| Abstract
| - Aryl radicals generated ortho to aryl substituents by flash vacuum pyrolysis (FVP) of thecorresponding aryl chlorides are shown to be capable of transferring hydrogen atoms between the orthoand ortho‘ positions (1,4-shifts of hydrogen atoms). In the examples described here, the rearranged arylradicals are trapped by subsequent radical cyclization reactions. For example, FVP of 2-(o-chlorophenyl)benzo[c]phenanthrene gives 1-phenylbenzo[ghi]fluoranthene as the major product by homolysis of the C−Clbond, 1,4-shift of a hydrogen atom out of the sterically congested cove region to the radical center, cyclizationof the rearranged radical, and rearomatization of the molecule by loss of the other cove region hydrogen.In a control experiment run under the same conditions, FVP of 2-phenylbenzo[c]phenanthrene, which lacksa radical precursor, gave primarily recovered starting material. When the FVP was repeated using 2-(2,6-dichlorophenyl)benzo[c]phenanthrene as the starting material, benzo[a]corannulene was obtained as themajor product, presumably by the same cascade of events to produce 1-(o-chlorophenyl)benzo[ghi]fluoranthene, which then suffers a second radical cyclization spontaneously under the high-temperatureconditions to give the geodesic polyarene.
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