ORGN 499 |
| Intramolecular photochemical [2+2] cycloaddition is one of the most sophisticated methods for the synthesis of strained polycyclic cage compounds. Irradiation of diphenylbicyclo[4.2.0]oct-3-ene-2,5-diones(1) bearing variously substituted Me groups resulted in the reversible intramolecular [2+2] cycloaddition between the excited enedione C=C double bond and the facing endo-phenyl ring to exclusively give pentacyclotetradeca-10,12-diene-2,7-diones(2).The equilibrated product ratios were much dependent on the substitution pattern of the Me-groups. The regiochemistry of these photoadditions was conformationally elucidated on the basis of the X-ray crystal structural analysis of 1. To obtain some information on the photoreversibility in the present intramolecular [2+2] cycloaddition of bicyclic diones, we have measured the absorption spectra of 1 and 2 in benzene. It was found that both the 1 and 2 have the comparable absorptions in the range of 300-340 nm which are responsible for cycloaddition and cycloreversion. We have also investigated the effects of exo-substituents or the substituents on endo- phenyl ring. |
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Physical Organic Chemistry, Metal-Mediated Reactions, Asymmetric Reactions and Syntheses
8:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Organic Chemistry |