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
The Front Cover illustrates the first example of an heterogeneous catalyst Chitosan@Cu(OAc)2-catalyzed remote trifluoromethylation of aminoquinolines at C5 position under mild conditions.In their Communication, C. Shen et al. demonstrate that the trifluoromethylation products can be isolated in good to excellent yields using this method. Most importantly, the heterogeneous catalyst Chitosan@Cu(OAc)2 can been recycled many times without significant loss of catalytic performance. This protocol proves that the chitosan-based catalyst can further set the stage for the efficient reuse of the heterogeneous copper catalyst in position-selective C-H activations. More information can be found in the Communication by C. Shen et al. on page 3560 in Issue 23, 2016 (DOI: 10.1002/cctc.201601068).
Chao Shen, Jun Xu, Beibei Ying, Pengfei Zhang
ChemCatChem, December 08, 2016, DOI: 10.1002/cctc.201601456. Read article
Active near acid: The first Ru-catalyzed C−H arylation of benzoic acids with readily available aryl (pseudo)halides, allowing the arylation of previously challenging hindered benzoic acids and the use of generally unreactive ortho-substituted haloarenes. Furthermore, our new protocol can efficiently be applied to indole carboxylic acids, thus allowing access to C7-, C6-, C5- and C4-arylated indole compounds; a departure from the classical enhanced reactivity of C2 and C3 in indole.
Marco Simonetti, Diego M. Cannas, Adyasha Panigrahi, Szymon Kujawa, Michal Kryjewski, Pan Xie, Igor Larrosa
Chem. Eur. J., December 05, 2016, DOI: 10.1002/chem.201605068. Read article
Let us count the ways… Catalysis by iron–hexadecafluorophthalocyanine enabled the aerobic coupling of diarylamines to form 2,2′-bis(arylamino)biaryl compounds, tetraarylhydrazines, or 5,6-dihydrobenzo[c]cinnolines. The chemoselectivity of these transformations was controlled by acid or base additives (see picture).
Raphael F. Fritsche, Gabriele Theumer, Olga Kataeva, Hans-Joachim Knölker
Angew. Chem. Int. Ed., December 05, 2016, DOI: 10.1002/anie.201610168. Read article
Phenols more than just great antioxidants: An efficient palladium-catalyzed ortho-alkenylation and acetoxylation of phenols is described. The reaction provides access to coumarins and benzofurans via a seven-membered cyclopalladated intermediate, showing complete regio- and diastereoselectivity.
Bin Li, Dong-Dong Guo, Shi-Huan Guo, Gao-Fei Pan, Ya-Ru Gao, Yong-Qiang Wang
Chem. Asian J., November 29, 2016, DOI: 10.1002/asia.201601413. Read article
A facile method for the regioselective acylation of 1,4-disubstituted 1,2,3-triazoles by using a Pd-catalyzed C–H bond activation strategy with tert-butyl hydroperoxide (TBHP) as an oxidant and an aromatic aldehyde as the acyl source has been developed. This approach was applied to a wide range of substrates to generate various 1,2,3-triazole derivatives that have a diaryl ketone scaffold.
Fen Zhao, Zhen Chen, Yaowen Liu, Kai Xie, Yubo Jiang
Eur. J. Org. Chem., November 22, 2016, DOI: 10.1002/ejoc.201601061. Read article
A tri-ing method: The remote C−H trifluoromethylation of N-(quinolin-8-yl)benzamide derivatives is accomplished with a user-friendly chitosan-based heterogeneous copper catalyst, CS@Cu(OAc)2, under mild conditions. The coupling products are obtained in good to excellent yields, the catalyst shows good recyclability, and the low-costing stable Langlois reagent is used as the “CF3” source. A single-electron-transfer process is thought to be involved.
Chao Shen, Jun Xu, Beibei Ying, Pengfei Zhang
ChemCatChem, November 22, 2016, DOI: 10.1002/cctc.201601068. Read article
Move azide: A simple and efficient method for the copper(II)-catalyzed C5 azidation of N-acylated 8-aminoquinolines by remote C−H activation is developed. On the basis of this reaction, C5-azidated 8-amidoquinolines are synthesized in moderate to good yields.
Yandong Dou, Zhenda Xie, Zongguo Sun, Hongli Fang, Chao Shen, Pengfei Zhang, Qing Zhu
ChemCatChem, November 15, 2016, DOI: 10.1002/cctc.201600874. Read article
Honggui Lv, William L. Xu, Kunhua Lin, Jingjing Shi, Wei Yi
Eur. J. Org. Chem., November 11, 2016, DOI: 10.1002/ejoc.201601212. Read article
An effective palladium-catalyzed direct arylation of 2-alkyl-imidazo[1,2-a]pyridine with alkynes towards 2-alkyl-imidazo[5,1,2-cd]indolizines through double C–H functionalization was developed. The catalyst precursor is an ionic palladium(II) complex bearing amido-functionalized N-heterocyclic carbene and triphenylphosphine ligands.
Sanjay Kumar Ghosh, Debalina Ghosh, Ratnava Maitra, Ya-Ting Kuo, Hon Man Lee
Eur. J. Org. Chem., November 08, 2016, DOI: 10.1002/ejoc.201601019. Read article
Kiss me quick: The C−H activation of CH4 to HCHO is explored under technically relevant conditions on porous Ce-rich Ce1−xZrxO2 thin films with the aim to address the material gap and mechanistic aspects. The migration of electron-rich oxygen vacancy sites to the surface is responsible for HCHO formation. A short contact time and fast excursion between CH4- and O2-rich compositions could improve the HCHO selectivity further.
Anjani Dubey, Sadhu K. Kolekar, Chinnakonda S. Gopinath
ChemCatChem, November 07, 2016, DOI: 10.1002/cctc.201600670. Read article
The RhIII-catalysed synthesis of 3-sulfonyloxindoles using 2-anilinopyridines and sulfonyl α-diazo esters is reported. Under similar conditions, ortho-alkylated 6-anilinopurine nucleobases/nucleosides were obtained by treating purine precursors with α-diazo esters. An intermediate-like rhodacycle, which is also an effective catalyst for these reactions, has been structurally characterised.
Srinivasarao Allu, Manjula Ravi, K. C. Kumara Swamy
Eur. J. Org. Chem., November 04, 2016, DOI: 10.1002/ejoc.201600968. Read article
A palladium-catalyzed intermolecular domino reaction involving a sequence of C–H activations is reported. This reaction provides a simple and efficient method for the synthesis of fused polycycles from simple starting materials. cod = cyclooctadiene, NMP = 1-methylpyrrolidin-2-one, TBAB = tetrabutylammonium bromide.
Hai-Yu He, Wei Wang, Xiao-Jun Yu, Jin Huang, Lei Jian, Hai-Yan Fu, Xue-Li Zheng, Hua Chen, Rui-Xiang Li
Eur. J. Org. Chem., November 03, 2016, DOI: 10.1002/ejoc.201601051. Read article
The Ir-catalyzed borylation of helicene has been studied. The monoborylation proceeds to give a mixture of 2- and 3-borylated products in good yields. The use of sterically demanding ligands favors the formation of the 3-borylated product. The monoborylated helicenes were arylated by using a Suzuki–Miyaura cross-coupling reaction or oxidized to the corresponding phenols in very good yields.
David Nečas, Reinhard P. Kaiser, Jan Ulč
Eur. J. Org. Chem., October 27, 2016, DOI: 10.1002/ejoc.201600979. 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