Type 3 ring opening reaction of cyclopropanated oxabenzonorbornadienes with alcohol nucleophiles |
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Authors: | Emily Carlson Rebecca Boutin William Tam |
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Institution: | Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, Department of Chemistry, University of Guelph, Guelph, Ontario, N1G 2W1, Canada |
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Abstract: | The first examples of a Type 3 ring opening reaction of cyclopropanated oxabenzonorbornadiene (CPOBD) were found to occur using alcohol nucleophiles under acid catalyzed conditions, yielding seven-membered rings via ring expansion. Optimization of the reaction determined the ideal conditions to be 10?mol% pTsOH at 40?°C using excess alcohol nucleophile as the solvent. The scope of the reaction investigated diverse alcohol nucleophiles and bridgehead substituents on the CPOBD; in both cases the steric properties of the substituent was found in influence the yield of the reaction. Alternative Type 3 products were observed when the bridgehead substituent was an ethyl or hydroxymethyl group and limited examples of Type 3 products were formed using a palladium catalyst with alcohol nucleophiles. Mechanisms have been proposed for the formation of the Type 3 product as well as the alternative Type 3 products. |
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Keywords: | Oxabenzonorbornadiene Ring expansion Cyclopropanation Nucleophilic ring opening reaction Acid catalysis |
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