Mechanistic Investigations of the Pd(0)-Catalyzed Enantioselective 1,1-Diarylation of Benzyl Acrylates

Catalysing (organo-)catalysis: Trends in the application of machine learning to enantioselective organocatalysis

Organocatalysis has established itself as a third pillar of homogeneous catalysis, besides transition metal catalysis and biocatalysis, as its use for enantioselective reactions has gathered significant interest over the last decades. Concurrent to this development, machine learning (ML) has been increasingly applied in the chemical domain to efficiently uncover hidden patterns in data and accelerate scientific discovery. While the uptake of ML in organocatalysis has been comparably slow, the last two decades have showed an increased interest from the community. This review gives an overview of the work in the field of ML in organocatalysis. The review starts by giving a short primer on ML for experimental chemists, before discussing its application for predicting the selectivity of organocatalytic transformations. Subsequently, we review ML employed for privileged catalysts, before focusing on its application for catalyst and reaction design. Concluding, we give our view on current challenges and future directions for this field, drawing inspiration from the application of ML to other scientific domains.

Fe-Catalyzed Fluoroalkyl(hetero)arylation of Vinyl Azaarenes: Rapid and Modular Synthesis of Unsymmetrical 1,1-Bis(hetero)arylalkanes

In contrast to transition-metal-catalyzed difunctionalization of activated alkenes, selective alkylarylation of vinyl azaarenes is underdeveloped. Consequently, the lack of modular and rapid syntheses of 1,1-bis(hetero)arylalkanes limits their exploration in medicinal chemistry. Herein we report a protocol using commercially available iron salts, bisphosphine ligands, fluoroalkyl halides, and Grignard reagents that enables the selective 1,2-fluoroalkyl(hetero)arylation of vinyl azaarenes. We demonstrate the versatility and robustness of the method through the selective synthesis of a range of unsymmetrical 1,1-bis(hetero)arylalkenes, including pyridine N-oxides, triazoles, pyrazines, carbazoles, indazoles, and 1,2-azaborines. Mechanistic insights from experimental and computational investigations support a radical pathway and provide insights into the role of non-covalent interactions in iron catalysis.

Electroenzymatic cascade reaction on a biohybrid boosts the chiral epoxidation reaction

The chiral epoxidation of styrene and its derivatives is an important transformation that has attracted considerable scientific interest in the chemical industry. Herein, we integrate enzymatic catalysis and electrocatalysis to propose a new route for the chiral epoxidation of styrene and its derivatives. Chloroperoxidase (CPO) functionalized with 1-ethyl-3-methylimidazolium bromide (ILEMB) was loaded onto cobalt nitrogen-doped carbon nanotubes (CoN@CNT) to form a biohybrid (CPO-ILEMB/CoN@CNT). H2O2 species were generated in situ through a two-electron oxygen reduction reaction (2e-ORR) at CoN@CNT to initiate the following enzymatic epoxidation of styrene by CPO. CoN@CNT had high electroactivity for the ORR to produce H2O2 at a more positive potential, prohibiting the conversion of FeIII to FeII in the heme of CPO to maintain enzymatic activity. Meanwhile, CoN@CNT could serve as an ideal carrier for the immobilization of CPO-ILEMB. Hence, the coimmobilization of CPO-ILEMB and CoN@CNT could facilitate the diffusion of intermediate H2O2, which achieved 17 times higher efficiency than the equivalent amounts of free CPO-ILEMB in bulk solution for styrene epoxidation. Notably, an enhancement (∼45%) of chiral selectivity for the epoxidation of styrene was achieved.

Pd-Catalyzed 1,3-Alkenylarylation of Skipped Diene via Metal Migration

We disclose a palladium-catalyzed difunctionalization of skipped diene with alkenyl triflates and arylboronic acids to produce 1,3-alkenylarylated products. The reaction proceeded efficiently with Pd(acac)2 as a catalyst and CsF as a base for a wide range of electron-deficient and electron-rich arylboronic acids as well as oxygen-heterocyclic, sterically hindered, and complex natural product-derived alkenyl triflates bearing various functional groups. The reaction produced 3-aryl-5-alkenylcyclohexene derivatives with 1,3-syn-disubstituted stereochemistry.

Nickel-Catalyzed 1,1-Aminoborylation of Unactivated Terminal Alkenes

Herein, we disclose a Ni-catalyzed 1,1-difunctionalization of unactivated terminal alkenes that enables the incorporation of two different heteroatom motifs across an olefin backbone, thus streamlining the access to α-aminoboronic acid derivatives from simple precursors. The method is characterized by its simplicity and generality across a wide number of coupling counterparts.

Directed Asymmetric Nickel-Catalyzed Reductive 1,2-Diarylation of Electronically Unactivated Alkenes

Transition-metal catalyzed intermolecular 1,2-diarylation of electronically unactivated alkenes has emerged as an extensive research topic in organic synthesis. However, most examples are mainly limited to terminal alkenes. Furthermore, transition-metal catalyzed asymmetric 1,2-diarylation of unactivated alkenes still remains unsolved and is a formidable challenge. Herein, we describe a highly efficient directed nickel-catalyzed reductive 1,2-diarylation of unactivated internal alkenes with high diastereoselectivities. More importantly, our further effort towards enantioselective 1,2-diarylation of the unactivated terminal and challenging internal alkenes is achieved, furnishing various polyarylalkanes featuring benzylic stereocenters in high yields and with good to high enantioselectivities and high diastereoselectivities. Interestingly, the generation of cationic Ni-catalyst by adding alkali metal fluoride is the key to increased efficiency of this enantioselective reaction.

Reductive-Delay Heck 1,1-Diarylation of Terminal Alkenes

Pd-catalyzed chemo- and regiocontrollable 1,1-diarylation of unactivated aliphatic alkenes with two aryl halides was developed. Under the cationic reductive-delay Heck pathway, the first aryl insertion is followed by β-H elimination, while the second aryl insertion is terminated by C-H bond formation.

Palladium(II)-catalyzed enantioselective intermolecular oxidative diarylation of internal enamides

The construction of vicinal stereogenic centers via the simultaneous formation of two C-C bonds across alkenes under oxidative conditions is a stubborn challenge. Herein, we report a Pd(II)-catalyzed highly enantioselective intermolecular oxidative 1,2-diarylation reaction of internal enamides with aryl boronic acids, enabling the expedient construction of two vicinal stereocenters with excellent diastereo-, and enantioselectivities.

α-Branched amines through radical coupling with 2-azaallyl anions, redox active esters and alkenes

α-Branched amines are fundamental building blocks in a variety of natural products and pharmaceuticals. Herein is reported a unique cascade reaction that enables the preparation of α-branched amines bearing aryl or alkyl groups at the β- or γ-positions. The cascade is initiated by reduction of redox active esters to alkyl radicals. The resulting alkyl radicals are trapped by styrene derivatives, leading to benzylic radicals. The persistent 2-azaallyl radicals and benzylic radicals are proposed to undergo a radical-radical coupling leading to functionalized amine products. Evidence is provided that the role of the nickel catalyst is to promote formation of the alkyl radical from the redox active ester and not promote the C-C bond formation. The synthetic method introduced herein tolerates a variety of imines and redox active esters, allowing for efficient construction of amine building blocks.

Stereoselective gem-C,B-Glycosylation via 1,2-Boronate Migration

A novel protocol is established for the long-standing challenge of stereoselective geminal bisglycosylations of saccharides. The merger of PPh₃ as a traceless glycosidic leaving group and 1,2-boronate migration enables the simultaneous introduction of C-C and C-B bonds at the anomeric stereogenic center of furanoses and pyranoses. The power of this method is showcased by a set of site-selective modifications of glycosylation products for the construction of bioactive conjugates and skeletons. A scarce metal-free 1,1-difunctionalization process of alkenes is also concomitantly demonstrated.

Palladium-catalyzed 1,1-alkynylbromination of alkenes with alkynyl bromides

The palladium-catalyzed 1,1-alkynylbromination of terminal alkenes with a silyl-protected alkynyl bromide is reported. The method tolerates a diverse range of alkenes including vinylarenes, acrylates, and even electronically unbiased alkene derivatives to afford propargylic bromides regioselectively. Mechanistic studies and DFT calculations indicate that the 1,1-alkynylbromination reaction proceeds via the migration of the Pd center followed by the formation of a π-allenyl Pd intermediate, leading to the stereoselective reductive elimination of the C(sp³)–Br bond at the propargylic positon.

The first Pd-catalyzed 1,1-alkynylbromination of terminal alkenes using alkynyl bromides, which provides direct access to a variety of functionalized propargylic bromides without the need for an external brominating reagent, is reported.

Enantioselective Reductive Divinylation of Unactivated Alkenes by Nickel-Catalyzed Cyclization Coupling Reaction

Catalytic asymmetric dicarbofunctionalization of tethered alkenes has emerged as a promising tool for producing chiral cyclic molecules; however, it typically relies on aryl-tethered alkenes to form benzene-fused compounds. Herein, we report an enantioselective cross-electrophile divinylation reaction of nonaromatic substrates, 2-bromo-1,6-dienes. The approach thus offers a route to new chiral cyclic architectures, which are key structural motifs found in various biologically active compounds. The reaction proceeds under mild conditions, and the use of chiral t-Bu-pmrox and 3,5-difluoro-pyrox ligands resulted in the formation of divinylated products with high chemo-, regio-, and enantioselectivity. The method is applicable for the incorporation of chiral hetero- and carbocycles into complex molecules.

Computational Discovery of Transition-metal Complexes: From High-throughput Screening to Machine Learning

Transition-metal complexes are attractive targets for the design of catalysts and functional materials. The behavior of the metal-organic bond, while very tunable for achieving target properties, is challenging to predict and necessitates searching a wide and complex space to identify needles in haystacks for target applications. This review will focus on the techniques that make high-throughput search of transition-metal chemical space feasible for the discovery of complexes with desirable properties. The review will cover the development, promise, and limitations of "traditional" computational chemistry (i.e., force field, semiempirical, and density functional theory methods) as it pertains to data generation for inorganic molecular discovery. The review will also discuss the opportunities and limitations in leveraging experimental data sources. We will focus on how advances in statistical modeling, artificial intelligence, multiobjective optimization, and automation accelerate discovery of lead compounds and design rules. The overall objective of this review is to showcase how bringing together advances from diverse areas of computational chemistry and computer science have enabled the rapid uncovering of structure-property relationships in transition-metal chemistry. We aim to highlight how unique considerations in motifs of metal-organic bonding (e.g., variable spin and oxidation state, and bonding strength/nature) set them and their discovery apart from more commonly considered organic molecules. We will also highlight how uncertainty and relative data scarcity in transition-metal chemistry motivate specific developments in machine learning representations, model training, and in computational chemistry. Finally, we will conclude with an outlook of areas of opportunity for the accelerated discovery of transition-metal complexes.

Nickel-Catalyzed Regioselective Alkenylarylation of γ,δ-Alkenyl Ketones via Carbonyl Coordination

We disclose a nickel-catalyzed reaction, which enabled us to difunctionalize unactivated γ,δ-alkenes in ketones with alkenyl triflates and arylboronic esters. The reaction was made feasible by the use of 5-chloro-8-hydroxyquinoline as a ligand along with NiBr2 ⋅DME as a catalyst and LiOtBu as base. The reaction proceeded with a wide range of cyclic, acyclic, endocyclic and exocyclic alkenyl ketones, and electron-rich and electron-deficient arylboronate esters. The reaction also worked with both cyclic and acyclic alkenyl triflates. Control experiments indicate that carbonyl coordination is required for the reaction to proceed.

Organozinc pivalates for cobalt-catalyzed difluoroalkylarylation of alkenes

Installation of fluorine into pharmaceutically relevant molecules plays a vital role in their properties of biology or medicinal chemistry. Direct difunctionalization of alkenes and 1,3-dienes to achieve fluorinated compounds through transition-metal catalysis is challenging, due to the facile β-H elimination from the Csp³‒[M] intermediate. Here we report a cobalt-catalyzed regioselective difluoroalkylarylation of both activated and unactivated alkenes with solid arylzinc pivalates and difluoroalkyl bromides through a cascade Csp³‒Csp³/Csp³‒Csp² bond formation under mild reaction conditions. Indeed, a wide range of functional groups on difluoroalkyl bromides, olefins, 1,3-dienes as well as (hetero)arylzinc pivalates are well tolerated by the cobalt-catalyst, thus furnishing three-component coupling products in good yields and with high regio- and diastereoselectivity. Kinetic experiments comparing arylzinc pivalates and conventional arylzinc halides highlight the unique reactivity of these organozinc pivalates. Mechanistic studies strongly support that the reaction involves direct halogen atom abstraction via single electron transfer to difluoroalkyl bromides from the in situ formed cobalt(I) species, thus realizing a Co(I)/Co(II)/Co(III) catalytic cycle.

Photoinduced 1,2-dicarbofunctionalization of alkenes with organotrifluoroborate nucleophiles via radical/polar crossover

Alkene 1,2-dicarbofunctionalizations are highly sought-after transformations as they enable a rapid increase of molecular complexity in one synthetic step. Traditionally, these conjunctive couplings proceed through the intermediacy of alkylmetal species susceptible to deleterious pathways including β-hydride elimination and protodemetalation. Herein, an intermolecular 1,2-dicarbofunctionalization using alkyl N-(acyloxy)phthalimide redox-active esters as radical progenitors and organotrifluoroborates as carbon-centered nucleophiles is reported. This redox-neutral, multicomponent reaction is postulated to proceed through photochemical radical/polar crossover to afford a key carbocation species that undergoes subsequent trapping with organoboron nucleophiles to accomplish the carboallylation, carboalkenylation, carboalkynylation, and carboarylation of alkenes with regio- and chemoselective control. The mechanistic intricacies of this difunctionalization were elucidated through Stern-Volmer quenching studies, photochemical quantum yield measurements, and trapping experiments of radical and ionic intermediates.

Enantioselective Heck-Matsuda Reactions: From Curiosity to a Game-Changing Methodology

The enantioselective palladium-catalyzed Heck arylation of olefins using arenediazonium salts is one of the last features in the evolution of a synthetic method known as the Heck-Matsuda reaction. This personal account highlights the development of the enantioselective Heck-Matsuda reaction in its initial stages, the challenges faced along the way, and the interesting findings that opened new synthetic opportunities, mainly from our laboratory, featuring the Heck-Matsuda reaction as a central player in the synthesis of bioactive and functional molecules.

Asymmetric Counteranion Directed Catalytic Heck/Tsuji-Trost Annulation of Aryl Iodides and 1,3-Dienes

A chiral anion-mediated asymmetric Heck/Tsuji-Trost reaction of aryl iodides and 1,3-dienes is presented. Chiral indoline derivatives could be afforded with remarkably higher yields and enantioselectivities than our previous chiral ligand-based method. Silver carbonate is employed as both base and halide scavenger to ensure fast and recyclable exchange of the catalytic amount of chiral anions. Fast salt metathesis, as well as the acceleration effect of the chiral anion, could both benefit the stereocontrol of the reaction.

Beyond hydrogen bonding: recent trends of outer sphere interactions in transition metal catalysis

The implementation of interactions beyond hydrogen bonding in the 2^nd coordination sphere of transition metal catalysts is rare. However, it has already shown great promise in last 5 years, providing new tools to control the activity and selectivity as here reviewed.

Carbamoyl Fluoride-Enabled Enantioselective Ni-Catalyzed Carbocarbamoylation of Unactivated Alkenes

A carbamoyl fluoride-enabled enantioselective Ni-catalyzed carbocarbamoylation of unactivated alkenes was developed, providing a broad range of chiral γ-lactams bearing an all-carbon quaternary center in 45-96% yield and 38-97% ee.

Walking metals: catalytic difunctionalization of alkenes at nonclassical sites

Migration of metals along a carbon chain is triggered by two of the most common organometallic elementary steps - β-hydride (β-H) elimination and alkene hydrometallation. This process heralds a new future for creating bonds at carbon sites that fall outside the tenets of the conventional wisdom for reactivity and bond formation, and provides an opportunity to leverage β-H elimination to advance the very reaction of alkene difunctionalization it is intrinsically predestined to disrupt. Almost four decades since its genesis, the early adventure for alkene difunctionalization by metal migration was sporadic, and its later development went on a hiatus primarily due to original impetus on arresting β-H elimination for vicinal alkene difunctionalization. With the recent surge on alkene difunctionalization, efforts have been gradually shifting to harnessing the process of β-H elimination to difunctionalize alkenes at sites other than the classical vicinal carbons, termed henceforth nonclassical reaction sites for pedagogical simplicity. In this review article, we extricate and examine the origin and the development of such reactions over the years. This review covers a wide range of reactions for the difunctionalization of alkenes at geminal (1,1), allylic (1,3) and remote (1,n) carbon sites with a variety of coupling partners. These reactions have enabled engineering of complex molecular frameworks with the generation of new carbon-carbon (C-C)/C-C, C-C/C-heteroatom (halogens, O, N, B) and C-B/C-B bonds. The development of these unique transformations is also presented with mechanistic hypotheses and experimental evidences put forward by researchers. Judged by the number of reports emerging recently, it is now strikingly evident that the field of alkene difunctionalization by metal migration has begun to gain momentum, which holds a great future prospect to develop into a synthetic method of enormous potential.

Nickel-Catalyzed α-Carbonylalkylarylation of Vinylarenes: Expedient Access to γ,γ-Diarylcarbonyl and Aryltetralone Derivatives

We report a Ni-catalyzed regioselective α-carbonylalkylarylation of vinylarenes with α-halocarbonyl compounds and arylzinc reagents. The reaction works with primary, secondary, and tertiary α-halocarbonyl molecules, and electronically varied arylzinc reagents. The reaction generates γ,γ-diarylcarbonyl derivatives with α-secondary, tertiary, and quaternary carbon centers. The products can be readily converted to aryltetralones, including a precursor to Zoloft, an antidepressant drug.

Copper-Catalyzed Asymmetric Radical 1,2-Carboalkynylation of Alkenes with Alkyl Halides and Terminal Alkynes

A copper-catalyzed intermolecular three-component asymmetric radical 1,2-carboalkynylation of alkenes has been developed, providing straightforward access to diverse chiral alkynes from readily available alkyl halides and terminal alkynes. The utilization of a cinchona alkaloid-derived multidentate N,N,P-ligand is crucial for the efficient radical generation from mildly oxidative precursors by copper and the effective inhibition of the undesired Glaser coupling side reaction. The substrate scope is broad, covering (hetero)aryl-, alkynyl-, and aminocarbonyl-substituted alkenes, (hetero)aryl and alkyl as well as silyl alkynes, and tertiary to primary alkyl radical precursors with excellent functional group compatibility. Facile transformations of the obtained chiral alkynes have also been demonstrated, highlighting the excellent complementarity of this protocol to direct 1,2-dicarbofunctionalization reactions with C(sp²/sp³)-based reagents.

Recent applications of chiral phosphoric acids in palladium catalysis

Through the combined action of palladium catalysts and chiral phosphoric acids (CPAs) a variety of catalytic asymmetric reactions have been realized during the past decade, including allylation, alkene functionalization, and C-H activation. This review surveys key examples across these various reaction types and examines the different mechanisms by which CPAs can affect stereoinduction in these reaction systems.

Recent progress of 1,1-difunctionalization of olefins

Olefins are a very important class of compounds and broadly used in the construction of various synthetic building blocks and practical industrial production. The difunctionalization of olefins provides one of the most powerful methods for the C-C or C-X bond formation with a rapid increase of the molecular complexity and synthetic value economically and effectively. Compared with the vigorous growth and abundant achievements of 1,2-difunctionalization of olefins, 1,1-difunctionalization is a relatively emerging and inadequately exploited research direction, despite being tremendously attractive from synthetic perspectives. In this minireview, we provide a brief overview of the advancements of 1,1-difunctionalization of olefins in the past twenty years, and prospects of future developments.

Enantioselective intramolecular [2 + 2] photocycloaddition using phosphoric acid as a chiral template

The enantioselective intramolecular [2 + 2] photocycloaddition of 4-bishomoally-2-quinolone (quinolinone) using phosphoric acid as a chiral template has been developed. Mechanistic studies using several NMR measurement techniques and density functional theory (DFT) calculations indicate that π-π interactions between the phenyl ring on phosphoric acid and quinolinone play important roles in the enantioselectivity.

Indium-mediated difunctionalization of iodoalkyl-tethered unactivated alkenes via an intramolecular cyclization and an ensuing palladium-catalyzed cross-coupling reaction with aryl halides

A cobalt-catalyzed, indium-mediated difunctionalization of iodoalkyl-tethered unactivated alkenes for accessing five-membered cyclic compounds via a cyclization/cross-coupling sequence was developed.

Site-selective acylation of natural products with BINOL-derived phosphoric acids

The site-selective acylation of a steroidal natural product 19-hydroxydehydroepiandrosterone catalyzed by 1,1'-Bi(2-napthol)-derived (BINOL) chiral phosphoric acids (CPA's) is described. Systematic variation and multivariate linear regression analysis reveal that the same steric parameters typically needed for high enantioselectivity with this class of CPAs are also required for site-selectivity in this case. Density functional theory calculations identify additional weak CH-π interactions as contributors to site discrimination. We further report a rare example of site-selective acylation of phenols through the evaluation of naringenin, a flavonoid natural product, using CPA catalysis. These results suggest that BINOL-derived CPA's may have broader applications in site-selective catalysis.

Internal acidity scale and reactivity evaluation of chiral phosphoric acids with different 3,3'-substituents in Brønsted acid catalysis

NMR H-bond analysis reveals an offset of internal and external acidities of catalysts and allows for a detailed reactivity analysis.

The concept of hydrogen bonding for enhancing substrate binding and controlling selectivity and reactivity is central in catalysis. However, the properties of these key hydrogen bonds and their catalyst-dependent variations are extremely difficult to determine directly by experiments. Here, for the first time the hydrogen bond properties of a whole series of BINOL-derived chiral phosphoric acid (CPA) catalysts in their substrate complexes with various imines were investigated to derive the influence of different 3,3′-substituents on the acidity and reactivity. NMR ¹H and ¹⁵N chemical shifts and ¹J_NH coupling constants of these hydrogen bonds were used to establish an internal acidity scale corroborated by calculations. Deviations from calculated external acidities reveal the importance of intermolecular interactions for this key feature of CPAs. For CPAs with similarly sized binding pockets, a correlation of reactivity and hydrogen bond strengths of the catalyst was found. A catalyst with a very small binding pocket showed significantly reduced reactivities. Therefore, NMR isomerization kinetics, population and chemical shift analyses of binary and ternary complexes as well as reaction kinetics were performed to address the steps of the transfer hydrogenation influencing the overall reaction rate. The results of CPAs with different 3,3′-substituents show a delicate balance between the isomerization and the ternary complex formation to be rate-determining. For CPAs with an identical acidic motif and similar sterics, reactivity and internal acidity correlated inversely. In cases where higher sterical demand within the binary complex hinders the binding of the second substrate, the correlation between acidity and reactivity breaks down.

Mechanistically Guided Predictive Models for Ligand and Initiator Effects in Copper-Catalyzed Atom Transfer Radical Polymerization (Cu-ATRP)

Copper-catalyzed atom transfer radical polymerization (Cu-ATRP) is one of the most widely used controlled radical polymerization techniques. Notwithstanding the extensive mechanistic studies in the literature, the transition states of the activation/deactivation of the growing polymer chain, a key equilibrium in Cu-ATRP, have not been investigated computationally. Therefore, the understanding of the origin of ligand and initiator effects on the rates of activation/deactivation is still limited. Here, we present the first computational analysis of Cu-ATRP activation transition states to reveal factors that affect the rates of activation and deactivation. The Br atom transfer between the polymer chain and the Cu catalyst occurs through an unusual bent geometry that involves pronounced interactions between the polymer chain end and the ancillary ligand on the Cu catalyst. Therefore, the rates of activation/deactivation are determined by both the electronic properties of the Cu catalyst and the ligand-initiator steric repulsions. In addition, our calculations revealed the important role of ligand backbone flexibility on the activation. These theoretical analyses led to the identification of three chemically meaningful descriptors, namely HOMO energy of the catalyst ( EHOMO), percent buried volume ( Vbur%), and distortion energy of the catalyst (Δ Edist), to describe the electronic, steric, and flexibility effects on reactivity, respectively. A robust and simple predictive model for ligand effect on reactivity is thereby established by correlating these three descriptors with experimental activation rate constants using multivariate linear regression. Validation using a structurally diverse set of ligands revealed the average error is less than ±2 kcal/mol compared to the experimentally derived activation energies. The same approach was also applied to develop a predictive model for reactivity of different alkyl halide initiators using R-X bond dissociation energy (BDE) and Cu-X halogenophilicity as descriptors.

Highly Enantioselective Cross-Electrophile Aryl-Alkenylation of Unactivated Alkenes

Enantioselective cross-electrophile reactions remain a challenging subject in metal catalysis, and with respect to data, studies have mainly focused on stereoconvergent reactions of racemic alkyl electrophiles. Here, we report an enantioselective cross-electrophile aryl-alkenylation reaction of unactivated alkenes. This method provides access to a number of biologically important chiral molecules such as dihydrobenzofurans, indolines, and indanes. The incorporated alkenyl group is suitable for further reactions that can lead to an increase in molecular diversity and complexity. The reaction proceeds under mild conditions at room temperature, and an easily accessible chiral pyrox ligand is used to afford products with high enantioselectivity. The synthetic utility of this method is demonstrated by enabling the modification of complex molecules such as peptides, indometacin, and steroids.

Disparate Catalytic Scaffolds for Atroposelective Cyclodehydration

Catalysts that control stereochemistry are prized tools in chemical synthesis. When an effective catalyst is found, it is often explored for other types of reactions, frequently under the auspices of different mechanisms. As successes mount, a unique catalyst scaffold may become viewed as "privileged". However, the mechanistic hallmarks of privileged catalysts are not easily enumerated or readily generalized to genuinely different classes of reactions or substrates. We explored the concept of scaffold uniqueness with two catalyst types for an unusual atropisomer-selective cyclodehydration: (a) C2-symmetric chiral phosphoric acids and (b) phosphothreonine-embedded, peptidic phosphoric acids. Pragmatically, both catalyst scaffolds proved fertile for enantioselective/atroposelective cyclodehydrations. Mechanistic studies revealed that the determinants of often equivalent and high atroposelectivity are different for the two catalyst classes. A data-descriptive classification of these asymmetric catalysts reveals an increasingly broad set of catalyst chemotypes, operating with different mechanistic features, that creates new opportunities for broad and complementary application of catalyst scaffolds in diverse substrate space.

Access to P-chiral phosphine oxides by enantioselective allylic alkylation of bisphenols

A novel biscinchona alkaloid-catalyzed highly enantioselective desymmetrization reaction of bisphenol compounds with achiral Morita-Baylis-Hillman carbonate agents was developed. Through the asymmetric allylic alkylation strategy, a broad range of optically active P-stereogenic phosphine oxides were generated with excellent to good yields (up to 99%) and high enantioselectivities (up to 98.5 : 1.5 e.r.). The reaction was further investigated by the linear free energy relationship (LFER) analysis. A possible transition state was proposed and furthered verified by theoretical calculations.