OVERCROWDED MOLECULES .16. THERMAL AND PHOTO-CHEMICAL REACTIONS OF (E,E)-BIS(BENZYLIDENE)SUCCINIC ANHYDRIDE

Irradiation of (E,E)-bis(benzylidene)succinic anhydride in toluene gives 1-phenyl-1,4-dihydronaphthalene-2,3-dicarboxylic anhydride; in the presence of trichloroacetic acid, cis- and trans-1-phenyl-1,2-dihydronaphthalene-2,3- dicarboxylic anhydrides are also formed; and in the presence of triethylamine, only 1-phenylnaphthalene-2,3-dicarboxylic anhydride and bis(benzyl)maleic anhydride are formed. The last two products are obtained exclusively when (E,E)-bis(benzylidene)succinic anhydride is heated in xylene containing triethylamine at 140 °C in o-dichlorobenzene at 180 °C, or on heating alone at 180°C. All the products are presumed to be formed through a 1,8a-dihydronaphthalene intermediate, and bis(benzyl)maleic anhydride via rearrangement of (E)-benzylidene-benzylsuccinic anhydride. The latter yields (E,E)-bis(benzylidene)succinic anhydride, the most sterically hindered of the geometrical isomers, on bromination with N-bromosuccinimide followed by dehydrobromination with 2,4,6-trimethylpyridine.