Manganese-Catalyzed Borylation of Unactivated Alkyl Chlorides

Photoredox/Cu-Catalyzed Decarboxylative C(sp3)-C(sp3) Coupling to Access C(sp3)-Rich gem-Diborylalkanes

gem-Diborylalkanes are highly valuable building blocks in organic synthesis and pharmaceutical chemistry due to their ability to participate in multi-step cross-coupling transformations, allowing for the rapid generation of molecular complexity. While progress has been made in their synthetic metholodology, the construction of β-tertiary and C(sp3)-rich gem-diborylalkanes remains a synthetic challenge due to substrate limitations and steric hindrance issues. An approach is presented that utilizes synergistic photoredox and copper catalysis to achieve efficient C(sp3)-C(sp3) cross-coupling of alkyl N-hydroxyphthalimide esters, which can easily be obtained from alkyl carboxylic acids, with diborylmethyl species, providing a series of C(sp3)-rich gem-diborylalkanes with 1°, 2°, and even 3° β positions. Furthermore, this approach can also be applied to complex medicinal compounds and natural products, offering rapid access to molecular complexity and late-stage functionalization of C(sp3)-rich drug candidates. Mechanistic experiments revealed that diborylmethyl Cu(I) species participated in both the photoredox process and the key C(sp3)-C(sp3) bond-forming step.

Synthesis of Secondary Boronates via Deaminative Cross-Coupling of Alkyl Nitroso Carbamates and Boronic Acids

A strategy for transition metal-free cross-coupling of alkyl nitroso-carbamates and boronic acids is reported. The N-nitroso carbamates are easily prepared from the corresponding amine in two simple steps. This method allows for the synthesis of a wide variety of secondary boronates, benzylic boronates and formal Csp3-Csp2 cross-coupling products under operationally simple conditions. Functional group tolerance is also demonstrated and applied in the modification of lysine to make non-canonical amino acids.

Visible Light-Mediated Late-Stage Thioetherification of Mercaptopurine Derivatives

We disclose herein a novel and general radical approach to alkylthiopurines, encompassing 4 types of thiopurines, as well as their corresponding ribosides. This strategy is achieved through visible light-mediated late-stage functionalization of the sulfur atoms of mercaptopurines. The in situ-generated disulfide was proposed as the pivotal neutral intermediate for this transformation. We present herein a novel photo-mediated homolytic C-S bond formation for the preparation of alkylthiopurines and alkylthiopurine nucleosides. Despite the presence of reactive sites for the Minisci reaction, chemoselective S-alkylation remained the predominant pathway. This method allows for the late-stage introduction of a broad spectrum of alkyl groups onto the sulfur atom of unprotective mercaptopurine derivatives, encompassing 2-, 6-, and 8-mercaptopurine rings. Organoborons serve as efficient and eco-friendly alkylating reagents, providing advantages in terms of readily availability, stability, and reduced toxicity. Further derivatization of the thioetherified nucleosides, together with anti-tumor assays, led to the discovery of potent anti-tumor agents with an IC50 value reaching 6.1 μM (Comp. 31 for Jurkat).

Dinuclear gold-catalyzed divergent dechlorinative radical borylation of gem-dichloroalkanes

The enormous and widespread use of organoboronic acids has prompted the development of innovative synthetic methodologies to meet the demands on structural diversity and functional group tolerance. The existing photoinduced defunctionalization radical borylation, typically focused on the conversion of one C-X bond (X= Br, I, or other leaving group) into only one C-B bond. Herein, we disclose a divergent radical dechloroborylation reaction enabled by dinuclear gold catalysis with visible light irradiation. A wide range of structurally diverse alkyl boronic, α-chloroboronic, and gem-diboronic esters can be synthesized in moderate to good yields (up to 92%). Its synthetic robustness is further demonstrated on a preparative scale and applied to late-stage diversification of complex molecules. The process hinges on a C-Cl bond relay activation in readily available gem-dichloroalkanes through inner-sphere electron transfer, overcoming the redox potential limits of unreactive alkyl chlorides.

Borylation of Stable C(sp3)-O Bonds of Alkyl Esters over Supported Au Catalysts

We report herein that supported gold catalysts efficiently promote the borylation of stable C(sp3)-O bonds of alkyl esters. The use of a disilane as an electron source and gold nanoparticles as a single-electron transfer catalyst is the key to generating alkyl radicals via the homolysis of stable C(sp3)-O bonds, thereby enabling cross-coupling between bis(pinacolato)diboron and linear and cyclic alkyl esters to afford the diverse alkyl boronates.

A General Method to Access Sterically Encumbered Geminal Bis(boronates) via Formal Umpolung Transformation of Terminal Diboron Compounds

General methods for the preparation of geminal bis(boronates) are of great interest due to their widespread applications in organic synthesis. While the terminal gem-diboron compounds are readily accessible, the construction of the sterically encumbered, internal analogues has remained a prominent challenge. Herein, we report a formal umpolung strategy to access these valuable building blocks. The readily available 1,1-diborylalkanes were first converted into the corresponding α-halogenated derivatives, which then serve as electrophilic components, undergoing a formal substitution with a diverse array of nucleophiles to form a series of C-C, C-O, C-S, and C-N bonds. This protocol features good tolerance to steric hindrance and a wide variety of functional groups and heterocycles. Notably, this strategy can also be extended to the synthesis of diaryl and terminal gem-diboron compounds, therefore providing a general approach to various types of geminal bis(boronates).

Cobalt-Catalyzed Electroreductive Alkylation of Unactivated Alkyl Chlorides with Conjugated Olefins

Reactions of unactivated alkyl chlorides under mild and sustainable conditions are rare compared to those of alkyl bromides or iodides. As a result, synthetic methods capable of modifying the vast chemical space of chloroalkane reagents, wastes, and materials are limited. We report the cobalt-catalyzed reductive addition of unactivated alkyl chlorides to conjugated alkenes. Co-catalyzed activation of alkyl chlorides is performed under electroreductive conditions, and the resulting reactions constitute formal alkyl-alkyl bond formation. In addition to developing an operationally simple methodology, detailed mechanistic studies provide insights into the elementary steps of a proposed catalytic cycle. In particular, we propose a switch in the mechanism of C-Cl bond activation from nucleophilic substitution to halogen atom abstraction, which is critical for efficiently generating alkyl radicals. These mechanistic insights were leveraged in designing ligands that enable couplings of primary, secondary, and tertiary alkyl chlorides.

Synthesis of Alkyl and Aryl Boronate Esters via CeO2-Catalyzed Borylation of Alkyl and Aryl Electrophiles Including Alkyl Chlorides

A recyclable protocol using a CeO2-nanorod catalyst for borylation of alkyl halides with B2pin2 (pin = OCMe2CMe2O) is reported. A wide range of synthetically useful alkyl boronate esters are readily obtained from primary and secondary alkyl electrophiles, including unactivated alkyl chlorides, demonstrating broad utility and functional group tolerance. Preliminary investigation revealed an involvement of in situ formed catalytically active boryl species. The catalyst can be reused for up to six runs without appreciable loss in activity. In addition, we have demonstrated the use of this recyclable catalyst for the borylation of aryl halides with B2pin2, providing valuable aryl boronate esters under neat conditions.

Photo-Triggered, Copper(II) Chloride-Catalyzed Radical Hydroalkylation and Hydrosilylation of Vinylboronic Esters To Access Alkylboronic Esters

Alkyl boronic acids and their derivatives constitute vital building blocks in organic synthesis and are important motifs identified in medicinal chemistry. Herein, we present a phototriggered, CuCl2-catalyzed radical hydroalkylation and hydrosilylation of vinylboronic esters to alkylboronic esters. This approach exhibits mild reaction conditions, utilization of easily accessible reagents, and scalability up to a gram scale. Further synthetic transformations of the hydrosilylation products and mechanistic studies are also demonstrated.

Metal-free C-H Borylation and Hydroboration of Indoles

The C-H borylation and hydroboration reactions have emerged as promising synthetic tools to construct organoboron compounds. Organoboron compounds of N-heterocycles, particularly indole derivatives, have found widespread application in a variety of fields. As a result, considerable advancement in the area of C-H borylation and hydroboration reactions of indoles was observed in the last few decades. Among the various synthetic methods applied, the metal-free approach has received special attention. This mini-review discusses the recent progress in the area of C-H borylation and hydroboration reactions of indoles under metal-free conditions, their scope, and brief mechanistic studies.

Nanobiocatalysts with inbuilt cofactor recycling for oxidoreductase catalysis in organic solvents

The major stumbling block in the implementation of oxidoreductase enzymes in continuous processes is their stark dependence on costly cofactors that are insoluble in organic solvents. We describe a chemical strategy that allows producing nanobiocatalysts, based on an oxidoreductase enzyme, that performs biocatalytic reactions in hydrophobic organic solvents without external cofactors. The chemical design relies on the use of a silica-based carrier nanoparticle, of which the porosity can be exploited to create an aqueous reservoir containing the cofactor. The nanoparticle core, possessing radial-centred pore channels, serves as a cofactor reservoir. It is further covered with a layer of reduced porosity. This layer serves as a support for the immobilisation of the selected enzyme yet allowing the diffusion of the cofactor from the nanoparticle core. The immobilised enzyme is, in turn, shielded by an organosilica layer of controlled thickness fully covering the enzyme. Such produced nanobiocatalysts are shown to catalyse the reduction of a series of relevant ketones into the corresponding secondary alcohols, also in a continuous flow fashion.

Iron-Catalyzed, Directed Benzylic Borylation

Herein, we describe an iron-catalyzed benzylic C-H borylation reaction. The reaction targets primary and secondary C(sp³)-H bonds to deliver high-value boronic esters under mild conditions with short (7-8 min) reaction times. Functional groups are well tolerated, and complete site selectivity is observed in the presence of multiple benzylic C-H bonds.

Direct deoxygenative borylation

Direct deoxygenative borylation is a highly enabling chemical transformation considering the attractive synthetic features of oxygenous feedstocks and organoboron compounds. Despite ranking among the synthetic ideality in different settings, such chemical space remained largely uncharted and underutilized until recent decades. This short review will summarize some key advances in the field of direct deoxy-borylation of alcohols, ethers, aldehydes, ketones, and carboxylic acids and organize these contributions based on substrate classes. In each representative, the general features, including reaction conditions, product scopes and mechanistic insights, will be highlighted and discussed.

Boryl Radicals Enabled a Three-Step Sequence to Assemble All-Carbon Quaternary Centers from Activated Trichloromethyl Groups

The construction of diversely substituted all-carbon quaternary centers has been a longstanding challenge in organic synthesis. Methods that add three alkyl substituents to a simple C(sp³) atom rely heavily on lengthy multiple processes, which usually involve several preactivation steps. Here, we describe a straightforward three-step sequence that uses a range of readily accessible activated trichloromethyl groups as the carbon source, the three C-Cl bonds of which are selectively functionalized to introduce three alkyl chains. In each step, only a single C-Cl bond was cleaved with the choice of an appropriate Lewis base-boryl radical as the promoter. A vast range of diversely substituted all-carbon quaternary centers could be accessed directly from these activated CCl₃ trichloromethyl groups or by simple derivatizations. The use of different alkene traps in each of the three steps enabled facile collections of a large library of products. The utility of this strategy was demonstrated by the synthesis of variants of two drug molecules, whose structures could be easily modulated by varying the alkene partner in each step. The results of kinetic and computational studies enabled the design of the three-step reaction and provided insights into the reaction mechanisms.

Modular Difunctionalization of Unactivated Alkenes through Bio-Inspired Radical Ligand Transfer Catalysis

Development of visible light-mediated atom transfer radical addition of haloalkanes onto unsaturated hydrocarbons has seen rapid growth in recent years. However, due to its radical chain propagation mechanism, diverse functionality other than the pre-existing (pseudo-)halide on the alkyl halide source cannot be incorporated into target molecules in a one-step, economic fashion. Inspired by the prominent reactivities shown by cytochrome P450 hydroxylase and non-heme iron-dependent oxygenases, we herein report the first modular, dual catalytic difunctionalization of unactivated alkenes via manganese-catalyzed radical ligand transfer (RLT). This RLT elementary step involves a coordinated nucleophile rebounding to a carbon-centered radical to form a new C-X bond in analogy to the radical rebound step in metalloenzymes. The protocol leverages the synergetic cooperation of both a photocatalyst and earth-abundant manganese complex to deliver two radical species in succession to minimally functionalized alkenes, enabling modular diversification of the radical intermediate by a high-valent manganese species capable of delivering various external nucleophiles. A broad scope (97 examples, including drugs/natural product motifs), mild conditions, and excellent chemoselectivity were shown for a variety of substrates and fluoroalkyl fragments. Mechanistic and kinetics studies provide insights into the radical nature of the dual catalytic transformation and support radical ligand transfer (RLT) as a new strategy to deliver diverse functionality selectively to carbon-centered radicals.

A Unified Synthetic Strategy to Introduce Heteroatoms via Electrochemical Functionalization of Alkyl Organoboron Reagents

Based on systematic electrochemical analysis, an integrated synthetic platform of C(sp³)-based organoboron compounds was established for the introduction of heteroatoms. The electrochemically mediated bond-forming strategy was shown to be highly effective for the functionalization of sp³-hybridized carbon atoms with significant steric hindrance. Moreover, virtually all the nonmetallic heteroatoms could be utilized as reaction partners using one unified protocol. The observed reactivity stems from the two consecutive single-electron oxidations of the substrate, which eventually generates an extremely reactive carbocation as the key intermediate. The detailed reaction profile could be elucidated through multifaceted electrochemical studies. Ultimately, a new dimension in the activation strategies for organoboron compounds was accomplished through the electrochemically driven reaction development.

Selective, Transition Metal-free 1,2-Diboration of Alkyl Halides, Tosylates, and Alcohols

Defunctionalization of readily available feedstocks to provide alkenes for the synthesis of multifunctional molecules represents an extremely useful process in organic synthesis. Herein, we describe a transition metal‐free, simple and efficient strategy to access alkyl 1,2‐bis(boronate esters) via regio‐ and diastereoselective diboration of secondary and tertiary alkyl halides (Br, Cl, I), tosylates, and alcohols. Control experiments demonstrated that the key to this high reactivity and selectivity is the addition of a combination of potassium iodide and N,N‐dimethylacetamide (DMA). The practicality and industrial potential of this transformation are demonstrated by its operational simplicity, wide functional group tolerance, and the late‐stage modification of complex molecules. From a drug discovery perspective, this synthetic method offers control of the position of diversification and diastereoselectivity in complex ring scaffolds, which would be especially useful in a lead optimization program.

The polymerization of carvacrol catalyzed by Mn-porphyrins: obtaining the desired product guided by the choice of solvent, oxidant, and catalyst

Less polar solvents could modulate the catalytic activity of Mn(iii)-porphyrins in carvacrol's oxidation leading to polymer/oligomer formation instead of thymoquinone formation.

Inorganometallics (Transition Metal-Metalloid Complexes) and Catalysis

While the formation and breaking of transition metal (TM)–carbon bonds plays a pivotal role in the catalysis of organic compounds, the reactivity of inorganometallic species, that is, those involving the transition metal (TM)–metalloid (E) bond, is of key importance in most conversions of metalloid derivatives catalyzed by TM complexes. This Review presents the background of inorganometallic catalysis and its development over the last 15 years. The results of mechanistic studies presented in the Review are related to the occurrence of TM–E and TM–H compounds as reactive intermediates in the catalytic transformations of selected metalloids (E = B, Si, Ge, Sn, As, Sb, or Te). The Review illustrates the significance of inorganometallics in catalysis of the following processes: addition of metalloid–hydrogen and metalloid–metalloid bonds to unsaturated compounds; activation and functionalization of C–H bonds and C–X bonds with hydrometalloids and bismetalloids; activation and functionalization of C–H bonds with vinylmetalloids, metalloid halides, and sulfonates; and dehydrocoupling of hydrometalloids. This first Review on inorganometallic catalysis sums up the developments in the catalytic methods for the synthesis of organometalloid compounds and their applications in advanced organic synthesis as a part of tandem reactions.

First-Row d-Block Element-Catalyzed Carbon-Boron Bond Formation and Related Processes

Organoboron reagents represent a unique class of compounds because of their utility in modern synthetic organic chemistry, often affording unprecedented reactivity. The transformation of the carbon-boron bond into a carbon-X (X = C, N, and O) bond in a stereocontrolled fashion has become invaluable in medicinal chemistry, agrochemistry, and natural products chemistry as well as materials science. Over the past decade, first-row d-block transition metals have become increasingly widely used as catalysts for the formation of a carbon-boron bond, a transformation traditionally catalyzed by expensive precious metals. This recent focus on alternative transition metals has enabled growth in fundamental methods in organoboron chemistry. This review surveys the current state-of-the-art in the use of first-row d-block element-based catalysts for the formation of carbon-boron bonds.

Saturated Boronic Acids, Boronates, and Trifluoroborates: An Update on Their Synthetic and Medicinal Chemistry

This review discusses recent advances in the chemistry of saturated boronic acids, boronates, and trifluoroborates. Applications of the title compounds in the design of boron-containing drugs are surveyed, with special emphasis on α-amino boronic derivatives. A general overview of saturated boronic compounds as modern tools to construct C(sp³ )-C and C(sp³ )-heteroatom bonds is given, including recent developments in the Suzuki-Miyaura and Chan-Lam cross-couplings, single-electron-transfer processes including metallo- and organocatalytic photoredox reactions, and transformations of boron "ate" complexes. Finally, an attempt to summarize the current state of the art in the synthesis of saturated boronic acids, boronates, and trifluoroborates is made, with a brief mention of the "classical" methods (transmetallation of organolithium/magnesium reagents with boron species, anti-Markovnikov hydroboration of alkenes, and the modification of alkenyl boron compounds) and a special focus on recent methodologies (boronation of alkyl (pseudo)halides, derivatives of carboxylic acids, alcohols, and primary amines, boronative C-H activation, novel approaches to alkene hydroboration, and 1,2-metallate-type rearrangements).

Base-Mediated Radical Borylation of Alkyl Sulfones

A practical and direct method was developed for the production of versatile alkylboronic esters via transition metal-free borylation of primary and secondary alkyl sulfones. The key to the success of the strategy is the use of bis(neopentyl glycolato) diboron (B 2 neop 2 ), with a stoichiometric amount of base as a promoter. The practicality and industrial potential of this protocol are highlighted by its wide functional group tolerance, the late-stage modification of complex compounds, no need for further transesterification, and operational simplicity. Radical clock, radical trap experiments, and EPR studies were conducted which show that the borylation process involves radical intermediates.

Unactivated Alkyl Chloride Reactivity in Excited-State Palladium Catalysis

Excited-state palladium catalysis is an efficient process for the alkylation of diverse organic compounds via the generation of alkyl radicals from alkyl bromides and iodides. However, the generation of alkyl radicals from more stable alkyl chlorides remains challenging. Herein, we demonstrate the excited-state palladium-catalyzed synthesis of oxindoles and isoquinolinediones via alkylation/annulation reaction by overcoming inherent limitations associated with unactivated C(sp³)-Cl bond activation at room temperature.

Electrochemical borylation of carboxylic acids

A simple electrochemically mediated method for the conversion of alkyl carboxylic acids to their borylated congeners is presented. This protocol features an undivided cell setup with inexpensive carbon-based electrodes and exhibits a broad substrate scope and scalability in both flow and batch reactors. The use of this method in challenging contexts is exemplified with a modular formal synthesis of jawsamycin, a natural product harboring five cyclopropane rings.

Direct deoxygenative borylation of carboxylic acids

Carboxylic acids are readily available, structurally diverse and shelf-stable; therefore, converting them to the isoelectronic boronic acids, which play pivotal roles in different settings, would be highly enabling. In contrast to the well-recognised decarboxylative borylation, the chemical space of carboxylic-to-boronic acid transformation via deoxygenation remains underexplored due to the thermodynamic and kinetic inertness of carboxylic C-O bonds. Herein, we report a deoxygenative borylation reaction of free carboxylic acids or their sodium salts to synthesise alkylboronates under metal-free conditions. Promoted by a uniquely Lewis acidic and strongly reducing diboron reagent, bis(catecholato)diboron (B2cat2), a library of aromatic carboxylic acids are converted to the benzylboronates. By leveraging the same borylative manifold, a facile triboration process with aliphatic carboxylic acids is also realised, diversifying the pool of available 1,1,2-alkyl(trisboronates) that were otherwise difficult to access. Detailed mechanistic studies reveal a stepwise C-O cleavage profile, which could inspire and encourage future endeavours on more appealing reductive functionalisation of oxygenated feedstocks.

Electrochemical Borylation of Alkyl Halides: Fast, Scalable Access to Alkyl Boronic Esters

Herein, a fast, scalable, and transition-metal-free borylation of alkyl halides (X = I, Br, Cl) enabled by electroreduction is reported. This process provides an efficient and practical access to primary, secondary, and tertiary boronic esters at a high current. More than 70 examples, including the late-stage borylation of natural products and drug derivatives, are furnished at room temperature, thereby demonstrating the broad utility and functional-group tolerance of this protocol. Mechanistic studies disclosed that B₂cat₂ serves as both a reagent and a cathodic mediator, enabling electroreduction of difficult-to-reduce alkyl bromides or chlorides at a low potential.

Generation of non-stabilized alkyl radicals from thianthrenium salts for C-B and C-C bond formation

Sulfonium salts bearing a positively charged sulfur atom with three organic substituents have intrigued chemists for more than a century for their unusual structures and high chemical reactivity. These compounds are known to undergo facile single-electron reduction to emerge as a valuable and alternative source of aryl radicals for organic synthesis. However, the generation of non-stabilized alkyl radicals from sulfonium salts has been a challenge for several decades. Here we report the treatment of S-(alkyl) thianthrenium salts to generate non-stabilized alkyl radicals as key intermediates granting the controlled and selective outcome of the ensuing reactions under mild photoredox conditions. The value of these reagents has been demonstrated through the efficient construction of alkylboronates and other transformations, including heteroarylation, alkylation, alkenylation, and alkynylation. The developed method is practical, and provides the opportunity to convert C-OH bond to C-B and C-C bonds.

Transition metal- and light-free radical borylation of alkyl bromides and iodides using silane

We report operationally simple and neutral conditions for borylation of alkyl bromides and iodides to alkyl boronic esters under transition metal- and light-free conditions. A series of substrates with a wide range of functional groups were effectively transformed into the borylation products in moderate to good yields. Mechanistic studies, including radical clock experiments and DFT calculations, gave detailed insight into the radical borylation process.

Advances in transition metal-free deborylative transformations of gem-diborylalkanes

Carbanions serve as key intermediates in a variety of chemical transformations. Particularly, α-borylcarbanions have received considerable attention in recent years because of their peculiar properties, including the ability of boron atom resonance to stabilise the adjacent negatively charged carbon atom. This feature article summarises recent progress in the synthetic utilisation of α-borylcarbanions, including carbon-carbon bond formation with alkyl halides, alkenes, N-heteroarenes, and carbonyls. Carbon-boron bond formation in organohalides mediated by α-borylcarbanions is also summarised.

Progress in the medicinal chemistry of organoboron compounds

The review aims to draw attention to the latest advances in the organoboron chemistry and therapeutic use of organoboron compounds. The synthetic strategies towards boron-containing compounds with proven in vitro and/or in vivo biological activities, including derivatives of boronic acids, benzoxaboroles, benzoxaborines and benzodiazaborines, are summarized. Approaches to the synthesis of hybrid structures containing an organoboron moiety as one of the pharmacophores are considered, and the effect of this modification on the pharmacological activity of the initial molecules is analyzed. On the basis of analysis of the published data, the most promising areas of research in the field of organoboron compounds are identified, including the latest methods of synthesis, modification and design of effective therapeutic agents.

The bibliography includes 246 references.

Practical and Selective sp3 C-H Bond Chlorination via Aminium Radicals

The introduction of chlorine atoms into organic molecules is fundamental to the manufacture of industrial chemicals, the elaboration of advanced synthetic intermediates and also the fine-tuning of physicochemical and biological properties of drugs, agrochemicals and polymers. We report here a general and practical photochemical strategy enabling the site-selective chlorination of sp3 C-H bonds. This process exploits the ability of protonated N-chloroamines to serve as aminium radical precursors and also radical chlorinating agents. Upon photochemical initiation, an efficient radical-chain propagation is established allowing the functionalization of a broad range of substrates due to the large number of compatible functionalities. The ability to synergistically maximize both polar and steric effects in the H-atom transfer transition state through appropriate selection of the aminium radical has provided the highest known selectivity in radical sp3 C-H chlorination.

Iron-Based Catalyst for Borylation of Unactivated Alkyl Halides without Using Highly Basic Organometallic Reagents

The mild borylation of alkyl bromides and chlorides with bis(neopentylglycolato)diborane (B₂neop₂) mediated by iron-bis amide is described. The reaction proceeds with a broad substrate scope and good functional group compatibility. Moreover, sufficient catalytic activity was obtained for primary and secondary alkyl halides. Mechanistic studies indicate that the reaction proceeds through a radical pathway.

Samarium(iii) catalyzed synthesis of alkenylboron compounds via hydroboration of alkynes

The homoleptic lanthanide complex Sm[N(TMS)₂]₃ is an efficient rare-earth catalyst for the hydroboration of alkynes to the corresponding alkenylboron compounds.

Practical and Modular Construction of C(sp3)-Rich Alkyl Boron Compounds

Alkyl boronic acids and esters play an important role in the synthesis of C(sp³)-rich medicines, agrochemicals, and material chemistry. This work describes a new type of transition-metal-free mediated transformation to enable the construction of C(sp³)-rich and sterically hindered alkyl boron reagents in a practical and modular manner. The broad generality and functional group tolerance of this method is extensively examined through a variety of substrates, including synthesis and late-stage functionalization of scaffolds relevant to medicinal chemistry. The strategic significance of this approach, with alkyl boronic acids as linchpins, is demonstrated through various downstream functionalizations of the alkyl boron compounds. This two-step concurrent cross-coupling approach, resembling formal and flexible alkyl-alkyl couplings, provides a general entry to synthetically challenging high Fsp³-containing drug-like scaffolds.

Electroreductive Carbofunctionalization of Alkenes with Alkyl Bromides via a Radical-Polar Crossover Mechanism

Electrochemistry grants direct access to reactive intermediates (radicals and ions) in a controlled fashion toward selective organic transformations. This feature has been demonstrated in a variety of alkene functionalization reactions, most of which proceed via an anodic oxidation pathway. In this report, we further expand the scope of electrochemistry to the reductive functionalization of alkenes. In particular, the strategic choice of reagents and reaction conditions enabled a radical-polar crossover pathway wherein two distinct electrophiles can be added across an alkene in a highly chemo- and regioselective fashion. Specifically, we used this strategy in the intermolecular carboformylation, anti-Markovnikov hydroalkylation, and carbocarboxylation of alkenes-reactions with rare precedents in the literature-by means of the electroreductive generation of alkyl radical and carbanion intermediates. These reactions employ readily available starting materials (alkyl halides, alkenes, etc.) and simple, transition-metal-free conditions and display broad substrate scope and good tolerance of functional groups. A uniform protocol can be used to achieve all three transformations by simply altering the reaction medium. This development provides a new avenue for constructing Csp3-Csp3 bonds.

Decarboxylative Borylation of Stabilized and Activated Carbon Radicals

Redox-active esters (RAEs) as active radical precursors have been extensively studied for C-B bond formations. However, the analogous transformations of stabilized radicals from the corresponding acid precursors remain challenging owing to the strong preference towards single-electron oxidation to the stable carbocations. This work describes a general strategy for rapid access to various aliphatic and aromatic boronic esters by mild photoinduced decarboxylative borylation. Both aryl and alkyl radicals could be generated from the leaving group-assisted N-hydroxybenzimidoyl chloride esters, even α-CF₃ substituted substrates could be activated for further elaboration.

Nickel-Catalyzed Cyanation of Unactivated Alkyl Sulfonates with Zn(CN)2

Cyanation of unactivated primary and secondary alkyl mesylates with Zn(CN)₂ catalyzed by nickel has been developed. The reaction provides an efficient route for the synthesis of alkyl nitriles with wide substrate scope, good functional group tolerance, and compatibility with heterocyclic compounds. Mechanistic studies indicate that alkyl iodide generated in situ serves as the reactive intermediate and the gradual release of alkyl iodide is crucial for the success of the reaction.