Polyphosphoric acid-catalysed cyclisation of derivatives of crotonophenone and chalcone is shown to be a general reaction which occurs without migration of aryl substituents evident with other Friedel-Crafts catalysts. Two other reactions, however, may intervene: hydrogenation and α-carbonyl cleavage. Thus 4-bromochalcone gives 3-(p-bromophenyl)-1- phenylpropan-1-one, 3-(p-bromophenyl) indan-1-one and some benzole acid. A ...
