| Abstract: | Further studies of the effects of substituents in the N-phenyl nucleus on the polyphosphoric acid-catalysed cyclisation of cinnamanilide to 4-phenyl-3,4-dihydrocarbostyril have confirmed that the isomerisation is prevented by a nitro group and retarded by other substituents in the ortho position to the NH- group. Although a methyl group ortho to the only position at which cyclisation can occur was also shown to retard the reaction, N-cinnamoyl-2,4,5-trichloroaniline was cyclised in moderate yield after prolonged heating, but the 2,4-dibromo and 2,5-dimethoxy analogues were not isomerised. Isomerisation of 2-cinnamamidobiphenyl to 4,8-diphenyl-3,4-dihydrocarbostyril was accompanied by cyclodehydration to 6-styrylphenanthridine. Five new derivatives of cinnamanilide and eight new derivatives of 4-phenyl-3,4-dihydrocarbostyril are described. |
