title: Syntheses of seven-membered rings: ruthenium-catalyzed intramolecular [5+2] cycloadditions.
abstract: The Ru-catalyzed intramolecular [5+2] cycloaddition of cyclopropylenynes is investigated with respect to the regio- and diastereoselectivity as well as the functional group compatibility of the reaction. Evidence for the mechanism as occurring through a ruthenacyclopentene intermediate is elucidated from 1) the study of the diastereoselectivity of the cycloaddition; 2) the effect of variation of substituents on the regioselectivity of cyclopropyl bond cleavage in 1,2-trans- and 1,2-cis-disubstituted cyclopropanes and 3) examples that clearly do not involve ruthenacyclohexene as intermediates as products still incorporate the cyclopropyl moiety. The scope and limitations of the Ru-catalyzed cycloaddition are discussed and compared with the Rh-catalyzed reaction. The potential power of this methodology towards natural product total synthesis is demonstrated by the formation of several polycyclic systems with the chosen reaction conditions and readily available cyclopropylenyne substrates.
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA. bmtrost@stanford.edu
authors.forename: Barry M
authors.initials: BM
authors.lastname: Trost
authors.forename: Hong C
authors.initials: HC
authors.lastname: Shen
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Horne
authors.forename: F Dean
authors.initials: FD
authors.lastname: Toste
authors.forename: Bernhard G
authors.initials: BG
authors.lastname: Steinmetz
authors.forename: Christopher
authors.initials: C
authors.lastname: Koradin
mesh_terms: D000475:Alkenes / Q000737:chemistry; D001688:Biological Products / Q000737:chemistry; D002384:Catalysis; D018360:Crystallography, X-Ray; D003500:Cyclization; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D000475:Alkenes; D001688:Biological Products; D012428:Ruthenium