CHEMISTRY OF ANTI-O,O'-DIBENZENE

A new and efficient preparation of anti-o,o'-dibenzene 1 has been achi eved in three steps from cis-3,5-cyclohexadiene-1,2-diol 25. Utilizing a method for deoxygenation of 1,2-diols developed in our laboratory, anti-tetraol 23 was converted to 1 in 65% yield on a 0.5 g scale. This has allowed us to explore the chemistry of anti-dibenzenes extensivel y. The kinetics for thermal reversion of 1 to benzene have been studie d in three different solvents. The direct photolysis of 1 to benzene h as been found to form excited benzene iu unit efficiency. This high ef ficiency of adiabatic photon up-conversion in the singlet manifold is unprecedented. No light was detected in the thermal dissociation of 1 in solution using various sensitizers. The chemiluminescence spectrum from the thermolysis of 1 in the presence of perylene has been recorde d and found to correspond to the emission of perylene excimer. Althoug h the efficiency of the chemiluminescent process was very low, it has proven to be one of a very few examples of chemiluminescent reactions from pure hydrocarbons. The possible mechanisms were discussed. Benzen e 1,4-endoperoxide 36 was formed during the photolysis of monoperoxide 34 at low temperature. Peroxide 36 underwent a quantitative concerted retrocycloaddition to benzene and singlet oxygen. The half-life of 36 was determined to be 29 min at -30 degrees C.