title: Pyrroloindolone synthesis via a Cp*Co(III)-catalyzed redox-neutral directed C-H alkenylation/annulation sequence.
abstract: A unique synthetic utility of a Cp*Co(III) catalyst in comparison with related Cp*Rh(III) catalysts is described. A C2-selective indole alkenylation/annulation sequence proceeded smoothly with catalytic amount of a [Cp*Co(III)(C6H6)](PF6)2 complex and KOAc. Intramolecular addition of an alkenyl-Cp*Co species to a carbamoyl moiety gave pyrroloindolones in 58-89% yield in one pot. Clear difference was observed between the catalytic activity of the Cp*Co(III) complex and those of Cp*Rh(III) complexes, highlighting the unique nucleophilic activity of the organocobalt species. The Cp*Co(III) catalysis was also suitable for simple alkenylation process of N-carbamoyl indoles, and broad range of alkynes, including terminal alkynes, were applicable to give C2-alkenylated indoles in 50-99% yield. Mechanistic studies on C-H activation step under Cp*Co(III) catalysis with the aid of an acetate unit as well as evaluation of the difference between organo-Co(III) species and organo-Rh(III) species are also described.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo , Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Hideya
authors.initials: H
authors.lastname: Ikemoto
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Yoshino
authors.forename: Ken
authors.initials: K
authors.lastname: Sakata
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsunaga
authors.forename: Motomu
authors.initials: M
authors.lastname: Kanai
mesh_terms: D000478:Alkylation; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D011758:Pyrroles / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D007211:Indoles; D009942:Organometallic Compounds; D011758:Pyrroles; D003035:Cobalt