Formation Of Cyclopent[A]Indene And Acenaphthylene From Allyl Esters Of Biphenyl Mono- And Di-Carboxylic Acids And From Biphenyl Dicarboxylic Anhydrides On Flash Vacuum Pyrolysis At 1000-1100 Degrees C

Flash vacuum pyrolysis at 1000-1100 degrees C of the allyl esters of the three isomeric biphenylcarboxylic acids, of the allyl esters of the 12 biphenyldicarboxylic acids and of the three biphenyldicarboxylic anhydrides gave pyrolysates which were examined by H-1 n.m.r. spectroscopy at temperatures below -50 degrees C. In all cases the spectra showed the presence of cyclopent[a]indene and acenaphthylene together with other products. Possible mechanisms for these ring contraction and cyclization processes are discussed and the results of pyrolyses of [2,3-C-13(2)]biphenyl-2,3-dicarboxylic anhydride, and [3,4-C-13(2)]- and (2-H-2(1))-biphenyl-3,4-dicarboxylic anhydrides are reported.