Selective tandem enyne metathesis for the synthesis of functionalized cycloheptadienes |
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Authors: | Steven T Diver Daniel A Clark Amol A Kulkarni |
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Institution: | Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260-3000, USA |
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Abstract: | The regio- and site-selective ring expansion of dienes and the regioselective ring expansion of substituted cyclopentenes provide 1,3-cycloheptadienes by enyne metathesis under methylene-free conditions. Site-selectivity results from differential ring strain among two different cycloalkenes in diene reactants. The high regioselectivity found in the ring expansion of tetrahydroindene (THI) is explained on the basis of a selective ring opening by the second generation Grubbs' ruthenium carbene complex. The ring opening of substituted cyclopentenes and cyclopentene contained in a bicyclic ring system was also achieved. The ring expansion of bicyclic dienes provided seven-membered dienes contained in the bicyclo5.2.0]nonane ring system. Details of the structural analysis are also discussed. A mechanistic analysis is provided to account for the data presented herein. |
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Keywords: | Ring synthesis Ring expansion Enyne metathesis Grubbs' catalyst 1 3-Cycloheptadiene Regioselectivity Site-selectivity |
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