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The transition metal-catalyzed C-H bond functionalization of azoles has emerged as one of the most important strategies to decorate these biologically important scaffolds. Despite significant progress in the C-H functionalization of various heteroarenes, the regioselective alkylation and alkenylation of azoles are still arduous transformations in many cases. This review covers recent advances in the direct C-H alkenylation, alkylation and alkynylation of azoles utilizing transition metal-catalysis. Moreover, the limitations of different strategies, chemoselectivity and regioselectivity issues will be discussed in this review.

Herein, we report a facile method for the alkenylation of a 4-thiazolidinone motif without using external acid and high-pressure gas, which are required in conventional Fujiwara-Moritani reactions. Mild reaction conditions, one-pot synthesis, and utilization of an oxidant made this process more feasible in comparison with previously reported methods. Functionalization of the slightly more acidic [Formula: see text] C-H bond with the less acidic [Formula: see text] C-H bond yielded the alkenylated motif. This pathway opens new possibilities for organic synthesis.

Palladium-catalyzed direct dialkenylation of cage B(4,5)-H bonds in o-carboranes has been achieved with the help of a carboxylic acid directing group, leading to the preparation of a series of 4,5-[trans-(ArCH=CH)]2-ocarboranes in high yields with excellent regioselectivity. The traceless directing group, eliminated during the course of the reaction, is responsible for controlling regioselectivity and dialkenylation. A possible catalytic cycle is proposed, involving a tandem sequence of Pd(II) -initiated cage B-H activation, alkene insertion, β-H elimination, reductive elimination, and decarboxylation., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An efficient method for C7-position-selective alkenylation of N-substituted indolines with alkenes is reported. Various 7-alkenylindolines were obtained in moderate to excellent yields in air in the presence of catalytic amounts of [Cp*IrCl2]2, AgOTf, and Cu(OAc)2. The protocol relies on the use of a carbonyl or carbamoyl group on the nitrogen atom of indoline as a directing group and is potentially applicable to the synthesis of 7-alkenylindoles and 7-alkylindoles., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A bimetallic Rh(II) catalyst promoted the C-H alkenylation of simple arenes at 1.0 equivalent without the use of a directing group. A phosphine ligand as well as cooperative reoxidation of Rh(II) with Cu(TFA)2 and V2O5 proved essential in providing monoalkenylated products in good yields and selectivities, especially with di- and trisubstituted arenes., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A palladium‐catalyzed highly C−S‐selective Stille cross‐coupling between aryl thianthrenium salts and tri‐ or tetrasubstituted alkenyl stannanes is described. Herein, critical challenges including site‐ and chemoselectivity control are well addressed through C−H thianthrenation and C−S alkenylation, thereby providing an expedient access to stereodefined tri‐ and tetrasubstituted alkenes in a stereoretentive fashion. Indeed, the palladium‐catalyzed Stille‐alkenylation of poly(pseudo)halogenated arenes displays privileged capability to differentiate C−S over C−I, C−Br, C−Cl bonds, as well as oxygen‐based triflates (C−OTf), tosylates (C−OTs), carbamates and sulfamates under mild reaction conditions. Sequential and multiple cross‐couplings via selective C−X functionalization should be widely applicable for increasing functional molecular complexity. Modular installation of stereospecific alkene motifs into pharmaceuticals illustrated the synthetic application of the present protocol in drug discovery. [ABSTRACT FROM AUTHOR]

Catalytic enantioselective alkenylation of aldehydes with easily accessible alkenyl halides promoted by a chiral cobalt complex derived from a newly developed tridentate bisoxazolinephosphine is presented. Such processes represent an unprecedented reaction pathway for cobalt catalysis and a general approach that enable rapid construction of highly diversified enantioenriched allylic alcohols containing a 1,1‐, 1,2‐disubstituted and trisubstituted alkene as well as axial stereogenicity in up to 99 % yield and 99 : 1 er without the need of preformation of alkenyl–metal reagents. DFT calculations revealed the origin of enantioselectivity. [ABSTRACT FROM AUTHOR]

A series of adamantyl-containing alkenes were synthesized by the alkenylation of adamantan-1-ol with secondary alcohols in the presence of sulfuric acid. The scope of application of this reaction was explored to show that the alkenylation reaction with symmetrical dialkylcarbinols occurs in a selective fashion. The alkenylation of adamantan-1-ol with sec-pentanol and its higher homologs gives a mixture of isomeric alkenes. The reactions of substituted adamantanols with isopropanol, butan-2-ol, and cyclohexanol in the presence of sulfuric acid were studied, and a series of new unsaturated derivatives of the adamantane series were obtained. [ABSTRACT FROM AUTHOR]

A novel alkenylation reaction between N‐hydroxyphthalimide (NHPI) esters and alkenyl sulfones is reported. It undergoes the formation of electron donor‐acceptor (EDA) complex and a series of alkenes are obtained in good to excellent yields. It has the advantages of simple operation, mild reaction conditions, and metal‐free. [ABSTRACT FROM AUTHOR]

Alkenylbenzene skeletons represent one of the most widely occurring structural motifs in pharmaceutical drugs, natural products, and advanced materials. The construction of alkenylbenzenes is promising through the use of a straightforward oxidative alkenylation protocol, particularly from unactivated alkenes. This is significant because unactivated alkenes are inexpensive raw materials that can be obtained in bulk quantities from petrochemical feedstocks and renewable resources. However, controlling the reactivity and regioselectivity of olefination with unbiased olefins remains a significant challenge, necessitating continuous efforts and potentially having a substantial impact on both organic synthesis and the industry. This review aims to provide an overview of the latest advances in regiocontrol strategies for oxidative alkenylation reactions with unactivated alkenes, which can be categorized into three types: 1) ligand‐promoted/accelerated reactions; 2) prefunctionalized olefins‐facilitated reactions; 3) directing group‐induced reactions. [ABSTRACT FROM AUTHOR]

Sequential C−H functionalization of molecules containing multiple C−H bonds can efficiently lead to structural diversity. Herein we present the first chelation‐assisted sequential α‐/β‐C−H functionalization of E‐styrenes with simple alkenes and alkynes in excellent regio‐ and stereo‐selectivity. The process involves α C−H functionalization by six‐membered exo‐cyclopalladation to result in tri‐ and tetrasubstituted 1,3‐dienes and β C−H functionalization through seven‐membered endo‐cyclopalladation to produce tetra‐ and pentasubstituted 1,3,5‐trienes in up to 97 % yield with up to >99/1 E/Z selectivity, both enabled by the chelation assistance of pyrazinamide. The protocol is demonstrated to be widely applicable, tolerant to a wide range of functional groups and bioactive fragments, and suitable for gram‐scale synthesis as well as one‐pot and two step preparation of trienes. Mechanistic experiments and density functional theory (DFT) calculations were performed to elucidate the selectivity and reactivity. [ABSTRACT FROM AUTHOR]

Herein, we report the direct intramolecular coupling of primary and secondary alcohols for the selective synthesis of macrocyclic olefins in the presence of Ni‐zeolite catalyst under continuous flow. This reaction proceeds via dehydration of secondary alcohols to alkenes, which subsequently undergo intramolecular dehydrative coupling reaction with a primary alcohol to obtain moderate yields of macrocyclic olefins. This reaction is also effective for the coupling of secondary‐secondary alcohols and alkene‐alcohols to produce diverse macrocyclic olefin products. This unique approach has various advantages including step‐economy, no additives and pre‐functionalization required, inexpensive and reusable catalyst, and exemplification with 23 macrocycles in different ring sizes. The continuous flow macrocyclisation afforded higher productivity and space‐time yield than the batch reaction conditions. [ABSTRACT FROM AUTHOR]

An emerging class of C−C coupling transformations that furnish drug‐like building blocks involves catalytic hydrocarbonation of alkenes. However, despite notable advances in the field, hydrocarbon addition to gem‐difluoroalkenes without additional electronic activation remains largely unsuccessful. This owes partly to poor reactivity and the propensity of difluoroalkenes to undergo defluorinative side reactions. Here, we report a nickel catalytic system that promotes efficient 1,2‐selective hydroarylation and hydroalkenylation, suppressing defluorination and providing straightforward access to a diverse assortment of prized organofluorides bearing difluoromethyl‐substituted carbon centers. In contrast to radical‐based pathways and reactions triggered by hydrometallation via a nickel‐hydride complex, our experimental and computational studies support a mechanism in which a catalytically active nickel‐bromide species promotes selective carbonickelation with difluoroalkenes followed by alkoxide exchange and hydride transfer, effectively overcoming the difluoroalkene's intrinsic electronic bias. [ABSTRACT FROM AUTHOR]

Despite remarkable successes in linear and branched vinyl (hetero) arene synthesis, regiodivergent C−H olefination with a single catalytic system has remained underdeveloped. Overcoming this limitation, a Pd/MPAA‐catalyzed regiodivergent C−H olefination of imidazo[1,2a] pyridine carboxamides with unactivated terminal alkenes to generate branched and linear olefinated products depending upon the electronic nature of alkenes is reported herein. Moreover, this protocol can be applied for C−H deuteriation of the corresponding heteroarenes with D2O as deuterium source. Preliminary experimental studies combined with computational investigations (DFT studies) suggest that regiodivergent olefination can be controlled by olefin insertion and β‐hydride elimination steps. [ABSTRACT FROM AUTHOR]

Herein, we report the reaction system based on Pd(II) catalyst and Tl(OCOCF3)3 for the electrophilic C3−H alkenylation of 2,6‐dialkokypyridines with alkenes. Synergistic action of the Pd/thioether ligand catalytic system and Tl(III) results in efficient C−H alkenylation of various nitrogen heteroaromatics with complete regioselectivity. Remarkably, the use of a sterically hindered thioether ligand and the Pd(II)/Tl(III) system enables mono‐selective C3(5)−H alkenylation of 2,6‐dialkoxypyridines, and subsequent introduction of a second, different alkene affords unsymmetrical, multi‐substituted pyridine derivatives. Mechanistic studies indicate that the reaction proceeds via electrophilic thallation of heteroarenes followed by Pd‐catalyzed Heck‐type reaction. The utility of this method is showcased by its application to the late‐stage functionalization of structurally complex bioactive molecules having 2,6‐dialkoxypyridine as a core structure. [ABSTRACT FROM AUTHOR]

A novel and effective RhIII- and PdII-controlled switchable C–H alkenylation of 2-pyridylthiophenes with alkenes is realized. The alkenylation reactions proceeded smoothly in a highly regio- and stereo-selective manner to afford a broad range of C3- and C5-alkenylated products. Depending on the catalyst employed, the reactions involve two typical approaches: C3-alkenylation via chelation-assisted rhodation and C5-alkenylation via electrophilic palladation. This regiodivergent synthetic protocol was successfully applied for the straightforward building of π-conjugated difunctionalized 2-pyridylthiophenes, which may show great potential in organic electronic materials. [ABSTRACT FROM AUTHOR]

A weak coordination guided Ru(II)‐catalyzed oxidative functionalization of arenes with unactivated olefins is developed, offering a wide variety of ortho‐alkenylated benzamides, acetophenones, and benzophenone in high yields. The protocol accommodates several bioactive molecules and allows downstream synthetic manipulations leading to a 2,3‐benzodiazepine scaffold. The reaction features a reversible metalation step and favors a regioselective β‐hydride elimination event. [ABSTRACT FROM AUTHOR]

Aryl alkenes represents one of the most widely occurring structural motif in countless drugs and natural products, and direct C−H functionalization of aryl alkenes provides atom‐ step efficient access toward valuable analogues. Among them, group‐directed selective olefinic α‐ and β‐C−H functionalization, bearing a directing group on the aromatic ring, has attracted remarkable attentions, including alkynylation, alkenylation, amino‐carbonylation, cyanation, domino cyclization and so on. These transformations proceed by endo‐ and exo−C−H cyclometallation and provide aryl alkene derivatives in excellent site‐ stereo‐selectivity. Enantio‐selective α‐ and β‐ olefinic C−H functionalization were also covered to synthesis axially chiral styrenes. [ABSTRACT FROM AUTHOR]

Herein we report, a rhodium‐catalyzed Fujiwara‐Moritani‐type reaction of unactivated terminal alkenes and benzoic acid derivatives bearing electron donating residues under mild conditions. The acid functionality acts as a traceless directing group delivering products alkenylated in meta‐position to the electron donating substituent in contrast to the usually obtained ortho‐ and para‐substitution in Friedel‐Crafts‐type reactions. Remarkably, the new C−C bond is formed to the C2 of the terminal olefin, in contrast to similar reported transformations. Initially formed mixtures of exo‐ and endo‐double bond isomers can be efficiently isomerized to the more stable endo‐products. [ABSTRACT FROM AUTHOR]

Precise stereocontrol of functionalized alkenes represents a long-standing research topic in organic synthesis. Nevertheless, the development of a catalytic, easily tunable synthetic approach for the stereodivergent synthesis of both E-selective and even more challenging Z-selective highly substituted 1,3-dienes from common substrates remains underexploited. Here, we report a photoredox and nickel dual catalytic strategy for the stereodivergent sulfonylalkenylation of terminal alkynes with vinyl triflates and sodium sulfinates under mild conditions. With a judicious choice of simple nickel catalyst and ligand, this method enables efficient and divergent access to both Z- and E-sulfonyl-1,3-dienes from the same set of simple starting materials. This method features broad substrate scope, good functional compatibility, and excellent chemo-, regio-, and stereoselectivity. Experimental and DFT mechanistic studies offer insights into the observed divergent stereoselectivity controlled by ligands. The stereoselective synthesis of 1,3-dienes represents a challenge in organic synthesis. Here, the authors report a ligand-controlled stereodivergent access to both Z- and E-sulfonyl-1,3-dienes via photoredox and nickel catalysis. [ABSTRACT FROM AUTHOR]

A palladium-catalysed, silver-assisted regioselective C2–H alkenylation of benzophospholes with terminal alkenes has been developed. The palladium catalysis accommodates styrenes and electron-deficient alkenes including ester, ketone, nitrile, and phosphonate. Thus, this protocol enables the rapid construction of various benzophosphole–vinylene conjugations from the two simple C–H starting substrates. Optical properties of newly synthesized C2-alkenylated benzophospholes are also investigated. [ABSTRACT FROM AUTHOR]

The synthesis of all-carbon tetrasubstituted olefins under mild reaction conditions is challenging because of the inevitable issues including significant steric hindrance and the uncontrolled Z/E stereoselectivity. In this paper, we report the synthesis of all-carbon tetrasubstituted alkenes from readily available carboxylic acids and alkenyl triflates with the synergistic catalysis of cyclo-octa-1,5-diene(tetramethyl-1,4-benzoquinone)nickel and visible light under an air atmosphere, thus avoiding the need for a glovebox or a Schlenk line. A wide range of aromatic carboxylic acids and cyclic and acyclic alkenyl triflates undergo the C-C coupling process smoothly, forming structurally diverse alkenes stereospecifically in moderate to good yields. The practicality of the method is further illustrated by the late-stage modification of complex molecules, the one pot synthesis and gram-scale applications. This is an important step towards the valuable utilization of carboxylic acids, and it also simplifies the experimental operation of metallophotoredox catalysis with moisture sensitive nickel(0) catalysis. Tetrasubstituted olefins have been explored as chemical synthons and can sometime have useful photophysical properties, but are sometimes difficult to synthesize with high selectivity in mild conditions. Here the authors present a method to make tetrasubstituted olefins via dual photo- and nickel catalysis, without the need for an inert atmosphere. [ABSTRACT FROM AUTHOR]

Pd-catalyzed alkenylations of metallocenes via C–H activation were developed using electronically tunable pyrazolonaphthyridine (PzNPy) ligands. Ferrocene was alkenylated using the most electron-deficient ligand in the series, whereas the less reactive ruthenocene needed balancing of the electrophilicity and stability of catalysts. Various alkenes were installed, allowing fine-tuning of redox potentials. [ABSTRACT FROM AUTHOR]

A visible‐light‐induced regioselective tandem enamido β‐C(sp2)−H alkylation/acrylamido alkylation/cyclizative alkenylation sequence of 3‐aza‐1,5‐dienes is presented. This protocol is regiospecific, features a broad substrate scope, and provides a direct access to 3,4‐dialkylated 4‐pyrrolin‐2‐ones from readily available N‐alkenylacrylamides. It is readily scalable to a gram scale, and could be induced by natural sunlight. [ABSTRACT FROM AUTHOR]

Herein we report the regio‐ and stereoselective synthesis of tetrasubstituted alkenes from N‐carbamoyl indoles and alkynes via ruthenium(II)‐catalyzed C−H alkenylation/directing group migration, in which the carbamoyl directing group is endowed with a dual role of auxiliary group and migrating acylation reagent via C−N bond cleavage. This method features broad substrate scope, high atom‐ and step‐economy, good functional group tolerance and mild redox‐neutral conditions at room temperature. A series of structurally diverse tetrasubstituted alkenes were synthesized in good to excellent yields, highlighting the efficiency of this method. [ABSTRACT FROM AUTHOR]

An unprecedented orthogonal cross-coupling between aromatic C(sp2) and aliphatic olefinic C(sp2) carbons of two same molecules via dual C–H bond activation in an intermolecular fashion has been developed using a distal ester-directing group. This new coupling reaction led to the synthesis of the highly functionalized 1,3-diaryl molecular architecture in very good yields and with high chemo- and regioselectivities. In addition, using ester as the distal directing group, ortho C–H olefination of α-methyl aryl acrylates and cinnamic esters with various alkenes has been achieved in very good yields and with a wide range of substrate scope. [ABSTRACT FROM AUTHOR]

Catalytic alkylation of stable alkenyl C−O electrophiles is synthetically appealing, but studies to date have typically focused on the reactions with alkyl Grignard reagents. We report herein a cross‐electrophile reaction of alkenyl acetates with alkyl bromides. This work has enabled a new method for the synthesis of aliphatic alkenes from alkenyl acetates to be established that can be used to add more structural complexity and molecular diversity with enhanced functionality tolerance. The method allows for a gram‐scale reaction and modification of biologically active molecules, and it affords access to useful building blocks. Preliminary mechanistic studies reveal that the NiI species plays an essential role for the success of the coupling of these two reactivity‐mismatched electrophiles. [ABSTRACT FROM AUTHOR]

The synthesis of alkenylated-o-carboranes via photoalkenylation of iodocarboranes with unactivated alkenes has been achieved. This strategy features a transition metal-free protocol, a light-promoted reaction under mild reaction conditions, broad substrate scope and good functional group tolerance. Control experiments suggest that the reaction may involve the cage C-centered radical species. [ABSTRACT FROM AUTHOR]

We have achieved an Ir(III)‐catalyzed temperature‐controlled divergent synthesis of tetrasubstituted alkenes and pyrrolo[1,2‐a]indole derivatives through C−H alkenylation/DG migration and [3+2] annulation, respectively. This method has various advantageous features: a) excellent regio‐ and stereoselectivity and good functional group tolerance, b) broad substrate scope and moderate to excellent yields, c) mild redox‐neutral reaction conditions and operational simplicity. [ABSTRACT FROM AUTHOR]

A three-component and redox-neutral trifluoromethylative alkenylation of unactivated alkenes with β-nitrostyrenes has been developed under visible-light. This metal-free protocol utilizes the easy to handle Langlois reagent (CF3SO2Na) as the CF3 source and is suitable for various unactivated alkenes and β-nitrostyrenes, affording a series of trifluoromethylated aromatic alkenes under mild conditions in good to excellent yields. [ABSTRACT FROM AUTHOR]

A method for the synthesis of a wide range of 1,2‐benzothiazines bearing pyridyl, amide, sulfonamide, alkenyl, as well as aryl groups in 3,4‐position has been developed using transition metal‐catalyzed C−H activation reactions of pyridylbenzothiazines with dioxazolones, tosyl azide, alkenes, alkynes, and diaryliodonium salts. The present reaction provides an efficient method for the synthesis of a variety of 3,4‐functionalized benzothiazines from readily available starting materials and benefits a broad substrate scope, high functional group tolerance, and good regioselectivity. [ABSTRACT FROM AUTHOR]

A photoredox‐catalyzed iminoalkenylation of γ‐alkenyl O‐acyl oximes has been developed. Readily available alkenylboronic acids serve as alkenylation reagents, leading to densely functionalized pyrrolines. Both (E)‐ and (Z)‐cinnamylpyrrolines are accessible depending on the reaction solvent. In dichloromethane, (E)‐cinnamylpyrrolines are produced through a photoredox‐mediated single‐electron‐transfer process. In tetrahydrofuran, (Z)‐cinnamylpyrrolines are generated by photocatalytic contra‐thermodynamic E‐to‐Z isomerization of (E)‐cinnamylpyrrolines though an energy‐transfer pathway. Two stereocenters are established with complete diastereoselectivity and only one diastereomer is isolated. [ABSTRACT FROM AUTHOR]

Herein, we describe a practical protocol for efficient, mild, visible‐light‐induced three‐component intermolecular trifluoromethyl‐alkenylation reactions of unactivated alkenes. The protocol has good functional group tolerance and a broad substrate scope. Using this protocol, we not only introduced a trifluoromethyl group into alkenes but also converted unactivated alkenes to styrene‐based activated alkenes, in addition to accomplishing late‐stage functionalization of pharmaceutical intermediates. [ABSTRACT FROM AUTHOR]

Borane dimethylsulfide (BMS) was found to be an efficient hydride source for nickel‐hydride catalyzed reductive migratory hydrofunctionalization reactions. Catalytic reductive migratory hydroarylation and migratory hydroalkenylation were achieved with BMS in high yields and with excellent regioselectivity. A large‐scale experiment employing as little as 0.5 equivalents of BH3 ⋅ Me2S as the hydride source delivered the desired migratory hydroarylation product in high yield and selectivity. [ABSTRACT FROM AUTHOR]

A NiH‐catalyzed migratory hydroalkenylation reaction of olefins with alkenyl bromides has been developed, affording benzylic alkenylation products with high yields and excellent chemoselectivity. The mild conditions of the reaction preclude olefinic products from undergoing further isomerization or subsequent alkenylation. Catalytic enantioselective hydroalkenylation of styrenes was achieved by using a chiral bisoxazoline ligand. [ABSTRACT FROM AUTHOR]

Dihydro‐1,4‐thiazine skeletons bearing olefin fragment at their α‐position were prepared through a Pd(OAc)2‐catalysed Fujiwara‐Moritani type reaction via C−H alkenylation with olefins. This approach is selective, generalizable to a wide range of olefins and requires only 1 eq. of Ag2CO3 without the need of co‐oxidant. The C−H bond activation proved to be strongly dependent on the olefin's substitution while unfused dihydro‐1,4‐thiazines seemed to be affected by the oxidation state of the sulfur atom. The utility of olefins obtained was demonstrated by their implication in the dipolar cycloaddition reaction with a non‐stabilized azomethine ylide. [ABSTRACT FROM AUTHOR]

Functionalization of the bio‐relevant heterocycles 2‐arylbenzo[d]oxazole and 2‐arylbenzo[d]thiazole has been achieved through Ru(II)‐catalyzed alkenylation with unactivated olefins leading to selective formation of the mono‐alkenylated products. This approach has a broad substrate scope with respect to the coupling partners, affords high yields, and works for gram scale synthesis using a readily available Ru‐based catalyst. Mechanistic studies reveal a C−H activation pathway for the dehydrogenative coupling leading to the alkenylation. However, the results of the ESI‐MS‐guided deuterium kinetic isotope effect studies indicate that the C−H activation stage may not be the rate‐determining step of the reaction. The use of a radical scavenging agent such as TEMPO did not show any detrimental effect on the reaction outcome, eliminating the possibility of the involvement of a free‐radical pathway. [ABSTRACT FROM AUTHOR]

Ruth linker is a C5 pyrimidine modified nucleoside analogue widely utilized for the incorporation of a primary amine in a synthetic oligonucleotide. The increasing demand for non-radioactive labeling, detection of biomolecules, and assembly of COVID-19 test kits has triggered a need for scale-up of Ruth linker. Herein, an efficient protocol involving a palladium-catalyzed Heck alkenylation is described. The synthesis has been optimized with a goal of low catalyst concentration, column-free isolation, high product purity, reproducibility, and shorter reaction time. The scalability and utility of the process have been demonstrated successfully on a 100 g scale (starting material). Additionally, for scale-up of the Heck alkenylation protocol, 7-phospha-1,3,5-triaza-adamantanebutane sulfonate (PTABS) as the coordinating caged phosphine ligand was also synthesized on a multigram scale after careful optimization of the conditions. [ABSTRACT FROM AUTHOR]

The dealkenylative alkenylation of alkene C(sp3)−C(sp2) bonds has been an unexplored area for C−C bond formation. Herein 64 examples of β‐alkylated styrene derivatives, synthesized through the reactions of readily accessible feedstock olefins with β‐nitrostyrenes by ozone/FeII‐mediated radical substitutions, are reported. These reactions proceed with good efficiencies and high stereoselectivities under mild reaction conditions and tolerate an array of functional groups. Also demonstrated is the applicability of the strategy through several synthetic transformations of the products, as well as the syntheses of the natural product iso‐moracin and the drug (E)‐metanicotine. [ABSTRACT FROM AUTHOR]

Metal‐catalyzed chelation‐assisted C−H olefinations have emerged as powerful tools for the construction of functionalized alkenes. Herein, we describe the rhoda‐electrocatalyzed C−H activation/alkenylation of arenes. The olefinations of challenging electron‐poor benzamides were thus accomplished in a fully dehydrogenative fashion under electrochemical conditions, avoiding stoichiometric chemical oxidants, and with H2 as the only byproduct. This versatile alkenylation reaction also features broad substrate scope and used electricity as a green oxidant. [ABSTRACT FROM AUTHOR]

In this communication, a ruthenium‐catalyzed ortho‐alkenylation of acylgermanes with electron‐deficient alkenes through direct C–H bond activation has been developed. With acylgermane as the directing group, this method provides a straightforward access to diverse acylgermanes derivatives with good functional group tolerance and site‐selectivity under mild reaction conditions. [ABSTRACT FROM AUTHOR]

In this work, several alkenylated benzo[1,2‐b:4,5‐b′]dithiophene were synthesized by Pd‐catalyzed C−H functionalization of benzo[1,2‐b:4,5‐b′]dithiophene with various alkenes. This direct alkenylation took place regioselectively at the C‐2 position of the fused heterocycle. The obtained compounds were structurally characterized by NMR and MS spectroscopic methods. Moreover, DFT calculations have been employed to shed light on the regioselectivity of the reaction as well as on the geometry and electronic properties of the newly formed C=C double bonds. [ABSTRACT FROM AUTHOR]

N-Aryl-substituted piperazines constitute the core of several pharmacologically pertinent targets such as the antidepressant trintellix. We herein demonstrate that novel N-iodoaryl-substituted allylic ketopiperazinonates are amenable to efficient CuBr-catalyzed alkenylation with simple alkenes to afford N-stilbeno or styrenyl piperazine derivatives. [ABSTRACT FROM AUTHOR]

A novel palladium(0)‐catalyzed intermolecular coupling reaction of 2‐gem‐dibromovinylanilines and N‐tosylhydrazones was reported to construct 2‐(1‐phenylvinyl)‐indoles efficiently. The indole bearing 1, 1‐disubstituted alkenes were obtained in one step with short reaction time, in high yields and broad substrate scope. The formed indole derivates could be easily transformed into much more valuable molecules. [ABSTRACT FROM AUTHOR]

Efficient and H2O-controlled selective thiocyanation and alkenylation of internal olefins, to afford tetrasubstituted olefins under electrochemical oxidation, has been successfully developed. This transformation can present a critical feature wherein neither exogenous oxidants nor catalysts are required. Notably, such an electrochemical oxidation-based synthetic strategy exhibits excellent tolerance towards functional groups and can be easily scaled up with good efficiency. [ABSTRACT FROM AUTHOR]

A highly enantioselective synthesis of 1,4‐enynes is described that proceeds through an organocatalytic reaction between propargyl alcohols and trialkenylboroxines. Our strategy relies on acid‐mediated generation of the carbocationic intermediate from propargyl alcohols followed by enantioselective alkenylation with trialkenylboroxines. A range of chiral 1,4‐enynes were obtained in moderate to good yields with high levels of enantioselectivity. Use of a highly acidic chiral N‐triflyl phosphoramide catalyst, which has two distant Lewis basic oxygen atoms, was found to be crucial for both high reactivity and selectivity in the present reaction. [ABSTRACT FROM AUTHOR]

In this personal account, we summarize our investigations on the α-alkylation and α-alkenylation reactions of ketones with nonactivated alkenes and alkynes, respectively. The serendipitous discovery of C–H alkylation/alkenylation of cyclic 1,2-diketones provided a proof of concept for a dual activation strategy. Extension to the α-alkylation and α-alkenylation of regular ketones was achieved by using 7-azaindoline as a bifunctional ligand. Subsequently, intramolecular coupling -between ketones and olefins was achieved with Rh- and Ru-based systems, respectively. Finally, branched-selective α-alkylation was achieved through an Ir-catalyzed enamide-mediated C–H alkylation. 1 Introduction 2 Serendipitous Discovery of α-Alkylation and α-Alkenylation of 1,2-Diketones through Enamine-Mediated C–H Activation 3 Intermolecular Ketone α-Alkylation of Regular Ketones with Nonactivated Olefins 4 Intermolecular Ketone α-Alkenylation of Regular Ketones with Nonactivated Alkynes 5 Intramolecular Ketone α-Alkylation of Regular Ketones with Nonactivated Olefins 6 Branched-Selective α-Alkylation of Regular Ketones with Non-activated Olefins 7 Conclusions and Outlook [ABSTRACT FROM AUTHOR]

Alkenes are ubiquitous in Nature and their functionalization continues to attract attention from the scientific community. On the other hand, activation of alkenyl sp2 C–H bonds is challenging due to their chemical properties. In this short account, we elucidate, discuss and describe the utilization of transition-metal catalysts in alkene activation and provide useful strategies to synthesize organic building blocks in an efficient and sustainable manner. 1 Introduction 2 Breakthrough 3 Controlling E / Z , Z / E Selectivity 3.1 Esters and Amides as Directing Groups 3.2 The Chelation versus Non-Chelation Concept 4 Other Alkene Derivatives 5 Intramolecular C–H Activation 6 Conclusion and Future Projects [ABSTRACT FROM AUTHOR]

Abstract: Directing group and substrate control strategies have frequently been employed for the regioselective C−H alkenylation of acid‐ and oxidant‐sensitive pyrrole heterocycles. We developed an undirected, aerobic strategy for the C−H alkenylation of N‐alkylpyrroles by ligand control. For C2‐alkenylation of electron‐rich N‐alkylpyrroles, an electrophilic palladium catalyst derived from Pd(OAc)2 and 4,5‐diazafluoren‐9‐one (DAF) was used. Alternatively, a combination of Pd(OAc)2 and a mono‐protected amino acid ligand, Ac‐Val‐OH, was useful for C5‐alkenylation of N‐alkylpyrroles possessing electron‐withdrawing groups at the C2 position. This approach based on the electronic effects of heterocycles and catalysts can rapidly provide a wide range of alkenyl pyrroles from readily available N‐alkylpyrroles and alkenes. [ABSTRACT FROM AUTHOR]