title: Palladium-catalyzed synthesis of endocyclic allenes and their application in stereoselective [2 + 2]cycloaddition with ketenes.
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.
authors.affiliation: Catalysis Research Center and Graduate School of Life Science, Hokkaido University, and SORST, Japan Science and Technology Agency, Kita-ku, Sapporo 001-0021, Japan.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Ogasawara
authors.forename: Atsushi
authors.initials: A
authors.lastname: Okada
authors.forename: Kiyohiko
authors.initials: K
authors.lastname: Nakajima
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D000466:Alkadienes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D003500:Cyclization; D005030:Ethylenes / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D015394:Molecular Structure; D010165:Palladium / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000466:Alkadienes; D005030:Ethylenes; D007659:Ketones; D010165:Palladium; C008223:ketene