The pyrolysis of polycarbonyl compounds. II. Synthesis of biphenylenes from phthalic anhydrides and other carbonyl compounds

Abstract

Pyrolysis of phthalic anhydride or o-sulphobenzoic anhydride at 700- 1100° and 0.1-10 mm produces benzyne, as shown by the formation of biphenylene and triphenylene. Biphenylene and several polychloro and polymethyl derivatives have been conveniently synthesized by pyrolysis of the corresponding phthalic anhydrides in yields ranging from 3 to 26%. These reactions afford further examples of the parallel between the pyrolytic and mass spectral fragmentations of certain aromatic carbonyl compounds. The yield of biphenylene obtained by pyrolysis of compounds structurally related to phthalic anhydride can be correlated with the instability of the corresponding molecular ions in the mass spectrometer.