Flash Vacuum Pyrolysis of [2,3-13C2]Triphenylene-2,3-dicarboxylic Anhydride: Formation of Labelled Cyclopent[hi]acephenanthrylene and Triphenylene

Flash vacuum pyrolysis (f.v.p.) of [2,3-13C2]triphenylene-2,3-dicarboxylic anhydride (c. 22·5% 13C2) at 950°C gave a pyrolysate which was analysed by 13C n.m.r. spectroscopy. The principal product was [2,3-13C2]triphenylene. The second major product was a 1 : 2 : 1 mixture of [4,7- 13C2]-, [4,6-13C2]- and [5,6-13C2]-cyclopent[hi]acephenanthrylene.