A tetrabromo-1,4-ethanonaphthalene and related dibromo-1,4-ethenonaphthalene

Abstract

(1RS,3RS,4RS,10SR)-2,2,3,10-Tetrabromo-1,2,3,4-tetrahydro-1,4-ethanonaphthalene, C12H10Br4, (I), is the first structure to be reported with four Br atoms bound to a 1,4-ethanonaphthalene framework and also the first which possesses three Br atoms in exo positions. Interactions between the Br atoms [three short intramolecular Br...Br distances of 3.1094 (4), 3.2669 (4) and 3.4415 (5) Å] have little effect on the C-C bond lengths but lead to significant twisting of the cage structure compared with the parent hydrocarbon, which is expected to be fully eclipsed at the two saturated C2H4 bridge positions. Chemically related (1SR,4RS)-2,3-dibromo-1,4-ethenonaphthalene, C12H8Br2, (II), obtained by double dehydrobromination of (I), represents the first structure of any halogen-substituted benzobarrelene. This cis-dibromide shows little evidence of steric congestion at the double bond [Br...Br = 3.5276 (8) Å] as a consequence of the large C-C-Br angles [average C=C-Br angle = 126.15 (10)°].

Accurate Crystal Structures of C12H9CN, C12H8(CN)2, and C16H11CN Valence Isomers Using Nonspherical Atomic Scattering Factors

“…50 Crystallography. The new single-crystal X-ray diffraction structures obtained in this work belong to four major structural categories: benzobarrelenes (1, 2) and a partially hydrogenated analogue 3, benzo-and naphthosemibullvalenes (4,11,13), benzocyclooctatetraenes (5,6,12,14), and di/tetrahydrocyclobuta[a]naphthalenes (DCBN, TCBN) (7,8,9,10). Because of the proclivity of photochemistry to produce many isomers via excited-state reactions, spread across all four categories are valence isomers with the formula C 13 H 9 N (2,4,5,6,7,8); two (11,12) are valence isomers of C 14 H 8 N 2 and two (13,14) are naphtho-rather than benzo-fused analogues of formula C 17 H 11 N. Atom labels are taken from the first exemplar (see Figure 1a) and applied to all structures for ease of comparison.…”

“…The Cremer-Pople puckering parameters, 90−92 hereafter referred to as puckering parameters, for the barrelene moieties of 1−3 (Table S1) all closely conform to boat geometry (Q = 0.7529−0.8487, θ ≈ π/2, φ ≈ π), consistent with the absence of steric effects in this substitution pattern (contrast a previously reported tetrabromobarrelene). 9 Benzo-and Naphthosemibullvalenes. Semibullvalenes have a characteristic three-ring system consisting of two fused fivemembered rings which are bridged (at C2A/C2B) to form a three-membered ring (Figure 2).…”

“…We have provided one of these entries in a previous report on a fully saturated tetrabromobenzobarrelene and 2,3-dibromo-1,4ethenonaphthalene, which is derived from the former by double dehydrobromination. 9 Selective saturation of the alkene "staves" of benzobarrelenes is possible. 10 Dihydrobenzobarrelenes (1,4-dihydro-1,4-ethanonaphthalenes, II in Chart 1) are of interest as spacers between antipodal redox sites 11 or as a vector to benzannulation via the Alder−Rickert reaction involving thermolytic removal of the saturated stave of the barrelene.…”

“…C 12 H 8 (CN) 2 Valence Isomers. Analogously to Scheme 1, dibromobenzobarrelene 16, made from the dehydrobromination of higher brominated barrelenes such as tetrabromo-1,4ethanonaphthalene, 9 reacts with CuCN to form the dinitrile 17, which is then photolyzed with 254 nm radiation to produce a mixture of 11, 12, and 18 (82, 6, and 12%, respectively), 9,80 which were separated by column chromatography (Scheme 3).…”

“…In all, about 20 structures of type I (Chart ) have been reported, excluding metal coordination complexes and those embedded into additional rings. We have provided one of these entries in a previous report on a fully saturated tetrabromobenzobarrelene and 2,3-dibromo-1,4-ethenonaphthalene, which is derived from the former by double dehydrobromination …”