title: Ruthenium-catalyzed cyclizations of enynes via a ruthenacyclopentene intermediate: development of three novel cyclizations controlled by a substituent on alkyne of enyne.
abstract: Three novel ruthenium-catalyzed cyclizations of enynes were developed. In each cyclization, a ruthenacyclopentene derived from enyne and Cp*RuCl(cod) is a common intermediate. When an enyne having an alkyl, an ester, or a formyl group on an alkyne was reacted with Cp*RuCl(cod) under ethylene gas, ethylene was inserted into the ruthenium-sp(2) carbon bond of ruthenacyclopentene to afford ruthenacycloheptene, and β-hydrogen elimination followed by reductive elimination occurred to give a cyclic compound having a 1,3-diene moiety. When an acyl group was placed on the alkyne, the carbonyl oxygen coordinated to the ruthenium metal of ruthenacyclopentene to produce a ruthenium carbene complex, which reacted with ethylene to give a cyclic compound having a cyclopropane ring on the substituent. On the other hand, when the substituent on the alkyne was pent-4-enyl, insertion of an alkene part into ruthenacyclopentene followed by reductive elimination gave a tricyclic compound by a ruthenium-catalyzed [2+2+2] cyclization of diene and an alkyne.
authors.affiliation: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Nozomi
authors.initials: N
authors.lastname: Saito
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tanaka
authors.forename: Miwako
authors.initials: M
authors.lastname: Mori
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sato
mesh_terms: D000466:Alkadienes / Q000138:chemical synthesis / Q000737:chemistry*; D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003500:Cyclization; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D000466:Alkadienes; D000480:Alkynes; D009942:Organometallic Compounds; D012428:Ruthenium