Palladium(0)-Catalyzed Directed syn-1,2-Carboboration and -Silylation: Alkene Scope, Applications in Dearomatization, and Stereocontrol by a Chiral Auxiliary

Nickel/photoredox-catalyzed three-component silylacylation of acrylates via chlorine photoelimination

The extensive utility of organosilicon compounds across a wide range of disciplines has sparked significant interest in their efficient synthesis. Although catalytic 1,2-silyldifunctionalization of alkenes provides a promising method for the assembly of intricate organosilicon frameworks with atom and step economy, its advancement is hindered by the requirement of an external hydrogen atom transfer (HAT) agent in photoredox catalysis. Herein, we disclose an efficient three-component silylacylation of α,β-unsaturated carbonyl compounds, leveraging a synergistic nickel/photoredox catalysis with various hydrosilanes and aroyl chlorides. This method enables the direct conversion of acrylates into valuable building blocks that contain both carbonyl and silicon functionalities through a single, redox-neutral process. Key to this reaction is the precise activation of the Si-H bond, achieved through chlorine radical-induced HAT, enabled by the photoelimination of a Ni-Cl bond. Acyl chlorides serve a dual role, functioning as both acylating agents and chloride donors. Our methodology is distinguished by its mild conditions and extensive substrate adaptability, significantly enhancing the late-stage functionalization of pharmaceuticals.

A Catalytic Three-Component Aminofluorination of Unactivated Alkenes with Electron-Rich Amino Sources

We present herein a copper-catalyzed three-component aminofluorination of unactivated alkenes with N-bromodialkylamines and readily available nucleophilic fluoride under the assistance of a bidentate auxiliary. This protocol exhibits excellent functional group tolerance toward a wide range of unactivated alkenes and N-bromodialkylamines to furnish the corresponding β-fluoroalkylamines in a highly regio- and diastereoselective manner. The appropriate choice of nucleophilic fluoro source is essential to make this reaction a reality. Further DFT calculations show that the exothermic ion exchange between external fluoride ion and Cu(II) intermediate provides additional driving force to the irreversible migratory insertion, which offsets the unfavorable reaction energetics associated with the subsequent C(sp3)-F reductive elimination. This finding offers a new avenue to catalytic intermolecular aminofluorination of unactivated alkenes with electron-rich amino sources via a remarkable reductive elimination of Cu(III) species to forge the C(sp3)-F bonds.

Radical-Dearomative Generation of Cyclohexadienyl Pd(II) toward the 3D Transformation of Nonactivated Phenyl Rings

Traditional palladium-catalyzed dearomatization of (hetero)arenes takes place via an ionic pathway and usually requires elevated temperatures to overcome the energy barrier of the dearomative insertion step. Herein, a combination of the radical and two-electron pathways is disclosed, which enables room temperature dearomative 3D transformations of nonactivated phenyl rings with Pd(0) as the catalyst. Experimental results together with density functional theory (DFT) calculations indicate a versatile π-allyl Pd(II) species, cyclohexadienyl Pd(II), possibly is involved in the dearomatization. This species is generated by combining the cyclohexadienyl radical and Pd(I). The cyclohexadienyl Pd(II) provides chemoselective (carboamination and trieneylation), regioselective (1,2-carboamination), and diastereoselective (carbonyl-group directed face selectivity) conversions.

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.

Base-mediated C-B bond activation of benzylic boronate for the rapid construction of β-silyl/boryl functionalized 1,1-diarylalkanes from aromatic alkenes

The effect of tBuOK on the existing state of benzylic boronates in the solution phase has been investigated in detail by NMR analysis and DFT calculations. It was determined that simply using an excess of tBuOK (2.0 equivalents) can result in the full deborylation of benzylic boronates to afford free benzyl potassium species. These mechanistic insights were leveraged for the facile construction of β-silyl/boryl functionalized 1,1-diarylalkanes from aromatic alkenes via the combination of base-mediated silylboration or diborylation of aromatic alkenes and nucleophilic-type reactions with various electrophiles. Based on further machine-learning-assisted screening, the scope of electrophiles for this transformation can be generalized to the challenging aromatic heterocycles. Late-stage functionalization performed on several drug-relevant molecules generates the highly valuable 1,1-diaryl framework.

Directed Nickel-Catalyzed Selective Arylhydroxylation of Unactivated Alkenes under Air

An expeditious and novel nickel-catalyzed selective arylhydroxylation of unactivated alkenes with arylboronic acids was developed. This protocol is compatible with β,γ- and γ,δ-alkene amides, including traditionally challenging internal alkenes, to provide important β-arylethylalcohol scaffolds. The free hydroxyl group in the final product could be smoothly further transformed into other functional groups. Control experiments indicated that the oxygen atom of the hydroxyl group in the product is derived from the oxygen in the air.

Recent advances in carbosilylation of alkenes and alkynes

Alkene and alkyne difunctionalization is a flexible process that allows the construction of two functional groups simultaneously in one step. On the other hand, carbosilylation, an ingenious difunctionalization pathway to concurrently incorporate both a silyl group and an organic functional group (alkyl, (hetero)aryl, alkenyl, alkynyl and allenyl) across a carbon-carbon multiple-bond system, is achieving immense interest in recent days. This review article provides a decade's update on the discoveries and developments in the synthesis of carbosilylated products from two very important carbon-carbon unsaturated substrates, alkenes and alkynes.

Regio- and chemoselective hydroamination of unactivated alkenes with anthranils via NiH-catalysis

A NiH-catalyzed polarity-reversed hydroamination of β,γ-, γ,δ- and δ,ε-unsaturated alkenes with electrophilic anthranils was developed. This reaction proceeds in a highly regio- and chemoselective manner to afford γ, δ and ε-arylamines bearing a carbonyl or alcohol functionality with 100% atom efficiency. Preliminary mechanistic studies indicate that the chemoselectivity is controlled by the base and the alcohol product is derived from the base-catalyzed hydrosilylation of the CO bond.

Copper-catalyzed defluorinative arylboration of vinylarenes with polyfluoroarenes

An unprecedented but challenging defluorinative arylboration has been achieved. Enabled by a copper catalyst, an interesting procedure on defluorinative arylboration of styrenes has been established. With polyfluoroarenes as the substrates, this methodology offers flexible and facile access to provide a diverse assortment of products under mild reaction conditions. In addition, by using a chiral phosphine ligand, an enantioselective defluorinative arylboration was also realized, affording a set of chiral products with unprecedented levels of enantioselectivity.

A Sterically Tuned Directing Auxiliary Promotes Catalytic 1,2-Carbofluorination of Alkenyl Carbonyl Compounds

The site-selective palladium-catalyzed three-component coupling of unactivated alkenyl carbonyl compounds, aryl- or alkenylboronic acids, and N-fluorobenzenesulfonimide is described herein. Tuning of the steric environment on the bidentate directing auxiliary enhances regioselectivity and facilitates challenging C(sp³ )-F reductive elimination from a Pd^IV intermediate to afford 1,2-carbofluorination products in moderate to good yields.

Dearomatizing [2+2+1] Spiroannulation of Indoles with Alkynes

A palladium-catalyzed dearomatizing [2+2+1] spiroannulation of indoles with two molecular internal alkynes is developed in the presence of Cu(OAc)₂/O₂ as the oxidant, in which a domino sequence including C-H activation of indole followed by consecutive Heck reactions is involved. A range of 3,3'-spiroindolines bearing tetrasubstituted cyclopentadiene moieties and exocyclic C═C bonds at C2 are obtained in moderate to excellent yields.

Palladium(II)-Catalyzed Regioselective Hydrocarbofunctionalization of N-Alkenyl Amides: Synthesis of Tryptamine Derivatives

The hydrocarbofunctionalization of allyl amines connected to the picolinamide directing group is developed under Pd(II) catalysis. The strategy is grounded on a nucleopalladation concept, and a wide range of indoles effectively participated to produce valuable tryptamine derivatives in high yields. Synthetic utilities were showcased through the substrate diversification bearing bioactive core, Pictet-Spengler cyclization, and β-carboline synthesis. A mechanistic study suggested an irreversible nucleopalladation step, while protodepalladation follows a reversible pathway.

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.

Light-Promoted Arylsilylation of Alkenes with Hydrosilanes

Herein, we report light-promoted photo/hydrogen atom transfer dual catalysis for arylsilylation of alkenes via the radical-radical cross-coupling with diverse hydrosilanes, which provides a simple and efficient method to prepare various organosilicon compounds with a wide range of substrate scope and good functional group tolerance under transition-metal- and chemical-oxidant-free conditions. Furthermore, the arylsilylation of alkenes can also proceed via the possible electron donor-acceptor complex under exogenous photocatalyst-free conditions.

Nickel-Catalyzed 1,2-Arylboration of Unactivated Alkenes to Access Boryl-Functionalized Aliphatic Amines

We report herein a three-component 1,2-arylboration of alkenyl amines bearing a cleavable picolinamide directing group. With aryl halides as electrophiles and B₂Pin₂ as nucleophiles, a wide range of alkenes could be converted into valuable boryl-functionalized aliphatic amines. The reaction proceeds with high levels of chemo- and regiocontrol and exhibits high functional group tolerance. In addition, the pinacol boronic ester group could undergo various transformations, indicating that the protocol could potentially provide a platform for versatile regioselective difunctionalization of alkenyl amines.

Picolinamides and Iodoalkynes Enable Palladium-Catalyzed syn-Aminoalkynylation of Di- and Trisubstituted Alkenes to Give Pyrrolidines

Palladium-catalyzed aminoalkynylation of electronically unbiased olefins with iodoalkynes is reported. The picolinamide auxiliary enables for the first time the syn-selective aminoalkynylation of mono-, di- and trisubstituted alkenes to afford the corresponding pyrrolidines in up to 97 % yield and as single diastereomers. Furthermore, through a C-H activation approach, the picolinamide allows the rapid synthesis of functionalized olefins, which are suitable cyclization precursors. Facile and orthogonal deprotection of the amides and Siⁱ Pr₃ -acetylenes in the products, and a subsequent Pictet-Spengler reaction is demonstrated.

1,2-Silylpyridylation Reaction of Aryl Alkenes with Silylboronate

A metal-free silyl-pyridylation of alkenes using silyl boronates and B₂pin₂ through a pyridine-mediated B-interelement activation has been demonstrated, which provides a practical strategy for a variety of C₄-silylalkylated pyridines. DFT calculations and control experiments show that the reaction proceeds through a silyl radical addition/radical-radical coupling sequence. This protocol features a broad substrate scope and excellent functional group compatibility, and thus it showcases great potential in the late-stage modification of bioactive molecules.

Nickel-Catalyzed Chemo- and Regioselective Arylcyanation of β,γ-Unsaturated Amides

A nickel-catalyzed intermolecular arylcyanation of 8-aminoquinolinyl β,γ-unsaturated amides is reported. The three-component reaction directly afforded diverse β-cyano γ-aryl amides with exclusive chemo- and regioselectivity. The synthetic practicality of this approach is further demonstrated through multigram scale reaction, expanded transformations of the nitrile product, late-stage modification of complex molecules, and direct drug synthesis.

Intermolecular Carbosilylation of α-Olefins with C(sp3 )-C(sp) Bond Formation Involving Silylium-Ion Regeneration

A regioselective addition of alkynylsilanes across unactivated, terminal alkenes is reported. The reaction is initiated by the capture of a sterically unhindered silylium ion by a silylated phenylacetylene derivative to form a bis(silylated) ketene‐like carbocation. This in situ‐generated key intermediate is the actual catalyst that maintains the catalytic cycle by a series of electrophilic addition reactions of silylium ions and β‐silicon‐stabilized carbocations. The computed reaction mechanism is fully consistent with the experimental findings. This unprecedented two‐component carbosilylation establishes a C(sp³)−C(sp) bond and a C(sp³)−Si bond in atom‐economic fashion.

Nickel-Catalyzed Regio- and Enantioselective Hydroamination of Unactivated Alkenes Using Carbonyl Directing Groups

The asymmetric addition of an N-H bond to various alkenes via a direct catalytic method is a powerful way of synthesizing value-added chiral amines. Therefore, the enantio- and regioselective hydroamination of unactivated alkenes remains an appealing goal. Here, we report the highly enantio- and regioselective Ni-catalyzed hydroamination of readily available unactivated alkenes bearing weakly coordinating native amides or esters. This method succeeds for both terminal and internal unactivated alkenes and has a broad amine coupling partner scope. The mild reaction process is well suited for the late-stage functionalization of complex molecules and has the potential to gain modular access to enantioenriched β- or γ-amino acid derivatives and 1,2- or 1,3-diamines. Mechanistic studies reveal that a chiral bisoxazoline-bound Ni specie effectively leverages carbonyl coordination to achieve enantio- and regioselective NiH insertion into alkenes.

Salt-Stabilized Silylzinc Pivalates for Nickel-Catalyzed Carbosilylation of Alkenes

We herein report the preparation of solid and salt-stabilized silylzinc pivalates from the corresponding silyllithium reagents via transmetalation with Zn(OPiv)₂ . These resulting organosilylzinc pivalates show enhanced air and moisture stability and unique reactivity in the silylative difunctionalization of alkenes. Thus, a practical chelation-assisted nickel-catalyzed regioselective alkyl and benzylsilylation of alkenes has been developed, which provides an easy method to access alkyl silanes with broad substrate scope and wide functional group compatibility. Kinetic experiments highlight that the OPiv-coordination is crucial to improve the reactivity of silylzinc pivalates. Furthermore, late-stage functionalizations of druglike molecules and versatile modifications of the products illustrate the synthetical utility of this protocol.

NiH-catalysed proximal-selective hydroalkylation of unactivated alkenes and the ligand effects on regioselectivity

Alkene hydrocarbonation reactions have been developed to supplement traditional electrophile-nucleophile cross-coupling reactions. The branch-selective hydroalkylation method applied to a broad range of unactivated alkenes remains challenging. Herein, we report a NiH-catalysed proximal-selective hydroalkylation of unactivated alkenes to access β- or γ-branched alkyl carboxylic acids and β-, γ- or δ-branched alkyl amines. A broad range of alkyl iodides and bromides with different functional groups can be installed with excellent regiocontrol and availability for site-selective late-stage functionalization of biorelevant molecules. Under modified reaction conditions with NiCl₂(PPh₃)₂ as the catalyst, migratory hydroalkylation takes place to provide β- (rather than γ-) branched products. The keys to success are the use of aminoquinoline and picolinamide as suitable directing groups and combined experimental and computational studies of ligand effects on the regioselectivity and detailed reaction mechanisms.

Difunctionalization of olefins is an ongoing and important focus of synthetic organic chemistry. Here the authors report a nickel-catalysed hydroalkylation of unactivated alkenes to obtain branched alkyl carboxylic acids or alkyl amines, using aminoquinoline and picolinamide as directing groups.

Mapping Ambiphile Reactivity Trends in the Anti-(Hetero)annulation of Non-Conjugated Alkenes via PdII /PdIV Catalysis

In this study, we systematically evaluate different ambiphilic organohalides for their ability to participate in anti-selective carbo- or heteroannulation with non-conjugated alkenyl amides under Pd^II /Pd^IV catalysis. Detailed optimization of the reaction conditions has led to protocols for synthesizing tetrahydropyridines, tetralins, pyrrolidines, and other carbo/heterocyclic cores via [n+2] (n=3-5) (hetero)annulation. Expansion of scope to otherwise unreactive ambiphilic haloketones through Pd^II /amine co-catalysis is also demonstrated. Compared to other annulation processes, this method proceeds via a distinct Pd^II /Pd^IV mechanism involving Wacker-type directed nucleopalladation. This difference results in unique reactivity and selectivity patterns, as revealed through assessment of reaction scope and competition experiments.

Remote arylalkylation of unactivated alkenes via 6- or 7-membered nickelacycles with excellent diastereofidelity

We developed a nickel-catalyzed remote arylalkylation of unactivated alkenes via kinetically and thermodynamically disfavored 6- and 7-membered nickelacycles.

The cobalt(ii)-catalyzed acyloxylation of picolinamides with bifunctional silver carboxylate via C–H bond activation

The cobalt(ii)-catalyzed C–H bond acyloxylation of picolinamides with bifunctional silver carboxylate has been developed. The mild and practical esterification provides an atom-economic route to access to polysubstituted naphthalene compounds.

NiH-catalyzed dearomative hydroalkylation of indoles

A NiH-catalyzed intermolecular dearomative hydroalkylation of indoles has been developed, which assembles an array of structurally diverse C2-alkylated indolines with moderate to excellent yields. This protocol exhibits good functional group...

Controllable access to trifluoromethyl-containing indoles and indolines: Palladium-catalyzed regioselective functionalization of unactivated alkenes with trifluoroacetimidoyl chlorides

The synthesis of diverse products from the same starting materials is always attractive in organic chemistry. Here, a palladium-catalyzed substrate-controlled regioselective functionalization of unactivated alkenes with trifluoroacetimidoyl chlorides has been developed, which provides a direct but controllable access to a variety of structurally diverse trifluoromethyl-containing indoles and indolines. In more detail, with respect to γ,δ-alkenes, 1,1-geminal difunctionalization of unactivated alkenes with trifluoroacetimidoyl chloride enables the [4 + 1] annulation to produce indoles; as for β,γ-alkenes, a [3 + 2] heteroannulation with the hydrolysis product of trifluoroacetimidoyl chloride through 1,2-vicinal difunctionalization of alkenes occurs to deliver indoline products. The structure of alkene substrates differentiates the regioselectivity of the reaction.

A palladium-catalyzed dual functionalization of unactivated alkenes with trifluoroacetimidoyl chlorides toward the synthesis of structurally diverse trifluoromethyl-containing indoles and indolines has been developed.

Regioselective 1,2-carbosulfenylation of unactivated alkenes via directed nickel catalysis

A removable bidentate picolinamide assisted regioselective 1,2-carbosulfenylation of unactivated alkenes with aryl/alkenylboronic acids and disulfide electrophiles has been developed with a cost-effective and air-stable Ni(ii) precatalyst.

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).

Directed nickel-catalyzed regio- and diastereoselective arylamination of unactivated alkenes

Few methods have been reported for intermolecular arylamination of alkenes, which could provide direct access to important arylethylamine scaffolds. Herein, we report an intermolecular syn-1,2-arylamination of unactivated alkenes with arylboronic acids and O-benzoylhydroxylamine electrophiles with Ni(II) catalyst. The cleavable bidentate picolinamide directing group facilitates formation of stabilized 4-, 5- or 6-membered nickelacycles and enables the difunctionalization of diverse alkenyl amines with high levels of regio-, chemo- and diastereocontrol. This general and practical protocol is compatible with broad substrate scope and high functional group tolerance. The utility of this method is further demonstrated by the site-selective modification of pharmaceutical agents.

Nickel-Catalyzed Dearomative Arylboration of Indoles: Regioselective Synthesis of C2- and C3-Borylated Indolines

Indole dearomatization is an important strategy to access indolines: a motif present in a variety of natural products and biologically active molecules. Herein, a method for transition-metal catalyzed regioselective dearomative arylboration of indoles to generate diverse indolines is presented. The method accomplishes intermolecular dearomatization of simple indoles through a migratory insertion pathway on substrates that lack activating or directing groups on the C2- or C3-positions. Synthetically useful C2- and C3-borylated indolines can be accessed through a simple change in N-protecting group in high regio- and diastereoselectivities (up to >40:1 rr and >40:1 dr) from readily available starting materials. Additionally, the origin of regioselectivity was explored experimentally and computationally to uncover the remarkable interplay between carbonyl orientation of the N-protecting group on indole, electronics of the C2-C3 π-bond, and sterics. The method enabled the first enantioselective synthesis of (-)-azamedicarpin.

γ-Selective C(sp3)-H amination via controlled migratory hydroamination

Remote functionalization of alkenes via chain walking has generally been limited to C(sp3)-H bonds α and β to polar-functional units, while γ-C(sp3)-H functionalization through controlled alkene transposition is a longstanding challenge. Herein, we describe NiH-catalyzed migratory formal hydroamination of alkenyl amides achieved via chelation-assisted control, whereby various amino groups are installed at the γ-position of aliphatic chains. By tuning olefin isomerization and migratory hydroamination through ligand and directing group optimization, γ-selective amination can be achieved via stabilization of a 6-membered nickellacycle by an 8-aminoquinoline directing group and subsequent interception by an aminating reagent. A range of amines can be installed at the γ-C(sp3)-H bond of unactivated alkenes with varying alkyl chain lengths, enabling late-stage access to value-added γ-aminated products. Moreover, by employing picolinamide-coupled alkene substrates, this approach is further extended to δ-selective amination. The chain-walking mechanism and pathway selectivity are investigated by experimental and computational methods.