5603-34-9Relevant articles and documents
Torsional Effects on the Conformations of Two Diastereomeric Tetracyclic Bis(hydrazines)
Nelsen, Stephen F.,Jens Wolff,Chang, Hao,Powell, Douglas R.
, p. 7882 - 7886 (1991)
The symmetrical tetraazatetracyclotetradecadiene (1) is bis(tert-butylated) (tert-butyl alcohol/H+) and bis(methylated) (methyllithium) to a 1:1 mixture of diastercomeric bis(tert-butylmethylhydrazines) with like alkyl groups anti (9a) and syn (9s). 9a has the expected C2 symmetry on the NMR time scale (both tert-butyl groups are directed away from the central CC bond, conformation Oi.Oi in Scheme II). 9s does not have the expected C, symmetry, but has one tert-butyl group directed away from the central CC bond and one directed toward it (conformations Oi.oI and Io.iO in Scheme II). Both diastereomers also crystallize in these conformations. AM 1 calculations carried out using VAMP both predict this result and show it to be caused by tetracyclic ring torsion (experimentally ～ 12.7° about the central CC bond for crystalline 9a, ～ 13.2° for 9s).
Diademane and Structurally Related Compounds, I. Preparation and Characteristic Reactions of Some Tris-?-homobenzene Hydrocarbons
Kaufmann, Dieter,Fick, Hans-Heinrich,Schallner, Otto,Spielmann, Werner,Meyer, Lueder-Ulrich,et al.
, p. 587 - 609 (2007/10/02)
Diademane (5) and 1,6-Homodiademane (6) are the first hydrocarbons with cis-tris-?-homobenzene skeletons.They were prepared by photoisomerization of the olefinic precursors 8 (snoutene) and 15 (4,5-homosnoutene), respectively.In an analogous reaction the bridged trans-tris-?-homobenzene 7 was formed from 17 (endo,exo-bishomobarrelene). 7 is more easily obtained from 17 by rhodium(I)-catalyzed isomerization or from exo,exo-bishomobarrelene 18 by thermal rearrangement.The unbridged 4 was prepared using a newly developed synthetic sequence starting from 1,3-cyclohexadiene.The thermal rearrangement of 5 and 6 to triquinancene (9) and 1,10-homotriquinancene (16) is very facile; the gas phase kinetic parameters (ln k (5) = 33.7 - 31600/RT and ln k (6) = 32.2 - 28300/RT, both first order) strongly corroborate, that these rearrangements are concerted ?2S + ?2S + ?2S> cycloreversions. -labelled 4 upon thermolysis yields a trans-bicyclonona-3,7-diene (31 22) with a 12C-labelling pattern, which proves its formation via a 3-step mechanism.The first step in this sequence most probably is a ?2S + ?2S + ?2S> cycloreversion with ln k = 30.8 - 42000/RT (first order).Only the bridged compound 7 does not follow the sample path, probably due to excessive ring strain in the transition state, and prefers a stepwise cycloreversion leading to 18 and at least 5 secondary products.
