Automated iterative Csp3-C bond formation

Catalytic Asymmetric Transfer Hydrogenation of Acylboronates: BMIDA as the Privileged Directing Group

Developing a general, highly efficient, and enantioselective catalytic method for the synthesis of chiral alcohols is still a formidable challenge. We report in this article the asymmetric transfer hydrogenation (ATH) of N-methyliminodiacetyl (MIDA) acylboronates as a general substrate-independent entry to enantioenriched secondary alcohols. ATH of acyl-MIDA-boronates with (het)aryl, alkyl, alkynyl, alkenyl, and carbonyl substituents delivers a variety of enantioenriched α-boryl alcohols. The latter are used in a range of stereospecific transformations based on the boron moiety, enabling the synthesis of carbinols with two closely related α-substituents, which cannot be obtained with high enantioselectivities using direct asymmetric hydrogenation methods, such as the (R)-cloperastine intermediate. Computational studies illustrate that the BMIDA group is a privileged enantioselectivity-directing group in Noyori-Ikariya ATH compared to the conventionally used aryl and alkynyl groups due to the favorable CH-O attractive electrostatic interaction between the η6-arene-CH of the catalyst and the σ-bonded oxygen atoms in BMIDA. The work expands the domain of conventional ATH and shows its huge potential in addressing challenges in symmetric synthesis.

Photogeneration of α-Bimetalloid Radicals via Selective Activation of Multifunctional C1 Units

Light-driven strategies that enable the chemoselective activation of a specific bond in multifunctional systems are comparatively underexplored in comparison to transition-metal-based technologies, yet desirable when considering the controlled exploration of chemical space. With the current drive to discover next-generation therapeutics, reaction design that enables the strategic incorporation of an sp3 carbon center, containing multiple synthetic handles for the subsequent exploration of chemical space would be highly enabling. Here, we describe the photoactivation of ambiphilic C1 units to generate α-bimetalloid radicals using only a Lewis base and light source to directly activate the C-I bond. Interception of these transient radicals with various SOMOphiles enables the rapid synthesis of organic scaffolds containing synthetic handles (B, Si, and Ge) for subsequent orthogonal activation. In-depth theoretical and mechanistic studies reveal the prominent role of 2,6-lutidine in forming a photoactive charge transfer complex and in stabilizing in situ generated iodine radicals, as well as the influential role of the boron p-orbital in the activation/weakening of the C-I bond. This simple and efficient methodology enabled expedient access to functionalized 3D frameworks that can be further derivatized using available technologies for C-B and C-Si bond activation.

Delocalized, asynchronous, closed-loop discovery of organic laser emitters

Contemporary materials discovery requires intricate sequences of synthesis, formulation, and characterization that often span multiple locations with specialized expertise or instrumentation. To accelerate these workflows, we present a cloud-based strategy that enabled delocalized and asynchronous design-make-test-analyze cycles. We showcased this approach through the exploration of molecular gain materials for organic solid-state lasers as a frontier application in molecular optoelectronics. Distributed robotic synthesis and in-line property characterization, orchestrated by a cloud-based artificial intelligence experiment planner, resulted in the discovery of 21 new state-of-the-art materials. Gram-scale synthesis ultimately allowed for the verification of best-in-class stimulated emission in a thin-film device. Demonstrating the asynchronous integration of five laboratories across the globe, this workflow provides a blueprint for delocalizing-and democratizing-scientific discovery.

Orthogonal sp3-Ge/B Bimetallic Modules: Enantioselective Construction and Enantiospecific Cross-Coupling

In this study, a series of enantioenriched sp3-Ge/B bimetallic modules were successfully synthesized via an enantioselective copper-catalyzed hydroboration of carbagermatrane (Ge)-containing alkenes. Orthogonal cross-coupling selectivity under different Pd-catalyzed conditions was achieved in an enantiospecific manner. Notably, the chiral secondary Ge exhibited a remarkable transmetallation ability prior to primary or secondary Bpin. The effectiveness of this Ge/B bimetallic strategy was further demonstrated through the development of new functional small molecules with Aggregation-Induced Emission (AIE) and Circularly Polarized Luminescence (CPL) performance. This represents the first successful example of synthesis of enantioenriched alkylgermanium reagents that permit enantiospecific cross-coupling reactions.

Triply Selective & Sequential Diversification at Csp 3: Expansion of Alkyl Germane Reactivity for C-C & C-Heteroatom Bond Formation

We report the triply selective and sequential diversification of a single Csp 3 carbon carrying Cl, Bpin and GeEt3 for the modular and programmable construction of sp3-rich molecules. Various functionalizations of Csp 3-Cl and Csp 3-BPin (e.g. alkylation, arylation, homologation, amination, hydroxylation) were tolerated by the Csp 3-GeEt3 group. Moreover, the methodological repertoire of alkyl germane functionalization was significantly expanded beyond the hitherto known Giese addition and arylation to alkynylation, alkenylation, cyanation, halogenation, azidation, C-S bond formation as well as the first demonstration of stereo-selective functionalization of a Csp 3-[Ge] bond.

Manganese Complex Catalyzed Sequential Multi-component Reaction: Enroute to a Quinoline-Derived Azafluorenes

The development of innovative synthetic strategies for constructing complex molecular structures is the heart of organic chemistry. This significance of novel reactions or reaction sequences would further enhance if they permitted the synthesis of new classes of structural motifs, which have not been previously created. The research on the synthesis of heterocyclic compounds is one of the most active topics in organic chemistry due to the widespread application of N-heterocycles in life and material science. The development of a new catalytic process that employs first-row transition metals to produce a range of heterocycles from renewable raw materials is considered highly sustainable approach. This would be more advantageous if done in an eco-friendly and atom-efficient manner. Herein we introduce, the synthesis of various new quinoline based azafluorenes via sequential dehydrogenative multicomponent reaction (MCR) followed by C(sp3)-H hydroxylation and annulation. Our newly developed, Mn-complexes have the ability to direct the reaction in order to achieve a high amount of desired functionalized heterocycles while minimizing the possibility of multiple side reactions. We also performed a series of control experiments, hydride trapping experiments, reaction kinetics, catalytic intermediate and DFT studies to comprehend the detailed reaction route and the catalyst's function in the MCR sequence.

Reaction Kinetics using a Chemputable Framework for Data Collection and Analysis

Automated chemistry platforms have been widely explored, but many focus on fixed tasks for chemical synthesis or analysis. However, a typical synthetic chemistry workflow utilizes both, such as kinetic measurements for reaction development and optimization. Due to their repetitive and time-consuming nature, kinetic measurements are often omitted, which limits the mechanistic investigation of reactions. Herein, we present a "Chemputer" platform with on-line analytics (UV/Vis, NMR) which automates routine kinetic measurements. The system's capabilities are showcased by exploring an inverse electron-demand Diels-Alder using initial rate measurements, a metal complexation using variable time normalization analysis (VTNA), and formation of a series of tosylamide derivatives using Hammett analysis. Over 60 individual experiments are presented which required minimal intervention, highlighting the significant time savings of automation. Owing to the modular design of the platform, which facilitates rapid integration of commercial analytical tools, our approach is widely accessible and adjustable to the reaction under investigation. The platform is operated using the chemical programming language, XDL, hence experimental procedures and results are stored in a precise, computer-readable format. We propose that widespread adoption of this reporting protocol in the chemical community could build a database of validated kinetic data beneficial for Machine Learning.

Programmable late-stage functionalization of bridge-substituted bicyclo[1.1.1]pentane bis-boronates

Modular functionalization enables versatile exploration of chemical space and has been broadly applied in structure-activity relationship (SAR) studies of aromatic scaffolds during drug discovery. Recently, the bicyclo[1.1.1]pentane (BCP) motif has increasingly received attention as a bioisosteric replacement of benzene rings due to its ability to improve the physicochemical properties of prospective drug candidates, but studying the SARs of C2-substituted BCPs has been heavily restricted by the need for multistep de novo synthesis of each analogue of interest. Here we report a programmable bis-functionalization strategy to enable late-stage sequential derivatization of BCP bis-boronates, opening up opportunities to explore the SARs of drug candidates possessing multisubstituted BCP motifs. Our approach capitalizes on the inherent chemoselectivity exhibited by BCP bis-boronates, enabling highly selective activation and functionalization of bridgehead (C3)-boronic pinacol esters (Bpin), leaving the C2-Bpin intact and primed for subsequent derivatization. These selective transformations of both BCP bridgehead (C3) and bridge (C2) positions enable access to C1,C2-disubstituted and C1,C2,C3-trisubstituted BCPs that encompass previously unexplored chemical space.

Computational prediction of complex cationic rearrangement outcomes

Recent years have seen revived interest in computer-assisted organic synthesis1,2. The use of reaction- and neural-network algorithms that can plan multistep synthetic pathways have revolutionized this field1,3-7, including examples leading to advanced natural products6,7. Such methods typically operate on full, literature-derived 'substrate(s)-to-product' reaction rules and cannot be easily extended to the analysis of reaction mechanisms. Here we show that computers equipped with a comprehensive knowledge-base of mechanistic steps augmented by physical-organic chemistry rules, as well as quantum mechanical and kinetic calculations, can use a reaction-network approach to analyse the mechanisms of some of the most complex organic transformations: namely, cationic rearrangements. Such rearrangements are a cornerstone of organic chemistry textbooks and entail notable changes in the molecule's carbon skeleton8-12. The algorithm we describe and deploy at https://HopCat.allchemy.net/ generates, within minutes, networks of possible mechanistic steps, traces plausible step sequences and calculates expected product distributions. We validate this algorithm by three sets of experiments whose analysis would probably prove challenging even to highly trained chemists: (1) predicting the outcomes of tail-to-head terpene (THT) cyclizations in which substantially different outcomes are encoded in modular precursors differing in minute structural details; (2) comparing the outcome of THT cyclizations in solution or in a supramolecular capsule; and (3) analysing complex reaction mixtures. Our results support a vision in which computers no longer just manipulate known reaction types1-7 but will help rationalize and discover new, mechanistically complex transformations.

Oxazaborolidinones: Steric Coverage Effect of Lewis Acidic Boron Center in Suzuki-Miyaura Coupling Reactions

It was demonstrated that α-hydroxycarboxamide is an excellent boron-protecting group. The reaction between α-hydroxycarboxamide and organoboronic acids produced stable oxazaborolidinones (OxBs), in which thesp 2 ${{_{{\rm sp}{^{2}}}}}$ -hybridized boron atom was sterically protected by α-hydroxycarboxamide. The alkyl groups of the α-hydroxycarboxamide moiety can dynamically cover the p-orbital of thesp 2 ${{_{{\rm sp}{^{2}}}}}$ -hybridized boron center, creating a small space around the boron atom, allowing for smooth transmetalation by a Pd catalyst and easy deprotection by water. This protecting phenomenon is effective for readily purification, Suzuki-Miyaura coupling reactions with unstable boronic acids and iterative cross-couplings.

MIDA- and TIDA-Boronates Stabilize α-Radicals Through B-N Hyperconjugation

Multifunctional organoboron compounds increasingly enable the simple generation of complex, Csp3 -rich small molecules. The ability of boron-containing functional groups to modify the reactivity of α-radicals has also enabled a myriad of chemical reactions. Boronic esters with vacant p-orbitals have a significant stabilizing effect on α-radicals due to delocalization of spin density into the empty orbital. The effect of coordinatively saturated derivatives, such as N-methyliminodiacetic acid (MIDA) boronates and counterparts, remains less clear. Herein, we demonstrate that coordinatively saturated MIDA and TIDA boronates stabilize secondary alkyl α-radicals via σB-N hyperconjugation in a manner that allows site-selective C-H bromination. DFT calculated radical stabilization energies and spin density maps as well as LED NMR kinetic analysis of photochemical bromination rates of different boronic esters further these findings. This work clarifies that the α-radical stabilizing effect of boronic esters does not only proceed via delocalization of radical character into vacant boron p-orbitals, but that hyperconjugation of tetrahedral boron-containing functional groups and their ligand electron delocalizing ability also play a critical role. These findings establish boron ligands as a useful dial for tuning reactivity at the α-carbon.

Regioselective Electrophilic Addition to Propargylic B(MIDA)s Enabled by β-Boron Effect

Electrophilic addition reaction to alkynes is of fundamental importance in organic chemistry, yet the regiocontrol when reacting with unsymmetrical 1,2-dialkyl substituted alkynes is often problematic. Herein, it is demonstrated that the rarely recognized β-boron effect can confer a high level of site-selectivity in several alkyne electrophilic addition reactions. A broad range of highly functionalized and complex organoborons are thus formed under simple reaction conditions starting from propargylic MIDA (N-methyliminodiacetic acid) boronates. These products are demonstrated to be valuable building blocks in organic synthesis. In addition to the regiocontrol, this study also observes a drastic rate enhancement upon B(MIDA) substitution. Theoretical calculation reveals that the highest occupied molecular obital (HOMO) energy level of propargylic B(MIDA) is significantly raised by 0.3 eV, and the preferential electrophilic addition to the γ position is due to its higher HOMO orbital coefficient and more negative natural bond orbital (NBO) charge compared to the β position. This study demonstrates the potential of utilizing the β-boron effect in stereoelectronic control of chemical transformations, which can inspire further research in this area.

Programmable Amine Synthesis via Iterative Boron Homologation

The value of Matteson-type reactions has been increasingly recognized for developing automated organic synthesis. However, the typical Matteson reactions almost exclusively focus on homologation of carbon units. Here, we report the detailed development of sequential insertion of nitrogen and carbon atoms into boronate C-B bonds, which provides a modular and iterative approach to access functionalized tertiary amines. A new class of nitrenoid reagents is uncovered to allow direct formation of aminoboranes from aryl or alkyl boronates via N-insertion. The one-pot N-insertion followed by controlled mono- or double-carbenoid insertion has been realized with widely available aryl boronates. The resulting aminoalkyl boronate products can undergo further homologation and various other transformations. Preliminary success on homologation of N,N-dialkylaminoboranes and sequential N- and C-insertions with alkyl boronates have also been achieved. To broaden the synthetic utility, selective removal of a benzyl or aryl substituent permits access to secondary or primary amine products. The application of this method has been demonstrated in the modular synthesis of bioactive compounds and the programmable construction of diamines and aminoethers. A plausible reaction mechanism, supported by preliminary NMR (nuclear magnetic resonance) and computational studies, is also proposed.

Robotic Modules for the Programmable Chemputation of Molecules and Materials

Before leveraging big data methods like machine learning and artificial intelligence (AI) in chemistry, there is an imperative need for an affordable, universal digitization standard. This mirrors the foundational requisites of the digital revolution, which demanded standard architectures with precise specifications. Recently, we have developed automated platforms tailored for chemical AI-driven exploration, including the synthesis of molecules, materials, nanomaterials, and formulations. Our focus has been on designing and constructing affordable standard hardware and software modules that serve as a blueprint for chemistry digitization across varied fields. Our platforms can be categorized into four types based on their applications: (i) discovery systems for the exploration of chemical space and novel reactivity, (ii) systems for the synthesis and manufacture of fine chemicals, (iii) platforms for formulation discovery and exploration, and (iv) systems for materials discovery and synthesis. We also highlight the convergent evolution of these platforms through shared hardware, firmware, and software alongside the creation of a unique programming language for chemical and material systems. This programming approach is essential for reliable synthesis, designing experiments, discovery, optimization, and establishing new collaboration standards. Furthermore, it is crucial for verifying literature findings, enhancing experimental outcome reliability, and fostering collaboration and sharing of unsuccessful experiments across different research labs.

Integrated System Built for Small-Molecule Semiconductors via High-Throughput Approaches

High-throughput synthesis of solution-processable structurally variable small-molecule semiconductors is both an opportunity and a challenge. A large number of diverse molecules provide a possibility for quick material discovery and machine learning based on experimental data. However, the diversity of the molecular structure leads to the complexity of molecular properties, such as solubility, polarity, and crystallinity, which poses great challenges to solution processing and purification. Here, we first report an integrated system for the high-throughput synthesis, purification, and characterization of molecules with a large variety. Based on the principle "Like dissolves like," we combine theoretical calculations and a robotic platform to accelerate the purification of those molecules. With this platform, a material library containing 125 molecules and their optical-electronic properties was built within a timeframe of weeks. More importantly, the high repeatability of recrystallization we design is a reliable approach to further upgrading and industrial production.

Chirality Sensing of N-Heterocycles via 19F NMR

Methods to rapidly detect and differentiate chiral N-heterocyclic compounds become increasingly important owing to the widespread application of N-heterocycles in drug discovery and materials science. We herein report a ¹⁹F NMR-based chemosensing approach for the prompt enantioanalysis of various N-heterocycles, where the dynamic binding between the analytes and a chiral ¹⁹F-labeled palladium probe create characteristic ¹⁹F NMR signals assignable to each enantiomer. The open binding site of the probe allows the effective recognition of bulky analytes that are otherwise difficult to detect. The chirality center distal to the binding site is found sufficient for the probe to discriminate the stereoconfiguration of the analyte. The utility of the method in the screening of reaction conditions for the asymmetric synthesis of lansoprazole is demonstrated.

A field guide to flow chemistry for synthetic organic chemists

Flow chemistry has unlocked a world of possibilities for the synthetic community, but the idea that it is a mysterious "black box" needs to go. In this review, we show that several of the benefits of microreactor technology can be exploited to push the boundaries in organic synthesis and to unleash unique reactivity and selectivity. By "lifting the veil" on some of the governing principles behind the observed trends, we hope that this review will serve as a useful field guide for those interested in diving into flow chemistry.

Computational approaches streamlining drug discovery

Computer-aided drug discovery has been around for decades, although the past few years have seen a tectonic shift towards embracing computational technologies in both academia and pharma. This shift is largely defined by the flood of data on ligand properties and binding to therapeutic targets and their 3D structures, abundant computing capacities and the advent of on-demand virtual libraries of drug-like small molecules in their billions. Taking full advantage of these resources requires fast computational methods for effective ligand screening. This includes structure-based virtual screening of gigascale chemical spaces, further facilitated by fast iterative screening approaches. Highly synergistic are developments in deep learning predictions of ligand properties and target activities in lieu of receptor structure. Here we review recent advances in ligand discovery technologies, their potential for reshaping the whole process of drug discovery and development, as well as the challenges they encounter. We also discuss how the rapid identification of highly diverse, potent, target-selective and drug-like ligands to protein targets can democratize the drug discovery process, presenting new opportunities for the cost-effective development of safer and more effective small-molecule treatments.

β-Boron Effect Enables Regioselective and Stereospecific Electrophilic Addition to Alkenes

Electrophilic addition to alkenes is a textbook-taught reaction, yet it is not always possible to control the regioselectivity of addition to unsymmetrical 1,2-disubstituted substrates. We report the observation and applications of the β-boron effect that accounts for high regioselectivity in electrophilic addition reactions to allylic MIDA (N-methyliminodiacetic acid) boronates. While the well-established β-silicon effect bears partial resemblance to the observed reactivity, the silyl group is typically lost during functionalization. In contrast, the boryl moiety is retained in the product when B(MIDA) is used as the nucleophilic stabilizer. Mechanistic studies elucidate the origin of this effect and demonstrate how σ(C-B) hyperconjugation helps stabilize the incipient carbocation. This transformation represents a rare example of the stereospecific hydrohalogenation of secondary allyl MIDA-boronates that proceeds in a syn-fashion.

Enantioselective Suzuki cross-coupling of 1,2-diboryl cyclopropanes

Herein, we describe the catalytic enantioselective cross-coupling of 1,2-bisboronic esters. Prior work on group specific cross coupling is limited to the use of geminal bis-boronates. This desymmetrization provides a novel approach to prepare enantioenriched cyclopropyl boronates with three contiguous stereocenters, that could be further derivatized through selective functionalization of the carbon-boron bond. Our results suggest that transmetallation, which is the enantiodetermining step, takes place with retention of stereochemistry at carbon.

Protection of Boronic Acids Using a Tridentate Aminophenol ONO Ligand for Selective Suzuki-Miyaura Coupling

Boronic acid protecting group chemistry powerfully enhances the versatility of Suzuki-Miyaura cross-coupling. Prominent examples include trifluoroborate salts, N-methyliminodiacetic acid (MIDA) boronates, and 1,8-diaminonaphthalene boronamides. In this work, we present a bis(2-hydroxybenzyl)methylamine (BOMA) ligand that forms tridentate complexes with boronic acids much like the MIDA ligand but the deprotection is facilitated by organic acids. The BOMA boronates showed considerable stability in both aqueous base and acid, and a variety of chemoselective reactions were performed on these boronates, including selective Suzuki-Miyaura coupling, palladium-catalyzed borylation, ester hydrolysis, alkylation, lithiation-borylation, and oxidative hydroxydeboronation.

Rational design of N-heterocyclic compound classes via regenerative cyclization of diamines

The discovery of reactions is a central topic in chemistry and especially interesting if access to compound classes, which have not yet been synthesized, is permitted. N-Heterocyclic compounds are very important due to their numerous applications in life and material science. We introduce here a consecutive three-component reaction, classes of N-heterocyclic compounds, and the associated synthesis concept (regenerative cyclisation). Our reaction starts with a diamine, which reacts with an amino alcohol via dehydrogenation, condensation, and cyclisation to form a new pair of amines that undergoes ring closure with an aldehyde, carbonyldiimidazole, or a dehydrogenated amino alcohol. Hydrogen is liberated in the first reaction step and the dehydrogenation catalyst used is based on manganese.

A Materials Acceleration Platform for Organic Laser Discovery

Conventional materials discovery is a laborious and time-consuming process that can take decades from initial conception of the material to commercialization. Recent developments in materials acceleration platforms promise to accelerate materials discovery using automation of experiments coupled with machine learning. However, most of the automation efforts in chemistry focus on synthesis and compound identification, with integrated target property characterization receiving less attention. In this work, an automated platform is introduced for the discovery of molecules as gain mediums for organic semiconductor lasers, a problem that has been challenging for conventional approaches. This platform encompasses automated lego-like synthesis, product identification, and optical characterization that can be executed in a fully integrated end-to-end fashion. Using this workflow to screen organic laser candidates, discovered eight potential candidates for organic lasers is discovered. The lasing threshold of four molecules in thin-film devices and find two molecules with state-of-the-art performance is tested. These promising results show the potential of automated synthesis and screening for accelerated materials development.

Closed-loop optimization of general reaction conditions for heteroaryl Suzuki-Miyaura coupling

General conditions for organic reactions are important but rare, and efforts to identify them usually consider only narrow regions of chemical space. Discovering more general reaction conditions requires considering vast regions of chemical space derived from a large matrix of substrates crossed with a high-dimensional matrix of reaction conditions, rendering exhaustive experimentation impractical. Here, we report a simple closed-loop workflow that leverages data-guided matrix down-selection, uncertainty-minimizing machine learning, and robotic experimentation to discover general reaction conditions. Application to the challenging and consequential problem of heteroaryl Suzuki-Miyaura cross-coupling identified conditions that double the average yield relative to a widely used benchmark that was previously developed using traditional approaches. This study provides a practical road map for solving multidimensional chemical optimization problems with large search spaces.

Isolation and Characterization of Heteroleptic Mononuclear Palladium(I) Complexes

Catalytic transformations involving Pd(0)/Pd(II) catalytic cycles are very well known, and processes involving high-valent Pd(III) and Pd(IV) and low-valent Pd(I) intermediates have also gained interest in recent years. Although low-valent Pd(I) intermediates are proposed in these catalytic cycles, isolated and characterized mononuclear Pd(I) species are very rare. Herein, we report the isolation of two heteroleptic mononuclear Pd(I) complexes stabilized by dithiapyridinophane ligands that were fully characterized by single-crystal X-ray diffraction; EPR, IR, UV-vis spectroscopies; and computational studies. Excitingly, one of these Pd(I) complexes shows Kumada Csp³-Csp² cross-coupling competency, and initial studies of the other shows direct evidence for Csp³-H bond activation proposed to occur at the Pd(I) center.

An all-round AI-Chemist with a scientific mind

The realization of automated chemical experiments by robots unveiled the prelude to an artificial intelligence (AI) laboratory. Several AI-based systems or robots with specific chemical skills have been demonstrated, but conducting all-round scientific research remains challenging. Here, we present an all-round AI-Chemist equipped with scientific data intelligence that is capable of performing basic tasks generally required in chemical research. Based on a service platform, the AI-Chemist is able to automatically read the literatures from a cloud database and propose experimental plans accordingly. It can control a mobile robot in-house or online to automatically execute the complete experimental process on 14 workstations, including synthesis, characterization and performance tests. The experimental data can be simultaneously analysed by the computational brain of the AI-Chemist through machine learning and Bayesian optimization, allowing a new hypothesis for the next iteration to be proposed. The competence of the AI-Chemist has been scrutinized by three different chemical tasks. In the future, the more advanced all-round AI-Chemists equipped with scientific data intelligence may cause changes to the landscape of the chemical laboratory.

The Impact of Boron Hybridisation on Photocatalytic Processes

Recently the fruitful merger of organoboron chemistry and photocatalysis has come to the forefront of organic synthesis, resulting in the development of new technologies to access complex (non)borylated frameworks. Central to the success of this combination is control of boron hybridisation. Contingent on the photoactivation mode, boron as its neutral planar form or tetrahedral boronate can be used to regulate reactivity. This Minireview highlights the current state of the art in photocatalytic processes utilising organoboron compounds, paying particular attention to the role of boron hybridisation for the target transformation.

A Convenient, Rapid, Conventional Heating Route to MIDA Boronates

A cheap, conventional, sealed heating reactor proved to be a useful alternative to a microwave reactor in the synthesis of a >20-member MIDA boronate library (MIDA = N-methyliminodiacetic acid). Reaction times were 10 min and work-ups were minimal, saving on energy and solvent usage.

Boryl-Dictated Site-Selective Intermolecular Allylic and Propargylic C-H Amination

For internal alkenes possessing two or more sets of electronically and sterically similar allylic protons, the site-selectivity for allylic C-H functionalization is fundamentally challenging. Previously, the negative inductive effect from an electronegative atom has been demonstrated to be effective for several inspiring regioselective C-H functionalization reactions. Yet, the use of an electropositive atom for a similar purpose remains to be developed. α-Aminoboronic acids and their derivatives have found widespread applications. Their current syntheses rely heavily on functional group manipulations. Herein we report a boryl-directed intermolecular C-H amination of allyl N-methyliminodiacetyl boronates (B(MIDA)s) and propargylic B(MIDA)s to give α-amino boronates with an exceptionally high level of site-selectivities (up to 300:1). A wide variety of highly functionalized secondary and tertiary α-amino boronates are formed in generally good to excellent yields, thanks to the mildness of the reaction conditions. The unsaturated double and triple bonds within the product leave room for further decorations. Mechanistic studies reveal that the key stabilization effect of the B(MIDA) moiety on its adjacent developing positive charge is responsible for the high site-selectivity and that a closed transition state might be involved, as the reaction is fully stereoretentive. An activation effect of B(MIDA) is also found.

Iterative Synthesis of Contorted Macromolecular Ladders for Fast-Charging and Long-Life Lithium Batteries

We report here an iterative synthesis of long helical perylene diimide (hPDI[n]) nanoribbons with a length up to 16 fused benzene rings. These contorted, ladder-type conjugated, and atomically precise nanoribbons show great potential as organic fast-charging and long-lifetime battery cathodes. By tuning the length of the hPDI[n] oligomers, we can simultaneously modulate the electrical conductivity and ionic diffusivity of the material. The length of the ladders adjusts both the conjugation for electron transport and the contortion for lithium-ion transport. The longest oligomer, hPDI[6], when fabricated as the cathode in lithium batteries, features both high electrical conductivity and high ionic diffusivity. This electrode material exhibits a high power density and can be charged in less than 1 min to 66% of its maximum capacity. Remarkably, this material also has exceptional cycling stability and can operate for up to 10,000 charging-discharging cycles without any appreciable capacity decay. The design principles described here chart a clear path for organic battery electrodes that are sustainable, fast-charging, and long lasting.

Digitizing Chemical Synthesis in 3D Printed Reactionware

Chemistry digitization requires an unambiguous link between experiments and the code used to generate the experimental conditions and outcomes, yet this process is not standardized, limiting the portability of any chemical code. What is needed is a universal approach to aid this process using a well-defined standard that is composed of syntheses that are employed in modular hardware. Herein we present a new approach to the digitization of organic synthesis that combines process chemistry principles with 3D printed reactionware. This approach outlines the process for transforming unit operations into digitized hardware and well-defined instructions that ensure effective synthesis. To demonstrate this, we outline the process for digitizing 3 MIDA boronate building blocks, an ester hydrolysis, a Wittig olefination, a Suzuki-Miyaura coupling reaction, and synthesis of the drug sulfanilamide.

In Situ Studies of Arylboronic Acids/Esters and R3SiCF3 Reagents: Kinetics, Speciation, and Dysfunction at the Carbanion-Ate Interface

Reagent instability reduces the efficiency of chemical processes, and while much effort is devoted to reaction optimization, less attention is paid to the mechanistic causes of reagent decomposition. Indeed, the response is often to simply use an excess of the reagent. Two reaction classes with ubiquitous examples of this are the Suzuki-Miyaura cross-coupling of boronic acids/esters and the transfer of CF₃ or CF₂ from the Ruppert-Prakash reagent, TMSCF₃. This Account describes some of the overarching features of our mechanistic investigations into their decomposition. In the first section we summarize how specific examples of (hetero)arylboronic acids can decompose via aqueous protodeboronation processes: Ar-B(OH)₂ + H₂O → ArH + B(OH)₃. Key to the analysis was the development of a kinetic model in which pH controls boron speciation and heterocycle protonation states. This method revealed six different protodeboronation pathways, including self-catalysis when the pH is close to the pK_a of the boronic acid, and protodeboronation via a transient aryl anionoid pathway for highly electron-deficient arenes. The degree of "protection" of boronic acids by diol-esterification is shown to be very dependent on the diol identity, with six-membered ring esters resulting in faster protodeboronation than the parent boronic acid. In the second section of the Account we describe ¹⁹F NMR spectroscopic analysis of the kinetics of the reaction of TMSCF₃ with ketones, fluoroarenes, and alkenes. Processes initiated by substoichiometric "TBAT" ([Ph₃SiF₂][Bu₄N]) involve anionic chain reactions in which low concentrations of [CF₃]^- are rapidly and reversibly liberated from a siliconate reservoir, [TMS(CF₃)₂][Bu₄N]. Increased TMSCF₃ concentrations reduce the [CF₃]^- concentration and thus inhibit the rates of CF₃ transfer. Computation and kinetics reveal that the TMSCF₃ intermolecularly abstracts fluoride from [CF₃]^- to generate the CF₂, in what would otherwise be an endergonic α-fluoride elimination. Starting from [CF₃]^- and CF₂, a cascade involving perfluoroalkene homologation results in the generation of a hindered perfluorocarbanion, [C₁₁F₂₃]^-, and inhibition. The generation of CF₂ from TMSCF₃ is much more efficiently mediated by NaI, and in contrast to TBAT, the process undergoes autoacceleration. The process involves NaI-mediated α-fluoride elimination from [CF₃][Na] to generate CF₂ and a [NaI·NaF] chain carrier. Chain-branching, by [(CF₂)₃I][Na] generated in situ (CF₂ + TFE + NaI), causes autoacceleration. Alkenes that efficiently capture CF₂ attenuate the chain-branching, suppress autoacceleration, and lead to less rapid difluorocyclopropanation. The Account also highlights how a collaborative approach to experiment and computation enables mechanistic insight for control of processes.

Stereocontrolled Total Synthesis of Bastimolide B Using Iterative Homologation of Boronic Esters

Bastimolide B is a polyhydroxy macrolide isolated from marine cyanobacteria displaying antimalarial activity. It features a dense array of hydroxylated stereogenic centers with 1,5-relationships along a hydrocarbon chain. These 1,5-polyols represent a particularly challenging motif for synthesis, as the remote position of the stereocenters hampers stereocontrol. Herein, we present a strategy for 1,5-polyol stereocontrolled synthesis based on iterative boronic ester homologation with enantiopure magnesium carbenoids. By merging boronic ester homologation and transition-metal-catalyzed alkene hydroboration and diboration, the acyclic backbone of bastimolide B was rapidly assembled from readily available building blocks with full control over the remote stereocenters, enabling the total synthesis to be completed in 16 steps (LLS).