Electrophilic intramolecular cyclization of functional derivatives of unsaturated compounds: V. Cyclization of anilides of styrylacetic acids in polyphosphoric acid

Anilides of styrylacetic acids at heating in polyphosphoric acid undergo an intramolecular cyclization giving 1,5-diarylpyrrolidin-2-ones, 5-aryl-1,3,4,5-tetrahydro-2H-benzazepin-2-ones, and 5-(3-fluorophenyl) dihydrofuran-2(3H)-one, where the ratio of the products depends on the character of the aromatic substituents in the amide and styrene fragments of the substrate.