Christopher Owen Bender

The Photochemistry of 2-Cyano-1,4-dihydro-1,4-ethenoanthracene

The direct photolysis of 2-cyano-1,4-dihydro-1,4-ethenoanthracene (5) yields 8-cyanocycloocta[b]-naphthalene (8, Φ = 0.02) and 1- and 6-cyanonaphtho[2,3-c]tricyclo-[3.3.0.02,8]octa-3,6-diene (6, Φ = 0.30 and 7, Φ = 0.04). The benzophenone sensitized irradiation of 5 yields 6 (Φ = 0.40) and 7 (Φ = 0.04) only. Deuterium labeling studies reveal that 8 derives from an initial 2π + 2π cycloaddition reaction which proceeds with bonding between the vinyl and vinylcyano bridges.

exo-10,11-Dibromo­tricyclo­[6.3.1.02,7]dodeca-2,4,6,9-tetra­ene

The title compound, C12H10Br2, is a bridged ring system based on a homobenzonorbornadiene framework. The exo configuration of one of the Br atoms was previously assigned via NMR correlations and has now been confirmed by the geometry of the solid-state structure. The compound features a Br—C—C—Br torsion angle of 66.68 (12)°, whereby the C atoms in the calculation are respectively sp 3- and sp 2-hybridized.

(5Z,7Z,9Z)-5,10-Di-bromo-benzo[8]annulene.

In the structure of the title compound, C12H8Br2, the two bromine substituents are oriented exo to the boat-shaped cyclooctatetraene at the two ring sites that are β to the ring fusion positions. The average Br—C bond distance is 1.919 (2) Å, the average distance for C=C double bonds that are Br substituted is 1.328 (2) Å, while the other two double-bond distances are 1.327 (2) and 1.398 (2) Å for the non-fused and fused bonds, respectively. Each type of ring interatomic distance is within s.u. of the average values for the four known structures, including the title compound, of benzo-fused cycloocatatetraenes that are not coordinated to a metal atom. The crystal structure features short Br⋯Br [3.6620 (3) Å] and C⋯H [2.834 (2) and 2.841 (2) Å] contacts.

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

(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)°].

Dimethyl 7-meth­oxy­tetra­cyclo­[6.4.0.02,4.03,7]dodeca-1(12),5,8,10-tetra­ene-3,4-dicarboxyl­ate

The title compound, C17H16O5, is a previously unreported substituted semibulvalene cage compound (that is, a tricyclic hydrocarbon formed from one cyclopropane and two cyclopentene rings which also has one double bond fused to a benzene ring). It has one methoxy substituent attached to the bridgehead C atom that links only the two cyclopentene rings and two methyl carboxylate groups located on the C atom shared by all three non-benzene rings and that shared only between the cyclopropane and the cyclopentene rings. The stereochemistry of the two enantiomers (racemate) that assemble in each unit cell is RRRS and SSSR. In the crystal, molecules are linked via C—H⋯O hydrogen bonds and C—H⋯π interactions, forming double-layered sheets lying perpendicular to the a axis.

THE PHOTOCHEMISTRY OF 2‐CYANO‐1,4‐DIHYDRO‐1,4‐ETHENOANTHRACENE

The direct photolysis of 2-cyano-1,4-dihydro-1,4-ethenoanthracene (5) yields 8-cyanocycloocta[b]-naphthalene (8, Φ = 0.02) and 1- and 6-cyanonaphtho[2,3-c]tricyclo-[3.3.0.02,8]octa-3,6-diene (6, Φ = 0.30 and 7, Φ = 0.04). The benzophenone sensitized irradiation of 5 yields 6 (Φ = 0.40) and 7 (Φ = 0.04) only. Deuterium labeling studies reveal that 8 derives from an initial 2π + 2π cycloaddition reaction which proceeds with bonding between the vinyl and vinylcyano bridges.