Connecting the complexity of stereoselective synthesis to the evolution of predictive tools

Synthetic methods have seemingly progressed to an extent where there is an apparent and increasing need for predictive models to navigate the vast chemical space. Methods for anticipating and optimizing reaction outcomes have evolved from simple qualitative pictures generated from chemical intuition to complex models constructed from quantitative methods like quantum chemistry and machine learning. These toolsets are rooted in physical organic chemistry where fundamental principles of chemical reactivity and molecular interactions guide their development and application. Here, we detail how the evolution of these methods is a successful outcome and a powerful response to the diverse synthetic challenges confronted and the innovative selectivity concepts introduced. In this review, we perform a periodization of organic chemistry focusing on strategies that have been applied to guide the synthesis of chiral organic molecules.

Chiral 3,3'-diaroyl BINOL phosphoric acids: syntheses and evaluation in asymmetric transfer hydrogenation, photophysical, and electrochemical studies

An efficient synthesis of enantiomerically pure 3,3'-diaroyl BINOLs is accomplished through chemoselective Weinreb ketone synthesis from the Weinreb amide derivative of chiral BINOL-3,3'-dicarboxylic acid using a Grignard reagent. This protocol facilitated the introduction of the aroyl group at the 3,3'-position of binaphthol. The 3,3'-diaroyl BINOL phosphoric acid has been prepared and evaluated for asymmetric transfer hydrogenation of 2-aryl/alkyl quinolines. The 3,3'-diaroyl BINOL phosphoric acids are found to be efficient catalysts in the hydrogenation of 2-aryl quinolines using Hantzsch ester to generate 2-aryl tetrahydroquinolines in excellent yields with moderate enantioselectivity. The presence of aroyl units, a photosensitizer core, in 3,3'-diaroyl BINOL prompted us to evaluate their photophysical and electrochemical properties, as these molecules may be a potential candidate for asymmetric photocatalysis.

Enantioselective Synthesis of Chiral 2,2-Difluoro-spiroindanone-dihydroquinazolinones by CPA-Catalyzed Cyclization Reactions

The synthesis of chiral gem-difluorinated spiro-heterocyclic compounds continues to be a significant challenge in organic chemistry due to their widespread applications across various fields. Therefore, efficient asymmetric approaches for the synthesis of gem-difluorinated spiroindanone-dihydroquinazolinones are particularly valuable, especially in the industrial manufacturing of chiral fluorinated drugs. Herein, we developed the CPA-catalyzed asymmetric enantioselective cyclization reactions of gem-difluoroalkyl 1,3-indandiones with anthranilamides to achieve various chiral 2,2-difluoro-spiroindanone-dihydroquinazolinones in good to high yields with excellent enantioselectivities. Moreover, the mechanism experiment proved that the gem-difluoro substitution pattern promotes the reaction.

Recent advances in the organocatalytic synthesis of chiral C3-spiro-cyclopentaneoxindoles

Although there have been various reviews on the asymmetric construction of C3-spirooxindoles, there is a scarcity of reviews focusing on the asymmetric organocatalytic synthesis of C3-spiro-cyclopentaneoxindole derivatives. This particular scaffold has garnered significant attention from synthetic chemists due to its relevance in medicinal chemistry. In this review, we provide an overview of recent advancements in the asymmetric organocatalytic synthesis of various C3-spiro-cyclopentaneoxindoles using organic catalysts. The work is divided into sections according to the type of catalysis, including covalent catalysis (amine catalysis and N-heterocyclic carbene catalysis) and non-covalent catalysis (chiral phosphoric acid catalysis, hydrogen bond catalysis, and phase transfer catalysis). Furthermore, we discuss existing challenges and future directions within this field. It is our belief that this review will serve as an informative resource for researchers engaged in synthesizing C3-spiro-cyclopentaneoxindoles and inspire further advancements in this area.

The Elusive Ternary Intermediates of Chiral Phosphoric Acids in Ion Pair Catalysis─Structures, Conformations, and Aggregation

In ion-pair catalysis, the last intermediate structures prior to the stereoselective transition states are of special importance for predictive models due to the high isomerization barrier between E- and Z-substrate double bonds connecting ground and transition state energies. However, in prior experimental investigations of chiral phosphoric acids (CPA) solely the early intermediates could be investigated while the key intermediate remained elusive. In this study, the first experimental structural and conformational insights into ternary complexes with CPAs are presented using a special combination of low temperature and relaxation optimized 15N HSQC-NOESY NMR spectroscopy to enhance sensitivity. Combined NMR investigations and theoretical calculations revealed three conformers of the ternary complex, of which one also closely resembles the previously calculated transition states. In addition, a 2:1:1 ternary complex as well as an unprecedent [3:3] dimeric species consisting of two ternary complexes was revealed. Given the importance of the ground state energies for the transition state interpretation in ion pair catalysis we believe that the presented experimental insight into the structural and conformational variety of the ternary complexes is a key to the future development of predictive models in ion pair catalysis.

Diastereodivergence in catalytic asymmetric conjugate addition of carbon nucleophiles

Catalytic asymmetric conjugate additions of carbon nucleophiles have emerged as a potent tool for constructing multi-stereogenic molecules with precise stereochemical control. This review explores the concept of diastereodivergence in such reactions, focusing on strategies to achieve selective access to diverse diastereomeric products upon carbon-carbon bond formation. Drawing from a rich array of examples, we delve into key approaches for controlling the stereochemical outcome of these transformations, including alteration of alkene geometry, fine-tuning of reaction parameters, synergistic catalysis, and isomerization of conjugate adducts. Additionally, we highlight the iterative strategies for conjugate additions, showcasing their potential for diastereodivergent synthesis of methyl-branched stereocenters in 1,3-relationships. By presenting a concentrated overview of this significant topic, this review aims to provide valuable insights into the design and execution of stereodivergent catalytic conjugate additions, offering new avenues for advancing stereoselective synthesis and structural diversity in organic synthesis.

Non-covalent organocatalyzed enantioselective cyclization reactions of α,β-unsaturated imines

Asymmetric cycloaddition is a straightforward strategy which enables the synthesis of structurally distinct cyclic derivatives which are difficult to access by other methodologies, using an efficient and atom-economical path from simple precursors. In recent years several asymmetric catalytic cyclization strategies have been accomplished for the construction of N-heterocycles using various catalytic systems such as chiral metal catalysts, chiral Lewis acids or chiral organocatalysts. This review presents an overview of the recent advances in enantioselective cyclization reactions of 1-azadienes catalyzed by non-covalent organocatalysts.

Bulk Stereoselective Cationic Polymerization of Vinyl Ethers by the Coordination of ZrCl4 with Tunable Spirocyclic Phosphoric Acids

Control over stereochemistry in poly(vinyl ether)s leads to a notable change in their physical properties, yet remains a grand challenge. Here, we demonstrate the bulk stereoselective cationic polymerization of vinyl ethers using ZrCl4 coordinated with a spirocyclic phosphoric acid (SPA). The widely variable substituents in SPAs exert a profound impact on the stereochemical and activity outcome of the polymerization: the % m of poly(vinyl ether)s linearly increases with the Hammett substituent constant (σ) of SPAs; the catalytic activity increases with the σ; the large steric hindrance groups lead to decreased polymerization activity. Mechanism studies suggest that the coordination of ZrCl4 with three equivalents of SPAs generates the chiral complex. The complex can abstract chlorine from the initiator/chain end to form the chiral ion pair allowing the selective facial addition of incoming monomers. The catalyst system features characteristics of no solvent, low loads, high tacticity control, high monomer scope, and recyclability.

Mechanism and origin of enantioselectivity for organocatalyzed asymmetric heteroannulation of alkynes in the construction of axially chiral C2-arylquinoline

Axially chiral C2-arylquinoline has been successfully constructed via asymmetric heteroannulation of alkynes catalyzed by chiral phosphoric acid with high yield and high enantioselectivity. Inspired by this intriguing work, theoretical calculations have been carried out, and the detailed reaction mechanism has been elaborated, in which the whole reaction can be divided into steps including hydrogen transfer, C-N bonding, annulation reaction and the final dehydration processes. The initial hydrogen-transfer reaction has two possible pathways, while the subsequent C-N bonding process has eight possible pathways. Then, after the annulation reaction and the final dehydration processes, the major product and byproduct were formed. QTAIM and IGMH analyses were used to illustrate the role of weak intermolecular interactions in the catalytic process, and the distortion/interaction and EDA analyses provided a deeper understanding of the origin of enantioselectivity. The calculated results are consistent with the experimental results. This work would provide valuable insights into asymmetric reactions catalyzed by chiral phosphoric acid.

First-Principles Characterization of Noncovalent Interactions in the Enantioselective Oxetane Ring Opening via SPHENOL-Based Chiral Phosphoric Acid Catalyst

The asymmetric ring-opening reaction of 3,3-substituted oxetanes catalyzed by chiral phosphoric acid (CPA) derived from a newly developed SPHENOL (2,2',3,3'-tetrahydro-1,1'-spirobi[phenalene]-9,9'-diol) framework was investigated by performing density functional calculations. The plausible transition states were traced by considering the oxetane activation mode. The energy profiles obtained for various substrates provide a rational understanding of the reaction at the atomic level. The truncation models help to attribute the reaction initiation and origin of enantioselectivity to three types of noncovalent interactions between the catalyst and the substrate. The Quantum theory of atoms in molecules (QTAIM), Noncovalent Interactions (NCI) Plots, and Wiberg Bond Index (WBI) provide conclusive evidence of the origin of stereoselectivity for the intramolecular desymmetrization of the five substrates considered here. The current study establishes that the SPHENOL-derived CPA catalyst forges enantioselective desymmetrization of 3,3-substituted oxetanes with higher enantiomeric excess in comparison to previously known SPINOL- and BINOL-derived CPA catalysts.

Chiral Brønsted Acid-Catalyzed Asymmetric Reaction via Vinylidene Ortho-Quinone Methides

Vinylidene ortho-quinone methides (VQMs) have been proven to be versatile and crucial intermediates in the catalytic asymmetric reaction in last decade, and thus have drawn considerable concentrations on account of the practical application in the construction of enantiomerically pure functional organic molecules. However, in comparison to the well established chiral Brønsted base-catalyzed asymmetric reaction via VQMs, chiral Brønsted acid-catalyzed reaction is rarely studied and there is no systematic summary to date. In this review, we summarize the recent advances in the chiral Brønsted acid-catalyzed asymmetric reaction via VQMs according to three types of reactions: a) intermolecular asymmetric nucleophilic addition to VQMs; b) intermolecular asymmetric cycloaddition of VQMs; c) intramolecular asymmetric cyclization of VQMs. Finally, we put forward the remained challenges and opportunities for potential breakthroughs in this area.

The Diversity and Evolution of Chiral Brønsted Acid Structures

The chemical space of chiral Brønsted acid catalysts is defined by quantity and complexity, reflecting the diverse synthetic challenges confronted and the innovative molecular designs introduced. Here, we detail how this successful outcome is a powerful demonstration of the benefits of utilizing both local structure searches and a comprehensive understanding of catalyst performance for effective and efficient exploration of Brønsted acid properties. In this concept article we provide an evolutionary overview of this field by summarizing the approaches to catalyst optimization, the resulting structures, and functions.

Umpolung Reactivity of in Situ Derived Aryl Hydrazones: An Asymmetric Brønsted Acid Catalyzed Strategy to Access Fused Pyrazolidines

Herein, we report an intriguing cascade strategy for synthesizing optically active fused pyrazolidines featuring three contiguous stereogenic centers. The formyl-tethered enones are templates for the developed umpolung reactivity, showcasing diverse substrate adaptability with various arylhydrazines. The chiral phosphoric acid catalyst offers stereochemical guidance, forming the fused pyrazolidines with commendable to excellent stereoselectivities. Additionally, the scalability, postsynthetic transformations, and instability of unacylated pyrazolidines have been successfully demonstrated.

Steric Engineering of Rotaxane Catalysts: Benefits and Limits of Using the Mechanical Bond in Catalyst Design

The mechanical bond is emerging as a novel design element in catalyst development. Here, we report a series of 1,1'-binaphthyl-2,2'-diol (BINOL) based catalysts in which the number of interlocked macrocycles is varied. Unsurprisingly, the macrocycles have a profound steric influence on the catalytic performance of these molecules. However, in the enantioselective transformations examined, the macrocycles are detrimental to catalyst stereoselectivity whereas in lactide polymerization, they increase the molecular weight of the polymeric product.

Advancement in Synthetic Strategies of Phosphorus Heterocycles: Recent Progress from Synthesis to Emerging Class of Optoelectronic Materials

Organophosphorus heterocycles have long been acknowledged for their significant potential across diverse fields, including catalysis, material science, and drug development. Incorporating phosphorus functionalities into organic compounds offers a means to effectively tailor their medicinal properties, augment biological responses, and enhance selectivity and bioavailability. The distinctive physical and photoelectric characteristics of phosphorus-containing conjugated compounds have garnered considerable interest as promising materials for organic optoelectronics. These compounds find extensive utility in various applications such as light-emitting diodes, photovoltaic cells, phosphole-based fluorophores, and semiconductors.

Catalytic enantioselective nitrone cycloadditions enabling collective syntheses of indole alkaloids

Tetrahydro-β-carboline skeletons are prominent and ubiquitous in an extraordinary range of indole alkaloid natural products and pharmaceutical compounds. Powerful synthetic approaches for stereoselective synthesis of tetrahydro-β-carboline skeletons have immense impacts and have attracted enormous attention. Here, we outline a general chiral phosphoric acid catalyzed asymmetric 1,3-dipolar cycloaddition of 3,4-dihydro-β-carboline-2-oxide type nitrone that enables access to three types of chiral tetrahydro-β-carbolines bearing continuous multi-chiral centers and quaternary chiral centers. The method displays different endo/exo selectivity from traditional nitrone chemistry. The distinct power of this strategy has been illustrated by application to collective and enantiodivergent total syntheses of 40 tetrahydro-β-carboline-type indole alkaloid natural products with divergent stereochemistry and varied architectures.

Organocatalysis as an enabling tool for enantioselective ring-opening reactions of cyclopropanes

The rich reactivity profile of cyclopropanes has been extensively explored to trigger new organic transformations that enable unusual disconnective approaches to synthesize molecular motifs that are not easily reached through conventional reactions. In particular, the chemistry of cyclopropanes has received special attention in the last decade, with multiple new approaches that capitalize on the use of organocatalysis for the activation of the cyclopropane scaffold. This situation has also opened the possibility of developing enantioselective variants of many reactions that until now were only carried out in an enantiospecific or diastereoselective manner. Our group has been particularly active in this field, focusing more specifically on the use of aminocatalysis and Brønsted acid catalysis as major organocatalytic activation manifolds to trigger new unprecedented transformations involving cyclopropanes that add to the current toolbox of general methodologies available to organic chemists for the enantioselective synthesis of chiral compounds.

Chiral Ligand-Concentration Mediating Asymmetric Transformations of Silver Nanoclusters: NIR-II Circularly Polarized Phosphorescence Lighting

Near infrared (NIR) emitter with circularly polarized phosphorescence (CPP), known as NIR CPP, has emerged as a key part in the research of cutting-edge luminescent materials. However, it remains a challenge to obtain nanoclusters with NIR CPP activity. Here, we propose an asymmetric transformation approach to efficiently synthesize two pairs of chiral silver nanoclusters (R/S-Ag29 and R/S-Ag16) using an achiral Ag10 nanocluster as starting material in the presence of different concentration chiral inducer (R/S)-1,1'-binaphthyl-2,2'-diyl hydrogenphosphate (R/S-BNP). R/S-Ag29, formed in the low-concentration R/S-BNP, exhibits a unique kernel-shell structure consisting of a distorted Ag13 icosahedron and an integrated cage-like organometallic shell with a C3 symmetry, and possesses a superatomic 6-electron configuration (1S2|1P4). By contrast, R/S-Ag16, formed in the high-concentration R/S-BNP, features a sandwich-like pentagram with AgI-pure kernel. Profiting from the hierarchically chiral structures and superatomic kernel-dominated phosphorescence, R/S-Ag29 exhibits infrequent CPP activity in the second near-infrared (975 nm) region, being the first instance of NIR-II CPP observed among CPL-active metal nanoclusters. This study presents a new approach to reduce the difficulty of de novo synthesis for chiral silver nanomaterials, and facilitates the design of CPP-active superatomic nanoclusters in NIR region.

Kinetic resolution of 1,1'-binaphthyl-2,2'-diamine derivatives by chiral calcium phosphate-catalyzed acylation

1,1'-Binaphthyl-2,2'-diamine (BINAM) is a useful axially chiral compound. The kinetic resolution of BINAM is one of the most crucial methods for synthesizing chiral BINAM. We have developed a chiral calcium phosphate-catalyzed kinetic resolution of BINAM by utilizing an acylation reaction to produce a mono-amide. The kinetic resolution of BINAM derivatives was achieved by using isobutyric anhydride in the presence of chiral calcium phosphate and 4-morpholinopyridine with up to s = 127. 6,6'-Substituted BINAM derivatives were also applicable for this reaction. The resulting mono-acylated BINAM could be transformed into BINAM by hydrolysis under acidic conditions.

Chiral Bis-phosphate Macrocycles for Catalytic, Efficient, and Enantioselective Electrophilic Fluorination

Incorporation of privileged catalytic scaffolds into a macrocyclic skeleton represents an attractive strategy to furnish supramolecular catalysis systems with enzyme-mimetic cavity and multi-site cooperation. Herein we reported the synthesis, structure, binding properties and catalytic application of a series of chiral bis-phosphate macrocycles toward the challenging asymmetric electrophilic fluorination. With a large, integrated chiral cavity and two cooperative phosphate sites, these macrocycles exhibited good inclusion toward 1,4-diazabicyclo[2.2.2]octane (DABCO) dicationic ammoniums through complementary ion-pair and C-H⋅⋅⋅O interactions, as confirmed by crystallographic and solution binding studies. In fluorocyclization of tryptamines with Selectfluor reagent which has a similar DABCO-based dicationic structure, only 2 mol% macrocycle catalyst afforded the desired pyrroloindoline products in moderate yields and up to 91 % ee. For comparison, the acyclic mono-phosphate analogue gave obviously lower reactivity and enantioselectivity (<20 % ee), suggesting a remarkable macrocyclic effect. The high catalytic efficiency and superior stereocontrol were ascribed to the tight ion-pair binding and cavity-directed noncovalent interaction cooperation.

Catalytic Atroposelective Synthesis of Axially Chiral Heterobiaryl Oxime Ethers via the One-Step Dynamic Kinetic Condensation Reaction

The catalytic atroposelective synthesis of axially chiral heterobiaryls was first developed through the direct one-step dynamic kinetic condensation reaction with the simple transformation of the C═O bond to the C═N bond, delivering a series of novel axially chiral heterobiaryl oxime ethers.

Csp2-H functionalization of phenols: an effective access route to valuable materials via Csp2-C bond formation

In the vast majority of top-selling pharmaceutical and industrial products, phenolic structural motifs are highly prevalent. Non-functionalized simple phenols serve as building blocks in the synthesis of value-added chemicals. It is worth mentioning that lignin, being the largest renewable biomass source of aromatic building blocks in nature, mainly consists of phenolic units, which enable the production of structurally diverse phenols. Given their remarkable applicability in the chemical value chain, many efforts have been devoted to increasing the molecular complexity of the phenolic scaffold. Among the key techniques, direct functionalization of Csp2-H is a powerful tool, enabling the construction of new Csp2-C bonds in an economical and atomic manner. Herein we present and summarize the large plethora of direct Csp2-H functionalization methods that enables scaffold diversification of simple, unprotected phenols, leading to the formation of new Csp2-C bonds. In this review article, we intend to summarize the contributions that appeared in the literature mainly in the last 5 years dealing with the functionalization of unprotected phenols, both catalytic and non-catalytic. Our goal is to highlight the key findings and the ongoing challenges in the stimulating and growing research dedicated to the development of new protocols for the valorization of phenols.

A genetic optimization strategy with generality in asymmetric organocatalysis as a primary target

A catalyst possessing a broad substrate scope, in terms of both turnover and enantioselectivity, is sometimes called "general". Despite their great utility in asymmetric synthesis, truly general catalysts are difficult or expensive to discover via traditional high-throughput screening and are, therefore, rare. Existing computational tools accelerate the evaluation of reaction conditions from a pre-defined set of experiments to identify the most general ones, but cannot generate entirely new catalysts with enhanced substrate breadth. For these reasons, we report an inverse design strategy based on the open-source genetic algorithm NaviCatGA and on the OSCAR database of organocatalysts to simultaneously probe the catalyst and substrate scope and optimize generality as a primary target. We apply this strategy to the Pictet-Spengler condensation, for which we curate a database of 820 reactions, used to train statistical models of selectivity and activity. Starting from OSCAR, we define a combinatorial space of millions of catalyst possibilities, and perform evolutionary experiments on a diverse substrate scope that is representative of the whole chemical space of tetrahydro-β-carboline products. While privileged catalysts emerge, we show how genetic optimization can address the broader question of generality in asymmetric synthesis, extracting structure-performance relationships from the challenging areas of chemical space.

Chiral phosphoric acid-catalyzed enantioselective [5+1] cycloaddition reaction of C,N-cyclic azomethine imines with isocyanides

The first catalytic enantioselective [5+1] cycloaddition reactions of C,N-cyclic azomethine imines with isocyanides are reported herein. The method displays a broad substrate scope and atom-economy. A series of chiral tetrahydroisoquinoline containing indole skeletons were obtained in up to 90% yield with 95% ee under mild reaction conditions. A possible catalytic model was also proposed.

A Flexible Synthesis of Polypropionates via Diastereodivergent Reductive Ring-Opening of Trisubstituted Secondary Glycidols

Polypropionates, characterized by their alternating sequence of stereocenters bearing methyl- and hydroxy-groups, are structurally diverse natural products of utmost importance.[1] Herein, we introduce a novel concept approach towards polypropionate synthesis featuring a diastereodivergent reductive epoxide-opening as a key step. Readily available and stereochemically uniform trisubstituted sec-glycidols serve as branching points for the highly selective synthesis of all isomers of polypropionate building blocks with three or more consecutive stereocenters. Stereodiversification is accomplished by an unprecedented mechanism-control over the stereochemically complementary modification of the epoxide's tertiary C-atom with excellent control of regio- and stereoselectivity. Since our method is not only suited for the preparation of specific targets but also for compound libraries, it will have a great impact on polypropionate synthesis.

Asymmetric Organocatalyzed Cyclization Cascade Reactions of 3,3-Difluoro-2-aryl-3H-indoles and Enamides

The direct functionalization of β-C(sp2)-H bonds in enamides has garnered increasing attention within the realm of organic synthesis. However, these remarkable advancements are predominantly dependent on transition metals; limited success has been achieved via organocatalytic catalysis. Herein, we report a CPA-catalyzed β-C(sp2)-H functionalization of enamides cascade intramolecular cyclization to synthesize the chiral dihydropyrimido[1,6-a]indoles bearing gem-difluoromethylene. Moreover, this methodology enables the synthesis of diverse chiral dihydropyrimido[1,6-a]indoles with outstanding enantioselectivities in moderate to high yields.

Nanomagnetic CoFe2O4@SiO2-EA-H3PO4 as a zwitterionic catalyst for the synthesis of bioactive pyrazolopyranopyrimidines and dihydropyrano[2,3-c]pyrazoles

This study presents the development of a phosphoric acid-based zwitterionic catalyst immobilized on CoFe2O4 nanoparticles [CoFe2O4@SiO2-EA-H3PO4]. The structure of the nanocatalyst CoFe2O4@SiO2-EA-H3PO4 was identified by applying several spectroscopic techniques, i.e. FT-IR, SEM, TEM, XRD, EDX, elemental Mapping, VSM, TGA, and BET techniques. The catalytic efficiency of CoFe2O4@SiO2-EA-H3PO4 was evaluated in the water-based multicomponent synthesis of pyrazolopyranopyrimidine and dihydropyrano[2,3-c]pyrazole derivatives. Subsequently, an exploration of the antibacterial properties of the compounds was conducted. The catalytic system offers several advantages, encompassing high efficiency, brief reaction duration, uncomplicated operation, and facile recycling of the catalyst.

MATEO: intermolecular α-amidoalkylation theoretical enantioselectivity optimization. Online tool for selection and design of chiral catalysts and products

The enantioselective Brønsted acid-catalyzed α-amidoalkylation reaction is a useful procedure is for the production of new drugs and natural products. In this context, Chiral Phosphoric Acid (CPA) catalysts are versatile catalysts for this type of reactions. The selection and design of new CPA catalysts for different enantioselective reactions has a dual interest because new CPA catalysts (tools) and chiral drugs or materials (products) can be obtained. However, this process is difficult and time consuming if approached from an experimental trial and error perspective. In this work, an Heuristic Perturbation-Theory and Machine Learning (HPTML) algorithm was used to seek a predictive model for CPA catalysts performance in terms of enantioselectivity in α-amidoalkylation reactions with R2 = 0.96 overall for training and validation series. It involved a Monte Carlo sampling of > 100,000 pairs of query and reference reactions. In addition, the computational and experimental investigation of a new set of intermolecular α-amidoalkylation reactions using BINOL-derived N-triflylphosphoramides as CPA catalysts is reported as a case of study. The model was implemented in a web server called MATEO: InterMolecular Amidoalkylation Theoretical Enantioselectivity Optimization, available online at: https://cptmltool.rnasa-imedir.com/CPTMLTools-Web/mateo . This new user-friendly online computational tool would enable sustainable optimization of reaction conditions that could lead to the design of new CPA catalysts along with new organic synthesis products.

Organocatalytic regio- and enantioselective C1-arylation of β,γ-alkynyl-α-imino esters with pyrrolo[2,1-a]isoquinolines

We herein report regio- and enantioselective arylation of β,γ-alkynyl-α-imino esters with pyrroloisoquinolines. Using chiral phosphoric acid catalysts, a wide range of novel axially chiral tetrasubstituted α-amino allenoates were accessed in good yields with excellent enantioselectivities. Notably, this transformation occurred preferentially at the sterically more hindered C1-position of pyrroloisoquinolines. The potential scalability and late-stage functionalization demonstrated the utility of the current protocol.

Enantioselective synthesis of 3-(N-indolyl)quinolines containing axial and central chiralities

Quinoline and indole are important core structures in biologically active compounds and materials. Atropisomeric biaryls consisting of quinoline and indole are a unique class of axially chiral molecules. We report herein enantioselective synthesis of 3-(N-indolyl)quinolines having both C-N axial chirality and carbon central chirality by a photoredox Minisci-type addition reaction catalyzed by a chiral lithium phosphate/Ir-photoredox complex. The catalytic system enabled access to a unique class of 3-(N-indolyl)quinolines with high chemo-, regio-, and stereoselectivities in good yields through the appropriate choice of an acid catalyst and a photocatalyst. This is the first example of the synthesis of 3-(N-indolyl)quinoline atropisomers in a highly enantioselective manner.

Combinatorial Ligand Assisted Simultaneous Control of Axial and Central Chirality in Highly Stereoselective C-H Allylation

The significance of stereoselective C-H bond functionalization thrives on its direct application potential to pharmaceuticals or complex chiral molecule synthesis. Complication arises when there are multiple stereogenic elements such as a center and an axis of chirality to control. Over the years cooperative assistance of multiple chiral ligands has been applied to control only chiral centers. In this work, we harness the essence of cooperative ligand approach to control two different stereogenic elements in the same molecule by atroposelective allylation to synthesize axially chiral biaryls from its racemic precursor. The crucial roles played by chiral phosphoric acid and chiral amino acid ligand in concert helped us to obtain one major stereoisomer out of four distinct possibilities.

Brønsted-Acid-Catalyzed Enantioselective Desymmetrization of 1,3-Diols: Access to Chiral β-Amino Alcohol Derivatives

Herein, we describe a Brønsted-acid-catalyzed enantioselective desymmetrization of 1,3-diols with alkynes through a hydroalkoxylation/hydrolysis process. The reaction leads to the atom-economical synthesis of valuable chiral β-amino alcohols under mild reaction conditions. Further synthetic transformations based on the β-amino alcohol moiety provide divergent approaches toward chiral N-containing heterocycles.

Enantioselective Multifunctionalization with Rh Carbynoids

Multifunctionalization from the interception of active intermediates is an attractive synthetic strategy for the efficient construction of complex molecular scaffolds in an atom and step economic fashion. However, the design of reactions involving metal carbynoids that exhibit carbene/carbocation behavior is currently limited, and developing catalyst-controlled highly enantioselective versions poses significant challenges. In this study, we present the first asymmetric trifunctionalization reactions with rhodium carbynoids. This reaction unveils the distinctive reactivity of the carbynoid precursor, enabling it to react with simultaneously two nucleophiles and one electrophile. This process involves the formation of two distinct carbene ylides with the alcohol/carbamate and the trapping of one ylide with the imine, resulting in the formation of three new bonds. Furthermore, this strategy allows for the divergent synthesis of a wide array of β-amino esters in high yields and exceptional enantioselectivity.

Modular and diverse synthesis of amino acids via asymmetric decarboxylative protonation of aminomalonic acids

Stereoselective protonation is a challenge in asymmetric catalysis. The small size and high rate of transfer of protons mean that face-selective delivery to planar intermediates is hard to control, but it can unlock previously obscure asymmetric transformations. Particularly, when coupled with a preceding decarboxylation, enantioselective protonation can convert the abundant acid feedstocks into structurally diverse chiral molecules. Here an anchoring group strategy is demonstrated as a potential alternative and supplement to the conventional structural modification of catalysts by creating additional catalyst-substrate interactions. We show that a tailored benzamide group in aminomalonic acids can help build a coordinated network of non-covalent interactions, including hydrogen bonds, π-π interactions and dispersion forces, with a chiral acid catalyst. This allows enantioselective decarboxylative protonation to give α-amino acids. The malonate-based synthesis introduces side chains via a facile substitution of aminomalonic esters and thus can access structurally and functionally diverse amino acids.

Visible-light-driven enantioselective intermolecular [2 + 2] photocyclization utilizing bathochromic excitation mediated by a chiral phosphoric acid

We report herein an enantioselective intermolecular [2 + 2] photocyclization of alkenyl 2-pyrrolyl ketones using the bathochromic shift mediated by a chiral phosphoric acid. This synthetic method provides access to cyclobutanes with up to 98% ee. According to the UV-Vis spectra, the bathochromic effect was observed by mixing alkenyl 2-pyrrolyl ketones and a chiral phosphoric acid. A non-linear correlation was observed between the ee of the catalyst and the ee of the cycloadduct, suggesting that both substrates bind to the chiral phosphoric acid and form a dimer complex before photocycloaddition.

Highly Enantioselective Synthesis of 3a-Fluorofuro[3,2-b]indolines via Organocatalytic Aza-Friedel-Crafts Reaction/Selective C-F Bond Activation

Fluoroalkylated compounds are of high interest in drug discovery and have inspired the evolution of diverse C-F bond activation methodologies. However, the selective activation of polyfluorinated compounds remains challenging. Herein, we describe an unprecedented strategy for synthesizing enantioenriched fluorofuro[3,2-b]indolines through the organocatalytic aza-Friedel-Crafts reaction coupled with selective C-F bond activation. These reactions feature excellent enantioselectivities (≤96% ee) and yields (≤96%) as well as good functional group compatibility. Mechanistic investigations by means of 19F nuclear magnetic resonance experiments provided sufficient support for silica gel as the key medium in this transformation.

Parallel kinetic resolution of aziridines via chiral phosphoric acid-catalyzed apparent hydrolytic ring-opening

We report a chiral phosphoric acid catalyzed apparent hydrolytic ring-opening reaction of racemic aziridines in a regiodivergent parallel kinetic resolution manner. Harnessing the acyloxy-assisted strategy, the highly stereocontrolled nucleophilic ring-opening of aziridines with water is achieved. Different kinds of aziridines are applicable in the process, giving a variety of enantioenriched aromatic or aliphatic amino alcohols with up to 99% yields and up to >99.5 : 0.5 enantiomeric ratio. Preliminary mechanistic study as well as product elaborations were inducted as well.

Activation Model and Origins of Selectivity for Chiral Phosphoric Acid Catalyzed Diradical Reactions

To develop new radical synthesis strategies, a profound understanding of the electronic transfer mechanism is critical. An activation model called relayed proton-coupled electron transfer (relayed-PCET) was developed and investigated for chiral phosphoric acid-catalyzed diradical reactions by density functional theory (DFT). The driving force of electron transfer from the nucleophile to the electrophile is the proton transfer that occurs via the chiral phosphoric acid (CPA) catalyst to the electrophile. Moreover, the origins of the selectivity can be explained by distortion of the catalyst, favorable hydrogen bonding, and strong interactions of the substrates with substituents of the CPAs.

A Lewis Acid-Controlled Enantiodivergent Epoxidation of Aldehydes

Two epoxidation catalysts, one of which consists of two VANOL ligands and an aluminum and the other that consists of two VANOL ligands and a boron, were compared. Both catalysts are highly effective in the catalytic asymmetric epoxidation of a variety of aromatic and aliphatic aldehydes with diazoacetamides, giving high yields and excellent asymmetric inductions. The aluminum catalyst is effective at 0 °C and the boron catalyst at -40 °C. Although both the aluminum and boron catalysts of (R)-VANOL give very high asymmetric inductions (up to 99% ee), they give opposite enantiomers of the epoxide. The mechanism, rate- and enantioselectivity-determining step, and origin of enantiodivergence are evaluated using density functional theory calculations.

Enantioselective Synthesis of Chiral Amides by a Phosphoric Acid Catalyzed Asymmetric Wolff Rearrangement

The enantioselective addition of potent nucleophiles to ketenes poses challenges due to competing background reactions and poor stereocontrol. Herein, we present a method for enantioselective phosphoric acid catalyzed amination of ketenes generated from α-aryl-α-diazoketones. Upon exposure to visible light, the diazoketones undergo Wolff rearrangement to generate ketenes. The phosphoric acid not only accelerates ketene capture by amines to form a single configuration of aminoenol intermediates but also promotes an enantioselective proton-transfer reaction of the intermediates to yield the products. Mechanistic studies elucidated the reaction pathway and explained how the catalyst expedited the transformation and controlled the enantioselectivity.

Enantioselective Alkynylation of 2-Aryl-3H-indol-3-ones via Cooperative Catalysis of Copper/Chiral Phosphoric Acid

A facile enantioselective alkynylation of cyclic ketimines attached to a neutral functional group utilizing the dual Cu(I)-CPA catalysis is described. The strategy of the alkynylation of 2-aryl-3H-indol-3-one directly to chiral propargylic amines containing indolin-3-one moiety in good yields and enantioselectivities. Moreover, gram-scale synthesis of chiral propargylamines based C2-quaternary indolin-3-ones was performed. The synthetic applications were confirmed by transformations of the products with no decrease in the yield and enantioselectivity.

All-round catalytic and atroposelective strategy via dynamic kinetic resolution for N-/2-/3-arylindoles

As the complexity of organic molecules utilized by mankind increases, the phenomenon of atropisomerism is more frequently encountered. While a variety of well-established methods enable the control of a stereogenic center, a catalytic method for controlling a stereogenic axis in one substrate is typically unavailable for controlling axial chirality in other substrates with a similar structure. Herein, we report o-amidobiaryl as a flexible platform for chiral phosphoric acid-catalyzed atroposelective dynamic kinetic resolution. To demonstrate our strategy, three distinct types of arylindoles were utilized and reacted intermolecularly with ketomalonate in the presence of chiral phosphoric acid. An investigation of 46 substrates having an aromatic ring in different positions yields the desired products with excellent enantioselectivities. Computational investigation into the origin of enantioselectivity highlights the importance of the NH group. Given the biological significance of indoles, antiproliferative effects have been investigated; our scaffold exhibits good efficacy in this regard.

Copper-Phosphido Catalysis: Enantioselective Addition of Phosphines to Cyclopropenes

We describe a copper catalyst that promotes the addition of phosphines to cyclopropenes at ambient temperature. A range of cyclopropylphosphines bearing different steric and electronic properties can now be accessed in high yields and enantioselectivities. Enrichment of phosphorus stereocenters is also demonstrated via a Dynamic Kinetic Asymmetric Transformation (DyKAT) process. A combined experimental and theoretical mechanistic study supports an elementary step featuring insertion of a CuI -phosphido into a carbon-carbon double bond. Density functional theory calculations reveal migratory insertion as the rate- and stereo-determining step, followed by a syn-protodemetalation.

Chiral Phosphoric Acid-Palladium(II) Complex Catalyzed Asymmetric Desymmetrization of Biaryl Compounds by C(sp3)-H Activation

Desymmetrization is an essential method for the synthesis of chiral compounds, particularly chiral biaryls. We have developed an enantioselective synthesis of axially chiral biaryls by desymmetrization using C(sp³)-H activation catalyzed by chiral palladium phosphate. Mechanistic studies show that C-H activation is the rate- and enantiomer-determining step. To the best of our knowledge, this is the first report of asymmetric desymmetrization of axially chiral compounds by C(sp³)-H activation.

Insights into Synergistic Effects of Counterion and Ligand on Diastereoselectivity Switch in Gold-Catalyzed Post-Ugi Ipso-Cyclization

The concept of diastereoselectivity switch in gold catalysis is investigated, which primarily depends on the effects of ligand and counterion. The origins of gold-catalyzed post-Ugi ipso-cyclization for the diastereoselective synthesis of spirocyclic pyrrol-2-one-dienone have been explored with density functional theory calculations. The reported mechanism emphasized the importance of the cooperation of ligand and counterion in diastereoselectivity switch, leading to the stereocontrolling transition states. Furthermore, the nonbonding interactions primarily between the catalyst and the substrate play a significant role in the cooperation of ligand and counterion. This work would be useful to further understand the reaction mechanism of gold-catalyzed cyclization and the effects of ligand and counterion.

Universal and divergent P-stereogenic building with camphor-derived 2,3-diols

The access to P-stereogenic motifs has always been considered a very challenging and high attractive mission in modern organic synthesis. While several chiral auxiliaries employed by the practical Jugé-Stephan-like methodology have been developed, new type of readily accessible bifunctional ligands toward P-stereogenic building still remain much desirable. Herein, we present a powerful chiral template, camphor-derived 2,3-diols named CAMDOL, which were designed and synthesized from the commercially cheap camphorquinone in high yields at 50 grams scale with a column-free purification. Diverse P(III)-chiral compounds and their borane forms including phosphinous acids, phosphinites, and phosphines, as well as the corresponding P(V)-chiral compounds including phosphinates, phosphine oxides, phosphinothioates, phosphine sulfides, and secondary phosphine oxides were afforded in high yields and ee values through the optimal 2,3-diphenyl CAMDOL platform. An unusual C³-OP bond cleavage following the first P-OC² bond breaking was observed during the ring-opening process when quenching by NH₄Cl solution, which generates a unique but valuable camphor-epoxide scaffold as by-product.

Enantioselective Catalysis with Pyrrolidinyl Gold(I) Complexes: DFT and NEST Analysis of the Chiral Binding Pocket

A new generation of chiral gold(I) catalysts based on variations of complexes with JohnPhos-type ligands with a remote C₂-symmetric 2,5-diarylpyrrolidine have been synthesized with different substitutions at the top and bottom aryl rings: from replacing the phosphine by a N-heterocyclic carbene (NHC) to increasing the steric hindrance with bis- or tris-biphenylphosphine scaffolds, or by directly attaching the C₂-chiral pyrrolidine in the ortho-position of the dialkylphenyl phosphine. The new chiral gold(I) catalysts have been tested in the intramolecular [4+2] cycloaddition of arylalkynes with alkenes and in the atroposelective synthesis of 2-arylindoles. Interestingly, simpler catalysts with the C₂-chiral pyrrolidine in the ortho-position of the dialkylphenyl phosphine led to the formation of opposite enantiomers. The chiral binding pockets of the new catalysts have been analyzed by DFT calculations. As revealed by non-covalent interaction plots, attractive non-covalent interactions between substrates and catalysts direct specific enantioselective folding. Furthermore, we have introduced the open-source tool NEST, specifically designed to account for steric effects in cylindrical-shaped complexes, which allows predicting experimental enantioselectivities in our systems.

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.

Enantioselective Synthesis of Fluorinated Indolizidinone Derivatives

The enantioselective synthesis of fluorinated indolizidinone derivatives has been developed. The process involved an enantioselective intramolecular aza-Michael reaction of conjugated amides bearing a pendant α,β-unsaturated ketone moiety, catalyzed by the (S)-TRIP-derived phosphoric acid, followed by dimethyltitanocene methylenation and ring closing metathesis (RCM). Final indolizidine-derived products comprise a fluorine-containing tetrasubstituted double bond generated by the RCM reaction, which is a challenging task. The whole synthetic sequence took place in acceptable overall yields with excellent enantioselectivities.

Stereospecific Nickel-Catalyzed Cross-Electrophile Coupling Reaction of Alkyl Mesylates and Allylic Difluorides to Access Enantioenriched Vinyl Fluoride-Substituted Cyclopropanes

Cross-electrophile coupling reactions involving direct C-O bond activation of unactivated alkyl sulfonates or C-F bond activation of allylic gem-difluorides remain challenging. Herein, we report a nickel-catalyzed cross-electrophile coupling reaction between alkyl mesylates and allylic gem-difluorides to synthesize enantioenriched vinyl fluoride-substituted cyclopropane products. These complex products are interesting building blocks with applications in medicinal chemistry. Density functional theory (DFT) calculations demonstrate that there are two competing pathways for this reaction, both of which initiate by coordination of the electron-deficient olefin to the low-valent nickel catalyst. Subsequently, the reaction can proceed by oxidative addition of the C-F bond of the allylic gem-difluoride moiety or by directed polar oxidative addition of the alkyl mesylate C-O bond.