- Photochemically generated bicyclic ortho-quinodimethanes: Photo- enolization of bicyclic aldehydes and ketones
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A photoenolization route to bicyclic ortho-quinodimethanes was investigated. Bicyclic photoenols were trapped in an intermolecular fashion with various dienophiles for the first time. All ortho-quinodimethane precursors were prepared via a selective route commencing with 1-indanol, α- tetralol and 1-benzosuberone. Irradiation afforded the E-photoenols exclusively which were trapped with equal efficiency except that derived from indane-4-carboxaldehyde. This low efficiency has been ascribed to rapid auto- oxidation of the aldehyde to carboxylic acid. The facial selectivity of the reaction between the photoenol from benzosuberan-9-carboxaldehyde and dimethyl fumarate was much lower when compared to the other aldehydes in this study. A distorted diene caused by the presence of the seven membered ring explains these results.
- Connolly, Terrence J.,Durst, Tony
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p. 15969 - 15982
(2007/10/03)
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- 1,2-Photoadditions of Stilbenes and Diarylacetylenes to Bicyclic 1,4-Cyclohexadienes: Propellanes and Substitutive 1,2-Adducts
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The photoreactions of stilbene, 4,4'-dichloro-, 4,4'-dicyano-, 4,4'-dimethoxystilbene, diphenylacetylene, and bis(4-cyanophenyl)acetylene with 2,3,4,7-tetrahydroindene and 1,4,5,8-tetrahydronaphthalene have been investigated.Despite severe steric hindrance and because of electrostatic support the propellanes 3, 12, 23, 26 are formed as the major -cycloadducts.The products of dehydrogenation 41, 44, 45 and hydrogenation 29 are obtained from them.Further major products of the photolyses are the substitutive 1,2-adducts 4, 5, 14, 15, 24, 27, whereas the ene-adduct s 25, 28 occur only in trace amounts.The mechanistic grounds are discussed in terms of diradicals with consideration of exciplex emissions and with the aid of comparative reactions involving 1,4-cyclohexadiene and methyl cinnamate.The protolyses of several propellanes with varing degrees of hydrogenation are described (decomposition, dehydrocyclization, intramolecular cycloaddition and 1,5-shift).The structures of the products have been determined spectroscopically (IR, UV, fluorescence, 1H-NMR, 13C-NMR) and in part by chemical degradation and independent synthesis.
- Kaupp, Gerd,Stark, Michael
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p. 2217 - 2237
(2007/10/02)
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