title: Epimerization reaction of a substituted vinylcyclopropane catalyzed by ruthenium carbenes: mechanistic analysis.
abstract: A novel ruthenium carbene-catalyzed epimerization of vinylcyclopropanes is reported. The reaction rate strongly depends on the presence of ruthenium ligands in solution. When the first-generation Grubbs catalyst is employed, a 5.3:1 equilibrium ratio of epimers is established quickly, but when a first-generation Hoveyda catalyst is employed, epimerization is observed only if an additional phosphine or nitrogen ligand is added. NMR and kinetic studies suggest that the isomerization reaction occurs through the intermediacy of a ruthenacyclopentene. The observation suggests that cyclopropylmethylidene ruthenium carbenes of synthetic utility may be accessible via ruthenacyclopentenes obtained via other routes.
authors.affiliation: Department of Chemical Development, Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Road, Ridgefield, Connecticut 06877, USA.
authors.forename: Xingzhong
authors.initials: X
authors.lastname: Zeng
authors.forename: Xudong
authors.initials: X
authors.lastname: Wei
authors.forename: Vittorio
authors.initials: V
authors.lastname: Farina
authors.forename: Elio
authors.initials: E
authors.lastname: Napolitano
authors.forename: Yibo
authors.initials: Y
authors.lastname: Xu
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Nizar
authors.initials: N
authors.lastname: Haddad
authors.forename: Nathan K
authors.initials: NK
authors.lastname: Yee
authors.forename: Nelu
authors.initials: N
authors.lastname: Grinberg
authors.forename: Sherry
authors.initials: S
authors.lastname: Shen
authors.forename: Chris H
authors.initials: CH
authors.lastname: Senanayake
mesh_terms: D002384:Catalysis; D003521:Cyclopropanes / Q000138:chemical synthesis* / Q000737:chemistry*; D006838:Hydrocarbons / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical; D008968:Molecular Conformation; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism; D014753:Vinyl Compounds / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D003521:Cyclopropanes; D006838:Hydrocarbons; D014753:Vinyl Compounds; C030011:carbene; D012428:Ruthenium; D008697:Methane