title: Different rearrangement behaviour of the cation or anion derived from the Diels-Alder adduct of 9-ferrocenylanthracene and 1,4-benzoquinone: ring-opening or paddlewheel formation.
abstract: Prototropic rearrangement of the Diels-Alder adduct (3a) of 9-ferrocenylanthracene and 1,4-benzoquinone potentially furnishes 9-ferrocenyl-1,4-dihydroxytriptycene (3b) incorporating a C(2v) symmetrical paddlewheel moiety. However, reaction of 3a with HBF(4) unexpectedly yields instead 9-ferrocenyl-10-(2,5-dihydroxyphenyl)anthracene (4) via cleavage of the C9-C12 bond to generate initially a ferrocenyl-stabilized cation. Treatment of 3a with sodium hydride and iodomethane yields 1,4-dimethoxy-9-ferrocenyltriptycene (3c) in high yield but, surprisingly, also leads to fission of the C9-C12 bond resulting, after methylation, in the formation of 9-hydroxy-9-ferrocenyl-10-(2-hydroxy-5-methoxyphenyl)dihydroanthracene (12), which readily dehydrates on silica to form 9-ferrocenyl-10-(2-hydroxy-5-methoxyphenyl)anthracene (8). The X-ray crystal structures of 3a, 3c and 4 are reported.
authors.affiliation: School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland. kirill.nikitin@ucd.ie
authors.forename: Kirill
authors.initials: K
authors.lastname: Nikitin
authors.forename: Helge
authors.initials: H
authors.lastname: Müller-Bunz
authors.forename: Yannick
authors.initials: Y
authors.lastname: Ortin
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McGlinchey