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Paper | Regular issue | Vol 60, No. 2, 2003, pp.365-372
Published online, 24th December, 2002
DOI: 10.3987/COM-02-9675
Novel [12+2] Cycloaddition of 2H-4,9-Methanocycloundeca[b]furan-2-ones with Enamines: Synthesis and Properties of 4,9-Methanocyclopentacycloundecenes and a Benzo-annulated Derivative

Makoto Nitta,* Akira Akaogi, and Hiroki Tomioka

*Department of Chemistry, School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan


Novel cycloaddition reactions of 2H-4,9-methanocycloundeca[b]furan-2-one and 3-chloro-substituted derivative with enamines underwent novel [12 + 2] cycloaddition reaction followed by decarboxylation and elimination of amine to give 4,9-methanocyclopentacycloundecene derivatives in modest yields. Upon treatment of DDQ, cyclohexane-annulated 5-chloro-4,9-methanocyclopentacyclo-undecene was dehydrogenated easily to give the first example of a benzo-annulated 4,9-methanocyclopentacycloundecene ring system. Chemical as well as spectroscopic properties of them were studied, and it was clarified that benzo-annulation causes an appreciable degree of bond alternation and reduced ring current.