Copper-Catalyzed Intermolecular Carboamination of Alkenes Induced by Visible Light

Recent advances in C(sp3)-N bond formation via metallaphoto-redox catalysis

The C(sp3)-N bond is ubiquitous in natural products, pharmaceuticals, biologically active molecules and functional materials. Consequently, the development of practical and efficient methods for C(sp3)-N bond formation has attracted more and more attention. Compared to the conventional ionic pathway-based thermal methods, photochemical processes that proceed through radical mechanisms by merging photoredox and transition-metal catalyses have emerged as powerful and alternative tools for C(sp3)-N bond formation. In this review, recent advances in the burgeoning field of C(sp3)-N bond formation via metallaphotoredox catalysis have been highlighted. The contents of this review are categorized according to the transition metals used (copper, nickel, cobalt, palladium, and iron) together with photocatalysis. Emphasis is placed on methodology achievements and mechanistic insight, aiming to inspire chemists to invent more efficient radical-involved C(sp3)-N bond-forming reactions.

Visible-light-induced copper-catalyzed oxidative esterification of α-azidoketones with diazoacetates: access to α-acyloxyacetates

A copper(II)-catalyzed 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-mediated synthesis of α-acyloxyacetates from α-azidoketones and diazoacetates under visible light at room temperature is described. This reaction involves an oxidative esterification process, leading to the formation of two new C-O bonds with the elimination of dinitrogen molecules in the overall process. 20 examples of α-acyloxyacetates were synthesized in high yields (70-86%) by coupling various α-azidoketones with diazoacetates. α-Azidoketones containing electron-donating groups (Me, MeO), electron-withdrawing groups (CN, NO2), halogen atoms (Cl, Br), and other aryl groups are compatible with various substituted diazoacetates (ethyl, tertiary butyl, benzyl), resulting in the formation of α-acyloxyacetates.

Rh(III)-Catalyzed Diastereo- and Enantioselective Regiodivergent (Hetero)Arylamidation of (Homo)Allylic Sulfides

A rhodium-catalyzed 3-component conjunctive diastereo- and regioselective arylamidation of (homo)allylic sulfides, organon boronic acids, and dioxazolones is reported. These reactions deliver the 1,2-insertion and 2,1-insertion arylamidation products, respectively, for allylic sulfides and homoallylic sulfides. The enantioselective arylamidation of terminal and internal allylic sulfides is achieved, furnishing various 1,3-N,S compounds featuring one or two contiguous stereocenters in high yields and with high diastereo- and enantioselectivities. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining steps induced by the native and easily removable sulfide group.

Photoexcitation of (diarylmethylene)amino benziodoxolones for alkylamination of styrene derivatives with carboxylic acids

The alkylamination of alkenes using pristine carboxylic acids was achieved by the photoexcitation of (diarylmethylene)amino benziodoxolones (DABXs), which serve as both an oxidant and an aminating reagent (an iminyl radical precursor). The developed method is a simple photochemical reaction without the need for external photosensitizers and shows a broad substrate scope for aliphatic carboxylic acids leading to the formation of primary, secondary, and tertiary alkyl radicals, thus enabling the facile synthesis of various structurally complex amines. Mechanistic investigations including transient absorption spectroscopy measurements using a laser flash photolysis (LFP) method disclosed the unique photochemical reactivity of DABXs, which undergoes homolysis of their I-N bonds to give an iminyl radical and ortho-iodobenzoyloxy radical, the latter of which participates in the single-electron oxidation of carboxylates.

Ligand-Enabled Carboamidation of Unactivated Alkenes through Enhanced Organonickel Electrophilicity

Catalytic carboamination of alkenes is a powerful synthetic tool to access valuable amine scaffolds from abundant and readily available alkenes. Although a number of synthetic approaches have been developed to achieve the rapid buildup of molecular complexity in this realm, the installation of diverse carbon and nitrogen functionalities onto unactivated alkenes remains underdeveloped. Here we present a ligand design approach to enable nickel-catalyzed three-component carboamidation that is applicable to a wide range of alkenyl amine derivatives via a tandem process involving alkyl migratory insertion and inner-sphere metal-nitrenoid transfer. With this method, various nitrogen functionalities can be installed into both internal and terminal unactivated alkenes, leading to differentially substituted diamines that would otherwise be difficult to access. Mechanistic investigations reveal that the tailored Ni(cod)(BQiPr) precatalyst modulates the electronic properties of the presumed π-alkene-nickel intermediate via the quinone ligand, leading to enhanced carbonickelation efficiency across the unactivated C═C bond. These findings establish nickel's ability to catalyze multicomponent carboamidation with a high efficiency and exquisite selectivity.

Trinuclear Gold-Catalyzed 1,2-Difunctionalization of Alkenes

Activated alkyl halides have been extensively explored to generate alkyl radicals with Ru- and Ir- photocatalysts for 1,2-difunctionalization of alkenes, but unactivated alkyl bromides remain challenging substrates due to their strong reduction potential. Here we report a three-component 1,2-difunctionalization reaction of alkenes, unactivated alkyl bromides and nucleophiles (e.g., amines and indoles) using a trinuclear gold catalyst [Au3 (tppm)2 ](OTf)3 . It can achieve the 1,2-aminoalkylation and 1,2-alkylarylation readily. This protocol has a broad reaction scope and excellent functional group compatibility (>100 examples with up to 96 % yield). It also affords a robust formal [2+2+1] cyclization strategy for the concise construction of pyrrolidine skeletons under mild reaction conditions. Mechanistic studies support an inner-sphere single electron transfer pathway for the successful cleavage of inert C-Br bonds.

Photoinduced Copper-Catalyzed Aminoalkylation of Amino-Pendant Olefins

The combination of photo and copper catalysts has emerged as a novel paradigm in organic catalysis, which provides access to the acceleration of chemical synthesis. Herein, we describe an aminoalkylation of amino-dependent olefins with maleimides through a cooperative photo/copper catalytic system. In this report, the strategy allows the generation of a broad complex of functionalized nitrogenous molecules including oxazolidinones, 2-pyrrolidones, imidazolidinones, thiazolidinones, pyridines, and piperidines in the absence of an external photosensitizer and base. The approach is achieved through a photoinduced Cu(I)/Cu(II)/Cu(III) complex species of nitrogen nucleophiles, intermolecular radical addition, and hydrogen atom transfer (HAT) processes. The plausible mechanism is investigated by a series of control experiments and theoretical tests, including radical scavenging experiments, deuterium labeling experiments, ultraviolet-visible absorption, and cyclic voltammetry (CV) tests.

Cu-Catalyzed Three-Component Carboamination of Electron Deficient Olefins

The copper-catalyzed three-component carboamination of atropates for the synthesis of α-aryl amino acid derivatives is presented. The scope of the reaction is explored with respect to all three coupling partners: the alkyl halide, the atropate, and the aryl amine. A total of 41 examples are included, with yields of ≤92%. Both primary and secondary aryl amines participate in the carboamination along with α-haloesters, nitriles, and perfluoroiodoalkanes. Mechanistic investigations support a radical mechanism involving Cu-mediated C-N bond formation with the radical adduct.

Cu-Catalyzed Polychloromethylamination of Styrenes through C(sp3 )-H Bond Cleavage

A copper-catalyzed three-component coupling reaction has been developed allowing the rapid building of valuable complex highly functionalized β-polychloromethyl amines from simple styrenes, arylamines, and dichloromethane/chloroform. Using aryldiazonium salts as a radical initiator, a series of corresponding products are obtained with moderate to good yields under a carbon dioxide or nitrogen atmosphere (50 psi). In addition, good functional group tolerance can be observed.

Photoactive Copper Complexes: Properties and Applications

Photocatalyzed and photosensitized chemical processes have seen growing interest recently and have become among the most active areas of chemical research, notably due to their applications in fields such as medicine, chemical synthesis, material science or environmental chemistry. Among all homogeneous catalytic systems reported to date, photoactive copper(I) complexes have been shown to be especially attractive, not only as alternative to noble metal complexes, and have been extensively studied and utilized recently. They are at the core of this review article which is divided into two main sections. The first one focuses on an exhaustive and comprehensive overview of the structural, photophysical and electrochemical properties of mononuclear copper(I) complexes, typical examples highlighting the most critical structural parameters and their impact on the properties being presented to enlighten future design of photoactive copper(I) complexes. The second section is devoted to their main areas of application (photoredox catalysis of organic reactions and polymerization, hydrogen production, photoreduction of carbon dioxide and dye-sensitized solar cells), illustrating their progression from early systems to the current state-of-the-art and showcasing how some limitations of photoactive copper(I) complexes can be overcome with their high versatility.

Visible-Light-Induced Photoredox-Catalyzed Selective 1,4-Difluoroalkylesterification of 1-Aryl-1,3-dienes

A selective three-component 1,4-difluoroalkylesterification of 1-aryl-1,3-dienes enabled by dual photoredox and copper catalysis is described. This protocol uses commercially available CF₂-reagents as radical precursors and carboxylic acids as oxygen-based nucleophiles, providing access to difluoroalkylated allylic esters. This protocol could be extended to intramolecular two-component 1,4-difluoroalkylesterification to access 3-substituted benzobutyrolactones. Preliminary mechanistic studies support a radical process.

A Counterion/Ligand-Tuned Chemo- and Enantioselective Copper-Catalyzed Intermolecular Radical 1,2-Carboamination of Alkenes

The copper-catalyzed enantioselective intermolecular radical 1,2-carboamination of alkenes with readily accessible alkyl halides is an appealing strategy for producing chiral amine scaffolds. The challenge arises from the easily occurring atom transfer radical addition between alkyl halides and alkenes and the issue of enantiocontrol. We herein describe a radical alkene 1,2-carboamination with sulfoximines in a highly chemo- and enantioselective manner. The key to the success of this process is the conceptual design of a counterion/highly sterically demanded ligand coeffect to promote the ligand exchange of copper(I) with sulfoximines and forge chiral C-N bonds between alkyl radicals and the chiral copper(II) complex. The reaction covers alkenes bearing distinct electronic properties, such as aryl-, heteroaryl-, carbonyl-, and aminocarbonyl-substituted ones, and various radical precursors, including alkyl chlorides, bromides, iodides, and the CF₃ source. Facile transformations deliver many chiral amine building blocks of interest in organic synthesis and related areas.

Recent advances in visible light-induced C(sp3)–N bond formation

Synthetic chemists have long focused on selective C(sp ³)-N bond-forming approaches in response to the high value of this motif in natural products, pharmaceutical agents and functional materials. In recent years, visible light-induced protocols have become an important synthetic platform to promote this transformation under mild reaction conditions. These photo-driven methods rely on converting visible light into chemical energy to generate reactive but controllable radical species. This Review highlights recent advances in this area, mostly after 2014, with an emphasis placed on C(sp ³)-H bond activations, including amination of olefins and carbonyl compounds, and cross-coupling reactions.

CuCl-photocatalyzed C-H amination of benzoxazoles

The direct coupling of benzoxazoles and amines was realized by visible light irradiation and CuCl catalysis. Various aminated benzoxazoles were successfully synthesized under mild conditions with air as an oxidant.

Copper-photocatalyzed ATRA reactions: concepts, applications, and opportunities

Atom transfer radical addition (ATRA) reactions are linchpin transformations in synthetic chemistry enabling the atom-economic difunctionalization of alkenes. Thereby a rich chemical space can be accessed through smart combinations of simple starting materials. Originally, these reactions required toxic and hazardous radical initiators or harsh thermal activation and thus, the recent resurgence and dramatic evolution of photocatalysis appeared as an attractive complement to catalyze such transformations in a mild and energy-efficient manner. Initially, this technique relied primarily on complexes of precious metals, such as ruthenium or iridium, to absorb the visible light. Hence, copper photocatalysis rapidly developed into a powerful alternative, not just from an economic point of view. Originally considered to be disadvantageous as a pathway for deactivation by quenching their excited state, the dynamic nature of Cu-complexes enables them to undergo facile ligand exchange and thus opens up special opportunities for transformations utilizing their inner-coordination sphere. Moreover, the ability of Cu(II), representing a persistent radical, to capture incipient radicals offers the possibility to access heretofore elusive two-component, but also three-component, ATRA reactions, not feasible with ruthenium or iridium catalysts. In this regard, the idea of using Cu(I)-substrate assemblies as active photocatalysts is an emerging field to achieve such 3-component coupling reactions even under enantioselective control, which is reflected by an increasing number of reports being covered in this review.

Visible light-induced functionalization of indazole and pyrazole: a recent update

Indazole and pyrazole are renowned as a prodigious class of heterocycles having versatile uses in medicinal as well as industrial chemistry. Considering sustainable approaches, recently, photocatalysis has become an indispensable tool in organic chemistry due to its application for the activation of small molecules and the use of a clean energy source. In this review, we have highlighted the use of metal-based photocatalysts, organic photoredox catalysts, energy transfer photocatalysts and electron-donor-acceptor complexes in the functionalization of indazole and pyrazole. This perspective is arranged based on the types of functionalization reactions on indazole and pyrazole. A detailed discussion regarding the reaction mechanism of each reaction is given to provide a comprehensive guide to the reader. Finally, a summary of existing challenges and the future outlook towards the development of efficient photocatalytic methods for functionalization of these heterocycles is also presented.

Visible Light-Induced Transition Metal Catalysis

In recent years, visible light-induced transition metal catalysis has emerged as a new paradigm in organic photocatalysis, which has led to the discovery of unprecedented transformations as well as the improvement of known reactions. In this subfield of photocatalysis, a transition metal complex serves a double duty by harvesting photon energy and then enabling bond forming/breaking events mostly via a single catalytic cycle, thus contrasting the established dual photocatalysis in which an exogenous photosensitizer is employed. In addition, this approach often synergistically combines catalyst-substrate interaction with photoinduced process, a feature that is uncommon in conventional photoredox chemistry. This Review describes the early development and recent advances of this emerging field.

Diversity-Oriented Synthesis of Fluoroalkylated Amines via Palladium-Catalyzed Divergent Fluoroalkylamination of 1,3-Dienes

Herein, we reported the first versatile and expeditious protocol for the diversity-oriented synthesis (DOS) of fluoroalkylated amines via the photoinduced palladium-catalyzed cross coupling of 1,3-dienes, amines and fluoroalkyl iodides, which...

Recent advances in visible-light mediated functionalization of olefins and alkynes using copper catalysts

Over the past decade, visible-light photoredox catalysis has blossomed as a powerful strategy and offers a discrete activation mode complementary to thermal controlled reactions. Visible-light-mediated photoredox catalysis also offers exciting...

Photo-induced copper-catalyzed sequential 1,n-HAT enabling the formation of cyclobutanols

Cyclobutanols are privileged cyclic skeletons in natural products and synthetic building blocks. C(sp3)-H functionalization is a prolonged challenge in organic synthesis. The synthesis of cyclobutanols through double C(sp3)-H bond functionalization remains elusive. Here we report the efficient synthesis of cyclobutanols through intermolecular radical [3 + 1] cascade cyclization, involving the functionalization of two C - H bonds through sequential hydrogen atom transfer. The copper complex reduces the iodomethylsilyl alcohols efficiently under blue-light irradiation to initiate the tandem transformation. The mild reaction tolerates a broad range of functional groups and allows for the facile generation of elaborate polycyclic structures.

Visible-light-mediated copper photocatalysis for organic syntheses

Photoredox catalysis has been applied to renewable energy and green chemistry for many years. Ruthenium and iridium, which can be used as photoredox catalysts, are expensive and scarce in nature. Thus, the further development of catalysts based on these transition metals is discouraged. Alternative photocatalysts based on copper complexes are widely investigated, because they are abundant and less expensive. This review discusses the scope and application of photoinduced copper-based catalysis along with recent progress in this field. The special features and mechanisms of copper photocatalysis and highlights of the applications of the copper complexes to photocatalysis are reported. Copper-photocatalyzed reactions, including alkene and alkyne functionalization, organic halide functionalization, and alkyl C-H functionalization that have been reported over the past 5 years, are included.

Nickel-Catalyzed 1,2-Carboamination of Alkenyl Alcohols

An alcohol-directed, nickel-catalyzed three-component umpolung carboamination of unactivated alkenes with aryl/alkenylboronic esters and electrophilic aminating reagents is reported. This transformation is enabled by specifically tailored O-(2,6-dimethoxybenzoyl)hydroxylamine electrophiles that suppress competitive processes, including undesired β-hydride elimination and transesterification between the alcohol substrate and electrophile. The reaction delivers the desired 1,2-carboaminated products with generally high regio- and syn-diastereoselectivity and exhibits a broad scope of coupling partners and alkenes, including complex natural products. Various mechanistic experiments and analysis of the stereochemical outcome with a cyclic alkene substrate, as confirmed by X-ray crystallographic analysis, support alcohol-directed syn-insertion of an organonickel(I) species.

Visible-Light-Induced Multicomponent Synthesis of γ-Amino Esters with Diazo Compounds

A visible-light-induced multicomponent reaction of ethyl diazoacetate, diarylamines, and styrene-type alkenes is described. This novel 1,2-difunctionalization of alkenes can be readily achieved under a simple operation and mild conditions, affording γ-amino esters as major products. The reaction proceeds through the generation of carbon-centered radicals from diazo compounds by a visible-light-promoted proton-coupled electron transfer (PCET) process. The carbon radicals then add to diverse alkenes, delivering new carbon radical species, and the final products are formed with N-centered radicals via a radical-radical coupling.

Copper-Catalyzed Three-Component Alkene Carbofunctionalization: C-N, C-O, and C-C Bond Formation from a Single Reaction Platform

A general system achieving three-component intermolecular carbofunctionalization of alkenes is presented, including carboetherification, carboesterification, carboarylation, and carboamination. The scope of the reaction is presented with respect to the carbon electrophile, the olefin, and the nucleophile. Furthermore, the synthesis of γ-lactams via a carboamination reaction is demonstrated in a telescoped three-step protocol.

Copper-catalyzed monochloromethylazidation to access transformable terminal alkyl chlorides using stoichiometric BrCH2Cl

Efficient copper-catalyzed 1,2-difunctionalization of alkenes with commercially available BrCH2Cl as a chloromethylating source was carried out, in which mild conditions, high reactivity, excellent functional-group tolerance, and late-stage modification of a bioactive molecule are demonstrated. This strategy offers a solution for the diverse syntheses of nitrogen-containing terminal alkyl chlorides, a common synthetic handle that is promising for multiple derivatizations. Mechanistic studies indicate that a chloromethyl radical is involved in the catalytic cycle.

Oxidative Three-Component Carboamination of Vinylarenes with Alkylboronic Acids

Three-component carboamination of alkenes is of significant interest due to the ease by which functionalized amines can be produced from readily available chemical building blocks. Previously, a variety of carbon-centered radical precursors have been studied as the carbon components for this reaction, however, the use of general alkyl sources has remained as an unsolved challenge. Herein we present our efforts to develop an oxidative carboamination protocol that utilizes alkylboronic acids as carbon-centered radical precursors. The presented work demonstrates 34 examples, ranging from 17 to 88% yields, with a broad scope in vinylarenes, amines, and alkylboronic acids. Preliminary mechanistic studies suggest that a single-electron oxidation of the alkylboronic acid generates a carbon-centered radical intermediate that adds across the olefin followed by C-N bond formation via Cu-mediated inner-sphere or carbocation-mediated pathways.

Photo-induced copper-catalyzed alkynylation and amination of remote unactivated C(sp3)-H bonds

A method for remote radical C-H alkynylation and amination of diverse aliphatic alcohols has been developed. The reaction features a copper nucleophile complex formed in situ as a photocatalyst, which reduces the silicon-tethered aliphatic iodide to an alkyl radical to initiate 1,n-hydrogen atom transfer. Unactivated secondary and tertiary C-H bonds at β, γ, and δ positions can be functionalized in a predictable manner.

Visible-Light-Induced Direct Csp2-H Radical Trifluoroethylation of Coumarins with 1,1,1-Trifluoro-2-iodoethane (CF3CH2I)

Herein, we developed the first visible-light-induced direct Csp²-H radical 2,2,2-trifluoroethylation of coumarins with commercially available and cheap reagent CF₃CH₂I at room temperature. This transformation proceeded smoothly under mild conditions and showed excellent functional group compatibility. The synthetic value of the protocol was also demonstrated by the successful functionalization of several pharmaceuticals.

Three-component photoredox 1,2-alkylamination of styrenes with alkanes and nitrogen nucleophiles via C(sp3)–H bond cleavage

A three-component photoredox 1,2-alkylamination of styrenes involving functionalization of C(sp3)–H bonds in alkyl halides instead of functionalization of C-halogen bonds is disclosed.

Photoredox-catalyzed 2,2,2-trifluoroethylation and 2,2-difluoroethylation of alkenes with concomitant introduction of a quinoxalin-2(1H)-one moiety

A photoredox-catalyzed three-component radical cascade reaction of alkenes, quinoxalin-2(1H)-ones, and ICH2CF3/ICH2CF2H is developed.

Visible light photocatalysis in the late-stage functionalization of pharmaceutically relevant compounds

The late stage functionalization (LSF) of complex biorelevant compounds is a powerful tool to speed up the identification of structure-activity relationships (SARs) and to optimize ADME profiles. To this end, visible-light photocatalysis offers unique opportunities to achieve smooth and clean functionalization of drugs by unlocking site-specific reactivities under generally mild reaction conditions. This review offers a critical assessment of current literature, pointing out the recent developments in the field while emphasizing the expected future progress and potential applications. Along with paragraphs discussing the visible-light photocatalytic synthetic protocols so far available for LSF of drugs and drug candidates, useful and readily accessible synoptic tables of such transformations, divided by functional groups, will be provided, thus enabling a useful, fast, and easy reference to them.

Synthesis of Benzylureas and Related Amine Derivatives via Copper-Catalyzed Three-Component Carboamination of Styrenes

A direct assembly of secondary benzylureas and related amine derivatives via copper-catalyzed carboamination of styrenes with potassium alkyltrifluoroborates and ureas, anilines, or an amide is reported. Terminal and 1,2-disubstituted alkenes, as well as dienes, participate in this three-component coupling reaction. The reaction mechanism likely involves the addition of an alkyl radical to the styrene, followed by metal-mediated oxidative coupling of the resulting benzylic radical with the amine derivative. Factors that impact substrate reactivity and regioselectivity are discussed.

Copper(i)-catalyzed intermolecular cyanoarylation of alkenes: convenient access to α-alkylated arylacetonitriles

A novel Cu(i)-catalyzed intermolecular cyanoarylation of alkenes with diaryliodonium salts as a radical arylating reagent and tetra-butylammonium cyanide as an electrophilic cyanating reagent was established. A broad range of α-alkylated arylacetonitriles were efficiently constructed in good to excellent yields under base- and oxidant-free and mild conditions.

Copper-Catalyzed 1,2-Aminocyanation of Unactivated Alkenes via Cyano Migration

A copper-catalyzed aminocyanation of alkenes has been achieved through distal cyano migration using O-benzoylhydroxylamines and N-fluorobenzenesulfonimides. This method offers a rapid approach to generate diverse β-amino and β-sulfonimido nitriles. These reactions feature mild conditions, tolerance of sensitive functional groups, and excellent regioselectivity. Mechanistic studies suggest that these transformations are initiated by a copper-catalyzed amination step followed by a cyano migration step.

Three-Component, Interrupted Radical Heck/Allylic Substitution Cascade Involving Unactivated Alkyl Bromides

Developing efficient and selective strategies to approach complex architectures containing (multi)stereogenic centers has been a long-standing synthetic challenge in both academia and industry. Catalytic cascade reactions represent a powerful means of rapidly leveraging molecular complexity from simple feedstocks. Unfortunately, carrying out cascade Heck-type reactions involving unactivated (tertiary) alkyl halides remains an unmet challenge owing to unavoidable β-hydride elimination. Herein, we show that a modular, practical, and general palladium-catalyzed, radical three-component coupling can indeed overcome the aforementioned limitations through an interrupted Heck/allylic substitution sequence mediated by visible light. Selective 1,4-difunctionalization of unactivated 1,3-dienes, such as butadiene, has been achieved by employing different commercially available nitrogen-, oxygen-, sulfur-, or carbon-based nucleophiles and unactivated alkyl bromides (>130 examples, mostly >95:5 E/Z, >20:1 rr). Sequential C(sp³)-C(sp³) and C-X (N, O, S) bonds have been constructed efficiently with a broad scope and high functional group tolerance. The flexibility and versatility of the strategy have been illustrated in a gram-scale reaction and streamlined syntheses of complex ether, sulfone, and tertiary amine products, some of which would be difficult to access via currently established methods.

Intermolecular radical carboamination of alkenes

Vicinal alkene carboamination is a highly efficient and practical synthetic strategy for the straightforward preparation of diverse and valuable amine derivatives starting from simple compounds. During the last decade that approach has found continuous research interests and various practical methods have been developed using transition-metal catalysis. Driven by the renaissance of synthetic radical chemistry, intermolecular radical alkene carboamination comprising a C-C bond and a C-N bond forming step has been intensively investigated recently culminating in novel strategies and improved protocols which complement existing methodologies. Radical alkene carboamination can be achieved via three different reaction modes. Such cascades can proceed through N-radical addition to an alkene with subsequent C-C bond formation leading to 2,1-carboamination products. Alternatively, the C-C bond can be installed prior to the C-N bond via initial C-radical addition to the alkene with subsequent β-amination resulting in 1,2-carboamination. The third mode comprises initial single electron oxidation of the alkene to the corresponding alkene radical cation that gets trapped by an N-nucleophile and the cascade is terminated by radical C-C bond formation. In this review, the three different conceptual approaches will be discussed and examples from the recent literature will be presented. Further, the reader will get insights into the mechanism of the different transformations.

C–C and C–X coupling reactions of unactivated alkyl electrophiles using copper catalysis

Copper catalysts enable cross-coupling reactions of unactivated alkyl electrophiles to generate C–C and C–X bonds.

The Persistent Radical Effect in Organic Synthesis

Radical-radical couplings are mostly nearly diffusion-controlled processes. Therefore, the selective cross-coupling of two different radicals is challenging and not a synthetically valuable transformation. However, if the radicals have different lifetimes and if they are generated at equal rates, cross-coupling will become the dominant process. This high cross-selectivity is based on a kinetic phenomenon called the persistent radical effect (PRE). In this Review, an explanation of the PRE supported by simulations of simple model systems is provided. Radical stabilities are discussed within the context of their lifetimes, and various examples of PRE-mediated radical-radical couplings in synthesis are summarized. It is shown that the PRE is not restricted to the coupling of a persistent with a transient radical. If one coupling partner is longer-lived than the other transient radical, the PRE operates and high cross-selectivity is achieved. This important point expands the scope of PRE-mediated radical chemistry. The Review is divided into two parts, namely 1) the coupling of persistent or longer-lived organic radicals and 2) "radical-metal crossover reactions"; here, metal-centered radical species and more generally longer-lived transition-metal complexes that are able to react with radicals are discussed-a field that has flourished recently.

Silver-Catalyzed Decarboxylative Alkylfluorination of Alkenes

A decarboxylation of alkyl carboxylic acids for alkylfluorination of alkene was developed, with the catalysis of silver(I) and Selectfluor as both the oxidant and fluorine source. This reaction is highly chemoselective, producing the decarboxylative alkylfluorination products rather than the competitive fluorination of aliphatic carboxylic acids. This practical transformation proceeds efficiently in aqueous media at room temperature and exhibits a large range of functional-group tolerance in various primary and secondary aliphatic carboxylates and alkenes.