Enantio-, diastereo-, and regioselective iridium-catalyzed asymmetric allylic alkylation of acyclic β-ketoesters

Regioselective Palladium-Catalyzed Chain-Growth Allylic Amination Polymerization of Vinyl Aziridines

Organometallic-mediated chain growth polymerization of readily accessible chemical building blocks is responsible for important commercial and technological advances in polymer science, but the incorporation of heteroatoms into the polymer backbone through these mechanisms remains a challenge. Transition metal π-allyl complexes are well-developed organometallic intermediates for carbon-heteroatom bond formation in small-molecule catalysis yet remain underexplored in polymer science. Here, we developed a regioselective palladium-phosphoramidite-catalyzed chain-growth allylic amination polymerization of vinyl aziridines for the synthesis of novel nitrogen-rich polymers via ambiphilic π-allyl complexes. The polymerization accessed a linear microstructure with four carbons between each nitrogen, which is challenging to achieve through other chain-growth polymerization approaches. The highly regioselective allylic amination polymerization demonstrated the characteristics of a controlled polymerization and was able to achieve molar masses exceeding 20 kg mol-1 with low dispersities (D̵ < 1.3). The identification of the polymer structure and well-defined chain ends were supported by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and chain extension experiments demonstrate opportunities for building more complex materials from this method. A Hammett study was performed to understand the role of the catalyst and monomer structure on regioselectivity, and the data supported a mechanism wherein regioselectivity was primarily controlled by the ligand-metal complex. Postpolymerization desulfonylation provided access to a novel polyamine that demonstrated broad anticancer activity in vitro, which highlights the benefits of unlocking novel polyamine microstructures through regioselective chain-growth allylic amination polymerization.

Recent Advances on the Catalytic Asymmetric Allylic α-Alkylation of Carbonyl Derivatives Using Free Allylic Alcohols

During the last years, the development of more sustainable and straightforward methodologies to minimize the generation of waste organic substances has acquired high importance within synthetic organic chemistry. Therefore, it is not surprising that many efforts are devoted to ameliorating already well-known successful methodologies, that is, the case of the asymmetric allylic allylation reaction of carbonyl compounds. The use of free alcohols as alkylating agents in this transformation represents a step forward in this sense since it minimizes waste production and the substrate manipulation. In this review, we aim to gather the most recent methodologies describing this strategy by paying special attention to the reaction mechanisms, as well as their synthetic applications.

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.

Catalytic Asymmetric α-Alkylation of Ketones with Unactivated Alkyl Halides

A catalytic, enantioselective method for direct α-alkylation of ketones with unactivated alkyl halides is realized by employing an α-enolizable ketone in a nickel-catalyzed C(sp3)-C(sp3) cross-coupling reaction. The key to the success is attributed to a unique bimetallic ligand. A variety of acyclic ketones and unactivated alkyl iodides can serve as suitable substrates under mild conditions to generate chiral ketones with α-quaternary carbon stereocenters in high yields with good enantioselectivities. A range of transformations based on the ketone moiety are also demonstrated to show the potential application of this method. Preliminary mechanistic studies support a dinickel-catalyzed cross-coupling mechanism.

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.

Asymmetric Synthesis of a Quaternary Carbon Stereogenic Center by Organocatalysis Using a Primary Amino Acid and Its Salt

In this personal account, our recent developments on the asymmetric synthesis of a quaternary carbon stereogenic center by organocatalysis using a primary amino acid and its salt as a catalyst are described in three chapters: (1) conjugate addition to nitroalkenes and vinyl ketones, (2) nucleophilic addition to π-allyl palladium complexes, and (3) nucleophilic substitution reactions with allyl and propargyl halides. By these methods, asymmetric α-allylation of α-branched aldehydes and ketones smoothly proceeded to give γ-nitroaldehydes, ketoaldehydes, α-allylated aldehydes, and α-allylated β-ketoesters possessing a quaternary carbon stereogenic center in good yields with high enantioselectivities.

Stereocontrolled α-Allylation of α-Branched N-tert-Butanesulfinyl Ketimines via a Michael-Wittig Cascade for the Construction of Acyclic Quaternary Stereocenters

A single-flask cascade of Michael addition and Wittig olefination was developed to allow the stereoselective α-allylic alkylation of α-branched N-tert-butanesulfinyl ketimines for the construction of acyclic quaternary stereocenters bearing two sterically and electronically similar substituents. In this process, tBuOK-promoted stereoselective α-deprotonation gives fully substituted aza-enolates with a stereodefined geometry, Michael addition with α,β-unsaturated phosphonates generates C-C bonds with exceptional stereocontrol, and finally paraformaldehyde trapping of the conjugate addition intermediate generates functionalized α-allylated imines.

Stereodivergent dehydrative allylation of β-keto esters using a Ru/Pd synergistic catalyst

α-Alkylation of a β-keto ester is a frequently used reaction for carbon–carbon bond formation. However, extension to a stereoselective reaction remains a significant challenge, because the product easily racemizes under acidic or basic conditions. Here, we report a hybrid system consisting of Pd and Ru complexes that catalyzes the asymmetric dehydrative condensation between cinnamyl-type allylic alcohols and β-keto esters. α-Non-substituted β-keto ester can be allylated to afford an α-mono-substituted product with high regio-, diastereo-, and enantioselectivity. No epimerization occurs owing to the nearly neutral conditions, which is achieved by a rapid proton transfer from Pd-enolate formation to Ru π-allyl complex formation. Four diastereomers can be synthesized on demand by changing the stereochemistry of the Pd or Ru complex. Eight stereoisomers with three adjacent stereogenic centers can be synthesized by employing diastereoselective reduction of the ketone in the products. The formal synthesis of (+)-pancratistatin demonstrates the utility of the reaction.

α-Alkylation of β-keto esters is a frequently used reaction for carbon–carbon bond formation, but a general, stereoselective version of this reaction is challenging to realize. Here, the authors report a combined ruthenium and palladium catalytic system for the asymmetric dehydrative condensation between cinnamyl-type allylic alcohols and β-keto esters.

Borylated Cyclopropanes as Spring-Loaded Entities: Access to Vicinal Tertiary and Quaternary Carbon Stereocenters in Acyclic Systems

Herein, we present the formation of acyclic frameworks bearing two consecutive stereocenters of either tertiary or quaternary nature starting from easily accessible cyclopropenes. This holistic approach involves a regio- and diastereoselective hydro- or carboborylation of substituted cyclopropenyl esters. Formation of boronate complexes of the latter via the addition of nucleophiles and subsequent stereospecific 1,2-migration with carbon–carbon bond cleavage delivered the title compounds.

Preparation of Distant Quaternary Carbon Stereocenters by Double Selective Ring-Opening of 1,1-Biscyclopropyl Methanol Derivatives

The diastereoselective double carbometalation reaction of cyclopropenes provides, in a single‐pot operation, two ω‐ene‐[1,1]‐bicyclopropyl ester derivatives. One regioisomer then undergoes a Pd‐catalyzed addition of aryl iodide to provide skipped dienes possessing several distant stereocenters including two congested quaternary carbon centers with excellent diastereoselectivity.

Doubly stereoconvergent construction of vicinal all-carbon quaternary and tertiary stereocenters by Cu/Mg-catalyzed propargylic substitution

The construction of vicinal, congested stereocenters with high selectivities is of general utility in chemistry. To build two such stereocenters in one step from readily available starting materials is very desirable, but remains challenging. We report here a doubly stereoconvergent, Cu/Mg-catalyzed asymmetric propargylic substitution reaction to convert simple starting materials to products with vicinal tertiary and all-carbon quaternary stereocenters in high yields and excellent diastereo- and enantioselectivities. Both the nucleophiles and the electrophiles employed in this transformation are racemic. This reaction uses earth abundant metal catalysts, operates under ambient conditions, and demonstrates broad substrate scope. The products of this reaction are functional group rich and synthetically versatile. Key to the success of this development is the devise of a Cu/Mg dual catalytic system and the identification of a bulky tridentate pyridinebisimidazoline (PyBim) ligand.

The construction of vicinal, congested stereocenters with high selectivities is of general utility in chemistry. Here the authors report a doubly-stereoconvergent, Cu/Mg-catalyzed asymmetric propargylic substitution reaction to convert simple starting materials to products with vicinal tertiary and all-carbon quaternary stereocenters in high yields and excellent diastereo- and enantioselectivities

Pd(0)-Catalyzed Deacylative Allylations (DaA) Strategy and Application in the Total Synthesis of Alkaloids

Natural product synthesis has been the prime focus for the development of new carbon-carbon bond forming transformations. In particular, the construction of molecules with all-carbon quaternary centers remain one of the most facinating targets. In this regard, transition-metal catalyzed processes have gained imporatnce owing to their mild nature. Towards this, Pd(0)-catalyzed decarboxylative allylations (DcA) is worth mentioning and has emerged as a convenient method for synthesis of molecules even in their enantioenriched form. However, in order to have a flexible approach that facilitate rapid production of derivatives by utilizing commercially available allyl alcohols, the concept of Pd(0)-catalyzed deacylative allylations (DaA) methodology gains popularity. In these reactions, the transfer of an acyl group has a functional role in activating the allylic alcohol (proelectrophile) toward reaction with Pd(0)-catalysts. We present here an Account on newly conceptualized deacylative allylations (DaA) methodology and its applications in the synthesis of various intermediates and building blocks. Further, its potential in the total synthesis of naturally occurring alkaloids have been summarized in this personal account.

Asymmetric construction of acyclic quaternary stereocenters via direct enantioselective additions of α-alkynyl ketones to allenamides

Acyclic quaternary stereocenters are widely present in a series of biologically active natural products and pharmaceuticals. However, development of highly efficient asymmetric catalytic methods for the construction of these privileged motifs represents a longstanding challenge in organic synthesis. Herein, an efficient chiral phosphoric acid catalyzed direct asymmetric addition of α-alkynyl acyclic ketones with allenamides has been developed, furnishing the acyclic all-carbon quaternary stereocenters with excellent regioselectivities and high enantioselectivities. Extensive and detailed experimental mechanistic studies were performed to investigate the mechanism of this reaction. Despite a novel covalent allyl phosphate intermediate was found in these reactions, further studies indicated that a SN2-type mechanism with the ketone nucleophiles is not very possible. Instead, a more plausible mechanism involving the elimination of the allyl phosphate to give the α,β-unsaturated iminium intermediate, which underwent the asymmetric conjugate addition with the enol form of ketone nucleophiles under chiral anion catalysis, was proposed. In virtue of the fruitful functional groups bearing in the chiral products, the diverse derivatizations of the chiral products provided access to a wide array of chiral scaffolds with quaternary stereocenters.

Transition-Metal-Catalyzed Monofluoroalkylation: Strategies for the Synthesis of Alkyl Fluorides by C-C Bond Formation

Alkyl fluorides modulate the conformation, lipophilicity, metabolic stability, and p K a of compounds containing aliphatic motifs and, therefore, have been valuable for medicinal chemistry. Despite significant research in organofluorine chemistry, the synthesis of alkyl fluorides, especially chiral alkyl fluorides, remains a challenge. Most commonly, alkyl fluorides are prepared by the formation of C-F bonds (fluorination), and numerous strategies for nucleophilic, electrophilic, and radical fluorination have been reported in recent years. Although strategies to access alkyl fluorides by C-C bond formation (monofluoroalkylation) are inherently convergent and complexity-generating, they have studied less than methods based on fluorination. This Review provides an overview of recent developments in the synthesis of chiral (enantioenriched or racemic) secondary and tertiary alkyl fluorides by monofluoroalkylation catalyzed by transition-metal complexes. We expect this contribution will illuminate the potential of monofluoroalkylations to simplify the synthesis of complex alkyl fluorides and suggest further research directions in this growing field.

Construction of Acyclic All-Carbon Quaternary Stereocenter Based on Asymmetric Michael Addition of Chiral Amine

Acyclic asymmetric quaternary stereocenters, which are composed of four carbon-carbon bonds, were finely constructed by utilizing a face-selective alkylation of enolate intermediates derived from an asymmetric Michael addition reaction of a chiral lithium amide with trisubstituted (E)-α,β-unsaturated esters. The present face-selective alkylation was able to employ diverse alkyl halides as an electrophile to afford various Michael adducts having an all-carbon quaternary stereocenter. With regard to the deprotection of the chiral auxiliary, N-iodosuccinimide used in our previous study did not work in the present cases; however, we found that pyridine iodine monochloride in the presence of H₂O was effective to remove the bornyl group and the benzyl group on the amino group to provide the β-amino ester derivative.

Catalytic Enantioselective Alkylation of Prochiral Enolates

The asymmetric alkylation of enolates is a particularly versatile method for the construction of α-stereogenic carbonyl motifs, which are ubiquitous in synthetic chemistry. Over the past several decades, the focus has shifted to the development of new catalytic methods that depart from classical stoichiometric stereoinduction strategies (e.g., chiral auxiliaries, chiral alkali metal amide bases, chiral electrophiles, etc.). In this way, the enantioselective alkylation of prochiral enolates greatly improves the step- and redox-economy of this process, in addition to enhancing the scope and selectivity of these reactions. In this review, we summarize the origin and advancement of catalytic enantioselective enolate alkylation methods, with a directed emphasis on the union of prochiral nucleophiles with carbon-centered electrophiles for the construction of α-stereogenic carbonyl derivatives. Hence, the transformative developments for each distinct class of nucleophile (e.g., ketone enolates, ester enolates, amide enolates, etc.) are presented in a modular format to highlight the state-of-the-art methods and current limitations in each area.

Tandem Iridium Catalysis as a General Strategy for Atroposelective Construction of Axially Chiral Styrenes

Axially chiral styrenes are of great interest since they may serve as a class of novel chiral ligands in asymmetric synthesis. However, only recently have strategies been developed for their enantioselective preparation. Thus, the development of novel and efficient methodologies is highly desirable. Herein, we reported the first tandem iridium catalysis as a general strategy for the synthesis of axially chiral styrenes enabled by Asymmetric Allylic Substitution-Isomerization (AASI) using cinnamyl carbonate analogues as electrophiles and naphthols as nucleophiles. In this approach, axially chiral styrenes were generated through two independent iridium-catalytic cycles: iridium-catalyzed asymmetric allylic substitution and in situ isomerization via stereospecific 1,3-hydride transfer catalyzed by the same iridium catalyst. Both experimental and computational studies demonstrated that the isomerization proceeded by iridium-catalyzed benzylic C-H bond oxidative addition, followed by terminal C-H reductive elimination. Amid the central-to-axial chirality transfer, the hydroxyl of naphthol plays a crucial role in ensuring the stereospecificity by coordinating with the Ir(I) center. The process accommodated broad functional group compatibility. The products were generated in excellent yields with excellent to high enantioselectivities, which could be transformed to various axially chiral molecules.

Enantioselective Synthesis of Quaternary Carbon Stereocenters by Asymmetric Allylic Alkylation: A Review

Quaternary stereocenters are of great importance to the three-dimensionality and enhanced properties of new molecules, but the synthetic challenges in creating quaternary stereocenters greatly hinder their wide use in drug discovery, organic material design, and natural product synthesis. The asymmetric allylic alkylation (AAA) of allylic substrates has proven to be a powerful methodology for enantioselective formation of structure skeletons bearing single or more quaternary carbon centers in modern asymmetric organocatalysis. AAA has certain advantages in constructing the tetrasubstituted stereocenters, including but not limited to mild reactive conditions, effective reaction rates, new functional group introduction, and carbon chains length extension. This review outlines the key considerations in the application of AAA reactions and summarizes the recent progress of AAA reactions in the enantioselective synthesis of products containing quaternary stereocenters. Meanwhile, a detailed discussion of the AAA reactions such as ligands, scope of substrates, transformations and the general reaction mechanisms is also provided. We hope this review could stimulate further advances in much broader areas, including organic synthesis, asymmetric catalysis, C-H activation, and symmetrical pharmaceutical chemistry.

Pd/Cu Dual-Catalyzed Asymmetric Synthesis of Highly Functional All-Carbon Quaternary Stereocenters from Vinyl Carbonates

The challenging metal-catalyzed asymmetric synthesis of highly functional quaternary carbon centers using decarboxylative C(sp³ )-C(sp³ ) bond formation reactions is reported. The key substrate, a vinyl cyclic carbonate, is activated to provide concomitantly both the requisite nucleophile (by formal umpolung) and electrophile reaction partner preceding the asymmetric cross-coupling process. A wide screening of reaction conditions, additives and catalyst precursors afforded a protocol that gave access to a series of compounds featuring densely functionalized, elusive quaternary carbon stereocenters in appreciable yield and with enantiomeric ratios (er's) of up to 90 : 10.

Palladium-Catalyzed Allenamide Carbopalladation/Allylation with Active Methine Compounds

A palladium-catalyzed allenamide carbopalladation/allylation with active methine compounds has been developed. Various indoles and isoquinolinones bearing a quaternary carbon center were achieved with good efficiency, a broad substrate scope and good functional group tolerance. This reaction underwent cascade oxidative addition, carbopalladation, and allylic alkylation, and two new C-C bonds were formed in one pot.

Iridium-Catalyzed Asymmetric Allylic Alkylation of Deconjugated Butyrolactams

Compared with the ever-growing list of nonprochiral nucleophiles in Ir-catalyzed asymmetric allylic substitution reactions, prochiral nucleophiles are less studied. We present a new prochiral nucleophile, namely, deconjugated butyrolactam, for Ir-catalyzed asymmetric allylic alkylation (AAA). This reaction provides access to α-allyl deconjugated butyrolactams with a moderate to good dr and an excellent er. This is the first AAA reaction of deconjugated butyrolactams. Allyl transposition through Cope rearrangement appears to proceed stereospecifically to form γ-allyl conjugated butyrolactams.

CuH-Catalyzed Regio- and Enantioselective Hydrocarboxylation of Allenes: Toward Carboxylic Acids with Acyclic Quaternary Centers

We report a method to prepare α-chiral carboxylic acid derivatives, including those bearing all-carbon quaternary centers, through an enantioselective CuH-catalyzed hydrocarboxylation of allenes with a commercially available fluoroformate. A broad range of heterocycles and functional groups on the allenes were tolerated in this protocol, giving enantioenriched α-quaternary and tertiary carboxylic acid derivatives in good yields with exclusive branched regioselectivity. The synthetic utility of this approach was further demonstrated by derivatization of the products to afford biologically important compounds, including the antiplatelet drug indobufen.

Mechanistic insights into rhodium-catalyzed enantioselective allylic alkylation for quaternary stereogenic centers

Installing quaternary stereogenic carbon is an arduous task of contemporary importance in the domain of asymmetric catalysis. To this end, an asymmetric allylic alkylation of α,α-disubstituted aldehydes by using allyl benzoate in the presence of Wilkinson's catalyst [Rh(Cl)(PPh₃)₃], (R)-BINOL–P(OMe) as the external ligand, and LiHMDS as the base has been reported to offer high enantioselectivity. The mechanistic details of this important reaction remain vague, which prompted us to undertake a detailed density functional theory (SMD_(THF)/B3LYP-D3) investigation on the nature of the potential active catalyst, energetic features of the catalytic cycle, and the origin of high enantioselectivity. We note that a chloride displacement from the native Rh-phosphine [Rh(Cl)(PPh₃)₃] by BINOL–P(OMe) phosphite and an ensuing MeCl elimination can result in the in situ formation of a Rh-phosphonate [Rh(BINOL–P Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O)(PPh₃)₃]. A superior energetic span (δE) noted with such a Rh-phosphonate suggests that it is likely to serve as an active catalyst. The uptake of allyl benzoate by the active catalyst followed by the turnover determining C–O bond oxidative addition furnishes a Rh-π-allyl intermediate, which upon interception by (Z)-Li-enolate (derived from α,α-disubstituted aldehyde) in the enantiocontrolling C–C bond generates a quaternary stereogenic center. The addition of the re prochiral face of the (Z)-Li-enolate to the Rh-bound allyl moiety leading to the R enantiomer of the product is found to be 2.4 kcal mol⁻¹ more preferred over the addition through its si face. The origin of the stereochemical preference for the re face addition is traced to improved noncovalent interactions (NCIs) and less distortion in the enantiocontrolling C–C bond formation transition state than that in the si face addition. Computed enantioselectivity (96%) is in very good agreement with the experimental value (92%), so is the overall activation barrier (δE of 17.1 kcal mol⁻¹), which is in conformity with room temperature reaction conditions.

The origin of high enantioselectivity in the formation of quaternary stereogenic carbon.

Asymmetric catalytic construction of fully substituted carbon stereocenters using acyclic α-branched β-ketocarbonyls: the “Methyl Rule” widely exists

This review illustrates the recent advances in catalytic asymmetric α-functionalization of acyclic β-ketocarbonyls. A thorough survey of all these reactions indicates the existance of a general principle which is called the “Methyl Rule”.

Access to Benzylic Quaternary Carbons from Aromatic Ketones

The construction of benzylic all-carbon quaternary stereocenters, which are ubiquitous in biomolecules and drugs, is a task of high practical significance. Herein, we disclose a highly efficient one-pot method of constructing all-carbon quaternary structural units from aryl ketones, revealing that the entire process involves three consecutive chemical events, namely nucleophilic addition, Meinwald 1,2-hydrogen migration, and alkylation. Interestingly, dimerization of acetophenones results in formation of 2,4-diarylfurans under the employed conditions rather than the quaternary carbon products.

Brønsted acid and Pd-PHOX dual-catalysed enantioselective addition of activated C-pronucleophiles to internal dienes

We describe the development of Pd-PHOX-catalysed enantioselective couplings of internal dienes with malononitrile and other activated C-pronucleophiles. Reactions are dramatically accelerated by the addition of Et3N·HBArF 4 as a Brønsted acid co-catalyst, enabling a suite of products bearing a variety of alkyl substituents at the stereogenic carbon to be prepared. A series of mechanism-oriented experiments reveal key aspects of the catalytic cycle and the importance of the non-coordinating BArF 4 counterion in not only promoting reactions of internal dienes but also additions of previously unreactive nucleophiles towards terminal dienes.

Palladium-catalyzed enantioselective decarboxylative allylic alkylation of fully substituted N-acyl indole-derived enol carbonates

The first enantioselective Pd-catalyzed decarboxylative allylic alkylation of fully substituted N-acyl indole-derived enol carbonates generates acyclic all-carbon quaternary stereocenters in excellent yields (up to 99%) and enantioselectivities (up to 98% ee) using a new electron-deficient phosphinoxazoline (PHOX) ligand.

The first enantioselective palladium-catalyzed decarboxylative allylic alkylation of fully substituted N-acyl indole-derived enol carbonates forming acyclic all-carbon quaternary stereocenters is reported. Excellent yields up to 99% and enantioselectivities up to 98% ee are obtained through the use of a new electron-deficient phosphinoxazoline (PHOX) ligand. Control of substrate enolate geometry is crucial for high selectivity. The obtained α-quaternary N-acyl indoles are formal ester equivalents, and represent a useful handle for further synthetic transformations.

Asymmetric organocatalytic conjugated addition of pyrazolin-5-ones to ortho-quinomethanes: construction of vicinal tertiary and all-carbon quaternary stereocenters

An organocatalytic conjugated addition of pyrazolin-5-ones to ortho-quinomethanes was developed to construct the vicinal tertiary and all-carbon quaternary stereocenters.

Iridium-Catalyzed Asymmetric Allylic Substitution Reactions

In this review, we summarize the origin and advancements of iridium-catalyzed asymmetric allylic substitution reactions during the past two decades. Since the first report in 1997, Ir-catalyzed asymmetric allylic substitution reactions have attracted intense attention due to their exceptionally high regio- and enantioselectivities. Ir-catalyzed asymmetric allylic substitution reactions have been significantly developed in recent years in many respects, including ligand development, mechanistic understanding, substrate scope, and application in the synthesis of complex functional molecules. In this review, an explicit outline of ligands, mechanism, scope of nucleophiles, and applications is presented.