Cobalt-Catalyzed Oxidative C−H/C−H Cross-Coupling between Two Heteroarenes

• Published in: Angewandte Chemie International Edition Vol. 55; no. 35; pp. 10414 - 10418
• Main Authors: Tan, Guangying, He, Shuang, Huang, Xiaolei, Liao, Xingrong, Cheng, Yangyang, You, Jingsong
• Format: Journal Article
• Language: English
• Published: WEINHEIM Blackwell Publishing Ltd 22.08.2016; Wiley; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Activation; bi(hetero)aryls; Chemical reactions; Chemistry; Chemistry, Multidisciplinary; Cobalt; cobalt catalysis; Coupling; Cross coupling; Deuterium; Electron paramagnetic resonance; Electron transfer; Exchanging; Functional anatomy; Functional groups; High resolution; High temperature; Hydrogen; Isotope effect; Mass spectrometry; Mass spectroscopy; oxidative C−H/C−H cross-coupling; Oxidizing agents; Physical Sciences; Reaction time; Science & Technology; SET pathway; Temperature effects; Trapping; DIRECT ARYLATION; bi(hetero) aryls; DIRECTED C(SP)-H; oxidative C-H/C-H cross-coupling; UNACTIVATED ARENES; INDOLES; BIDENTATE-CHELATION ASSISTANCE; ALIPHATIC AMIDES; FUNCTIONALIZATION; SET pathway; ARYL HALIDES; BOND ACTIVATION; cobalt catalysis; AMINOQUINOLINE BENZAMIDES; bi(hetero)aryls; oxidative C−H/C−H cross-coupling
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201604580

The first example of cobalt‐catalyzed oxidative C−H/C−H cross‐coupling between two heteroarenes is reported, which exhibits a broad substrate scope and a high tolerance level for sensitive functional groups. When the amount of Co(OAc)2⋅4 H2O is reduced from 6.0 to 0.5 mol %, an excellent yield is still obtained at an elevated temperature with a prolonged reaction time. The method can be extended to the reaction between an arene and a heteroarene. It is worth noting that the Ag2CO3 oxidant is renewable. Preliminary mechanistic studies by radical trapping experiments, hydrogen/deuterium exchange experiments, kinetic isotope effect, electron paramagnetic resonance (EPR), and high resolution mass spectrometry (HRMS) suggest that a single electron transfer (SET) pathway is operative, which is distinctly different from the dual C−H bond activation pathway that the well‐described oxidative C−H/C−H cross‐coupling reactions between two heteroarenes typically undergo. A bidentate 8‐quinolinyl ligand assists the cobalt‐catalyzed title reaction between two (hetero)arenes exhibiting a broad substrate scope and a high tolerance level for sensitive functional groups. The preliminary mechanistic study suggests that a single electron transfer pathway is operative.