunctionalization

There is a pressing need for methods that can connect enantioenriched organic compounds with readily accessible building blocks via asymmetric functionalization of unreactive chemical bonds in organic synthesis and medicinal chemistry. Herein, the asymmetric chemoselective cleavage of two unactivated C(Ar)-O bonds in the same molecule is disclosed for the first time through an unusual nickel-catalyzed carbomagnesiation. This reaction facilitates the evolution of a novel atroposelective ring-opening difunctionalization. Utilizing readily available dibenzo bicyclic substrates, diverse valuable axially chiral biaryls are furnished with high efficiencies. Synthetic elaborations showcase the application potential of this method. The features of this method include good atom-economy, multiple roles of the nucleophile, and a simple catalytic system that enables the precise magnesiation of an α-C(Ar)-O bond and arylation of a β-C(Ar)-O bond.

Atroposelective catalysis

Atropisomeric compounds-stereoisomers that arise from the restricted rotation about a single bond-have attracted widespread attention in recent years due to their immense potential for applications in a variety of fields, including medicinal chemistry, catalysis and molecular nanoscience. This increased interest led to the invention of new molecular motors, the incorporation of atropisomers into drug discovery programmes and a wide range of novel atroposelective reactions, including those that simultaneously control multiple stereogenic axes. A diverse set of synthetic methodologies, which can be grouped into desymmetrizations, (dynamic) kinetic resolutions, cross-coupling reactions and de novo ring formations, is available for the catalyst-controlled stereoselective synthesis of various atropisomer classes. In this Review, we generalize the concepts for the catalyst-controlled stereoselective synthesis of atropisomers within these categories with an emphasis on recent advancements and underdeveloped atropisomeric scaffolds beyond stereogenic C(sp2)-C(sp2) axes. We also discuss more complex systems with multiple stereogenic axes or higher-order stereogenicity.

Bifunctional Squaramide-Catalyzed Oxidative Kinetic Resolution: Simultaneous Access to Axially Chiral Thioether and Sulfoxide

Axially chiral thioethers and sulfoxides emerge as two pivotal classes of ligands and organocatalysts, which have remarkable features in the stereoinduction of various asymmetric transformations. However, the lack of easy methods to access such molecules with diverse structures has hampered their broader utilization. Herein, an oxidative kinetic resolution for sulfides using a chiral bifunctional squaramide as the catalyst with cumene hydroperoxide as the terminal oxidant is established. This asymmetric approach provides a variety of axially chiral thioethers as well as sulfoxides bearing both axial and central chirality, with excellent diastereo- and enantioselectivities. This catalytic system also successfully extends to the kinetic resolution of benzothiophene-based sulfides. Preliminary mechanism investigation indicates that the multiple hydrogen bonding interactions between the bifunctional squaramide catalyst and substrates play a crucial role in determining the enantioselectivity and reactivity.

Application of Cyclic Diaryliodonium Salts in the Synthesis of Axially Chiral Natural Product Analogues

The application of cyclic diaryliodonium salts in the synthesis of bioactive natural product analogues was demonstrated. Axially chiral biaryls were obtained via the enantioselective ring opening of cyclic diaryliodonium salts. Regioselective borylation was key in accessing both enantiomers of a biphenol key intermediate in eight steps overall. 8,8″-Amino biflavones were synthesized, their bioactivity profiled, and the eutomer identified. The structure-activity relationship was probed.

Phosphine-Catalyzed Stereospecific and Enantioselective Desymmetrizative [3+2] Cycloaddition of MBH Carbonates and N-(2-tert-Butylphenyl)maleimides

Herein, we report an l-valine-derived amide phosphine-catalyzed [3+2] cyclization of MBH carbonates and N-(2-tert-butylphenyl)maleimides via asymmetric desymmetrization. Bicyclic N-aryl succinimide derivatives bearing three continuous chiral centers with a remote C-N atropisomeric chirality were constructed stereospecifically and enantioselectively. A wide variety of MBH carbonates could be employed in this process to deliver highly optically pure succinimide derivatives in moderate to excellent yields.

Palladium-Catalyzed Atroposelective Suzuki-Miyaura Coupling to Construct Axially Chiral Tetra-Substituted α-Boryl Styrenes

Palladium-catalyzed Suzuki-Miyaura (SM) coupling is a valuable method for forming C─C bonds, including those between aryl moieties. However, achieving atroposelective synthesis of axially chiral styrenes via SM coupling remains challenging. In this study, a palladium-catalyzed atroposelective Suzuki-Miyaura coupling between gem-diborylalkenes and aryl halides is presented. Using the monophosphine ligand Me-BI-DIME (L2), a range of axially chiral tetra-substituted acyclic styrenes with high yields and excellent enantioselectivities are successfully synthesized. Control experiments reveal that the gem-diboryl group significantly influences the product enantioselectivities and the coupling prefers to occur at sites with lower steric hindrance. Additionally, the alkenyl boronate group in the products proves versatile, allowing for various transformations while maintaining high optical purities.

Catalytic asymmetric synthesis of planar-chiral dianthranilides via (Dynamic) kinetic resolution

Chirality constitutes an inherent attribute of nature. The catalytic asymmetric synthesis of molecules with central, axial, and helical chirality is a topic of intense interest and is becoming a mature field of research. However, due to the difficulty in synthesis and the lack of a prototype, less attention has been given to planar chirality arising from the destruction of symmetry on a single planar ring. Herein, we report the catalytic asymmetric synthesis of planar-chiral dianthranilides, a unique class of tub-shaped eight-membered cyclic dilactams. This protocol is enabled by cinchona alkaloid-catalyzed (dynamic) kinetic resolution. Under mild conditions, various C2- or C1-symmetric planar-chiral dianthranilides have been readily prepared in high yields with excellent enantioselectivity. These dianthranilides can serve as an addition to the family of planar-chiral molecules. Its synthetic value has been demonstrated by kinetic resolution of racemic amines via acyl transfer, enantiodivergent synthesis of the natural product eupolyphagin, and preliminary antitumor activity studies.

Atropisomeric Carboxylic Acids Synthesis via Nickel-Catalyzed Enantioconvergent Carboxylation of Aza-Biaryl Triflates with CO2

Upgrading CO2 to value-added chiral molecules via catalytic asymmetric C-C bond formation is a highly important yet challenging task. Although great progress on the formation of centrally chiral carboxylic acids has been achieved, catalytic construction of axially chiral carboxylic acids with CO2 has never been reported to date. Herein, we report the first catalytic asymmetric synthesis of axially chiral carboxylic acids with CO2, which is enabled by nickel-catalyzed dynamic kinetic asymmetric reductive carboxylation of racemic aza-biaryl triflates. A variety of important axially chiral carboxylic acids, which are valuable but difficult to obtain via catalysis, are generated in an enantioconvergent version. This new methodology features good functional group tolerance, easy to scale-up, facile transformation and avoids cumbersome steps, handling organometallic reagents and using stoichiometric chiral materials. Mechanistic investigations indicate a dynamic kinetic asymmetric transformation process induced by chiral nickel catalysis.