title: Syntheses, X-ray crystal structures and reactivity of fluorenylidene- and dibenzosuberenylidene-allenes: convenient precursors to dispirotetracenes, di-indenotetracenes and 2-phenyl-11bH-dibenz[cd,h]azulene.
abstract: 3,3-(Biphenyl-2,2'-diyl)-1-alpha,alpha,alpha-trifluoro-p-tolyl-allene, 9, sequentially forms head-to-tail, 12, cis-tail-to-tail, 13, and trans tail-to-tail, 14, 1,2-dialkylidene-cyclobutane dimers, each of which has been characterised by X-ray crystallography. Thermolysis at 180 degrees C yields the dispirotetracene, 15, and di-indenotetracene, 16; the latter compound forms an air-stable Diels-Alder adduct, 17, with N-methylmaleimide. In contrast, the dibenzo[a,d]cycloheptenylidene-allenes, (C(14)H(10))C=C=C(Br)Ph, 20a, and (C(14)H(10))C=C=C(H)Ph, 21a, do not dimerise under relatively mild conditions. However, protonation of the bromo-allene, 20a, and subsequent addition of hydride, provide a facile entry to the difficultly accessible bowl-shaped dibenz[cd,h]azulene framework, as in 30, that had not previously been structurally characterised. Among others, the X-ray crystal structures of 12, 13, 14, 17, 20a, 21a and 30 are reported.
authors.affiliation: School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Emilie V
authors.initials: EV
authors.lastname: Banide
authors.forename: Crystal
authors.initials: C
authors.lastname: O'Connor
authors.forename: Natasha
authors.initials: N
authors.lastname: Fortune
authors.forename: Yannick
authors.initials: Y
authors.lastname: Ortin
authors.forename: Sandra
authors.initials: S
authors.lastname: Milosevic
authors.forename: Helge
authors.initials: H
authors.lastname: Müller-Bunz
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McGlinchey