title: Rhodium N-heterocyclic carbene-catalyzed [4 + 2] and [5 + 2] cycloaddition reactions.
abstract: [reactions: see text] A rhodium complex of N-heterocyclic carbene (NHC) has been developed for intra- and intermolecular [4 + 2] and intramolecular [5 + 2] cycloaddition reactions. This is the first use of a transition-metal NHC complex in a Diels-Alder-type reaction. For the intramolecular [4 + 2] cycloaddition reactions, all the dienynes studied were converted to their corresponding cycloadducts in 91-99% yields within 10 min. Moreover, up to 1900 turnovers have been obtained for the intramolecular [4 + 2] cycloaddition at 15-20 degrees C. For the intermolecular [4 + 2] cycloadditions, high yields (71-99%) of the corresponding cycloaddition products were obtained. The reaction time and yield were highly dependent upon the diene and the dienophile. For the intramolecular [5 + 2] cycloaddition reactions, all the alkyne vinylcyclopropanes studied were converted to their corresponding cycloadducts in 91-98% yields within 10 min. However, the catalytic system was not effective for an intermolecular [5 + 2] cycloaddition reaction.
authors.affiliation: Intelligent Textile System Research Center, Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-747, Korea.
authors.forename: Sang Ick
authors.initials: SI
authors.lastname: Lee
authors.forename: Se Yeoun
authors.initials: SY
authors.lastname: Park
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Park
authors.forename: Il Gu
authors.initials: IG
authors.lastname: Jung
authors.forename: Soo Young
authors.initials: SY
authors.lastname: Choi
authors.forename: Young Keun
authors.initials: YK
authors.lastname: Chung
authors.forename: Bun Yeoul
authors.initials: BY
authors.lastname: Lee
mesh_terms: D002384:Catalysis; D003500:Cyclization; D006838:Hydrocarbons / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D015394:Molecular Structure; D012238:Rhodium / Q000737:chemistry*
chemical_list: D006838:Hydrocarbons; C030011:carbene; D012238:Rhodium; D008697:Methane