Formation of cyclopent[hi]acephenanthrylene from 1,2-, 1,3-, 1,4- and 2,3-triphenylenedicarboxylic acid derivatives on flash vacuum pyrolysis at >900°c

Article abstract of DOI:10.1071/CH9960965

The processes involved in the conversion of triphenylene, C₁₈H₁₂, into cyclopent[hi]acephenanthrylene, C₁₈H₁₀, under flash vacuum pyrolytic conditions at 900-1100°C have been investigated by pyrolysing triphenylene-1,2- and -2,3-dicarboxylic anhydrides and diallyl triphenylene-1,3- and -1,4-dicarboxylates to give the corresponding didehydrotriphenylenes in the gas phase. These didehydro intermediates are converted into mixtures of cyclopent[hi]acephenanthrylene and triphenylene in different yields and proportions. Pyrolysis of 9,10-diethynylphenanthrene, C₁₈H₁₀, yields cyclopent[hi]acephenanthrylene in good yield. Pyrolysis of 1-nitrothphenylene and allyl triphenylene-2-carboxylate to give the triphenylen1-yl and -2-yl radicals leads to formation of the same products. Mechanisms involving radical rearrangements (C₁₈H₁₁ species) and benzyne-cyclopentadienylidenecarbene and ethyne-ethenylidene rearrangements (C₁₈H₁₀ species) are discussed.