title: Ruthenium-catalyzed cyclization of epoxide with a tethered alkyne: formation of ketene intermediates via oxygen transfer from epoxides to terminal alkynes.
abstract: Treatment of (o-ethynyl)phenyl epoxides with TpRuPPh(3)(CH(3)CN)(2)PF(6) (10 mol %) in hot toluene (100 degrees C, 3-6 h) gave 2-naphthols or 1-alkylidene-2-indanones very selectively with isolated yields exceeding 72%, depending on the nature of the epoxide substituents. Surprisingly, the reaction intermediate proved to be a ruthenium-pi-ketene species that can be trapped efficiently by alcohol to give an ester compound. This phenomenon indicates a novel oxygen transfer from epoxide to its terminal alkyne catalyzed by a ruthenium complex. A plausible mechanism is proposed on the basis of reaction products and the deuterium-labeling experiment. The 2-naphthol products are thought to derive from 6-endo-dig cyclization of (o-alkenyl)phenyl ketene intermediates, whereas 1-alkylidene-2-indanones are given from the 5-endo-dig cyclization pathway.
authors.affiliation: Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, Republic of China.
authors.forename: Reniguntala J
authors.initials: RJ
authors.lastname: Madhushaw
authors.forename: Ming-Yuan
authors.initials: MY
authors.lastname: Lin
authors.forename: Shariar Md Abu
authors.initials: SM
authors.lastname: Sohel
authors.forename: Rai-Shung
authors.initials: RS
authors.lastname: Liu