Computationally Guided Catalyst Design in the Type I Dynamic Kinetic Asymmetric Pauson-Khand Reaction of Allenyl Acetates

Data-Driven Virtual Screening of Conformational Ensembles of Transition-Metal Complexes

Transition-metal complexes serve as highly enantioselective homogeneous catalysts for various transformations, making them valuable in the pharmaceutical industry. Data-driven prediction models can accelerate high-throughput catalyst design but require computer-readable representations that account for conformational flexibility. This is typically achieved through high-level conformer searches, followed by DFT optimization of the transition-metal complexes. However, conformer selection remains reliant on human assumptions, with no cost-efficient and generalizable workflow available. To address this, we introduce an automated approach to correlate CREST(GFN2-xTB//GFN-FF)-generated conformer ensembles with their DFT-optimized counterparts for systematic conformer selection. We analyzed 24 precatalyst structures, performing CREST conformer searches, followed by full DFT optimization. Three filtering methods were evaluated: (i) geometric ligand descriptors, (ii) PCA-based selection, and (iii) DBSCAN clustering using RMSD and energy. The proposed methods were validated on Rh-based catalysts featuring bisphosphine ligands, which are widely employed in hydrogenation reactions. To assess general applicability, both the precatalyst and its corresponding acrylate-bound complex were analyzed. Our results confirm that CREST overestimates ligand flexibility, and energy-based filtering is ineffective. PCA-based selection failed to distinguish conformers by DFT energy, while RMSD-based filtering improved selection but lacked tunability. DBSCAN clustering provided the most effective approach, eliminating redundancies while preserving key configurations. This method remained robust across data sets and is computationally efficient without requiring molecular descriptor calculations. These findings highlight the limitations of energy-based filtering and the advantages of structure-based approaches for conformer selection. While DBSCAN clustering is a practical solution, its parameters remain system-dependent. For high-accuracy applications, refined energy calculations may be necessary; however, DBSCAN-based clustering offers a computationally accessible strategy for rapid catalyst representations involving conformational flexibility.

Dynamic Kinetic Asymmetric Hydroacylation: Racemization by Soft Enolization

We report a dynamic kinetic asymmetric transformation (DyKAT) of racemic aldehydes by Rh-catalyzed hydroacylation of acrylamides. This intermolecular hydroacylation generates 1,4-ketoamides with high enantio- and diastereoselectivity. DFT and experimental studies provide mechanistic insights and reveal an unexpected Rh-catalyzed pathway for aldehyde racemization. Our study represents a pioneering kinetic resolution by intermolecular hydroacylation and contributes to the growing field of stereoconvergent catalysis featuring C-C bond construction.

Machine-Learning-Based Design of Metallocene Catalysts for Controlled Olefin Copolymerization

Polyolefins are versatile materials for various purposes, but their functionality should be fine-tuned for target applications including the mitigation of adverse environmental impacts. Producing such polymers with desired properties requires catalysts that can control polymerization at an atomistic level. However, complex reaction mechanisms and very limited experimental data make it difficult to design new efficient catalysts using conventional computational and data-driven approaches. Here, we present a pragmatic strategy based on data-efficient predictive models combined with a genetic algorithm to design new catalysts for controlled ethylene/hexene copolymerization. By deriving the chemically intuitive descriptors from the mechanistic analysis of the polymerization, we achieved the promising predictive models with small data applicable to various core structures and different experimental conditions, respectively. We screened catalysts through a virtual screening scheme combining a genetic algorithm and predictive models using chemically intuitive descriptors and considered their synthesizability through the manual inspections of experts. As a result, we successfully designed nine catalysts with desired comonomer ratios and diverse core structures.

Microwave-Assisted One-Pot Synthesis of Diverse Tribenzo[a,f,h]azulen-10-ones

Azulene-type polycyclic hydrocarbons have recently attracted a great deal of attention from researchers; however, their structure-property correlations and possible uses are not being fully explored due to the lack of effective synthesis techniques. Herein, we report a hitherto unexplored one-pot, microwave-assisted synthetic strategy toward diverse tribenzo[a,f,h]azulen-10-ones by tandem Suzuki coupling and a subsequent cyclo-condensation process. The strategy provides tribenzo[a,f,h]azulen-10-ones in good to excellent yields with structural versatility, including thiophene-embedded tribenzo[a,f,h]azulen-10-ones. In addition, UV-visible absorption studies have been used to investigate their structural and photophysical properties. This strategy offers a new platform for promptly synthesizing numerous unexplored azulenone units.

An efficient and flexible approach for local distortion: distortion distribution analysis enabled by fragmentation

Distortion can play crucial roles in influencing structures and properties, as well as enhancing reactivity or selectivity in many chemical and biological systems. The distortion/interaction or activation-strain model is a popular and powerful method for deciphering the origins of activation energies, in which distortion and interaction energies dictate an activation energy. However, decomposition of local distortion energy at the atomic scale remains less clear and straightforward. Knowing such information should deepen our understanding of reaction processes and improve reaction design. Herein, an efficient, general and flexible fragmentation-based approach was proposed to evaluate local distortion energies for various chemical and biological molecules, which can be obtained computationally and/or experimentally. Moreover, our distortion analysis is readily applicable to multiple structures from molecular dynamics (or the minimum energy path) as well as can be evaluated by different computational chemistry methods. Our systematic analysis shows that our approach not only aids computational and experimental chemists in visualizing (relative) distortion distributions within molecules (distortion map) and identifies the key distorted pieces, but also offers deeper understanding and insights into structures, reaction mechanisms and dynamics in various chemical and biological systems. Furthermore, our analysis offers indices of local distortion energy, which can potentially serve as a new descriptor for multi-linear regression (MLR) or machine learning (ML) modelling.

Stereo-Differentiating Asymmetric Rh(I)-Catalyzed Pauson-Khand Reaction: A DFT-Informed Approach to Thapsigargin Stereoisomers

We report a stereo-differentiating dynamic kinetic asymmetric Rh(I)-catalyzed Pauson-Khand reaction, which provides access to an array of thapsigargin stereoisomers. Using catalyst-control, a consistent stereochemical outcome is achieved at C2─for both matched and mismatched cases─regardless of the allene-yne C8 stereochemistry. The stereochemical configuration for all stereoisomers was assigned by comparing experimental vibrational circular dichroism (VCD) and 13C NMR to DFT-computed spectra. DFT calculations of the transition-state structures corroborate experimentally observed stereoselectivity and identify key stabilizing and destabilizing interactions between the chiral ligand and allene-yne PKR substrates. The robust nature of our catalyst-ligand system places the total synthesis of thapsigargin and its stereoisomeric analogues within reach.

Radical-Based Enantioconvergent Reductive Couplings of Racemic Allenes and Aldehydes

Transition metal-catalyzed radical-based enantioconvergent reactions have become a powerful strategy to synthesize enantiopure compounds from racemic starting materials. However, existing methods primarily address precursors with central chirality, neglecting those with axial chirality. Herein, we describe the enantioconvergent reductive coupling of racemic allenes with aldehydes, facilitated by a photoredox, chromium, and cobalt triple catalysis system. This method selectively affords one product from sixteen possible regio- and stereoisomers. The protocol leverages CoIII-H mediated hydrogen atom transfer (MHAT) and Cr-catalyzed radical-polar crossover for efficient stereoablation of axial chirality and asymmetric addition, respectively. Supported by mechanistic insights from control experiments, deuterium labeling, and DFT calculations, our approach offers synthetic chemists a valuable tool for creating enantioenriched chiral homoallylic alcohols, promising to advance radical-based strategies for synthesizing complex chiral molecules.

Systematic Parameter Determination Aimed at a Catalyst-Controlled Asymmetric Rh(I)-Catalyzed Pauson-Khand Reaction

Transition metal-catalyzed carbocyclization reactions have revolutionized the synthesis of complex cyclic organic compounds. Yet, subtle substrate changes can significantly alter reaction pathways. The asymmetric Rh(I)-catalyzed Pauson-Khand reaction (PKR) exemplifies such a reaction, hindered by a narrow substrate scope and competing reactivity modes. In this study, we identified parameters predictive of the yield and enantioselectivity in the catalyst-controlled asymmetric PKR, using 1,6-enynes with a 2,2-disubstituted alkene. In this way, ring-fused cyclopentenones can be formed with chiral quaternary carbon centers. Using bisphosphine ligand parameters from palladium complexes, including the energy of the Pd lone pair orbital and the angle formed by the phosphorus aryl groups on the ligand, we established strong correlations with experimental ln(er) (R 2 = 0.99 and 0.91) for two distinct precursors. Solvent dipole moments correlated with ln(er) for high-dipole-moment precursors (R 2 = 0.94), while Abraham's hydrogen bond basicity is more relevant for low-dipole-moment precursors (R 2 = 0.93). Additionally, counterions were found to have a significant impact on the PKR reactivity and selectivity, as does the steric demand of the alkyne substituent of the enyne precursor. In the latter case, ln(er) correlates with Sterimol B1 values for products from different alkyne substituents (R 2 = 0.99). Furthermore, the computed C≡C wavenumber of the enyne precursor can be directly aligned with the yield of asymmetric PKRs.

Thapsigargin: a promising natural product with diverse medicinal potential - a review of synthetic approaches and total syntheses

Thapsigargin, a sesquiterpene lactone, naturally occurring in the roots and fruits of the Mediterranean shrub Thapsia garganica L, is known to the practitioners of traditional medicines since the medieval ages as a cure for rheumatic pain, lung diseases, and female infertility. This naturally occurring guaianolide has shown remarkable activity for Sarco endoplasmic reticulum Ca2+ ATPase inhibition, which eventually renders it fit as a potential candidate for anti-cancer drugs. Mipsagargin, a prodrug derived from thapsigargin, is under clinical trials for the treatment of glioblastoma. Recently, thapsigargin has shown promise as an antiviral against SARS-CoV-2. Limited natural availability and challenging synthesis have prompted research into new synthetic pathways. This review discusses significant synthetic approaches and total syntheses of thapsigargin reported to date.

Paving the road towards automated homogeneous catalyst design

In the past decade, computational tools have become integral to catalyst design. They continue to offer significant support to experimental organic synthesis and catalysis researchers aiming for optimal reaction outcomes. More recently, data-driven approaches utilizing machine learning have garnered considerable attention for their expansive capabilities. This Perspective provides an overview of diverse initiatives in the realm of computational catalyst design and introduces our automated tools tailored for high-throughput in silico exploration of the chemical space. While valuable insights are gained through methods for high-throughput in silico exploration and analysis of chemical space, their degree of automation and modularity are key. We argue that the integration of data-driven, automated and modular workflows is key to enhancing homogeneous catalyst design on an unprecedented scale, contributing to the advancement of catalysis research.

Classification of Hemilabile Ligands Using Machine Learning

Hemilabile ligands have the capacity to partially disengage from a metal center, providing a strategy to balance stability and reactivity in catalysis, but they are not straightforward to identify. We identify ligands in the Cambridge Structural Database that have been crystallized with distinct denticities and are thus identifiable as hemilabile ligands. We implement a semi-supervised learning approach using a label-spreading algorithm to augment a small negative set that is supported by heuristic rules of ligand and metal co-occurrence. We show that a heuristic based on coordinating atom identity alone is not sufficient to identify whether a ligand is hemilabile, and our trained machine-learning classification models are instead needed to predict whether a bi-, tri-, or tetradentate ligand is hemilabile with high accuracy and precision. Feature importance analysis of our models shows that the second, third, and fourth coordination spheres all play important roles in ligand hemilability.

Stereochemical Stability of Planar-Chiral Benzazepine Tricyclics: Inversion Energies of P- and S-Alkene Ligands

Inversion barriers ΔG‡ for planar chiral phosphine-alkene and sulfonamide-alkene hybrid ligands based on phenyl-dibenz[b,f]azepine have been determined by density-functional theory calculations. Analysis of the structural and electronic characteristics of the minima and transition states explains the magnitudes of ΔG‡ and the geometrical changes during the inversion process. The steric repulsion caused by bulky substituents attached to the azepine nitrogen atom has a pronounced effect on the ΔG‡ value, explaining, inter alia, the stereochemical stability of the P- and S-alkene ligands when compared to the fluxional parent compound where X = H.

Computational molecular refinement to enhance enantioselectivity by reinforcing hydrogen bonding interactions in major reaction pathway

Computational analyses have revealed that the distortion of a catalyst and the substrates and their interactions are key to determining the stability of the transition state. Hence, two strategies "distortion strategy" and "interaction strategy" can be proposed for improving enantiomeric excess in enantioselective reactions. The "distortion strategy" is used as a conventional approach that destabilizes the TS (transition state) of the minor pathway. On the other hand, the "interaction strategy" focuses on the stabilization of the TS of the major pathway in which an enhancement of the reaction rate is expected. To realize this strategy, we envisioned the TS stabilization of the major reaction pathway by reinforcing hydrogen bonding and adopted the chiral phosphoric acid-catalysed enantioselective Diels-Alder reaction of 2-vinylquinolines with dienylcarbamates. The intended "interaction strategy" led to remarkable improvements in the enantioselectivity and reaction rate.

Computational Study on the Co-Mediated Intramolecular Pauson–Khand Reaction of Fluorinated and Chiral N-Tethered 1,7-Enynes

The Co₂(CO)₈-mediated intramolecular Pauson–Khand reaction is an elegant approach to obtain cyclopentenone derivatives containing asymmetric centers. In this work, we employed density functional theory calculations at the M11/6-311+G(d,p) level of theory to investigate the mechanism and reactivity for the Pauson–Khand reaction of fluorinated and asymmetric N-tethered 1,7-enynes. The rate-determining step was found to be the intramolecular alkene insertion into the carbon–cobalt bond. The stereoselectivity of the alkene insertion step was rationalized by the different transition states showing the coordination of the alkene through the Re- and Si-face. The effects of different fluorine groups and steric effects on both the alkenyl and alkynyl moieties were also theoretically investigated.

Allylic C-H amination cross-coupling furnishes tertiary amines by electrophilic metal catalysis

Intermolecular cross-coupling of terminal olefins with secondary amines to form complex tertiary amines-a common motif in pharmaceuticals-remains a major challenge in chemical synthesis. Basic amine nucleophiles in nondirected, electrophilic metal-catalyzed aminations tend to bind to and thereby inhibit metal catalysts. We reasoned that an autoregulatory mechanism coupling the release of amine nucleophiles with catalyst turnover could enable functionalization without inhibiting metal-mediated heterolytic carbon-hydrogen cleavage. Here, we report a palladium(II)-catalyzed allylic carbon-hydrogen amination cross-coupling using this strategy, featuring 48 cyclic and acyclic secondary amines (10 pharmaceutically relevant cores) and 34 terminal olefins (bearing electrophilic functionality) to furnish 81 tertiary allylic amines, including 12 drug compounds and 10 complex drug derivatives, with excellent regio- and stereoselectivity (>20:1 linear:branched, >20:1 E:Z).

Rh(I)-Catalyzed Allenic Pauson-Khand Reaction to Access the Thapsigargin Core: Influence of Furan and Allenyl Chloroacetate Groups on Enantioselectivity

Thapsigargin (Tg) is a potent SERCA pump inhibitor with the potential to treat cancer and COVID-19. We have extended the scope of the asymmetric allenic Pauson-Khand reaction to furan-tethered allene-ynes, a stereoconvergent transformation affording the 5,7,5-ring system of Tg in good yields and high enantioselectivity. Computational studies of the oxidative cyclization step show that the furan and chloroacetate groups contribute to this high selectivity.

Carboxylation of a Palladacycle Formed via C(sp3 )-H Activation: Theory-Driven Reaction Design

Theory-driven organic synthesis is a powerful tool for developing new organic transformations. A palladacycle(II), generated from 8-methylquinoline via C(sp³ )-H activation, is frequently featured in the scientific literature, albeit that the reactivity toward CO₂ , an abundant, inexpensive, and non-toxic chemical, remains elusive. We have theoretically discovered potential carboxylation pathways using the artificial force induced reaction (AFIR) method, a density-functional-theory (DFT)-based automated reaction path search method. The thus obtained results suggest that the reduction of Pd(II) to Pd(I) is key to promote the insertion of CO₂ . Based on these computational findings, we employed various one-electron reductants, such as Cp*₂ Co, a photoredox catalyst under blue LED irradiation, and reductive electrolysis ((+)Mg/(-)Pt), which afforded the desired carboxylated products in high yields. After screening phosphine ligands under photoredox conditions, we discovered that bidentate ligands such as dppe promoted this carboxylation efficiently, which was rationally interpreted in terms of the redox potential of the Pd(II)-dppe complex as well as on the grounds of DFT calculations. We are convinced that these results could serve as future guidelines for the development of Pd(II)-catalyzed C(sp³ )-H carboxylation reactions with CO₂ .

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.

Asymmetric Total Synthesis of Bufospirostenin A

The first and asymmetric total synthesis of bioactive bufospirostenin A, an unusual spirostanol with rearranged A/B rings, was accomplished. The synthetically challenging [5-7-6-5] tetracyclic ring system, found in bufospirostenin A and some other natural products, was efficiently constructed by the unique intramolecular rhodium-catalyzed Pauson-Khand reaction of an alkoxyallene-yne. The 11 stereocenters in the final product, including the 10 contiguous stereocenters, were installed diastereoselectively.

Palladium-Catalyzed Enantioselective Heck Carbonylation with a Monodentate Phosphoramidite Ligand: Asymmetric Synthesis of (+)-Physostigmine, (+)-Physovenine, and (+)-Folicanthine

Reported herein is the development of the first enantioselective monodentate ligand assisted Pd-catalyzed domino Heck carbonylation reaction with CO. The highly enantioselective domino Heck carbonylation of N-aryl acrylamides and various nucleophiles, including arylboronic acids, anilines, and alcohols, in the presence of CO was achieved. A novel monodentate phosphoramidite ligand, Xida-Phos, has been developed for this reaction and it displays excellent reactivity and enantioselectivity. The reaction employs readily available starting materials, tolerates a wide range of functional groups, and provides straightforward access to a diverse array of enantioenriched oxindoles having β-carbonyl-substituted all-carbon quaternary stereocenters, thus providing a facile and complementary method for the asymmetric synthesis of bioactive hexahydropyrroloindole and its dimeric alkaloids.

Brønsted-acid-catalyzed one-pot tandem annulation/[5 + 2]-cycloaddition of o-propargyl alcohol benzaldehydes with alkynes: regioselective and stereoselective synthesis of dibenzo[a,f]azulen-12-ones

The one-pot synthesis of dibenzo[a,f]azulen-12-ones has been established starting from o-propargyl alcohol benzaldehydes and alkynes.

Iridium-Catalyzed Asymmetric Synthesis of Functionally Rich Molecules Enabled by (Phosphoramidite,Olefin) Ligands

The catalytic, asymmetric synthesis of complex molecules has been a core focus of our research program for some time because developments in the area can have an immediate impact on the identification of novel strategies for the synthesis of value-added molecules. In concert with this central interest, we have emphasized the design of ligand scaffolds as a tactic to discover and develop novel chemistry and overcome well-recognized synthetic challenges. Based on our group's work on chiral pool-derived diolefin ligands, we designed and implemented a class of hybrid (phosphoramidite,olefin) ligands, which combines the properties of both phosphoramidite and olefin motifs to impact, fine-tune, and even override the inherent reactivity of the metal center. Specifically, we have utilized these unique modifying ligands to address several recognized limitations in the field of iridium-catalyzed, asymmetric allylic substitution. The methods we have documented typically employ branched, unprotected allylic alcohols as substrates and obviate the need for rigorous exclusion of air and moisture. Following Takeuchi's seminal report demonstrating the high aptitude of Ir(I)-phosphite catalysts for  branch-selective allylic substitution, concerted efforts from numerous research laboratories have led to a broadening of the synthetic utility of this reaction class. The first section of this Account outlines the process leading to our discovery of an unprecedented (phosphoramidite,olefin) ligand and its validation in the first iridium-catalyzed amination of branched, unprotected allylic alcohols. This section continues with our work involving heteroatom-based nucleophiles within inter- and intramolecular etherification, thioetherification and spiroketalization processes. The second section highlights the use of readily available carbon nucleophiles possessing sp, sp², and sp³ hybridization in a series of enantioselective carbon-carbon bond-forming reactions. We describe how alkylzinc, allylsilane, and several classes of organotrifluoroborate nucleophiles can be coupled enantioselectively to enable construction of several key motifs including 1,5-dienes, 1,4-dienes, and 1,4-enynes. Since the unique electronic and steric properties of this class of ligands renders the (η³-allyl)-Ir(III) intermediate highly electrophilic, even weak nucleophiles such as alkyl olefins can be used. We also show that more nucleophilic alkene motifs such as enamines and in situ generated ketene acetals smoothly participate in substitution reactions with allylic alcohols to yield valuable piperidines and γ,δ-unsaturated esters, respectively. The concept of stereodivergent dual catalysis, which synergistically combines chiral amine catalysis with iridium catalysis to furnish α-allylated aldehydes containing two independently controllable stereocenters is then discussed. This process has enabled the independent, stereoselective synthesis of all four possible product stereoisomers from a single set of starting materials, and was highlighted in the stereodivergent synthesis of Δ⁹-tetrahydrocannabinol. This Account concludes with an overview of our organometallic mechanistic studies regarding relevant intermediates within the catalytic cycle of this class of allylic substitution. These studies have allowed us to better understand the origin of the unique characteristics exhibited by this catalyst in comparison to related systems.

Retooling Asymmetric Conjugate Additions for Sterically Demanding Substrates with an Iterative Data-Driven Approach

The development of catalytic enantioselective methods is routinely carried out using easily accessible and prototypical substrates. This approach to reaction development often yields asymmetric methods that perform poorly using substrates that are sterically or electronically dissimilar to those used during the reaction optimization campaign. Consequently, expanding the scope of previously optimized catalytic asymmetric reactions to include more challenging substrates is decidedly nontrivial. Here, we address this challenge through the development of a systematic workflow to broaden the applicability and reliability of asymmetric conjugate additions to substrates conventionally regarded as sterically and electronically demanding. The copper-catalyzed asymmetric conjugate addition of alkylzirconium nucleophiles to form tertiary centers, although successful for linear alkyl chains, fails for more sterically demanding linear α,β-unsaturated ketones. Key to adapting this method to obtain high enantioselectivity was the synthesis of modified phosphoramidite ligands, designed using quantitative structure–selectivity relationships (QSSRs). Iterative rounds of model construction and ligand synthesis were executed in parallel to evaluate the performance of 20 chiral ligands. The copper-catalyzed asymmetric addition is now more broadly applicable, even tolerating linear enones bearing tert-butyl β-substituents. The presence of common functional groups is tolerated in both nucleophiles and electrophiles, giving up to 99% yield and 95% ee across 20 examples.

Rhodium-Catalyzed Pauson-Khand-Type Cyclization of 1,5-Allene-Alkynes: A Chirality Transfer Strategy for Optically Active Bicyclic Ketones

An efficient chirality transfer in the [RhCl(CO)₂ ]₂ -catalyzed [2+2+1] cyclization of optically active axially chiral 1,3-disubstituted allenynes with CO to access optically active bicyclopentenone compounds has been developed. The distal C=C bond of allenes reacted with the alknye unit and CO to afford [4.3.0]-bicyclic products with high ee values under mild reaction conditions with an excellent selectivity.

Ti(II) and Rh(I) Complexes as Reagents toward a Thapsigargin Core

A novel approach toward the [5-7]fused bicyclic core of thapsigargin, a subnanomolar inhibitor of the endo/sarcoplasmic calcium ATPase (SERCA), is presented. The synthetic route includes an original Ti(II)-mediated hydroxy-directed reductive coupling of an enantiomerically enriched propargylic alcohol and an intramolecular Rh(I)-catalyzed cyclocarbonylation reaction as key steps. Interestingly, through the first experiments of titanocene-mediated reductive cyclization of a 1,8-enyne, a seven-membered cycle was isolated as a unique product with a total diastereoselectivity.

Understanding the Reactivity and Selectivity of Fluxional Chiral DMAP-Catalyzed Kinetic Resolutions of Axially Chiral Biaryls

Fluxional chiral DMAP-catalyzed kinetic resolutions of axially chiral biaryls were examined using density functional theory. Computational analyses lead to a revised understanding of this reaction in which the interplay of numerous non-covalent interactions control the conformation and flexibility of the active catalyst, the preferred mechanism, and the stereoselectivity. Notably, while the DMAP catalyst itself is confirmed to be highly fluxional, electrostatically driven π⋅⋅⋅π⁺ interactions render the active, acylated form of the catalyst highly rigid, explaining its pronounced stereoselectivity.

Mechanistically Guided Design of Ligands That Significantly Improve the Efficiency of CuH-Catalyzed Hydroamination Reactions

Using a mechanically guided ligand design approach, a new ligand (SEGFAST) for the CuH-catalyzed hydroamination reaction of unactivated terminal olefins has been developed, providing a 62-fold rate increase over reactions compared to DTBM-SEGPHOS, the previous optimal ligand. Combining the respective strengths of computational chemistry and experimental kinetic measurements, we were able to quickly identify potential modifications that lead to more effective ligands, thus avoiding synthesizing and testing a large library of ligands. By optimizing the combination of attractive, noncovalent ligand-substrate interactions and the stability of the catalyst under the reaction conditions, we were able to identify a finely tuned hybrid ligand that greatly enables accelerated hydrocupration rates with unactivated alkenes. Moreover, a modular and robust synthetic sequence was devised, which allowed for the practical, gram-scale synthesis of these novel hybrid ligand structures.

Mechanistic Insights into the Ni-Catalyzed Reductive Carboxylation of C-O Bonds in Aromatic Esters with CO2 : Understanding Remarkable Ligand and Traceless-Directing-Group Effects

The mechanism of the Ni⁰ -catalyzed reductive carboxylation reaction of C(sp² )-O and C(sp³ )-O bonds in aromatic esters with CO₂ to access valuable carboxylic acids was comprehensively studied by using DFT calculations. Computational results revealed that this transformation was composed of several key steps: C-O bond cleavage, reductive elimination, and/or CO₂ insertion. Of these steps, C-O bond cleavage was found to be rate-determining, and it occurred through either oxidative addition to form a Ni^II intermediate, or a radical pathway that involved a bimetallic species to generate two Ni^I species through homolytic dissociation of the C-O bond. DFT calculations revealed that the oxidative addition step was preferred in the reductive carboxylation reactions of C(sp² )-O and C(sp³ )-O bonds in substrates with extended π systems. In contrast, oxidative addition was highly disfavored when traceless directing groups were involved in the reductive coupling of substrates without extended π systems. In such cases, the presence of traceless directing groups allowed for docking of a second Ni⁰ catalyst, and the reactions proceed through a bimetallic radical pathway, rather than through concerted oxidative addition, to afford two Ni^I species both kinetically and thermodynamically. These theoretical mechanistic insights into the reductive carboxylation reactions of C-O bonds were also employed to investigate several experimentally observed phenomena, including ligand-dependent reactivity and site-selectivity.

Computational design of high-performance ligand for enantioselective Markovnikov hydroboration of aliphatic terminal alkenes

Finding optimal chiral ligands for transition-metal-catalyzed asymmetric reactions using trial-and-error methods is often time-consuming and costly, even if the details of the reaction mechanism are already known. Although modern computational analyses allow the prediction of the stereoselectivity, there are only very few examples for the attempted design of chiral ligands using a computational approach for the improvement of the stereoselectivity. Herein, we report a systematic method for the design of chiral ligands for the enantioselective Markovnikov hydroboration of aliphatic terminal alkenes based on a computational and experimental evaluation sequence. We developed a three-hindered-quadrant P-chirogenic bisphosphine ligand that was designed in accordance with the design guidelines derived from this method, which allowed the Markovnikov hydroboration to proceed with high enantioselectivity (up to 99% ee).

Dynamic kinetic asymmetric transformations of β-halo-α-keto esters byN,N′-dioxide/Ni(ii)-catalyzed carbonyl-ene reaction

An effective dynamic kinetic asymmetric transformation of racemic β-halo-α-keto esters through carbonyl-ene reaction was realised.

Do two oxidants (ferric-peroxo and ferryl-oxo species) act in the biosynthesis of estrogens? A DFT calculation

Density functional theory calculations were performed in order to reveal the mysterious catalytic step of the biosynthesis of estrogens. The results indicated two reactive oxidants, ferric-peroxo and ferryl-oxo (compound I) species, to participate in the conversion of androgens to estrogens. The ferric-peroxo species was determined, according to our derived mechanism, to act in the oxidation of 19-OH androgen to yield the 19,19-gem-diol intermediate and generate the ferryl-oxo (compound I) species. This species was then modeled to effect, in the final step, an abstraction of H from an O–H group of 19,19-gem-diol to give the experimentally observed products. We considered our new mechanistic scenario to reasonably explain the latest experimental observations and to provide deep insight complementing the newly accepted compound I (Cpd I) mechanism.

Density functional theory calculations were performed in order to reveal the mysterious catalytic step of the biosynthesis of estrogens.

Mechanistic studies: enantioselective palladium(ii)-catalyzed intramolecular aminoarylation of alkenes by dual N–H and aryl C–H bond cleavage

The role of PGA and the origin of the enantioselectivity in the palladium(ii)-catalyzed intramolecular aminoarylation of alkenes.