FORMATION OF CYCLOPENT[A]INDENE AND ACENAPHTHYLENE FROM ALLYL ESTERS OF BIPHENYL MONO-CARBOXYLIC 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 t he three isomeric biphenylcarboxylic acids, of the allyl esters of the 12 biphenyldicarboxylic acids and of the three biphenyldicarboxylic a nhydrides gave pyrolysates which were examined by H-1 n.m.r. spectrosc opy at temperatures below -50 degrees C. In all cases the spectra show ed the presence of cyclopent[a]indene and acenaphthylene together with other products. Possible mechanisms for these ring contraction and cy clization 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.