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C–H Activation

The possibility of direct introduction of a new functionality (or a new C–C bond) via direct C–H bond transformation is a highly attractive strategy in covalent synthesis. The range of substrates is virtually unlimited, including hydrocarbons, complex organic compounds of small molecular weight, and synthetic and biological polymers. Below is a list of recent articles on this topic. For a review, see

  1. Xiao Chen, Keary M. Engle, Dong-Hui Wang, Jin-Quan Yu*
    Palladium(II)-Catalyzed C–H Activation/C–C Cross-Coupling Reactions: Versatility and Practicality
    Angew. Chem. 2009, 121, 5196–5217; Angew. Chem. Int. Ed. 2009, 48, 5094–5115

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Recent Articles

David A. Siler, Jeffrey D. Mighion, Erik J. Sorensen
An Enantiospecific Synthesis of Jiadifenolide [Communication]

An Enantiospecific Synthesis of Jiadifenolide

Establishing the framework: A Robinson annulation, van Leusen homologation, and a desymmetrizing C-H oxidation enabled an enantiospecific synthesis of the neurotrophic natural product jiadifenolide. From a pulegone-derived building block, a key propellane intermediate was constructed through the use of simple reagents in a highly diastereoselective fashion. A short series of oxidations of this tricylic framework allowed progression to the natural product.

Angew. Chem. Int. Ed., Apr 23, 2014, DOI: 10.1002/anie.201402335

Silver-Catalyzed Oxidative Activation of Benzylic C-H Bonds for the Synthesis of Difluoromethylated Arenes

Selectfluor serves as the fluorine source and AgNO3 as the catalyst in the oxidative activation of benzylic C-H bonds. This method was developed to transform methylated arenes with various functional groups into difluoromethylated arenes. The reaction is operationally simple and amenable to gram-scale synthesis.

Angew. Chem. Int. Ed., Apr 23, 2014, DOI: 10.1002/anie.201400225

Karolina Kwapien, Joachim Paier, Joachim Sauer, Michael Geske, Ulyana Zavyalova, Raimund Horn, Pierre Schwach, Annette Trunschke, Robert Schlögl
Sites for Methane Activation on Lithium-Doped Magnesium Oxide Surfaces [Communication]

Sites for Methane Activation on Lithium-Doped Magnesium Oxide Surfaces

The energy barriers for methane activation by hydrogen abstraction at oxygen radical sites are unrealistically low. C-H bonds can also heterolytically add onto a regular MgO ion pair at morphological defects such as steps and corners. Release of methyl radicals into the gas phase will happen only in the presence of O2.

Angew. Chem. Int. Ed., Apr 23, 2014, DOI: 10.1002/anie.201310632

Huixin Fan, Yaping Shang, Weiping Su
Palladium-Catalyzed Direct Arylation of Polyfluoroarenes with Organosilicon Reagents [Short Communication]

Palladium-Catalyzed Direct Arylation of Polyfluoroarenes with Organosilicon Reagents

Palladium-catalyzed intermolecular C–H bond arylation between polyfluoroarenes and organosilicon reagents is developed for the synthesis of polyfluorobiarenes. This method is simple and compatible with a broad range of functional groups and furnishes the corresponding products.

Eur. J. Org. Chem., Apr 17, 2014, DOI: 10.1002/ejoc.201402091

Chiharu Suzuki, Keisuke Morimoto, Koji Hirano, Tetsuya Satoh, Masahiro Miura
Ruthenium- and Rhodium-Catalyzed Dehydrogenative ortho-Alkenylation of Benzylamines via Free Amino Group Directed C-H Bond Cleavage [Communication]

Jing-Heng Meng, Xiao-Jiao Deng, Zi-Yu Li, Sheng-Gui He, Wei-Jun Zheng
Thermal Methane Activation by La6O10 Cluster Anions [Communication]

Thermal Methane Activation by La6O10− Cluster Anions

Stable and reactive: The La6O10 cluster anion works in thermal methane activation although this cluster is quite stable in terms of obtaining and losing an additional electron (VDE=4.06 eV). The reaction facilitated by the oxygen-centered radical follows a hydrogen-atom transfer mechanism (see figure).

Chem. Eur. J., Apr 15, 2014, DOI: 10.1002/chem.201400218

Daniel Winkelhaus, Douglas W. Stephan
Boron Perturbed Click Reactions Prompt Aromatic C-H Activations [Communication]

Boron Perturbed Click Reactions Prompt Aromatic C-H Activations

Click on B: The reaction of bis(pentafluorophenyl)boron alkynes and azides leads to unusual N3BC heterocycles (see scheme) resulting from aromatic C-H activation of benzene and toluene. While subsequent treatment of the heterocycle with PMe3 gave the P-B adduct, reaction with PtBu3 effected deprotonation to generate the corresponding phosphonium salt.

Angew. Chem. Int. Ed., Apr 11, 2014, DOI: 10.1002/anie.201402567

Iridium-Catalyzed Enantioselective C-H Alkylation of Ferrocenes with Alkenes Using Chiral Diene Ligands

Director’s cut: The first catalytic and enantioselective C-H alkylation of ferrocene derivatives with various alkenes was achieved. A cationic iridium complex, having a chiral diene ligand, and an isoquinolyl moiety as a directing group are essential for regioselective and enantioselective C-H bond activation. coe=cyclooctene, NaBARF=sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate.

Angew. Chem. Int. Ed., Apr 11, 2014, DOI: 10.1002/anie.201402518

Anis Tlili, Johannes Schranck, Jola Pospech, Helfried Neumann, Matthias Beller
Ruthenium-Catalyzed Hydroaroylation of Styrenes in Water through Directed C-H Bond Activation [Communication]

Ruthenium-Catalyzed Hydroaroylation of Styrenes in Water through Directed C-H Bond Activation

Three-Component Hydroaroylation: Hydroaroylation through C-H activation of (hetero)arenes bearing ortho-directing groups (DGs) proceeds in the presence of a ruthenium catalyst, carbon monoxide, and styrenes. The shown coupling process provides selective and atom-economic access to (hetero)- aromatic ketones.

ChemCatChem, Apr 11, 2014, DOI: 10.1002/cctc.201402031

Copper-Catalyzed Intramolecular Oxidative C(sp3)–H Amidation of 2-Aminoacetophenones: Efficient Synthesis of Indoline-2,3-diones

An efficient synthesis of diverse indoline-2,3-diones from 2-aminoacetophenones through copper-catalyzed intramolecular C(sp3)–H amidation is reported. The reaction proceeds in DMSO by using O2 as the sole oxidant to provide the desired products in moderate to good yields; Piv = pivaloyl.

Eur. J. Org. Chem., Apr 10, 2014, DOI: 10.1002/ejoc.201400012

Substrate-Dependent H/D Kinetic Isotope Effects and the Role of the Di(μ-oxo)diiron(IV) Core in Soluble Methane Monooxygenase: A Theoretical Study

Very large kinetic isotope effects (KIEs) were observed for the H-transfer of CH4 and CH3CN in the C-H activation by soluble methane monooxygenase; however, a relatively small KIE was observed for CH3NO2. Variational transition-state-theory calculations including tunneling revealed that the diverse KIE values originated mostly from substrate-dependent tunneling (see figure). The H-transfer dynamics and the role of the diiron core depend on the substrates.

Chem. Eur. J., Apr 08, 2014, DOI: 10.1002/chem.201303466

Jia-Xuan Yan, Hu Li, Xiang-Wei Liu, Jiang-Ling Shi, Xin Wang, Zhang-Jie Shi
Palladium-Catalyzed C(sp3)-H Activation: A Facile Method for the Synthesis of 3,4-Dihydroquinolinone Derivatives [Communication]

Palladium-Catalyzed C(sp3)-H Activation: A Facile Method for the Synthesis of 3,4-Dihydroquinolinone Derivatives

3,4-Dihydroquinolinones were synthesized by the palladium-catalyzed, oxidative-addition-initiated activation and arylation of inert C(sp3)-H bonds. Pd(OAc)2 and P(o-tol)3 were used as the catalyst and ligand, respectively, to improve the efficiency of the reaction. A further advantage of this reaction is that it could be performed in air.

Angew. Chem. Int. Ed., Apr 06, 2014, DOI: 10.1002/anie.201402562

Marcel Sickert, Harald Weinstabl, Brendan Peters, Xiao Hou, Mark Lautens
Intermolecular Domino Reaction of Two Aryl Iodides Involving Two C-H Functionalizations [Communication]

Intermolecular Domino Reaction of Two Aryl Iodides Involving Two C-H Functionalizations

Pendulum Reaction: 1 Pd complex catalyzes the intermolecular reaction of 2 aryl iodides to form 3 new C-C bonds through 2 C-H activations and 1 carbopalladation. The intermolecular domino reaction of two aryl iodides gives fused biaryls with a high level of convergence and efficiency. The key to success lies in the choice of an appropriate bulky Pd catalyst, which allows the aryl iodides to be distinguished in the key step.

Angew. Chem. Int. Ed., Apr 03, 2014, DOI: 10.1002/anie.201400807

Ruoyu He, Zhi-Tang Huang, Qi-Yu Zheng, Congyang Wang
Manganese-Catalyzed Dehydrogenative [4+2] Annulation of N-H Imines and Alkynes by C-H/N-H Activation [Communication]

Manganese-Catalyzed Dehydrogenative [4+2] Annulation of N-H Imines and Alkynes by C-H/N-H Activation

Hidden talents: The ability of manganese(I) to catalytically induce C-H and N-H bond cleavage, and C-C and C-N bond formation, has been recognized using the title reaction. The reaction produces H2 as the major by-product and eliminates the need for any oxidants, external ligands, or additives, and thus tolerating a wide range of functionalities.

Angew. Chem. Int. Ed., Apr 02, 2014, DOI: 10.1002/anie.201402575

C-H Bond Activation during and after the Reactions of a Metallacyclic Amide with Silanes: Formation of a μ-Alkylidene Hydride Complex, Its H–D Exchange, and β-H Abstraction by a Hydride Ligand

A tantalum metallacyclic complex undergoes intramolecular C-H activation upon reaction with H3SiPh to give a Ta/μ-alkylidene/hydride complex, which then undergoes β-H abstraction to form a complex with a bridging tantalaaziridine ligand (see scheme).

Chem. Eur. J., Mar 28, 2014, DOI: 10.1002/chem.201303166

Dan Mao, Gang Hong, Shengying Wu, Xin Liu, Jianjun Yu, Limin Wang
Lewis-Acid-Catalyzed Benzylic Reactions of 2-Methylazaarenes with Aldehydes [Full Paper]

Lewis-Acid-Catalyzed Benzylic Reactions of 2-Methylazaarenes with Aldehydes

Lewis-acid-promoted benzylic reactions of 2-methylazaarenes with common aldehydes have been extensively investigated for the first time. Series of azaarene derivatives including 2-(pyridin-2-yl)ethanols and 2-alkenylazaarenes were synthesized with wide substrate scopes by employing different catalysts that were optimized on the basis of the structures of the 2-methylazaarenes and the products.

Eur. J. Org. Chem., Mar 27, 2014, DOI: 10.1002/ejoc.201400073

Amidines for Versatile Ruthenium(II)-Catalyzed Oxidative C-H Activations with Internal Alkynes and Acrylates

Ring road: Cationic ruthenium(II) complexes allowed for efficient C-H activation on (hetero)aryl amidines with alkynes and alkenes, thereby providing a step-economical access to diversely decorated isoquinolines and isoindolines, respectively (see scheme).

Chem. Eur. J., Mar 27, 2014, DOI: 10.1002/chem.201304944

Ruthenium(II)-Catalyzed Synthesis of Isochromenes by C-H Activation with Weakly Coordinating Aliphatic Hydroxyl Groups

Cationic ruthenium(II) complexes enabled highly efficient oxidative annulation of alkynes with benzylic alcohols to deliver isochromenes (see scheme). This aliphatic hydroxyl-directed C-H/O-H activation proceeded efficiently under an atmosphere air. Mechanistic studies were indicative of an irreversible C-H metalation as the rate-limiting step.

Chem. Eur. J., Mar 27, 2014, DOI: 10.1002/chem.201400161

Christoph Kornhaaß, Christian Kuper, Lutz Ackermann
Ferrocenylalkynes for Ruthenium-Catalyzed Isohypsic C-H/N-O Bond Functionalizations [Update]

Juanjuan Du, Yaxi Yang, Huijin Feng, Yuanchao Li, Bing Zhou
Rhodium-Catalyzed Direct Amination of Arenes with Nitrosobenzenes: A New Route to Diarylamines [Full Paper]

Rhodium-Catalyzed Direct Amination of Arenes with Nitrosobenzenes: A New Route to Diarylamines

A RhIII-catalyzed addition of aryl C-H bonds to nitrosobenzenes, followed by cleavage of the resulting hydroxylamines in situ, is reported (see scheme). Different directing groups, such as N-based heterocycles and ketoximes, can be used in this C-H amination process, providing valuable diarylamines in excellent yields. Most importantly, this process provides a new method for attaching arylamine groups to aromatic rings.

Chem. Eur. J., Mar 26, 2014, DOI: 10.1002/chem.201400221

Shira D. Halperin, Hope Fan, Stanley Chang, Rainer E. Martin, Robert Britton
A Convenient Photocatalytic Fluorination of Unactivated C-H Bonds [Communication]

A Convenient Photocatalytic Fluorination of Unactivated C-H Bonds

The direct fluorination of unactivated C(sp3)-H bonds is catalyzed by the inexpensive photocatalyst tetrabutylammonium decatungstate (TBADT). This convenient reaction provides direct access to a wide range of fluorinated organic molecules, including structurally complex natural products, acyl fluorides, and fluorinated amino acids.

Angew. Chem. Int. Ed., Mar 25, 2014, DOI: 10.1002/anie.201400420

Antonio Zucca, Luca Maidich, Veronica Carta, Giacomo L. Petretto, Sergio Stoccoro, Maria Agostina Cinellu, Maria I. Pilo, Guy J. Clarkson
Cyclometalated Complexes of Platinum(II) with 2-Vinylpyridine [Full Paper]

Cyclometalated Complexes of Platinum(II) with 2-Vinylpyridine

The synthesis, and analytical and spectroscopic characterization of a series of cyclometalated complexes of platinum(II) with 2-vinylpyridine (L) is reported in detail. The five-membered cyclometalated ring is particularly stable, likely due to partial electronic delocalisation.

Eur. J. Inorg. Chem., Mar 20, 2014, DOI: 10.1002/ejic.201400052

Aerobic Double Dehydrogenative Cross Coupling between Cyclic Saturated Ketones and Simple Arenes

A simple and sustainable one-pot aerobic double dehydrogenative reaction under mild conditions for the introduction of arenes in the β-position of cyclic ketones has been developed (see scheme). Starting from the corresponding saturated ketone, this reaction sequence proceeds under relatively low Pd catalyst loading and involves catalytic amounts of electron-transfer mediators (ETMs) under ambient oxygen pressure.

Chem. Eur. J., Mar 13, 2014, DOI: 10.1002/chem.201402063

Darapaneni Chandra Mohan, Sadu Nageswara Rao, Chitrakar Ravi, Subbarayappa Adimurthy
Copper(I) Iodide Catalyzed Aerobic Oxidative C-N and C-S bond formations through C-H Activation: Synthesis of Functionalized Imidazo[1,2-a]pyridines [Communication]

Copper(I) Iodide Catalyzed Aerobic Oxidative C-N and C-S bond formations through C-H Activation: Synthesis of Functionalized Imidazo[1,2-a]pyridines

Cop that! A general and efficient method for the synthesis of imidazo[1,2-a]pyridines through C-H activation with methyl ketones in water catalyzed by copper(I) iodide is described. One-pot, three-component coupling reactions to access sulfenylimidazo[1,2-a]pyridines have also been developed. MCR=multicomponent reaction.

Asian J. Org. Chem., Mar 11, 2014, DOI: 10.1002/ajoc.201402004

Cytochrome P450 Catalyzed Oxidative Hydroxylation of Achiral Organic Compounds with Simultaneous Creation of Two Chirality Centers in a Single C-H Activation Step

Two birds with one stone: Two new centers of chirality are created by the cytochrome P450 catalyzed regio-, diastereo-, and enantioselective oxidative hydroxylation of appropriate achiral compounds. When using either wild type cytochrome P450 BM3 or mutants generated by directed evolution, a high preference for one of the four stereotopic H atoms is observed depending on the nature of the X moiety in the substrate.

Angew. Chem. Int. Ed., Mar 03, 2014, DOI: 10.1002/anie.201310892

Rajendran Suresh, Shanmugam Muthusubramanian, Rajendran Senthil Kumaran, Govindaswamy Manickam
C2-Arylation of Substituted Pyridine N-oxides with Heteroaryl Carboxylic Acids by Palladium-Catalyzed Decarboxylative Coupling [Communication]

C2-Arylation of Substituted Pyridine N-oxides with Heteroaryl Carboxylic Acids by Palladium-Catalyzed Decarboxylative Coupling

Taking NO for an answer: C2-Arylation of substituted pyridine N-oxides with heteroaryl carboxylic acids through a palladium-catalyzed decarboxylative coupling is described. Pyridine N-oxides connected to other heteroaryl rings can be obtained in a single step. The regioselectivity with respect to both components is excellent. Further, pyridine N-oxides were used to study the efficiency of decarboxylative coupling compared with aryl halide coupling.

Asian J. Org. Chem., Mar 03, 2014, DOI: 10.1002/ajoc.201400013

A Commercially Available Tantalum Catalyst for the Highly Regioselective Intermolecular Hydroaminoalkylation of Styrenes

Highly regioselective intermolecular hydroaminoalkylation reactions of styrenes are achieved in the presence of the commercially available homoleptic catalyst [Ta(NMe2)5]. The process activates the α-C–H bonds of N-methylanilines and 1,2,3,4-tetrahydroquinoline and gives access to the corresponding branched hydroaminoalkylation products in good-to-excellent yields.

Eur. J. Org. Chem. 2014, No. 13, 2790-2797

Shiguang Pan, Takayuki Wakaki, Naoto Ryu, Takanori Shibata
Ir(III)-Catalyzed C7-Position-Selective Oxidative C-H Alkenylation of Indolines with Alkenes in Air [Communication]

Ir(III)-Catalyzed C7-Position-Selective Oxidative C-H Alkenylation of Indolines with Alkenes in Air

Lettin' the cat outta the bag: An efficient IrIII-catalyzed oxidative coupling of N-substituted indolines with various alkenes at the C7-position in air assisted by a carbonyl or carbamoyl group as a directing group is reported. The catalyst was prepared from [Cp*IrCl2]2 and AgOTf. A variety of 7-alkenylindolines were obtained in moderated to high yields. The reaction is potentially applicable to the synthesis of 7-alkylindoles and 7-alkenylindoles.

Chem. Asian J. 2014, 9, No. 05, 1257-1260

Copper- and Palladium-Cocatalyzed Intramolecular C–H Functionalization/C–N Bond Formation: A Route to the Synthesis of Indoloisoquinoline Derivatives

A new approach to the synthesis of indoloisoquinoline derivatives is described. The activation of the indole C2–H bond is accomplished here by using a Pd(OAc)2 and Cu(OTf)2 bi-catalytic system. In this reaction aldoximes are converted into the corresponding isoquinolines in open atmosphere under mild reaction condition.

Eur. J. Org. Chem. 2014, No. 13, 2806-2812

Xiao-Feng Xia, Yu-Qi Wang, Lu-Lu Zhang, Xian-Rong Song, Xue-Yuan Liu, Yong-Min Liang
Palladium-Catalyzed C-H Activation and Intermolecular Annulation with Allenes [Full Paper]

Palladium-Catalyzed C-H Activation and Intermolecular Annulation with Allenes

A new and efficient PdII-catalyzed intermolecular annulation of N-benzoylsulfonamide with allenes for the synthesis of 3,4-dihydroisoquinolin-1(2H)-ones is reported (see scheme). This C-H functionalization is compatible with ambient air and moisture, and it can be applied to terminal or internal allenes with different synthetically attractive functional groups. Control experiments and a kinetic isotope effect study were conducted and a plausible mechanism is proposed.

Chem. Eur. J. 2014, 20, No. 17, 5087-5091

Christophe Aïssa, Kelvin Y. T. Ho, Daniel J. Tetlow, María Pin-Nó
Diastereoselective Carbocyclization of 1,6-Heptadienes Triggered by Rhodium-Catalyzed Activation of an Olefinic C-H Bond [Communication]

Diastereoselective Carbocyclization of 1,6-Heptadienes Triggered by Rhodium-Catalyzed Activation of an Olefinic C-H Bond

Folding alkenes: Described is the first example of a rhodium(I)-catalyzed functionalization of an olefinic C-H bond with a 1,6-heptadiene reagent. This carbocyclization is completely diastereoselective and creates at least three stereogenic centers from simple prochiral substrates. The directing group can easily be converted into other functional groups.

Angew. Chem. Int. Ed. 2014, 53, No. 16, 4209-4212

Xiaodong Tang, Liangbin Huang, Yanli Xu, Jidan Yang, Wanqing Wu, Huanfeng Jiang
Copper-Catalyzed Coupling of Oxime Acetates with Sodium Sulfinates: An Efficient Synthesis of Sulfone Derivatives [Communication]

Copper-Catalyzed Coupling of Oxime Acetates with Sodium Sulfinates: An Efficient Synthesis of Sulfone Derivatives

Copper brings us together: The title reaction involves copper-catalyzed N-O bond cleavage, activation of a vinyl sp2 C-H bond and C-S bond formation; it uses simple oxime acetates and sodium sulfinates to synthesize sulfonylvinylamine products without the need for additional oxidants or additives. Upon hydrolysis, useful β-ketosulfones are obtained.

Angew. Chem. Int. Ed. 2014, 53, No. 16, 4205-4208

Palladium(II)-Catalyzed ortho-C-H Arylation/Alkylation of N-Benzoyl α-Amino Ester Derivatives

C-H activation: The transformation of N-benzoyl amino acid ester derivatives (Gly, Asp) has been studied, in which the ortho-C-H activation/C-C bond formation was achieved by using the synergistic system Pd(OAc)2/AgOAc and halide compounds as coupling partners in t-Amyl-OH under air (see scheme).

Chem. Eur. J. 2014, 20, No. 16, 4548-4553

Hypervalent Iodine-Mediated Selective Oxidative Functionalization of (Thio)chromones with Alkanes

Hypervalent iodine: An efficient IIII-mediated selective oxidative functionalization of alkanes with chromones and (thio)chromones has been developed. The developed methodology provides a direct access to the 2-alkyl chromones under metal-free and ambient conditions. Both cyclic and acyclic alkanes can be selectively functionalized (see scheme).

Chem. Eur. J. 2014, 20, No. 16, 4568-4572

Elise Salanouve, Ghania Bouzemame, Sébastien Blanchard, Etienne Derat, Marine Desage-El Murr, Louis Fensterbank
Tandem C-H Activation/Arylation Catalyzed by Low-Valent Iron Complexes with Bisiminopyridine Ligands [Full Paper]

Tandem C-H Activation/Arylation Catalyzed by Low-Valent Iron Complexes with Bisiminopyridine Ligands

A radical choice! A low-valent iron complex with non-innocent bisiminopyridine ligands performs C-H activation/arylation of unactivated aryl compounds (see figure). The reaction likely involves ligand-based radicals, whereas previously reported iron-based systems imply substrate-based radicals.

Chem. Eur. J. 2014, 20, No. 16, 4754-4761

Bingxian Liu, Tao Zhou, Bin Li, Shansheng Xu, Haibin Song, Baiquan Wang
Rhodium(III)-Catalyzed Alkenylation Reactions of 8-Methylquinolines with Alkynes by C(sp3)-H Activation [Communication]

Rhodium(III)-Catalyzed Alkenylation Reactions of 8-Methylquinolines with Alkynes by C(sp3)-H Activation

Highly regio- and stereoselective alkenylation reactions of 8-methylquinolines with alkynes give 8-allylquinolines in good yields. These reactions are catalyzed by [{Cp*RhCl2}2] (Cp*=C5Me5) and proceed by C(sp3)-H bond activation.

Angew. Chem. Int. Ed. 2014, 53, No. 16, 4191-4195

Qing Gu, Hamad H. Al Mamari, Karolina Graczyk, Emelyne Diers, Lutz Ackermann
Iron-Catalyzed C(sp2)-H and C(sp3)-H Arylation by Triazole Assistance [Communication]

Iron-Catalyzed C(sp2)-H and C(sp3)-H Arylation by Triazole Assistance

With a little help: A versatile iron catalyst allows the arylation of C(sp2)-H and C(sp3)-H bonds in the presence of a modular and removable triazolyldimethylmethyl (TAM) auxiliary, whose structure can be varied through 1,3-dipolar azide–alkyne cycloadditions.

Angew. Chem. Int. Ed. 2014, 53, No. 15, 3868-3871

Xuesong Wu, Yan Zhao, Guangwu Zhang, Haibo Ge
Copper-Catalyzed Site-Selective Intramolecular Amidation of Unactivated C(sp3)-H Bonds [Communication]

Copper-Catalyzed Site-Selective Intramolecular Amidation of Unactivated C(sp3)-H Bonds

Getting ahead on tams: The intramolecular dehydrogenative amidation of aliphatic amides, directed by a bidentate ligand, was developed using a copper-catalyzed sp3 C-H bond functionalization process to deliver β-lactams. The reaction favors the C-H bonds of β-methyl groups over the unactivated methylene C-H bonds, as well as aromatic C(sp2)-H bonds and unactivated secondary C(sp3)-H bonds of rings.

Angew. Chem. Int. Ed. 2014, 53, No. 14, 3706-3710

ortho-Benzoxylation of N-Alkyl Benzamides with Aromatic Acids Catalyzed by Ruthenium(II) Complex

C-H bond activation: A highly regioselective ortho-benzoxylation of benzamides with substituted benzoic acids in the presence of a ruthenium catalyst is described. Further, Ru-catalyzed alkenylation is carried out at the ortho C-H bond of benzoxylated N-alkyl benzamides with alkenes in water solvent. Subsequently, the benzoxyl moiety of N-alkyl benzamides was converted into the hydroxyl group in the presence of base or acid (see scheme).

Chem. Eur. J. 2014, 20, No. 14, 4092-4097

Irina E. Tsyshchuk, Daria V. Vorobyeva, Alexander S. Peregudov, Sergey N. Osipov
Cu-Catalyzed Carbenoid Functionalization of Indoles by Methyl 3,3,3-Trifluoro-2-diazopropionate [Full Paper]

Cu-Catalyzed Carbenoid Functionalization of Indoles by Methyl 3,3,3-Trifluoro-2-diazopropionate

An efficient Cu-catalyzed direct CH-functionalization of indoles with methyl 3,3,3-trifluoro-2-diazopropionate has been developed. The reactions proceed within a few minutes under low catalyst loading to give the corresponding C3 or C2 substitution products with high regioselectivity. This method has been successfully applied for the synthesis of trifluoromethyl-containing paullone.

Eur. J. Org. Chem. 2014, No. 12, 2480-2486

Choon Wee Kee, Ke Min Chan, Ming Wah Wong, Choon-Hong Tan
Selective Bromination of sp3 C-H Bonds by Organophotoredox Catalysis [Full Paper]

Selective Bromination of sp3 C-H Bonds by Organophotoredox Catalysis

Lights on! Aided by morpholine, bromination of sp3 C-H bonds can be achieved under visible light irradiation by using a low loading of Eosin Y as a photoredox catalyst, a low-power household lamp as a light source, and CBr4 as the source of bromine. The potential to use this reaction for mild and regioselective bromination of sp3 C-H bonds in complex molecules is exemplified by the bromination of (+)-sclareolide and acetate-protected estrone.

Asian J. Org. Chem. 2014, 3, No. 04, 536-544

Changduo Pan, Ablimit Abdukader, Jie Han, Yixiang Cheng, Chengjian Zhu
Ruthenium-Catalyzed C7 Amidation of Indoline C-H Bonds with Sulfonyl Azides [Communication]

Ruthenium-Catalyzed C7 Amidation of Indoline C-H Bonds with Sulfonyl Azides

Synthetic methods: A ruthenium-catalyzed direct C7 amidation of indoline C-H bonds with sulfonyl azides was developed (see scheme, DCE=1,2-dichloroethane). This procedure allows the synthesis of a variety of 7-amino-substituted indolines in good yields. The good functional-group tolerance as well as the mild conditions are prominent features of this method.

Chem. Eur. J. 2014, 20, No. 13, 3606-3609

Haizhu Yu, Chen Wang, Yimeng Yang, Zhi-Min Dang
Mechanistic Study on Rh-Catalyzed Stereoselective C-C/C-H Activation of tert-Cyclobutanols [Full Paper]

Mechanistic Study on Rh-Catalyzed Stereoselective C-C/C-H Activation of tert-Cyclobutanols

Three out of five steps in the Rh-catalyzed stereoselective transformation of aryl-substituted tert-cyclobutanols into indanols were shown by DFT calculations to make important contributions to determining the stereoselectivity, while the rate-determining step is the 1,4-Rh transfer. The present study corroborated the previous proposal that the reaction occurs by metalation, β-C elimination, 1,4-Rh transfer, C=O insertion, and a final catalyst-regeneration step (see figure).

Chem. Eur. J. 2014, 20, No. 13, 3839-3848

Zechao Wang, Qinshan Tian, Xin Yu, Chunxiang Kuang
Palladium-Catalyzed Acylation of 2-Aryl-1,2,3-triazoles with Aldehydes [Communication]

Zhen Wang, Jizhi Ni, Yoichiro Kuninobu, Motomu Kanai
Copper-Catalyzed Intramolecular C(sp3)-H and C(sp2)-H Amidation by Oxidative Cyclization [Communication]

Copper-Catalyzed Intramolecular C(sp3)-H and C(sp2)-H Amidation by Oxidative Cyclization

Silver ox: By using a Cu(OAc)2 catalyst and an Ag2CO3 oxidant in dichloroethane solvent, C(sp3)-H amidation proceeded at a terminal methyl group as well as at the internal benzylic position of an alkyl chain. This reaction has a broad substrate scope, and various β-lactams were obtained in excellent yield, even on a gram scale. Use of CuCl2 and Ag2CO3 under an O2 atmosphere led to 2-indolinone selectively synthesized by C(sp2)-H amidation. DMSO=dimethylsulfoxide.

Angew. Chem. Int. Ed. 2014, 53, No. 13, 3496-3499

Marie-Laure Louillat, Agostino Biafora, Fabien Legros, Frederic W. Patureau
Ruthenium-Catalyzed Cross-Dehydrogenative ortho-N-Carbazolation of Diarylamines: Versatile Access to Unsymmetrical Diamines [Communication]

Ruthenium-Catalyzed Cross-Dehydrogenative ortho-N-Carbazolation of Diarylamines: Versatile Access to Unsymmetrical Diamines

No–No–No: Amination of a non-acidic C-H bond, no pre-activation of the coupling partners, no chelate-assisting directing group. Dehydrogenative C–N cross-coupling through the ortho-N-carbazolation of unprotected, secondary anilines has been achieved using a Ru catalyst with O2 as the terminal oxidant. The reactions proceed in an intermolecular fashion, selectively in the ortho position.

Angew. Chem. Int. Ed. 2014, 53, No. 13, 3505-3509

Zhao-Lei Yan, Wen-Liang Chen, Ya-Ru Gao, Shuai Mao, Yan-Lei Zhang, Yong-Qiang Wang
Palladium-Catalyzed Intermolecular C-2 Alkenylation of Indoles Using Oxygen as the Oxidant [Update]

Probing the Limits of Ligand Steric Bulk: Backbone C-H Activation in a Saturated N-Heterocyclic Carbene

How big is too big? The consequences of extremely high steric loading have been probed in late transition metal complexes featuring the expanded ring N-heterocyclic carbene 6-Dipp (Dipp=diisopropyl phenyl). In the presence of [(6-Dipp)Au]+, the first example of backbone C-H activation of a saturated N-heterocyclic carbene is revealed, proceeding via a mechanism which involves free carbene in addition to the AuI centre (see illustration, Mes=mesityl).

Chem. Eur. J. 2014, 20, No. 13, 3825-3830

Copper-Catalyzed Trifluoromethylation of Internal Olefinic C-H Bonds: Efficient Routes to Trifluoromethylated Tetrasubstituted Olefins and N-Heterocycles

CuII-catalyzed trifluoromethylation of internal olefins has been achieved by using Cu(OH)2 as a catalyst and TMSCF3 as a trifluoromethylating reagent (see scheme). The push–pull effect from the olefin substrates facilitates the internal olefinic C-H bond trifluoromethylation. A mechanism involving radicals is proposed, and derivatization of the resultant CF3 olefins led to multifunctionalized CF3 olefins and trifluoromethylated N-heterocycles.

Chem. Eur. J. 2014, 20, No. 12, 3439-3445

Tao Zhang, Zisong Qi, Xueyun Zhang, Lamei Wu, Xingwei Li
RhIII-Catalyzed Hydroacylation Reactions between N-Sulfonyl 2-Aminobenzaldehydes and Olefins [Communication]

RhIII-Catalyzed Hydroacylation Reactions between N-Sulfonyl 2-Aminobenzaldehydes and Olefins

Synthetically practical hydroacylation reactions have been realized between N-sulfonyl 2-aminobenzaldehydes and olefins under RhIII catalysis by means of a C-H activation pathway. Different categories of olefins, including aliphatic ones, are viable substrates. A different selectivity such as oxidative coupling could take place when Ag2CO3 was used as an oxidant (see scheme).

Chem. Eur. J. 2014, 20, No. 12, 3283-3287

Engineering of P450pyr Hydroxylase for the Highly Regio- and Enantioselective Subterminal Hydroxylation of Alkanes

Get a handle on it: Highly regio- and enantioselective subterminal hydroxylation of n-octane and propylbenzene was observed with P450 enzymes obtained by the directed evolution of terminal-selective P450pyr hydroxylase (see scheme). The engineered enzymes with their fully altered selectivities are useful for the functionalization of alkanes and the preparation of enantiomerically pure alcohols.

Angew. Chem. Int. Ed. 2014, 53, No. 12, 3120-3124

C-H Bond Arylation in the Synthesis of Aryltetralin Lignans: A Short Total Synthesis of Podophyllotoxin

Testing a new tactic: In a concise synthesis of podophyllotoxin with a crucial palladium-catalyzed arylation step, subtle conformational effects govern reductive elimination pathways from the high-valent palladium center. This route to aryltetralin lignan derivatives may be of interest in drug discovery.

Angew. Chem. Int. Ed. 2014, 53, No. 12, 3115-3119

Qing Xiao, Xiangtai Meng, Motomu Kanai, Yoichiro Kuninobu
Palladium-Catalyzed C-H Fluorosilylation of 2-Phenylpyridines: Synthesis of Silafluorene Equivalents [Communication]

Palladium-Catalyzed C-H Fluorosilylation of 2-Phenylpyridines: Synthesis of Silafluorene Equivalents

Treatment of 2-phenylpyridines with amino(1,3,2-dioxaborolan-2-yl)diphenylsilane produced fluorosilylated 2-phenylpyridines in good to excellent yields under palladium catalysis. This reaction is the first example of C-H fluorosilylation. A Lewis acid–base interaction exists between the silicon and nitrogen atoms, and the obtained fluorosilylated products can be regarded as silafluorene equivalents.

Angew. Chem. Int. Ed. 2014, 53, No. 12, 3168-3172

Wolfram R. Grüning, Georges Siddiqi, Olga V. Safonova, Christophe Copéret
Bipyridine Periodic Mesoporous Organosilica: A Solid Ligand for the Iridium-Catalyzed Borylation of C-H Bonds [Communication]

Harit U. Vora, Anthony P. Silvestri, Casper J. Engelin, Jin-Quan Yu
Rhodium(II)-Catalyzed Nondirected Oxidative Alkenylation of Arenes: Arene Loading at One Equivalent [Communication]

Rhodium(II)-Catalyzed Nondirected Oxidative Alkenylation of Arenes: Arene Loading at One Equivalent

Down to one: A C-H alkenylation of simple arenes without the need for an excess amount of the arene was possible with a bimetallic RhII catalyst (see scheme). A phosphine ligand as well as a combination of the oxidants Cu(TFA)2 and V2O5 proved essential for the efficient synthesis of monoalkenylated products with good selectivity, especially for di- and trisubstituted arene substrates.

Angew. Chem. Int. Ed. 2014, 53, No. 10, 2683-2686

Chao Feng, Teck-Peng Loh
Rhodium-Catalyzed C-H Alkynylation of Arenes at Room Temperature [Communication]

Rhodium-Catalyzed C-H Alkynylation of Arenes at Room Temperature

Hot rhod: A rhodium-catalyzed, electronically reversed Sonogashira reaction between unbiased arenes and the hypervalent iodine reagent 1 proceeds through C-H activation. This reaction displays excellent functional-group tolerance and high efficiency, and thus opens a new synthetic pathway to access functionalized alkynes. Cp*=C5Me5, DCE=1,2-dichloroethane, Piv=pivaloyl, TIPS=triisopropylsilyl.

Angew. Chem. Int. Ed. 2014, 53, No. 10, 2722-2726

α-MsO/TsO/Cl Ketones as Oxidized Alkyne Equivalents: Redox-Neutral Rhodium(III)-Catalyzed C-H Activation for the Synthesis of N-Heterocycles

Who needs alkynes? α-Halo and pseudohalo ketones (as C(sp3)-based electrophiles) are utilized as oxidized alkyne equivalents in RhIII-catalyzed redox-neutral annulations to efficiently generate diverse N-heterocycles. Owing to the mild reaction conditions, a variety of functional groups are tolerated.

Angew. Chem. Int. Ed. 2014, 53, No. 10, 2754-2758

Suman K Roy, Subhas Samanta, Nabanita Saha Chowdhury, Tapan K. Mondal, Sreebrata Goswami
Double Carom-H Activation Associated with Etheral Oxygen Insertion to Phenazine Architecture in Oxidisable Ruthenium(III) Complexes: A Mechanistic Insight [Communication]

Double Carom-H Activation Associated with Etheral Oxygen Insertion to Phenazine Architecture in Oxidisable Ruthenium(III) Complexes: A Mechanistic Insight

Unprecedented examples of double aromatic ring C-H bond activation associated with C-O bond formation reactions to phenazine architecture in RuIII complexes are presented. The chemical transformations have led to formation of new RuIV complexes with angular pentacyclo heterocyclic ligands (see scheme).

Chem. Eur. J. 2014, 20, No. 10, 2712-2717

Imen Smari, Chiraz Youssef, Kedong Yuan, Anissa Beladhria, Hamed Ben Ammar, Bechir Ben Hassine, Henri Doucet
Formyl Substituent at C-4 of Pyrazoles: A Temporary Protecting Group for Regioselective Palladium-Catalyzed Direct Arylation at C-5 [Full Paper]

Formyl Substituent at C-4 of Pyrazoles: A Temporary Protecting Group for Regioselective Palladium-Catalyzed Direct Arylation at C-5

Pyrazoles with an aldehyde function at C-4 underwent a palladium-catalyzed direct arylation reaction to provide a regioselective approach to 5-aryl-substituted pyrazoles. The formyl substituent can be easily removed by using a Pd catalyst and, therefore, is considered a temporary protecting group.

Eur. J. Org. Chem. 2014, No. 08, 1778-1786

José Luis García Ruano, José Alemán, Alejandro Parra, Leyre Marzo
Sulfonyl Acetylenes as Alkynylating Reagents Under Radical or Anionic Conditions [Microreview]

Sulfonyl Acetylenes as Alkynylating Reagents Under Radical or Anionic Conditions

We summarize a powerful methodology for the alkynylation of C(sp3), C(sp2), and C(sp) carbon atoms, as well as some heteroatoms, with alkynylsulfones. It is based on the fact that β-substituted sulfonylacetylenes undergo unexpected anti-Michael addition of organolithiums and radical species, giving intermediates that evolve into alkynyl derivatives in situ by elimination of the anion or radical TolSO2.

Eur. J. Org. Chem. 2014, No. 08, 1577-1588

Christian Adler, Alexander Bekurdts, Detlev Haase, Wolfgang Saak, Marc Schmidtmann, Rüdiger Beckhaus
Bulky Titanium Amides: C–H Bond Activation under Mild Conditions [Full Paper]

Bulky Titanium Amides: C–H Bond Activation under Mild Conditions

The solid-state structures of tetrahedral and octahedral titanium amide complexes with bulky dicyclohexylamido ligands reveal a characteristic close contact between the titanium atom and a carbon atom in the β-position. The exchange of a chlorine atom by a bulky pentafulvene ligand increases this effect. The introduction of other sterically demanding amines to complexes initiates a spontaneous C–H activation.

Eur. J. Inorg. Chem. 2014, No. 08, 1289-1302

Substrate-Directed Hydroacylation: Rhodium-Catalyzed Coupling of Vinylphenols and Nonchelating Aldehydes

COs with a local branch: A hydroacylation of vinylphenols with aryl, alkenyl, and alkyl aldehydes gave the branched products: α-aryl ketone precursors to benzofurans. This cross-coupling enabled access to eupomatenoid natural products in four steps or less from eugenol (see scheme; cod=1,5-cyclooctadiene). Aldehyde decarbonylation was avoided by use of an anionic directing group on the alkene and a small-bite-angle diphosphine ligand.

Angew. Chem. Int. Ed. 2014, 53, No. 09, 2455-2459

Propane Activation by Palladium Complexes with Chelating Bis(NHC) Ligands and Aerobic Cooxidation

Reoxidation by dioxygen: The combination of C-H activation by a homogeneous catalytic palladium complex with a vanadiumoxo co-catalyst allows the selective aerobic oxidation of propane with dioxygen (see scheme).

Angew. Chem. Int. Ed. 2014, 53, No. 09, 2485-2488

Weifeng Song, Sebastian Lackner, Lutz Ackermann
Nickel-Catalyzed C-H Alkylations: Direct Secondary Alkylations and Trifluoroethylations of Arenes [Communication]

Nickel-Catalyzed C-H Alkylations: Direct Secondary Alkylations and Trifluoroethylations of Arenes

In an absence of activation: A robust nickel(II) catalyst enabled secondary alkylations of unactivated aryl C-H bonds with secondary alkyl bromides and chlorides with ample substrate scope. Based on this system the first C-H trifluoroethylations of arenes with unactivated C-H bonds could be carried out (see scheme; Q=8-quinolinyl).

Angew. Chem. Int. Ed. 2014, 53, No. 09, 2477-2480

Rhodium(III)-Catalyzed C-H Activation and Indole Synthesis With Hydrazone as an Auto-Formed and Auto-Cleavable Directing Group

Hydrazones were employed as auto-formed and auto-cleavable directing groups (DGauto) for RhIII-catalyzed C-H activation. This strategy, which was inspired by the venerable Fischer indole synthesis, was successfully applied for efficient and external-oxidant-free synthesis of unprotected indoles from readily available aryl hydrazines and alkynes.

Chem. Eur. J. 2014, 20, No. 08, 2352-2356

Gold-Catalyzed Cyclization of Diynes: Controlling the Mode of 5-endo versus 6-endo Cyclization—An Experimental and Theoretical Study by Utilizing Diethynylthiophenes

Two gold centers combined for cyclization: Diynes containing a 3,4-thiophene backbone cyclize under gold catalysis, via gold–vinylidenes and C-H activation, generating pentaleno[c]thiophenes. Switching the diyne backbone changes the cyclization pathway. A DFT study analyzed the influence of the diyne backbone and gave an explanation for the 5-endo versus 6-endo selectivity (see figure).

Chem. Eur. J. 2014, 20, No. 08, 2215-2223

Debalina Ghosh, Jhen-Yi Lee, Chian-Yu Liu, Yen-Hsin Chiang, Hon Man Lee
Direct C-H Arylations of Unactivated Arenes Catalyzed by Amido-Functionalized Imidazolium Salts [Communication]

Matthew P. Conley, Murielle F. Delley, Georges Siddiqi, Giuseppe Lapadula, Sébastien Norsic, Vincent Monteil, Olga V. Safonova, Christophe Copéret
Polymerization of Ethylene by Silica-Supported Dinuclear CrIII Sites through an Initiation Step Involving C-H Bond Activation [Communication]

Polymerization of Ethylene by Silica-Supported Dinuclear CrIII Sites through an Initiation Step Involving C-H Bond Activation

Three is better than two: CrIII silicates, in contrast to the CrII analogues, were found to be efficient ethylene-polymerization catalysts that initiate the reaction without a cocatalyst through the heterolytic splitting of an ethylene C-H bond across a Cr-O bond (see picture). This study provides clues about the active sites and initiation mechanism of the industrial Phillips catalyst.

Angew. Chem. Int. Ed. 2014, 53, No. 07, 1872-1876

Vaibhav P. Mehta, José-Antonio García-López, Michael F. Greaney
Ruthenium-Catalyzed Cascade C-H Functionalization of Phenylacetophenones [Communication]

Ruthenium-Catalyzed Cascade C-H Functionalization of Phenylacetophenones

Carbon coupling cascade: Arylacetophenones react with Michael acceptors under ruthenium catalysis to set up triple and quadruple C-H functionalization pathways. Through choice of reaction conditions, novel indanone carbacycles, indeno indene carbacycles, and indeno furanone heterocycles can each be accessed in a single step.

Angew. Chem. Int. Ed. 2014, 53, No. 06, 1529-1533

Jamshid Rajabi, Mélanie M. Lorion, Vu Linh Ly, Frédéric Liron, Julie Oble, Guillaume Prestat, Giovanni Poli
Dormant versus Evolving Aminopalladated Intermediates: Toward a Unified Mechanistic Scenario in PdII-Catalyzed Aminations [Full Paper]

Dormant versus Evolving Aminopalladated Intermediates: Toward a Unified Mechanistic Scenario in PdII-Catalyzed Aminations

Asleep or awake? Unsaturated N nucleophiles react through two competing pathways under PdII catalysis: C-H allylic activation and aminopalladation. New data are in accord with the initial generation of a high-energy cyclic aminopalladated intermediate (API) that can either evolve along different pathways such as β-H elimination, oxidation, or carbopalladation, or lay dormant, the latter leading to alternative types of reactivity, such as allylic C-H activation or [3,3]-sigmatropic rearrangement, gaining the upper hand (see scheme; Ts=p-toluenesulfonyl).

Chem. Eur. J. 2014, 20, No. 06, 1539-1546

Visible-Light-Facilitated 5-exo-trig Cyclization of 1,6-Dienes with Alkyl Chlorides: Selective Scission of the C(sp3)–H Bond in Alkyl Chlorides

The 5-exo-trig cyclization of 1,6-dienes with alkyl chlorides through a visible-light-facilitated radical strategy is presented. This is achieved by selectively splitting the C(sp3)–H bond adjacent to the chloride atom to form an alkyl radical. bpy = 2,2'-bipyridyl.

Eur. J. Org. Chem. 2014, No. 06, 1177-1181

tBu3P-Coordinated 2-Phenylaniline-Based Palladacycle Complexes as Precatalyst for Pd-Catalyzed Coupling Reactions of Aryl Halides with Polyfluoroarenes by a C–H Activation Strategy

A tBu3P-coordinated 2-phenylaniline-based palladacycle complex was found to be an efficient precatalyst for Pd-catalyzed coupling reactions of aryl halides with polyfluoroarenes that operates through a C–H activation strategy, with good to excellent product yields being observed.

Eur. J. Org. Chem. 2014, No. 06, 1327-1332

Direct Access to 4,5-Disubstituted [2.2]Paracyclophanes by Selective ortho-Halogenation with Pd-Catalyzed C–H Activation

We present a regioselective ortho-halogenation of [2.2]paracyclophanes by palladium-catalyzed C–H activation with O-methylaldoxime as a directing group. As exemplarily shown, this new protocol in combination with the subsequent deprotection provides practical access to various ortho-disubstituted [2.2]paracyclophanes.

Eur. J. Org. Chem. 2014, No. 06, 1287-1295

Shota Konishi, Soichiro Kawamorita, Tomohiro Iwai, Patrick G. Steel, Todd B. Marder, Masaya Sawamura
Site-Selective C-H Borylation of Quinolines at the C8 Position Catalyzed by a Silica-Supported Phosphane–Iridium System [Communication]

Site-Selective C-H Borylation of Quinolines at the C8 Position Catalyzed by a Silica-Supported Phosphane–Iridium System

Mono-P-ly: Site-selective C-H borylation of quinoline derivatives at the C8 position was achieved by using a heterogeneous Ir catalyst system based on the silica-supported cage-type monophosphane ligand Silica-SMAP. The efficient synthesis of a corticotropin-releasing factor1 (CRF1) receptor antagonist based on a late-stage C-H borylation strategy demonstrates the utility of the C8 borylation reaction.

Chem. Asian J. 2014, 9, No. 02, 434-438

Philipp J. Gritsch, Christian Leitner, Magnus Pfaffenbach, Tanja Gaich
The Witkop Cyclization: A Photoinduced C-H Activation of the Indole System [Minireview]

The Witkop Cyclization: A Photoinduced C-H Activation of the Indole System

To wit: The title reaction resembles a photoinduced electron-transfer process, and allows the direct formation of medium-sized lactams by C-H activation of the indole nucleus. Therefore it is a versatile tool for the construction of polycyclic indole alkaloid scaffolds.

Angew. Chem. Int. Ed. 2014, 53, No. 05, 1208-1217

Rational Perturbation of the Fluorescence Quantum Yield in Emission-Tunable and Predictable Fluorophores (Seoul-Fluors) by a Facile Synthetic Method Involving C-H Activation

It's all in the design: Seoul-Fluors with predictable photophysical properties, including a fluorescent reactive-oxygen-species sensor that was not previously accessible, were synthesized efficiently by coinage-metal-catalyzed intramolecular 1,3-dipolar cycloaddition and subsequent palladium-mediated C-H activation (see scheme). The quantum yield of the products could be controlled systematically by altering the electronic nature of the substituents.

Angew. Chem. Int. Ed. 2014, 53, No. 05, 1346-1350

Fangdong Hu, Ying Xia, Fei Ye, Zhenxing Liu, Chen Ma, Yan Zhang, Jianbo Wang
Rhodium(III)-Catalyzed ortho Alkenylation of N-Phenoxyacetamides with N-Tosylhydrazones or Diazoesters through C-H Activation [Communication]

Rhodium(III)-Catalyzed ortho Alkenylation of N-Phenoxyacetamides with N-Tosylhydrazones or Diazoesters through C-H Activation

The coupling reaction of N-phenoxyacetamides with N-tosylhydrazones or diazoesters proceeds through RhIII-catalyzed C-H bond activation. ortho-Alkenyl phenols are obtained in good yields and with excellent regio- and stereoselectivity.

Angew. Chem. Int. Ed. 2014, 53, No. 05, 1364-1367

Li-Hua Tian , Jing-Heng Meng , Xiao-Nan Wu, Yan-Xia Zhao, Xun-Lei Ding, Sheng-Gui He, Tong-Mei Ma
Reactivity of Oxygen Radical Anions Bound to Scandia Nanoparticles in the Gas Phase: C-H Bond Activation [Full Paper]

Reactivity of Oxygen Radical Anions Bound to Scandia Nanoparticles in the Gas Phase: C-H Bond Activation

Size does matter: Size-dependent reactivity of (Sc2O3)NO (N=1–18) clusters in hydrogen atom abstraction from n-butane was found by mass spectrometry and DFT calculations. Larger (Sc2O3)NO clusters generally have a higher reactivity than smaller ones (see figure). Atomic oxygen radical anions are responsible for the high reactivity of (Sc2O3)NO in the C-H bond activation.

Chem. Eur. J. 2014, 20, No. 04, 1167-1175

Kai Wang, Gen Luo, Jianquan Hong, Xigeng Zhou, Linhong Weng, Yi Luo, Lixin Zhang
Homometallic Rare-Earth Metal Phosphinidene Clusters: Synthesis and Reactivity [Communication]

Homometallic Rare-Earth Metal Phosphinidene Clusters: Synthesis and Reactivity

A rare gathering: Two new trinuclear μ3-bridged rare-earth metal phosphinidene complexes were synthesized by treatment of the corresponding carbene precursors with phenylphosphine; some new transformation patterns of phosphinidenes are revealed. A possible pathway for reaction of these phosphinidene complexes with CS2 was determined by DFT calculations.

Angew. Chem. Int. Ed. 2014, 53, No. 04, 1053-1056

Palladium-Catalyzed ortho-Selective C-H Deuteration of Arenes: Evidence for Superior Reactivity of Weakly Coordinated Palladacycles

Weaker is better! Phenylacetic acids and benzoic acids are suitable substrates for a palladium-catalyzed ortho-selective C-H deuteration of arenes with deuterated acetic acid (see scheme; R=H, alkyl, CF3, OMe, NO2, Cl, F). This reaction demonstrates the superior reactivity of weakly coordinated palladacycle intermediates in C-H functionalization reactions.

Angew. Chem. Int. Ed. 2014, 53, No. 03, 734-737

Modular Synthesis of Triarylmethanes through Palladium-Catalyzed Sequential Arylation of Methyl Phenyl Sulfone

Unsymmetric triarylmethanes have been synthesized starting from methyl phenyl sulfone as an inexpensive and readily available template. The three aryl groups were installed through two sequential palladium-catalyzed C-H arylation reactions, followed by an arylative desulfonation.

Angew. Chem. Int. Ed. 2014, 53, No. 03, 742-746

Towards Ideal Synthesis: Alkenylation of Aryl C-H Bonds by a Fujiwara–Moritani Reaction

Chemical power tools: The Fujiwara–Moritani reaction is the palladium-catalyzed coupling reaction of a simple aryl C-H bond with an alkenyl C-H bond to form a new C-C bond (see scheme). This Minireview focuses on the advances in the past five years related to the activation of various aryl C-H bonds in this coupling reaction.

Chem. Eur. J. 2014, 20, No. 03, 634-642

Microwave-Assisted, Rhodium(III)-Catalyzed N-Annulation Reactions of Aryl and α,β-Unsaturated Ketones with Alkynes

Ring road: One-pot N-annulation reactions of aryl and α,β-unsaturated ketones with alkynes in the presence of NH4OAc under microwave (MW) irradiation conditions have been developed (see scheme). These processes lead to the rapid formation of the respective isoquinoline and pyridine derivatives. In addition, an approach for the synthesis of pyridines that involves four-component reactions is presented.

Chem. Eur. J. 2014, 20, No. 01, 323-333

The Cross-Dehydrogenative Coupling of Csp3-H Bonds: A Versatile Strategy for C-C Bond Formations

Waste not, want not: The title CDC reactions have emerged as versatile tools for selective and waste-minimized C-C bond formations. They rely on the direct coupling of two different C-H bonds under oxidative conditions. This Review focuses on the recent progress in cross-dehydrogenative Csp3-C formation and provides a comprehensive overview on existing procedures and employed methodologies.

Angew. Chem. Int. Ed. 2014, 53, No. 01, 74-100

Surajit Haldar, Sujit Mahato, Chandan K. Jana
Metal- and Oxidant-Free Direct sp3 C-H Arylation of Pyrrolidine [Communication]

Metal- and Oxidant-Free Direct sp3 C-H Arylation of Pyrrolidine

Out of metal! A metal- and oxidant-free method for direct sp3 C-H arylation of pyrrolidine has been developed. As an alternative to metal-mediated reactions, the method relies on a highly atom economic three-component reaction, which is selective for single regioisomers of aryl pyrrolidines that are important in chemistry as well as in biology. The method, operating under simple and mild reaction conditions, is very efficient, even on a multigram scale.

Asian J. Org. Chem. 2014, 3, No. 01, 44-47

New Site-Selective Organoradical Based on Hypervalent Iodine Reagent for Controlled Alkane sp3 C-H Oxidations

Large Iodine: The site-selective oxidation of unactivated secondary sp3 C-H bonds was accomplished by using a newly defined reactive hypervalent iodine(III) radical in the presence of tert-butyl hydroperoxide (see scheme). Recent studies on hypervalent iodine radicals have significantly contributed to the further development and design of organic molecules in radical oxidation chemistry.

ChemCatChem 2014, 6, No. 01, 76-78

Yinuo Wu, Jun Wang, Fei Mao, Fuk Yee Kwong
Palladium-Catalyzed Cross-Dehydrogenative Functionalization of C(sp2)-H Bonds [Focus Review]

Palladium-Catalyzed Cross-Dehydrogenative Functionalization of C(sp2)-H Bonds

Caught in the cross-fire: This Review highlights the recent developments in catalytic cross-dehydrogenative coupling (CDC) reactions, which join together two aromatic C-H fragments through a palladium-catalyzed dehydrogenative pathway.

Chem. Asian J. 2014, 9, No. 01, 26-47

Ahmed Kamal, Vunnam Srinivasulu, Manda Sathish, Yellaiah Tangella, V. Lakshma Nayak, M. P. Narasimha Rao, Nagula Shankaraiah, Narayana Nagesh
Palladium-Catalyzed Aryl C-H Activation and Tandem ortho-Hydroxylation/Alkoxylation of 2-Aryl Benzimidazoles: Cytotoxicity and DNA-Binding Studies [Full Paper]

Palladium-Catalyzed Aryl C-H Activation and Tandem ortho-Hydroxylation/Alkoxylation of 2-Aryl Benzimidazoles: Cytotoxicity and DNA-Binding Studies

Do it in tandem: An efficient regioselective aryl C-H activation and tandem o-hydroxylation/alkoxylation method for 2-aryl benzimidazoles has been developed using a Pd(OAc)2/oxone/Cs2CO3 catalytic system. Some of the compounds have significant IC50 values ranging from 1–10 μM in selected human cancer cell lines. The DNA-binding potential of the compounds was also investigated by UV/vis, fluorescence, and circular dichroism spectroscopy.

Asian J. Org. Chem. 2014, 3, No. 01, 68-76

Jordan Sun Ho, Luis C. Misal Castro, Yoshinori Aihara, Mamoru Tobisu, Naoto Chatani
Ruthenium(II)-Catalyzed Chelation-Assisted Arylation of C-H Bonds with Diaryliodonium Salts [Communication]

Ruthenium(II)-Catalyzed Chelation-Assisted Arylation of C-H Bonds with Diaryliodonium Salts

Chelation-assisted arylation of the ortho C-H bonds in 2-arylpyridine derivatives was achieved by using [Ru(OAc)2(p-cymene)] as the catalyst and diaryliodonium salts as the arylation reagent.

Asian J. Org. Chem. 2014, 3, No. 01, 48-51

© Wiley-VCH 2013.