title: Rh(III) -catalyzed C-H activation: a versatile route towards various polycyclic pyridinium salts.
abstract: An efficient and convenient method for the synthesis of highly substituted polycyclic pyridinium salts from the reaction of various 2-aryl-pyridines and 2-aryl-sp(2) -nitrogen-atom-containing heterocycles with alkynes through rhodium(III)-catalyzed CH activation and annulation under an O2 atmosphere is described. A possible mechanism that involves the chelation-assisted CH activation of the 2-aryl-pyridine substrate, insertion of the alkyne, and reductive elimination is proposed. This mechanism was supported by the isolation of a five-membered rhodacycle (I'). In addition, kinetic isotope studies were performed to understand the intimate reaction mechanism.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu, 30013 (Taiwan), Fax: (+86) 3572-4698.
authors.forename: Ching-Zong
authors.initials: CZ
authors.lastname: Luo
authors.forename: Parthasarathy
authors.initials: P
authors.lastname: Gandeepan
authors.forename: Jayachandran
authors.initials: J
authors.lastname: Jayakumar
authors.forename: Kanniyappan
authors.initials: K
authors.lastname: Parthasarathy
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Chang
authors.forename: Chien-Hong
authors.initials: CH
authors.lastname: Cheng
mesh_terms: D002384:Catalysis; D006860:Hydrogen Bonding; D007700:Kinetics; D015394:Molecular Structure; D011083:Polycyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011726:Pyridinium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*; D012492:Salts / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D011083:Polycyclic Compounds; D011726:Pyridinium Compounds; D012492:Salts; D012238:Rhodium
keywords: CH activation; alkynes; fluorescence; pyridinium salts; rhodium