title: Hexabromotricyclobutabenzene and hexabromohexaradialene: their nickel-mediated one-pot syntheses and crystal structure.
abstract: The reaction of hexakis(dibromomethyl)benzene with [(Bu3 P)2 -Ni(COD)] (COD = 1,5-cyclooctadiene) in DMF at 65-70°C yielded a mixture of the title compounds. The mixture was separated by column chromatography to yield hexabromotricyclobutabenzene (3 a) and hexabromohexaradialene (4) in 24 and 16% yields, respectively. (1) H and (13) C NMR spectroscopy suggest that 3 is obtained as the syn-all-trans isomer 3 a, and the symmetric anti-all-trans isomer 3 b is not obtained at all. The X-ray structures of 3 a and 4 are reported. The hexaradialene 4 has a chair conformation, and deviates from planarity by 43.6°. Heat or radical impurities cause the clean transformation of 3 a to 4.
authors.affiliation: Department of Chemistry, Technion-Israel Institute of Technology Haifa 32000 (Israel), Fax: Int. code +(4)823-3735, e-mail: stanger@techunix.technion.ac.il.
authors.forename: A
authors.initials: A
authors.lastname: Stanger
authors.forename: N
authors.initials: N
authors.lastname: Ashkenazi
authors.forename: R
authors.initials: R
authors.lastname: Boese
authors.forename: D
authors.initials: D
authors.lastname: Bläser
authors.forename: P
authors.initials: P
authors.lastname: Stellberg
keywords: crystal structure; cyclobutenes; nickel; radialenes; radical reactions