Ruthenium-catalyzed cyclization of epoxide with a tethered alkyne: formation of ketene intermediates via oxygen transfer from epoxides to terminal alkynes

Reniguntala J Madhushaw; Ming-Yuan Lin; Shariar Md Abu Sohel; Rai-Shung Liu

doi:10.1021/ja049943c

Ruthenium-catalyzed cyclization of epoxide with a tethered alkyne: formation of ketene intermediates via oxygen transfer from epoxides to terminal alkynes

J Am Chem Soc. 2004 Jun 9;126(22):6895-9. doi: 10.1021/ja049943c.

Authors

Reniguntala J Madhushaw¹, Ming-Yuan Lin, Shariar Md Abu Sohel, Rai-Shung Liu

Affiliation

¹ Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, Republic of China.

PMID: 15174858
DOI: 10.1021/ja049943c

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.