Substituent control of regiospecific pathways in di-.pi.-methane photorearrangements which utilize benzo-vinyl bonding schemes

Photoelectron spectra of ortho- and meta-substituted benzonorbornadienes. Relationships to regioselectivities in triplet di-.pi.-methane rearrangements

“…Although these have been applied, for the most part, to intermolecular reactions such as cycloadditions, the benzonorbornadiene di-7r-methane rearrangement may be considered formally as the attack of a triplet excited benzene on an ethylene, so that these intermolecular treatments are relevant. The various methods may be roughly classified as (1) orbital interaction methods, (2) configuration interaction methods, and (3) bond-order methods. Before embarking on the discussion of benzonorbornadiene di-Tr-methane regioselectivity, we wish to show the similarities between, indeed identities of, these various models.…”

Donor-Acceptor Substituted Benzo-, Naphtho- and Phenanthro-Fused Norbornadienes

“…One approach could be to couple the isomerization reaction with loss of aromaticity of a fused benzene ring as shown for the benzo-fused couple 1 NBD /1 QC in Scheme 1. Yet, irradiation of derivatives of 1 NBD with various substituents at the benzene ring did not result in QC formation but instead in rearrangement reactions [8][9][10]. Along this line, some of us recently investigated benzo-fused dihydroazulene/vinylheptafulvene (DHA/VHF) derivatives [11,12].…”

Organic photochemistry. 41. Photochemistry of bichromophoric molecules. Photochemistry and photophysics of 2-methylenebenznorbornene and related molecules in protic media

“…The spectral data follow: IR (neat) 3.43, 6.84, 6.88, 7.44, 7.78, 9.0, and 13.3 µ; >H NMR (CDC13, 90 MHz) 7.05-7.26 (m, aromatic, 4 ), 3.55-3.85 (m, side-chain methylene, 8 ). 4 3.20-3.33 (m), , 3.33-3.45 (m), 2.40-3.01 (m, H2ex, Hs, and Hg), 3 2.04 (m, 73ex2ex = 9 Hz, the other coupling constants are not discernible owing to poor signal to noise), 7 1.83 (dm, 77en7ex = 9 Hz), 7 .05-7.35 (m, aromatic, 4 ), 3.52-3.93 (m, side-chain methylene, 8 ), 5 3.15-3.34 (m), 8 2.41-2.65 (m), 2 1.87 (dt, 72ex3ex = 5.5, 72ex2en -72ex3en - 12 Hz), 1.35-1.78 (m, H2em H4ex, and H4en), Caled for C16H21CIO2: m/e 280.122.…”

“…The spectral data follow: IR (neat) 3.44,6.10, 6.27, 6.85, 6.89, 7.36,9.25, 10.15, 11.0, 13,25, and 13.65 µ; NMR (CDC13, 90 MHz) 7.52-7.68 (m, aromatic, 1 H), 7.12-7.36 (m, aromatic, 3 ), 3 5.90 (ddd. 732 = 17, 73i = 10,734 = 8 Hz), 2 5.17 (dd, 723 = 17 , 72, = 2 Hz), , 5.08 (dd, 712 = 2,7,3 = 10 Hz), 4 3.79 (dt, 743 = 743 = 8, 746 = 6 Hz), 5 3.06 (ddm, 734 = 8 , 756 = 16 Hz), 6 2.52 (ddm, J6S = 16, Jm = 6 Hz), 2.09 (s, methyl, 3 ), 1.90 (s, methyl, 3 H); mass spectrum m/e 184 (molecular ion) and 43 (base ion).…”