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 potassium salt of a borasilene–chloride adduct was synthesized and isolated. Its reactivity and single-crystal X-ray diffraction analysis revealed the double-bond character of its Si=B bond and reduced Lewis acidity. This adduct provides a cyclic product by formal intramolecular C−H insertion across the Si=B bond, possibly via the corresponding base-free borasilene.
Yuko Suzuki, Shintaro Ishida, Sota Sato, Hiroyuki Isobe, Takeaki Iwamoto
Angew. Chem. Int. Ed., March 22, 2017, https://doi.org/10.1002/anie.201612545 Read article
From ugly duckling to beautiful C1: Although CO2 may represent an ideal C1 source, it is challenging to use it as a raw material and direct carboxylation with CO2 has mainly been confined to highly reactive species. However, recent significant breakthroughs have been made in photochemical carboxylation of challenging, un-acidic, C(sp3)−H bonds, including benzylic, allylic and amine C−H bonds.
Yong-Yuan Gui, Wen-Jun Zhou, Jian-Heng Ye, Da-Gang Yu
ChemSusChem, March 21, 2017, https://doi.org/10.1002/cssc.201700205 Read article
Gimme the light! Benzylic C−H bonds of toluene derivatives are directly arylated with aryl halides by means of a nickel–dtbbpy catalyst under irradiation with UV light; dtbbpy=4,4′-di-tert-butyl-2,2′-bipyridine.
Naoki Ishida, Yusuke Masuda, Norikazu Ishikawa, Masahiro Murakami
Asian J. Org. Chem., March 21, 2017, https://doi.org/10.1002/ajoc.201700115 Read article
Remote Destination: Substitution of C−H bonds at positions previously inaccessible are now performed via an σ-alkyl-PdII species. A specially designed substrate directs the carbopalladated species resulting from intramolecular cyclization towards C−H activation at remote position.
Vaibhav P. Mehta, José-Antonio García-López
ChemCatChem, March 14, 2017, https://doi.org/10.1002/cctc.201601624 Read article
Photocatalytic approaches involving the activation of substrates through hydrogen atom transfer (HAT) offer unique opportunities in organic synthesis. This microreview summarizes the most recent advances in this rapidly developing area, collecting the selected examples according to the nature of the species promoting the HAT process.
Luca Capaldo, Davide Ravelli
Eur. J. Org. Chem., March 02, 2017, https://doi.org/10.1002/ejoc.201601485 Read article
Iron grafted over mesoporous silica (8 wt %Fe/SBA-15) is a sustainable, efficient heterogeneous iron catalyst for direct arylation of biphenyl methane C(sp3)−H and benzene C(sp2)−H bonds (see scheme; DDQ=2,3-dichloro-5,6-dicyano-1,4-benzoquinone, DCE=dichloroethane; DTBP=di-tert-butyl peroxide). Unlike homogeneous iron, the 8 wt %Fe/SBA-15 catalyst does not need support from an electron-withdrawing group and additives to arylate benzene and could be successfully recycled five times.
C. Rajendran, G. Satishkumar
ChemCatChem, March 01, 2017, https://doi.org/10.1002/cctc.201601562 Read article
Finding the best catalyst: A set of P450 BM3 variants was tested for stereoselective hydroxylation of benzoic acid derivatives, with the goal of synthesizing phthalides and isocoumarins. We obtained variants giving access to R- and S-configured products constituting a new route to a class of compounds that are valuable synthons for a variety of natural products.
Claudia Holec, Ute Hartrampf, Katharina Neufeld, Jörg Pietruszka
ChemBioChem, February 24, 2017, https://doi.org/10.1002/cbic.201600685 Read article
Two is better than one to generate cyclometalated Cp*IrIII phosphoramidate complexes by sequential intramolecular B–H and C(sp3)–H bond-activation events. Such complexes represent a first step in an overall Ir-catalyzed process for organophosphate functionalization. Cp* = pentamethylcyclopentadienyl; Mes = mesityl.
Marcus W. Drover, Cheyenne J. Christopherson, Laurel L. Schafer, Jennifer A. Love
Eur. J. Inorg. Chem., February 13, 2017, https://doi.org/10.1002/ejic.201601518 Read article
Only a little bit of iodine: A synthetic strategy for an iodine-mediated sulfonylation of quinoline N-oxides has been developed. A wide variety of 2-sulfonyl quinoline derivatives were synthesized by reacting various quinoline N-oxides with different sodium sulfinates in the presence of sub-stoichiometric amounts of I2 in one pot, after 2 h at room temperature.
Wen-Kai Fu, Kai Sun, Chen Qu, Xiao-Lan Chen, Ling-Bo Qu, Wen-Zhu Bi, Yu-Fen Zhao
Asian J. Org. Chem., February 08, 2017, https://doi.org/10.1002/ajoc.201700001 Read article
Porphyrins are suitable photoredox catalysts for the direct C–H arylation of heteroarenes with aryl diazonium salts. The reaction involves photoelectron transfer from a porphyrin in its exited state to a diazonium salt.
Katarzyna Rybicka-Jasińska, Burkhard König, Dorota Gryko
Eur. J. Org. Chem., January 27, 2017, https://doi.org/10.1002/ejoc.201601518 Read article