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New route for catalytic CC bond cleavage Alkynes are highly energetic species, and in catalytic reactions they normally couple with other molecules to give complex compounds via cleavage of one or two bonds. However, most studies on alkyne CC bond cleavage have focused on stoichiometric organometallic reactions. And the few studies that have focused on catalytic reactions have required organic promoters such as 2-aminopyridine or 2-aminophenol to facilitate alkyne cleavage. Chemistry professor Rai-Shung Liu and coworkers at National Tsing-Hua University, in Taiwan, now report a ruthenium-catalyzed method that splits terminal ethynyl alcohols attached to a variety of alkyl and aryl substrates into terminal alkenes and CO without organic promoters [J. Am. Chem. Soc., 125, 9294 (2003)]. The best results were achieved with a tris(pyrazolyl)borate ruthenium complex in toluene using lithium triflate as a Lewis acid cocatalyst. The researchers used isotopic labeling studies to elucidate a proposed mechanism that includes generation of a metal-vinylidene intermediate. They are using their findings to develop new catalytic processes. |
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