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

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.

N-Alkoxyphthalimides as Nitrogen Electrophiles to Construct C-N Bonds via Reductive Cross-Coupling

N-Alkoxyphthalimides, one kind of phthalimide derivative, have great importance in synthesis, mainly used as free radical precursors. While the phthalimide unit, for a long time, was treated as part of the waste stream. Construction of C-N bonds has always been a hot spot, especially in reductive cross-coupling. Herein, a nickel-catalyzed reductive cross-coupling reaction of N-methoxyphthalimides with alkyl halides is described, where N-methoxyphthalimides serve as nitrogen electrophiles. This tactic provides a new approach to construct C-N bonds under mild neutral conditions. Alkyl chlorides, bromides, iodides, and sulfonates are all fit to this transformation. Moreover, the reaction could tolerate a broad substrate scope, especially base-sensitive functional groups (boron or silicon groups), as well as competitive nucleophilic groups (phenols and amides), which are incompatible with traditional Gabriel synthesis under basic conditions, demonstrating a complementary role of this work to Gabriel synthesis.

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.

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.

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.

Copper-Catalyzed Highly Selective Hydrosilylation of Silyl or Boryl Alkene: A Method for Preparing Chiral Geminated Disilyl and Borylsilyl Reagents

The copper-catalyzed highly selective hydrosilylation of silyl or boryl alkene has been developed. This chemistry could afford a practical method for preparing chiral geminated disilyl and borylsilyl reagents, which are useful organosilanes and versatile synthons for organic synthesis. The experimental data suggested that this reaction could be compatible with a variety of functional groups. Furthermore, the utility of the gem-dimetal compounds, which could be prepared by this chemistry, has been well illustrated by further transformations.

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...