Nickel-Catalyzed, Reductive C(sp3 )-Si Cross-Coupling of α-Cyano Alkyl Electrophiles and Chlorosilanes

A general copper catalytic system for cross-coupling of aryl iodides with chlorosilanes under reductive conditions

Directly forged linkages between commercially available electrophiles are powerful synthetic tools for chemical bond construction. This strategy could eliminate the pre-synthesis of reactive organometallic reagents in couplings with electrophiles, thus providing efficient, easily-handled and step-economical routes in organic synthesis. Reported approaches are mainly utilized in carbon-carbon bond formations, whereas carbon-silicon bond construction employing halosilanes with carbon electrophiles is still underexplored. Copper-catalysis has made significant achievements in the coupling reactions of carbon halides in the past decades, yet silyl electrophiles are seldom involved in these systems. Herein, we establish a practical, efficient, and economical copper system catalyzing the construction of Csp2-Si bonds by directly using aryl/vinyl iodides with various chlorosilanes under ligand-free and reductive conditions, thus providing a general platform for organosilane synthesis with broad scope, high functionality tolerance, scalability and operational simplicity. An unprecedented mechanistic motif was obtained to suggest that the copper catalyst was likely to lower the energy barrier in the reaction of the in situ generated arylzinc with halosilanes, rather than proceed via the traditional metal-aryl species.

One-Pot Sequential Alcohol Activation and Nickel-Catalyzed Cross-Electrophile Coupling with Chlorosilanes

A formal deoxygenative silylation of primary alcohols is reported. The one-pot procedure consists of an in situ bromination of the alcohol and a subsequent nickel-catalyzed cross-electrophile coupling of the formed alkyl bromide and various vinyl-substituted chlorosilanes. The key to success is the compatibility of the nickel catalysis as well as the chlorosilane electrophile with the byproducts of the preceding bromination step, especially with triphenylphosphine oxide likely acting as a weak ligand for the excess nickel catalyst used.

Fe/Mn-Synergistic Promoted C(sp3)-Bi Cross-Coupling of Alkyl Chlorides with Chlorobismuthanes to Access Air-Stable Alkylbismuthanes

Alkylating bismuthanes containing C(sp3)-Bi bonds were first disclosed as early as 1850, but their development remains severely limited, especially the synthetic method. Herein, we developed the first Fe/Mn-synergistic promoted C(sp3)-Bi cross-coupling of alkyl halides with chlorobismuthanes, which can access alkylbismuthanes in satisfactory yields with various functional group compatibility (cyano, ester, aldehyde, and amide). Inactivated alkyl chlorides/bromides, as well as cyclic and acyclic alkyl electrophiles, smoothly yielded the corresponding products. Gram-scale synthesis and late-stage modification of drug molecules were also conducted. The synthesized alkylbismuthanes also could be alkylation reagents toward C(sp3)-C(sp2), C(sp3)-Se, C(sp3)-S, and C(sp3)-N bonds.

Electrochemical Synergistic Ni/Co-Catalyzed Carbonylative Cross-Electrophile Coupling of Aryl and Alkyl Halides with CO

Accessing unsymmetric ketones and achieving their carbon isotope labeling are crucial yet challenging tasks in both synthetic and medicinal chemistry. We report here an efficient electrochemical nickel-/cobalt-catalyzed carbonylative cross-electrophile coupling reaction. This method allows for the modular synthesis of a library of unsymmetric ketones from simple building blocks, including aryl halides, alkyl halides, and gaseous CO. The simultaneous use of nickel and cobalt salts as concerted catalysts ensures the high efficiency of this three-component carbonylative coupling. Furthermore, electrochemical reduction avoids the use of stoichiometric reductants, making this protocol more sustainable and attractive. The broad substrate scope and late-stage 13C isotope labeling of complex molecules derived from biologically active compounds highlight the practicality of this method.

Collaborative Reduction-Induced Nickel-Catalytic Selective C-S Coupling of Aryl Di/Trithiosulfonates with Aryl Halides

Metal-catalytic conversion of polysulfide reagents is a major challenge in organic synthesis due to its challenging activation modes of multiple S-S bonds. The utilization of aryl di- and trithiosulfonates in nickel-catalyzed reductive coupling with aryl halides has been unexplored. Herein, we unprecedentedly describe PPh3 and Zn-collaborative reduction-induced nickel-catalytic selective C-S coupling of aryl di/trithiosulfonates with aryl halides to access sulfides over common disulfides or trisulfides. Diverse mechanistic studies indicate that the key design of such a reaction could be attributed to the employment of PPh3 and MgCl2, which collaborate with Zn for the improved reduction potential that enables selective reductive cleavage of PhSO2(S)naryl (n = 2, 3) to electrophilic sulfur species for reductive sulfuration in a controllable fashion.

Cross-Electrophile Coupling: Principles, Methods, and Applications in Synthesis

Cross-electrophile coupling (XEC), defined by us as the cross-coupling of two different σ-electrophiles that is driven by catalyst reduction, has seen rapid progression in recent years. As such, this review aims to summarize the field from its beginnings up until mid-2023 and to provide comprehensive coverage on synthetic methods and current state of mechanistic understanding. Chapters are split by type of bond formed, which include C(sp3)-C(sp3), C(sp2)-C(sp2), C(sp2)-C(sp3), and C(sp2)-C(sp) bond formation. Additional chapters include alkene difunctionalization, alkyne difunctionalization, and formation of carbon-heteroatom bonds. Each chapter is generally organized with an initial summary of mechanisms followed by detailed figures and notes on methodological developments and ending with application notes in synthesis. While XEC is becoming an increasingly utilized approach in synthesis, its early stage of development means that optimal catalysts, ligands, additives, and reductants are still in flux. This review has collected data on these and various other aspects of the reactions to capture the state of the field. Finally, the data collected on the papers in this review is offered as Supporting Information for readers.

Nickel-catalyzed stereospecific reductive cross-coupling of vinyl chlorosilanes with axially chiral biaryl electrophiles

Enantioenriched organosilanes are important chiral molecules in materials science and organic synthesis. The synthesis of axially chiral organosilanes is particularly significant in terms of applications. Herein, we report a Ni-catalyzed reductive cross-electrophile coupling of vinyl chlorosilanes with sterically hindered chiral biaryl electrophiles for the synthesis of atropisomeric biaryl organosilanes. Various enantioenriched axially chiral vinylsilanes are accessible in high efficiency under mild conditions. The synthetic transformations and applications of new chiral silicon-containing alkene ligands are demonstrated.

Nickel-Catalyzed Reductive Protocol to Access Silacyclobutanes with Unprecedented Functional Group Tolerance

While significant progress has been made in the area of transition metal-catalyzed ring-opening and formal cycloaddition reactions of 1,1-disubstituted silacyclobutanes (SCBs), synthesizing these SCBs-particularly those bearing additional functional groups-continues to present synthetic challenges. In this context, we present a novel Ni-catalyzed reductive coupling reaction that combines 1-chloro-substituted silacyclobutanes with aryl or vinyl halides and pseudohalides, thereby obviating the need for organometallic reagents. This method facilitates the generation of 1,1-disubstituted silacyclobutanes with a remarkable tolerance for various functional groups. This approach serves as a complementary and more step-economical alternative to the commonly used yet moisture- and air-sensitive nucleophilic substitution reactions involving Grignard or lithium reagents. Our initial mechanistic studies indicate that this reaction is initiated by oxidative cleavage of the Si-Cl bond in 1-chlorosilacyclobutanes, which represents a distinct mechanism from the previously documented reductive coupling processes involving carbon electrophiles and chlorosilanes.

Nickel-Catalyzed Desulfurative Cross-Coupling of Aryl Iodides with Heteroaromatic Thioethers via C-S Bond Cleavage

Herein, we present a Ni-catalyzed direct cross-coupling of heteroaromatic thioethers with aryl iodides via selective C(sp2)-S bond cleavage under reductive conditions, thereby providing various biaryl frameworks with high efficiency. Mechanistic studies suggested Mo(CO)6 played a crucial role in facilitating the activation of the C(sp2)-S bond. This protocol demonstrated a wide substrate scope, operational simplicity, and good functional group compatibility. Furthermore, the utility of this reaction was highlighted by facile scale-up and sequential modification of heteroaryl frameworks.

Nickel-catalyzed selective disulfide formation by reductive cross-coupling of thiosulfonates

Developing innovative methodologies for disulfide preparation is of importance in contemporary organic chemistry. Despite significant advancements in nickel-catalyzed reductive cross-coupling reactions for forming carbon-carbon and carbon-heteroatom bonds, the synthesis of S-S bonds remains a considerable challenge. In this context, we present a novel approach utilizing nickel catalysts for the reductive cross-coupling of thiosulfonates. This method operates under mild conditions, offering a convenient and efficient pathway to synthesize a wide range of both symmetrical and unsymmetrical disulfides from readily available, bench-stable thiosulfonates with exceptional selectivity. Notably, this approach is highly versatile, allowing for the late-stage modification of pharmaceuticals and the preparation of various targeted compounds. A comprehensive mechanistic investigation has been conducted to substantiate the proposed hypothesis.

Electroreductive Cross-Coupling between Aromatic Aldehydes and Chlorosilanes Enabling the Synthesis of α-Silyl Alcohols

α-Silyl alcohols are powerful structural motifs for pharmaceutical chemistry, materials chemistry, and organic synthesis. The limitations of current synthetic techniques encompass a requirement for difficult-to-obtain silyl precursors, noble-metal catalysts, and narrow substrate scopes. Here, we developed a general synthetic method for α-silyl alcohols through electroreductive cross-coupling of aldehydes and chlorosilane. This method features easily available reagents, mild conditions, and a wide substrate scope. The establishment of this protocol will provide an alternative for access to α-silyl alcohols.

Aliphatic Hydrosilanes via Nickel-Catalyzed Reductive Csp3-Si Coupling of Primary Alkyl Bromides and Chlorohydrosilanes

The reductive C-Si coupling of chlorosilanes offers efficient access to organosilanes, but its potential for constructing aliphatic ones remains largely unexplored. This manuscript presents a nickel-catalyzed Csp3-Si coupling reaction of unactivated alkyl-Br and R2Si(H)Cl. This work establishes a new approach for synthesizing highly functionalized aliphatic hydrosilanes from readily available chemical feedstocks. The reaction is easily scalable and can accommodate various functional groups, including carboxylic acids, which are usually incompatible with basic conditions.

From Quaternary Carbon to Tertiary C(sp3)-Si and C(sp3)-Ge Bonds: Decyanative Coupling of Malononitriles with Chlorosilanes and Chlorogermanes Enabled by Ni/Ti Dual Catalysis

Transition-metal-catalyzed C-Si/Ge cross-coupling offers promising avenues for the synthesis of organosilanes/organogermanes, yet it is fraught with long-standing challenges. A Ni/Ti-catalyzed strategy is reported here, allowing the use of disubstituted malononitriles as tertiary C(sp3) coupling partners to couple with chlorosilanes and chlorogermanes, respectively. This method enables the catalytic cleavage of the C(sp3)-CN bond of the quaternary carbon followed by the formation of C(sp3)-Si/C(sp3)-Ge bonds from ubiquitously available starting materials. The efficiency and generality are showcased by a broad scope for both of the coupling partners, therefore holding the potential to synthesize structurally diverse quaternary organosilanes and organogermanes that were difficult to access previously.

Cobalt-catalyzed cross-electrophile coupling of alkynyl sulfides with unactivated chlorosilanes

Herein, we disclose a highly efficient cobalt-catalyzed cross-electrophile alkynylation of a broad range of unactivated chlorosilanes with alkynyl sulfides as a stable and practical alkynyl electrophiles. Strategically, employing easily synthesized alkynyl sulfides as alkynyl precursors allows access to various alkynylsilanes in good to excellent yields. Notably, this method avoids the utilization of strong bases, noble metal catalysts, high temperature and forcing reaction conditions, thus presenting apparent advantages, such as broad substrate scope (72 examples, up to 97% yield), high Csp-S chemo-selectivity and excellent functional group compatibility (Ar-X, X = Cl, Br, I, OTf, OTs). Moreover, the utilities of this method are also illustrated by downstream transformations and late-stage modification of structurally complex natural products and pharmaceuticals. Mechanistic studies elucidated that the cobalt catalyst initially reacted with alkynyl sulfides, and the activation of chlorosilanes occurred via an SN2 process instead of a radical pathway.

Enantioselective and Regiodivergent Synthesis of Propargyl- and Allenylsilanes through Catalytic Propargylic C-H Deprotonation

We report a highly enantioselective intermolecular C-H bond silylation catalyzed by a phosphoramidite-ligated iridium catalyst. Under reagent-controlled protocols, propargylsilanes resulting from C(sp3)-H functionalization, as well the regioisomeric and synthetically versatile allenylsilanes, could be obtained with excellent levels of enantioselectivity and good to excellent control of propargyl/allenyl selectivity. In the case of unsymmetrical dialkyl acetylenes, good to excellent selectivity for functionalization at the less-hindered site was also observed. A variety of electrophilic silyl sources (R3SiOTf and R3SiNTf2), either commercial or in situ-generated, were used as the silylation reagents, and a broad range of simple and functionalized alkynes, including aryl alkyl acetylenes, dialkyl acetylenes, 1,3-enynes, and drug derivatives were successfully employed as substrates. Detailed mechanistic experiments and DFT calculations suggest that an η3-propargyl/allenyl Ir intermediate is generated upon π-complexation-assisted deprotonation and undergoes outer-sphere attack by the electrophilic silylating reagent to give propargylic silanes, with the latter step identified as the enantiodetermining step.

Achieving Nickel-Catalyzed Reductive C(sp2)-B Coupling of Bromoboranes via Reversing the Activation Sequence

Transition metal-catalyzed reductive cross-couplings to build C-C/Si bonds have been developed, but the reductive cross-coupling to create the C(sp2)-B bond has not been explored. Herein, we describe a nickel-catalyzed reductive cross-coupling between aryl halides and bromoboranes to construct a C(sp2)-B bond. This protocol offers a convenient approach for the synthesis of a wide range of aryl boronate esters, using readily available starting materials. Mechanistic studies indicate that the key to the success of the reaction is the activation of the B-Br bond of bromoboranes with a Lewis base such as 2-MeO-py. The activation ensures that bromoboranes will react with the active nickel(I) catalyst prior to aryl halides, which is different from the sequence of the general nickel-catalyzed reductive C(sp2)-C/Si cross-coupling, where the oxidative addition of an aryl halide proceeds first. Notably, this approach minimizes the production of undesired homocoupling byproduct without the requirement of excessive quantities of either substrate.

Nickel-Catalyzed Reductive Cross-Coupling of Propargylic Acetates with Chloro(vinyl)silanes: Access to Silylallenes

Because of their various reactivities, propargyl acetates are refined chemical intermediates that are extensively applied in pharmaceutical synthesis. Currently, reactions between propargyl acetates and chlorosilanes may be the most effective method for synthesizing silylallenes. Nevertheless, owing to the adaptability and selectivity of substrates, transition metal catalysis is difficult to achieve. Herein, nickel-catalyzed reductive cross-coupling reactions between propargyl acetates and substituted vinyl chlorosilanes for the synthesis of tetrasubstituted silylallenes are described. Therein, metallic zinc is a crucial reductant that effectively enables two electrophilic reagents to selectively construct C(sp2)-Si bonds. Additionally, a Ni-catalyzed reductive mechanism involving a radical process is proposed on the basis of deuteration-labeled experiments.

Nickel-Catalyzed C(sp3)-Sb Coupling of Chlorostibines with Unactivated Alkyl Chlorides and In Vitro Anticancer Activity of Products

In this study, we present a nickel-catalyzed reductive C(sp3)-Sb coupling of unactivated alkyl chlorides with chlorostibines. This approach is highly versatile, tolerating various functional groups such as acetal, alkene, nitrile, amine, ester, silyl ether, thioether, and various heterocyclic compounds. Notably, the late-stage modification of bioactive molecules and the satisfactory anticancer activity against cancerous MDA-MB-231 also demonstrate the potential application.

Ligand-modulated nickel-catalyzed regioselective silylalkylation of alkenes

Organosilicon compounds have shown tremendous potential in drug discovery and their synthesis stimulates wide interest. Multicomponent cross-coupling of alkenes with silicon reagents is used to yield complex silicon-containing compounds from readily accessible feedstock chemicals but the reaction with simple alkenes remains challenging. Here, we report a regioselective silylalkylation of simple alkenes, which is enabled by using a stable Ni(II) salt and an inexpensive trans-1,2-diaminocyclohexane ligand as a catalyst. Remarkably, this reaction can tolerate a broad range of olefins bearing various functional groups, including alcohol, ester, amides and ethers, thus it allows for the efficient and selective assembly of a diverse range of bifunctional organosilicon building blocks from terminal alkenes, alkyl halides and the Suginome reagent. Moreover, an expedient synthetic route toward alpha-Lipoic acid has been developed by this methodology.

Cobalt-Promoted Electroreductive Cross-Coupling of Prop-2-yn-1-yl Acetates with Chloro(vinyl)silanes

An electroreductive cross-coupling of prop-2-yn-1-yl acetates with chloro(vinyl)silanes for producing tetrasubstituted silylallenes is developed. The method enables the formation of a new C─Si bond through the cathodic reduction formation of the silyl radical, radical addition across the C≡C bond, the alkenyl anion intermediate formation, and deacetoxylation and represents a mild, practical route to the synthesis of silylallenes. Mechanistic studies reveal that CoCl2 acts as the mediator to promote the formation of the alkenyl anion intermediate via electron transfer.

Facile preparation of organosilanes from benzylboronates and gem-diborylalkanes mediated by KOtBu

Methods to efficiently synthesize organosilanes are valuable in the fields of synthetic chemistry and materials science. During the past decades, boron conversion has become a generic and powerful approach for constructing carbon-carbon and other carbon-heteroatom bonds, but its potential application in forming carbon-silicon remains unexplored. Herein, we describe an alkoxide base-promoted deborylative silylation of benzylic organoboronates, geminal bis(boronates) or alkyltriboronates, allowing for straightforward access to synthetically valuable organosilanes. This selective deborylative methodology exhibits operational simplicity, broad substrate scope, excellent functional group compatibility and convenient scalability, providing an effective and complementary platform for the generation of diversified benzyl silanes and silylboronates. Detailed experimental results and calculated studies revealed an unusual mechanistic feature of this C-Si bond formation.

Nickel-Catalyzed Reductive [4 + 1] Sila-Cycloaddition of 1,3-Dienes with Dichlorosilanes

Transition-metal-catalyzed sila-cycloaddition has been a promising tool for accessing silacarbocycle derivatives, but the approach has been limited to a selection of well-defined sila-synthons. Herein, we demonstrate the potential of chlorosilanes, which are industrial feedstock chemicals, for this type of reaction under reductive nickel catalysis. This work extends the scope of reductive coupling from carbocycle to silacarbocycle synthesis and from single C-Si bond formation to sila-cycloaddition reactions. The reaction proceeds under mild conditions and shows good substrate scope and functionality tolerance, and it offers new access to silacyclopent-3-enes and spiro silacarbocycles. The optical properties of several spiro dithienosiloles as well as structural variations of the products are demonstrated.

Nonbasic Synthesis of Thioethers via Nickel-Catalyzed Reductive Thiolation Utilizing NBS-Like N-Thioimides as Electrophilic Sulfur Donors

The nonbasic synthesis of unsymmetrical thioethers via nickel-catalyzed reductive thiolation between aryl(hetero) iodides and N-thioimides is illustrated. N-Bromosuccinimide (NBS)-like N-thioimides were found quite reactive toward thiolation with carbon electrophiles, and a series of structurally varied thioethers were successfully prepared under mild reaction conditions. The transformation was featured with the new application of the NBS-like reagents, good functional group tolerance, and late-stage modification of biologically active scaffolds, thus providing an expeditious and efficient platform to construct polyfunctional thioethers.

Transition-Metal-Catalyzed Cross-Coupling of Chlorosilanes

Chlorosilanes are the most accessible feedstock chemical in the organosilicon world. Cross-coupling involving chlorosilanes by transition metal catalysis offers a promising way for the production of organosilanes, which play essential roles in many important research areas, including agriculture, medicinal chemistry, and material science. This chemistry is firstly realized by coupling chlorosilanes with organometallic species and then extended to the silyl-Heck reaction with alkenes. Very recently, the cross-electrophile coupling of chlorosilanes has also been established. In this review, we summarize the progress of this chemistry.

1 Introduction

2 Cross-Coupling of Chlorosilanes with Organometallic Reagents

3 The Silyl-Heck Reaction of Chlorosilanes and Alkenes

4 Reductive Cross-Coupling of Chlorosilanes with Electrophiles

5 Summary and Outlook

Diverse Alkyl-Silyl Cross-Coupling via Homolysis of Unactivated C(sp3)-O Bonds with the Cooperation of Gold Nanoparticles and Amphoteric Zirconium Oxides

Since C(sp³)-O bonds are a ubiquitous chemical motif in both natural and artificial organic molecules, the universal transformation of C(sp³)-O bonds will be a key technology for achieving carbon neutrality. We report herein that gold nanoparticles supported on amphoteric metal oxides, namely, ZrO₂, efficiently generated alkyl radicals via homolysis of unactivated C(sp³)-O bonds, which consequently promoted C(sp³)-Si bond formation to give diverse organosilicon compounds. A wide array of esters and ethers, which are either commercially available or easily synthesized from alcohols participated in the heterogeneous gold-catalyzed silylation by disilanes to give diverse alkyl-, allyl-, benzyl-, and allenyl silanes in high yields. In addition, this novel reaction technology for C(sp³)-O bond transformation could be applied to the upcycling of polyesters, i.e., the degradation of polyesters and the synthesis of organosilanes were realized concurrently by the unique catalysis of supported gold nanoparticles. Mechanistic studies corroborated the notion that the generation of alkyl radicals is involved in C(sp³)-Si coupling and the cooperation of gold and an acid-base pair on ZrO₂ is responsible for the homolysis of stable C(sp³)-O bonds. The high reusability and air tolerance of the heterogeneous gold catalysts as well as a simple, scalable, and green reaction system enabled the practical synthesis of diverse organosilicon compounds.

Nickel-Catalyzed Reductive Coupling of Chlorosilanes

Organosilanes play essential roles in many important research areas. The use of readily available chlorosilanes to catalytically access these compounds is synthetically appealing but remains a long-standing challenge. Nickel-catalyzed reductive cross-coupling reaction has recently emerged as a promising protocol to arrive at this goal. This strategy allows the chlorosilanes to be coupled with various carbon electrophiles under mild conditions. These reactions afford organosilanes with improved molecular diversity, structural complexity, and functional group compatibility. This Concept article summarizes the recent advance on nickel-catalyzed reductive C-Si couplings of chlorosilanes.

Nickel-Catalyzed Cross-Electrophile 1,2-Silyl-Arylation of 1,3-Dienes with Chlorosilanes and Aryl Bromides

Catalytic, three-component, cross-electrophile reactions have recently emerged as a promising tool for molecular diversification, but studies have focused mainly on the alkyl-carbonations of alkenes. Herein, the scope of this method has been extended to conjugated dienes and silicon chemistry through silylative difunctionalization of 1,3-dienes with chlorosilanes and aryl bromides. The reaction proceeds under mild conditions to afford 1,2-linear-silylated products, a selectivity that is different to those obtained from conventional methods via an intermediary of H(C)-η³ -π-allylmetal species. Preliminary mechanistic studies reveal that chlorosilane reacts with 1,3-diene first and then couples with aryl bromide.

Mechanistic views and computational studies on transition-metal-catalyzed reductive coupling reactions

Transition-metal-catalyzed reductive coupling reactions have been considered as a powerful tool to convert two electrophiles into value-added products. Numerous related reports have shown the fascinating potential. Mechanistic studies, especially theoretical studies, can provide important implications for the design of novel reductive coupling reactions. In this review, we summarize the representative advancements in theoretical studies on transition-metal-catalyzed reductive coupling reactions and systematically elaborate the mechanisms for the key steps of reductive coupling reactions. The activation modes of electrophiles and the deep insights of selectivity generation are mechanistically discussed. In addition, the mechanism of the reduction of high-oxidation-state catalysts and further construction of new chemical bonds are also described in detail.

Regioselective Ni-Catalyzed reductive alkylsilylation of acrylonitrile with unactivated alkyl bromides and chlorosilanes

Transition-metal catalyzed carbosilylation of alkenes using carbon electrophiles and silylmetal (-B, -Zn) reagents as the nucleophiles offers a powerful strategy for synthesizing organosilicones, by incorporating carbon and silyl groups across on C-C double bonds in one step. However, to the best of our knowledge, the study of silylative alkenes difunctionalization based on carbon and silyl electrophiles remains underdeveloped. Herein, we present an example of silylative alkylation of activated olefins with unactivated alkyl bromides and chlorosilanes as electrophiles under nickel catalysis. The main feature of this protocol is employing more easily accessible substrates including primary, secondary and tertiary alkyl bromides, as well as various chlorosilanes without using pre-generated organometallics. A wide range of alkylsilanes with diverse structures can be efficiently assembled in a single step, highlighting the good functionality tolerance of this approach. Furthermore, successful functionalization of bioactive molecules and synthetic applications using this method demonstrate its practicability.

Reductive Cross-Coupling of Unreactive Electrophiles

Transition-metal-catalyzed reductive coupling of electrophiles has emerged as a powerful tool for the construction of molecules. While major achievements have been made in the field of cross-couplings between organic halides and pseudohalides, an increasing number of reports demonstrates reactions involving more readily available, low-cost, and stable, but unreactive electrophiles. This account summarizes the recent results in our laboratory focusing on this topic. These findings typically include deoxygenative C-C coupling of alcohols, reductive alkylation of alkenyl acetates, reductive C-Si coupling of chlorosilanes, and reductive C-Ge coupling of chlorogermanes.The reductive deoxygenative coupling of alcohols with electrophiles is synthetically appealing, but the potential of this chemistry remains to be disclosed. Our initial study focused on the reaction of allylic alcohols and aryl bromides by the combination of nickel and Lewis acid catalysis. This method offers a selectivity that is opposite to that of the classic Tsuji-Trost reactions. Further investigation on the reaction of benzylic alcohols led to the foundation of a dynamic kinetic cross-coupling strategy with applications in the nickel-catalyzed reductive arylation of benzylic alcohols and cobalt-catalyzed enantiospecific reductive alkenylation of allylic alcohols. The titanium catalysis was later established to produce carbon radicals directly from unactivated tertiary alcohols via C-OH cleavage. The development of their coupling reactions with carbon fragments delivers new methods for the construction of all-carbon quaternary centers. These reactions have shown high selectivity for the functionalization of tertiary alcohols, leaving primary and secondary alcohols intact. Alkenyl acetates are inexpensive, stable, and environmentally friendly and are considered the most attractive alkenyl reagents. The development of reductive alkylation of alkenyl acetates with benzyl ammoniums and alkyl bromides offers mild approaches for the conversion of ketones into aliphatic alkenes.Extensive studies in this field have enabled us to extend the cross-electrophile coupling from carbon to silicon and germanium chemistry. These reactions harness the ready availability of chlorosilanes and chlorogermanes but suffer from the challenge of their low reactivity toward transition metals. Under reductive nickel catalysis, a broad range of alkenyl and aryl electrophiles couple well with vinyl- and hydrochlorosilanes. The use of alkyl halides as coupling partners led to the formation of functionalized alkylsilanes. The C-Ge coupling seems less substrate-dependent, and various common chlorogermanes couple well with aryl, alkenyl, and alkyl electrophiles. In general, functionalities such as Grignard-sensitive groups (e.g., acid, amide, alcohol, ketone, and ester), acid-sensitive groups (e.g., ketal and THP protection), alkyl fluoride and chloride, aryl bromide, alkyl tosylate and mesylate, silyl ether, and amine are tolerated. These methods provide new access to organosilicon and organogermanium compounds, some of which are challenging to obtain otherwise.

Nickel-Catalyzed Reductive C(sp2 )-Si Coupling of Chlorohydrosilanes via Si-Cl Cleavage

We report here a new method for the synthesis of organohydrosilanes from phenols and ketones. This method is established through reductive C-Si coupling of chlorohydrosilanes via unconventional Si-Cl cleavage. The reaction offers access to aryl- and alkenylhydrosilanes with a scope that is complementary to those of the established methods. Electron-rich, electron-poor, and ortho-/meta-/para-substituted (hetero)aryl electrophiles, as well as cyclic and acyclic alkenyl electrophiles, were coupled successfully. Functionalities, including Grignard-sensitive groups (e.g., primary amine, amide, phenol, ketone, ester, and free indole), acid-sensitive groups (e.g., ketal and THP protection), alkyl-Cl, pyridine, furan, thiophene, Ar-Bpin, and Ar-SiMe₃ , were tolerated. Gram-scale reaction, incorporation of -Si(H)R₂ into complex biologically active molecules, and derivatization of formed organohydrosilanes are demonstrated.

Nickel-Catalyzed Reductive Csp3-Ge Coupling of Alkyl Bromides with Chlorogermanes

Reductive cross-coupling provides facile access to organogermanes, but it remains largely unexplored. Herein we report a nickel-catalyzed reductive Csp³-Ge coupling of alkyl bromides with chlorogermanes. This work has established a new method for producing alkylgermanes. The reaction proceeds under very mild conditions and tolerates various functionalities including ether, alcohol, alkene, nitrile, amine, ester, phosphonates, amides, ketone, and aldehyde. The application of this method to the modification of bioactive molecules is demonstrated.

NiH-catalyzed C(sp3)–Si coupling of alkenes with vinyl chlorosilanes

A novel NiH-catalyzed highly selective cross-coupling of alkenes with vinyl chlorosilanes is developed. Using this practical chemistry, various benzyl organosilanes could be produced with good functional group tolerance.

Stereo-divergent synthesis of silyl-enynes via palladium-catalyzed coupling of alkynes and iodosilanes

We report a palladium-catalyzed coupling reaction of alkynes and silicon electrophiles, affording stereodefined silyl-enynes. Either E- or Z-enynes can be formed in high yields and in a highly stereoselective manner...

Nickel-Catalyzed Reductive C-Ge Coupling of Aryl/Alkenyl Electrophiles with Chlorogermanes

Cross-electrophile coupling has emerged as a promising tool for molecular synthesis; however, current studies have focused mainly on forging C-C bonds. We report a cross-electrophile C-Ge coupling reaction and thereby demonstrate the possibility of constructing organogermanes from carbon electrophiles and chlorogermanes. The reaction proceeds under mild conditions and offers access to both aryl and alkenyl germanes. Electron-rich, electron-poor, and ortho-/meta-/para-substituted (hetero)aryl electrophiles, as well as cyclic and acyclic alkenyl electrophiles, were coupled. Gram-scale reaction, incorporation of the -GeR₃ moiety into complex biologically active molecules, and derivatization of formed organogermanes are demonstrated.

Nickel-Catalyzed Cross-Electrophile C(sp3)-Si Coupling of Unactivated Alkyl Bromides with Vinyl Chlorosilanes

Cross-electrophile C-Si coupling has emerged as a promising tool for the construction of organosilanes, but the potential of this method remains largely unexplored. Herein, we report a C(sp³)-Si coupling of unactivated alkyl bromides with vinyl chlorosilanes. The reaction proceeds under mild conditions, and it offers a new approach to alkylsilanes. Functionalities such as Grignard-sensitive groups (e.g., acid, amide, alcohol, ketone, and ester), acid-sensitive groups (e.g., ketal and THP protection), alkyl fluoride and chloride, aryl bromide, alkyl tosylate and mesylate, silyl ether, and amine were tolerated. Incorporation of the -Si(vinyl)R₂ moiety into complex molecules and the immobilization of a glass surface by formed organosilanes were demonstrated.

Nickel-Catalyzed Reductive Cross-Coupling of Alkyl Bromides and Chlorosilanes

A novel nickel-catalyzed highly selective reductive cross-coupling of alkyl bromides and chlorosilanes to construct the C-Si bond has been developed. Under benign reaction conditions, a series of structurally interesting organosilanes can be accessed without Ni-catalyzed isomerization. The utility of this chemistry is illustrated by further transformations of the product. Moreover, the radical mechanism of the reaction is illustrated by control experiments.

Nickel-Catalyzed, Reductive C(sp3 )-Si Cross-Coupling of α-Cyano Alkyl Electrophiles and Chlorosilanes

A nickel/zinc-catalyzed cross-electrophile coupling of alkyl electrophiles activated by an α-cyano group and chlorosilanes is reported. Elemental zinc is the stoichiometric reductant in this reductive coupling process. By this, a C(sp3 )-Si bond can be formed starting from two electrophilic reactants whereas previous methods rely on the combination of carbon nucleophiles and silicon electrophiles or vice versa.