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  • Title: Palladium-catalyzed synthesis of endocyclic allenes and their application in stereoselective [2 + 2]cycloaddition with ketenes.
    Author: Ogasawara M, Okada A, Nakajima K, Takahashi T.
    Journal: Org Lett; 2009 Jan 01; 11(1):177-80. PubMed ID: 19055426.
    Abstract:
    Palladium-catalyzed reactions of various 2-bromo-3-exo-methylenecycloalkenes with a stabilized nucleophile were examined. When the carbocycles were nine-membered or larger, the corresponding endocyclic allenes were isolated in excellent yields. In a reaction of the eight-membered cyclic substrate, initial formation of a cycloocta-1,2-diene derivative was detected; however, it dimerized slowly. The seven-membered carbocycle was inert to the reaction. Using a chiral Pd-catalyst, an axially chiral endocyclic allene was obtained in 65% ee. The cyclic allenes were applied to [2 + 2]cycloaddition with ketenes, and the stereoselectivity was studied.
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