title: Cp*Co(III) Catalyzed Site-Selective C-H Activation of Unsymmetrical O-Acyl Oximes: Synthesis of Multisubstituted Isoquinolines from Terminal and Internal Alkynes.
abstract: The synthesis of isoquinolines by site-selective C-H activation of O-acyl oximes with a Cp*Co(III) catalyst is described. In the presence of this catalyst, the C-H activation of various unsymmetrically substituted O-acyl oximes selectively occurred at the sterically less hindered site, and reactions with terminal as well as internal alkynes afforded the corresponding products in up to 98 % yield. Whereas the reactions catalyzed by the Cp*Co(III) system proceeded with high site selectivity (15:1 to 20:1), use of the corresponding Cp*Rh(III) catalysts led to low selectivities and/or yields when unsymmetrical O-acyl oximes and terminal alkynes were used. Deuterium labeling studies indicate a clear difference in the site selectivity of the C-H activation step under Cp*Co(III) and Cp*Rh(III) catalysis.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan).
authors.forename: Bo
authors.initials: B
authors.lastname: Sun
authors.affiliation: Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812 (Japan).|ACT-C (Japan) Science and Technology Agency (Japan).
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Yoshino
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan). kanai@mol.f.u-tokyo.ac.jp.
authors.forename: Motomu
authors.initials: M
authors.lastname: Kanai
authors.affiliation: Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812 (Japan). smatsuna@pharm.hokudai.ac.jp.|ACT-C (Japan) Science and Technology Agency (Japan). smatsuna@pharm.hokudai.ac.jp.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsunaga
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D003517:Cyclopentanes / Q000737:chemistry*; D007546:Isoquinolines / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010091:Oximes / Q000737:chemistry*
chemical_list: D000480:Alkynes; D003517:Cyclopentanes; D007546:Isoquinolines; D009942:Organometallic Compounds; D010091:Oximes; D003035:Cobalt
keywords: CH activation; cobalt; isoquinolines; transition-metal catalysis