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
Regioselective intermolecular sulfonylamidation of unactivated secondary C(sp3)−H bonds has been achieved using IrIII catalysts. N,N′-bichelating ligand plays a crucial role in enabling iridium nitrene insertion into secondary C(sp3)−H bonds via an outer-sphere pathway. This method tolerates a broad range of linear and branched-chain N-alkylamides, and provides efficient access to diverse γ-sulfonamido-substituted aliphatic amines.
Xinsheng Xiao, Cheng Hou, Zhenhui Zhang, Zhuofeng Ke, Jianyong Lan, Huanfeng Jiang, Wei Zeng
Angew. Chem. Int. Ed., August 26, 2016, DOI: 10.1002/anie.201606531. Read article
Which way to go: NH indoles and 3H-indoles were synthesized by ruthenium(II)-catalyzed C−H activation of imidamides and intermolecular coupling with diazo compounds under mild conditions. The coupling of α-diazoketoesters afforded NH indoles by cleavage of the C(N2)−C(acyl) bond whereas α-diazomalonates gave 3H-indoles by C=N bond cleavage.
Yunyun Li, Zisong Qi, He Wang, Xifa Yang, Xingwei Li
Angew. Chem. Int. Ed., August 25, 2016, DOI: 10.1002/anie.201606316. Read article
Under high pressure, the C≡N bond of acetonitrile is expected to polymerize into conjugated C=N bonds. It is however shown that when compressing CH3CN at 25 GPa, a hydrogen atom transfers along the −H2C−H⋅⋅⋅NC− hydrogen bond, which triggers the polymerization to form a dimer, 1D chain, and 2D nanoribbon. Finally, it converts into a graphitic polymer accompanied by the release of ammonia.
Haiyan Zheng, Kuo Li, George D. Cody, Christopher A. Tulk, Xiao Dong, Guoying Gao, Jamie J. Molaison, Zhenxian Liu, Mikhail Feygenson, Wenge Yang, Ilia N. Ivanov, Leonardo Basile, Juan-Carlos Idrobo, Malcolm Guthrie, Ho-kwang Mao
Angew. Chem. Int. Ed., August 25, 2016, DOI: 10.1002/anie.201606198. Read article
DDQ can do: Visible-light-induced aerobic C(sp3)−H oxygenations of benzylic substrates are efficiently performed by using a co-catalytic system of 3DDQ* (DDQ=2,3-dichloro-5,6-dicyano-1,4-benzoquinone) and tert-butyl nitrite. The photocatalytic method offers a dramatic increase in reaction rate compared to the thermal protocol.
Fabian Rusch, Jan-Christian Schober, Malte Brasholz
ChemCatChem, August 22, 2016, DOI: 10.1002/cctc.201600704. Read article
In this account we summarize and discuss synthetic solutions for the realization of palladium catalyzed, ortho-directed C-H functionalization of aniline derivatives under mild reaction conditions for the construction of new carbon-carbon and carbon-oxygen bonds.
Orsolya Tischler, Balázs Tóth, Zoltán Novák
The Chemical Record, August 09, 2016, DOI: 10.1002/tcr.201600059. Read article
An efficient method for the hydrothermal dehydrogenation of cyclohexanone to phenol using recyclable Pd/C catalyst without external O2 and H2 was first reported. Pd/C as catalyst exhibited excellent catalytic performance and hydrothermal stability for the present transformation, and phenol was produced from cyclohexanone in 60.4 % yield with 100 % selectivity. TON of 8.27 and TOF of 3.31 h−1 were achieved.
Zhiyuan Song, Dezhang Ren, Jun Fu, Yunjie Liu, Tian Wang, Fangming Jin, Zhibao Huo
ChemistrySelect, July 22, 2016, DOI: 10.1002/slct.201600527. Read article
Bhaskar Mondal, Lisa Roy, Frank Neese, Shengfa Ye
Isr. J. Chem., July 19, 2016, DOI: 10.1002/ijch.201600028. Read article
Ruhuai Mei, Lutz Ackermann
Adv. Synth. Catal., July 8, 2016, DOI: 10.1002/adsc.201600384. Read article.
Not half biaryls: The highly efficient [RhIIICp*]-catalyzed directed C-H bromination and iodination reaction of 2-aryl isoquinolines/pyridines affords atropisomeric biaryl compounds in good yields.
Kiseong Kim, Jaeyong Hyun, Jin Kim, Hyunwoo Kim
Asian J. Org. Chem., July 08, 2016, DOI: 10.1002/ajoc.201600259. Read article
Zechao Wang, Yahui Li, Fengxiang Zhu, Xiao-Feng Wu
Adv. Synth. Catal., June 15, 2016, DOI: 10.1002/adsc.201600395. Read article.
Xiaoxu Yang, Xiqing Jin, Congyang Wang
Adv. Synth. Catal., May 9, 2016, DOI: 10.1002/adsc.201600128. Read article.
All positions in carbohydrates have been functionalized through C–H bond cleavage, hence paving the way for easy access to complex modified sugars or natural products. This review presents the methods available for C–H functionalization in carbohydrate chemistry and gives an overview position-by-position.
Tobias Gylling Frihed, Mikael Bols, Christian Marcus Pedersen
Eur. J. Org. Chem., March 21, 2016, DOI: 10.1002/ejoc.201600121. Read article.
This microreview presents work surrounding the development and study of Tp-supported platinum group metal complexes for stoichiometric and catalytic C–H bond activation. From κ2- and κ3-coordination modes to increased sterics to electronic parameters, Tp and related ligands have played an important role in the observed reactivity of Ru, Rh and Pt-mediated C–H bond activation reactions.
Bradley A. McKeown, John P. Lee, Jiajun Mei, Thomas R. Cundari, T. Brent Gunnoe
Eur. J. Inorg. Chem., February 12, 2016, DOI: 10.1002/ejic.201501470. Read article.
The IrIII complex [TpMe2Ir(C6H5)2(N2)] [TpMe2 = hydridotris(3,5-dimethylpyrazolyl)borate] reacts with different olefins to yield organometallic compounds that derive from allylic C–H activations in processes that also generate organic coupling products that involve the vinylic positions of the olefin.
Crispín Cristóbal, Laura L. Santos, Rubén Gutiérrez-González, Eleuterio Alvarez, Margarita Paneque, Manuel L. Poveda
Eur. J. Inorg. Chem., January 19, 2016, DOI: 10.1002/ejic.201501253. Read article.
Two in one: The Ir–imine-functionalized protic N-heterocyclic carbene (pNHC) complex was obtained through a chelate-assisted C2-H bond activation in the cationic Nimidazole-Ir complex. New homo- and heterodinuclear complexes could be prepared by in situ deprotonation of either the neutral Nimidazole-Ir complex or the Ir pNHC complex followed by addition of metal precursors (see scheme).
Fan He, Marcel Wesolek, Andreas A. Danopoulos, Pierre Braunstein
Chem. Eur. J., January 15, 2016, DOI: 10.1002/chem.201504030. Read article.
Ligands of tomorrow: Chiral spirocyclic sultams are rapidly assembled in a [3+2] annulation from N-sulfonyl ketimines and alkynes. The transformation is catalyzed by rhodium complexes equipped with the atropchiral biaryl Cpx ligand, and provides the sultams in excellent yields and high enantioselectivities.
Manh V. Pham, Nicolai Cramer
Chem. Eur. J., January 11, 2016, DOI: 10.1002/chem.201504998. Read article.
Chains linked: Through the interplay of high-resolution scanning tunneling microscopy imaging and density functional theory calculations, the stepwise homocoupling of alkyl chains on Cu(110) is demonstrated, proceeding from the intact chain, via the dehydrogenative intermediates, to the final coupling products.
Liangliang Cai, Qiang Sun, Chi Zhang, Yuanqi Ding, Wei Xu
Chem. Eur. J., January 8, 2016, DOI: 10.1002/chem.201504152. Read article.
Access the inaccessible: A copper-catalyzed 8-amide chelation-induced remote C-H amination of quinolines has been developed (see scheme). This direct amination with readily available azodicarboxylates proceeded with perfect C5-regioselectivity offering amino-substituted 8-aminoquinolines in high yields (up to 96 %).
Harekrishna Sahoo, Mallu Kesava Reddy, Isai Ramakrishna, Mahiuddin Baidya
Chem. Eur. J., January 7, 2016, DOI: 10.1002/chem.201504207. Read article.
Origin of the activation: The inner surface structures of the pore wall in mesoporous α-Fe2O3 are mainly comprised of turbostratic ribbons and K crystal faces. They show excellent catalytic performance for methane activation, during which the C-H bonds are converted into C-O bonds in an O2 atmosphere at 140 °C (see figure).
Bing Dong, Zhen Han, Yongbo Zhang, Youyi Yu, Aiguo Kong, Yongkui Shan
Chem. Eur. J., January 7, 2016, DOI: 10.1002/chem.201503183. Read article.
A blockbuster catalyst: Well-defined ruthenium(II) phosphinous acid (PA) complexes were identified as powerful catalysts for highly selective C-H arylations with ample scope, which enabled low catalyst loadings and gave step-economical access to blockbuster drugs. Mechanistic studies were supportive of a PA-assisted C-H activation.
Daniel Zell, Svenja Warratz, Dmitri Gelman, Simon J. Garden, Lutz Ackermann
Chem. Eur. J., December 22, 2015, DOI: 10.1002/chem.201504851. Read article.
Alkynes on a gold Tr(i)p! Various peptides and one model protein were functionalized with ethynyl moieties at their tryptophan residues using Waser’s reagent, TIPS-EBX, under gold(I) catalysis (see scheme; TIPS=triisopropylsilyl). The reaction proceeded in a regio- and chemoselective manner leading to C2 substitution at the tryptophan residues only. Subsequently, the terminal alkyne was used to label one of the model peptides with a fluorophore by means of copper-catalyzed click chemistry.
Morten Borre Hansen, František Hubálek, Troels Skrydstrup, Thomas Hoeg-Jensen
Chem. Eur. J., December 22, 2015, DOI: 10.1002/chem.201504462. Read article.
Rhoad to alkaloids! A Rh-catalyzed intramolecular C-H bond activation/annulation of aldehydes and alkyne–amines provides a novel efficient method for the synthesis of various protoberberine salts and natural products in high yield under mild reaction conditions.
Jayachandran Jayakumar, Chien-Hong Cheng
Chem. Eur. J., December 22, 2015, DOI: 10.1002/chem.201504378. Read article.
In two shakes: Oxidative annulation by double C-H activation/alkyne insertion reaction was achieved by a nickel/NHC system. A Ni0/NiII catalytic cycle is proposed as the main catalytic cycle. The alkyne plays a double role as a two-component coupling partner and as a hydrogen acceptor.
Luis C. Misal Castro, Atsushi Obata, Yoshinori Aihara, Naoto Chatani
Chem. Eur. J., December 21, 2015, DOI: 10.1002/chem.201504596. Read article.
Influential solvent: Efficient access to atropo-enantioenriched biaryl moieties through asymmetric direct C-H activation, by using enantiopure sulfoxide as both the directing group and chiral auxiliary, is reported (see scheme). The key role of 1,1,1,3,3,3-hexafluoropropanol (HFIP) solvent is investigated.
Quentin Dherbassy, Geoffrey Schwertz, Matthieu Chessé, Chinmoy Kumar Hazra, Joanna Wencel-Delord, Françoise Colobert
Chem. Eur. J., December 18, 2015, DOI: 10.1002/chem.201503650. Read article.
The crucial role of gold in the transformation of ethane to ethene and dihydrogen is observed in the reaction between C2H6 and Au2VO3+ clusters with closed-shell electronic structures. The first C-H activation is initiated by gold rather than an oxygen species. The Au-Au dimer formed during the reactions plays important roles in converting ethane into ethene and making dihydrogen energetically more favorable.
Ya-Ke Li, Zi-Yu Li, Yan-Xia Zhao, Qing-Yu Liu, Jing-Heng Meng, Sheng-Gui He
Chem. Eur. J., December 17, 2015, DOI: 10.1002/chem.201503676. Read article.
Three is a magic number: On treatment of triazoles with [Rh2(C7H15CO2)4], the rhodium catalyst plays three roles, denitrogenation, C-H bond activation, and stereoselective cyclization, providing a new method for heterocycle synthesis. Intramolecular C-H bond insertion takes place at the benzylic position to give pyrrolidines and related heterocycles in good yields.
Masato Senoo, Ayana Furukawa, Takeshi Hata, Hirokazu Urabe
Chem. Eur. J., December 14, 2015, DOI: 10.1002/chem.201503823. Read article.
DDAism: Dehydrogenative cycloadditions have attracted significant attention in synthetic chemistry. This Minireview highlights the recent efforts towards the development of dehydro or dehydrogenative Diels–Alder reactions to construct diverse aromatic compounds by a concerted pathway or a stepwise process.
Wenbo Li, Liejin Zhou, Junliang Zhang
Chem. Eur. J., November 24, 2015, DOI: 10.1002/chem.201503571. Read article.
A directed heterogeneous C-H activation/halogenation reaction catalyzed by readily synthesized Pd@MOF nanocatalysts was developed (see scheme). The heterogeneous Pd catalysts used were a novel and environmentally benign Fe-based metal–organic framework (MOF) (Pd@MIL-88B-NH2(Fe)) and the previously developed Pd@MIL-101-NH2(Cr). Very high conversions and selectivities were achieved under very mild reaction conditions and in short reaction times.
Vlad Pascanu, Fabian Carson, Marta Vico Solano, Jie Su, Xiaodong Zou, Magnus J. Johansson, Belén Martín-Matute
Chem. Eur. J., October 20, 2015, DOI: 10.1002/chem.201502918. Read article.