title: Cobalt-Catalyzed Dual Annulation of o-Halobenzaldimine with Alkyne: A Powerful Route toward Bioactive Indenoisoquinolinones.
abstract: A cobalt-catalyzed dual annulation reaction for the synthesis of variously substituted indenoisoquinolinones from 2-bromobenzaldehydes, amines, and methyl 2-(ethynyl)benzoates has been developed. This method could also be applied to the synthesis of an array of highly functionalized bioactive indenoisoquinolinones and their derivatives. A possible mechanism of the cobalt catalysis is proposed, involving imine formation from bromobenzaldehyde and the amine, followed by a series of oxidative addition, alkyne insertion, cyclization reactions, and carbon-carbon double-bond migration. The regioselective alkyne insertion plays an important role for the success of the second annulation.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013 (Taiwan).
authors.forename: Chuan-Che
authors.initials: CC
authors.lastname: Liu
authors.affiliation: Department of Chemistry, Tamkang University, New Taipei City, 25137 (Taiwan). jchsieh@mail.tku.edu.tw.
authors.forename: Jen-Chieh
authors.initials: JC
authors.lastname: Hsieh
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013 (Taiwan).
authors.forename: Rajendra Prasad
authors.initials: RP
authors.lastname: Korivi
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013 (Taiwan). chcheng@mx.nthu.edu.tw.
authors.forename: Chien-Hong
authors.initials: CH
authors.lastname: Cheng
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry; D003500:Cyclization; D007192:Indenes / Q000737:chemistry*; D007546:Isoquinolines / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000480:Alkynes; D007192:Indenes; D007546:Isoquinolines; D003035:Cobalt
keywords: azametallacycles; cobalt; indenes; isoquinoline; zinc