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]azuleneElectronic supplementary information (ESI) available: Synthetic details and NMR data for molecules 20b, 20c, 21a, 21b, 23c and 24a. CCDC reference numbers 769734 (12), 769736 (13), 769735 (14), 769744 (17), 769738 (20a), 769745 (20b), 769739 (21a), 769742 (23c), 769737 (24a), 769743 (30), 7697

• Main Authors: Banide, Emilie V, O'Connor, Crystal, Fortune, Natasha, Ortin, Yannick, Milosevic, Sandra, Müller-Bunz, Helge, McGlinchey, Michael J
• Format: Journal Article
• Language: English
• Published: 07.09.2010
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/c004868b

3,3-(Biphenyl-2,2′-diyl)-1-α,α,α-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 °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&z.dbd;C&z.dbd;C(Br)Ph, 20a , and (C 14 H 10 )C&z.dbd;C&z.dbd;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[ c d , 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. 3,3-(Biphenyl-2,2′-diyl)-1-α,α,α-trifluoro- p -tolyl-allene, 9 , sequentially forms a series of 1,2-dialkylidene-cyclobutane dimers and, ultimately, a dispirotetracene and a di-indenotetracene; the latter compound forms a Diels-Alder adduct with N -methylmaleimide.