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
A family of pyridyl–oxazole oligomers with either linear or branched connectivity of their subunits is synthesized. According to circular dichroism spectroscopy, some of the members of this family enhance the helicity of a partially folded c-myc G-quadruplex.
Natalia Rizeq, Savvas N. Georgiades
Eur. J. Org. Chem., November 24, 2015, DOI: 10.1002/ejoc.201501269. Read article.
An advantageous combination: The stereoselective synthesis of ε-isomers of dimethyl esters of 1,3-diaminotruxillic acid is easily achieved in three steps (see scheme): 1) regioselective C-H-ortho-palladation of (Z)-2-aryl-4-aryliden-5(4H)-oxazolones; 2) efficient [2+2]-photocycloaddition of the C=C exocyclic bonds using LED light sources of different wavelengths in continuous flow microreactors; and 3) depalladation by hydrogenation in methanol.
Elena Serrano, Alberto Juan, Angel García-Montero, Tatiana Soler, Francisco Jiménez-Márquez, Carlos Cativiela, M. Victoria Gomez, Esteban P. Urriolabeitia
Chem. Eur. J., November 24, 2015, DOI: 10.1002/chem.201503742. 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.
Substituted 7-deazapurine nucleobase analogues were prepared by C–H borylation, Suzuki coupling and further functional group transformations.
Martin Klečka, Lenka Poštová Slavetínská, Michal Hocek
Eur. J. Org. Chem., November 17, 2015, DOI: 10.1002/ejoc.201501177. Read article.
The first introduction of 2-bromo-3,3,3-trifluoropropene (BTP) by directed C–H bond functionalization is described. The products were obtained in good yields, and the method represents a straightforward route to α-(trifluoromethyl)styrenes.
Qun Zhao, Tatiana Besset, Thomas Poisson, Jean-Philippe Bouillon, Xavier Pannecoucke
Eur. J. Org. Chem., November 16, 2015, DOI: 10.1002/ejoc.201501217. Read article.
In this review, we discuss recent progress in two classes of first-row transition-metal-catalyzed dehydrogenative reaction of C(sp3)–H bonds: (1) intramolecular cyclizations for C–C bond formation, and (2) directed site-selective C–H functionalizations.
Jinmin Miao, Haibo Ge
Eur. J. Org. Chem., November 11, 2015, DOI: 10.1002/ejoc.201501186. Read article.
Two pyridine rings are substituted for benzene rings in ortho-phenylene hexamers, which are stacked in a helical conformation. Directive stacking of pyridine rings effectively stabilizes a 3:1 helical conformation, as compared with other possible conformers, even in CDCl3.
Yuichiro Tokoro, Nobuhiko Ohtsuka, Ayumi Toh, Shin-ichi Fukuzawa
Eur. J. Org. Chem., November 9, 2015, DOI: 10.1002/ejoc.201501270. Read article.
A photoredox catalytic, metal-free method for C–H functionalization α to amines is developed. This transformation directly affords bis(indolyl)alkane products in good to excellent yields. The process hinges on a pivotal 1,5-H migration to an aryl radical intermediate, which ultimately leads to a reactive azacarbenium ion.
Saad Shaaban, Alexander Roller, Nuno Maulide
Eur. J. Org. Chem., November 6, 2015, DOI: 10.1002/ejoc.201501149. Read article.
Light can build a bridge: Photolysis of [FeFe]-hydrogenase model complexes in hydrocarbon matrices at 85 K results in intramolecular β-hydride activation of the dithiolate bridge, formation of bridging carbonyl isomers, and in instances of a dithiolene based bridge, generation of 16e−/18e− 10 π-electron aromatic metallacycles.
Wyatt A. Thornley, Thomas E. Bitterwolf
Chem. Eur. J., November 6, 2015, DOI: 10.1002/chem.201503826. Read article.
I see two and I see three: Two novel and highly efficient methods for the selective synthesis of C2- and C3-sulfonylindoles by employing iodide and copper catalysts, respectively, are described. Mechanistic studies point to the crucial role of the electronic properties of the sulfonylated intermediates. phen=1,10-phenantroline, TBHP=tert-butyl hydroperoxide.
Yong Yang, Wanmei Li, Chengcai Xia, Beibei Ying, Chao Shen, Pengfei Zhang
ChemCatChem, November 05, 2015, DOI: 10.1002/cctc.201500917. Read article
Iron for selectivity: An iron catalyst combined with a mild organic oxidant promotes the regioselective synthesis of 2-pyridones and isoquinolones from an alkene- or arylamide and an internal alkyne, respectively. The regioselectivity reflects the sensitivity of the reaction to steric effects because of the compact size of iron.
Tatsuaki Matsubara, Laurean Ilies, Eiichi Nakamura
Chem. Asian J., November 04, 2015, DOI: 10.1002/asia.201501095. Read article
Two in a row: A palladium-catalyzed regioselective double C-H activation of (E)-3-styryl-1H-indoles and alkenes for the synthesis of functionalized carbazoles has been described (see scheme). The reaction features a variety of olefin substrates, which are readily switchable by subtle tuning of the reaction conditions.
Rakesh K. Saunthwal, Monika Patel, Sonu Kumar, Abhinandan K. Danodia, Akhilesh K. Verma
Chem. Eur. J., November 3, 2015, DOI: 10.1002/chem.201503657. Read article.
H2 evolution: The direct functionalization of a C(sp3)-H bond adjacent to an O atom is a powerful tool for the conventional derivatization of ethers. The addition of β-keto esters to oxonium species, which is rarely observed in photocatalysis proceeds under oxidant-free conditions by merging a commercial dyad photosensitizer and an easily available cobaloxime complex (see scheme; SET=single-electron transfer).
Ming Xiang, Qing-Yuan Meng, Jia-Xin Li, Yi-Wen Zheng, Chen Ye, Zhi-Jun Li, Bin Chen, Chen-Ho Tung, Li-Zhu Wu
Chem. Eur. J., October 30, 2015, DOI: 10.1002/chem.201503361. Read article.
Under scrutiny: The oxidative cross-coupling of phenylboronic acid with thiophenes (see scheme, left) was probed by several mechanistic tools. For example, absolute reaction rates were determined (middle) and a Hammett analysis was performed (right). Based on these data, a mechanistic model for the reaction is proposed.
Ingo Schnapperelle, Stefan Breitenlechner, Thorsten Bach
Chem. Eur. J., October 30, 2015, DOI: 10.1002/chem.201503067. Read article.
Functionalized ferrocenes: Planar chiral ferrocenes have received great attention in view of their increasing importance in the fields of asymmetric catalysis, enantioselective synthesis, and materials science. Recently, several novel methods have been developed to synthesize enantioenriched planar chiral ferrocenes by means of transition-metal-catalyzed enantioselective CH activation. The significance of these results is summarized in this minireview.
Dao-Yong Zhu, Ping Chen, Ji-Bao Xia
ChemCatChem, October 28, 2015, DOI: 10.1002/cctc.201500895. 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.
What a complement: Depending on the electronic properties of the heteroarenes, a matching reactive intermediate could be selected; that is, carbanions for nitroheteroaromatics, alkylpalladium species for electron-deficient heteroarenes, and electrophilic radicals for electron-rich heteroarenes.
Ha-Lim Jang, Hyun Tae Kim, Eun Jin Cho, Jung Min Joo
Asian J. Org. Chem., October 15, 2015, DOI: 10.1002/ajoc.201500388. Read article
Mellow Me: A phosphinic amide as a directing group for the ortho C−H alkenylation overcomes the pronounced reactivity differences usually seen with secondary (with NH group) and tertiary (with NMe group) anilides. The methyl-substituted anilide is even more reactive than its unsubstituted counterpart (see scheme). The C-7-selective C−H alkenylation of indoline is also demonstrated.
Lin-Yu Jiao, André V. Ferreira, Martin Oestreich
Chem. Asian J., September 24, 2015, DOI: 10.1002/asia.201500829. Read article
Sole purpose: Phthalide skeletons have been synthesized through a RhIII-catalyzed C−H olefination of benzoic acids under mild conditions using oxygen as the sole oxidant. Aromatic acids bearing different functional groups were treated with diverse alkenes to afford the desired cyclized lactones or uncyclized alkenylarenes in moderate-to-excellent yields.
Quandi Jiang, Changlei Zhu, Huaiqing Zhao, Weiping Su
Chem. Asian J., July 28, 2015, DOI: 10.1002/asia.201500601. Read article
Any weather is PEPPSI weather: A method that allows salicylaldehydes to be efficiently transformed into meta-arylated phenol derivatives through a cascade oxidation/arylation/protodecarboxylation sequence is presented. We demonstrate that the aldehyde functional group can be used as a convenient removable directing group to control site selectivity in C−H activation.
Junfei Luo, Sara Preciado, Solomon Olatokunbo Araromi, Igor Larrosa
Chem. Asian J., June 25, 2015, DOI: 10.1002/asia.201500506. Read article