Abstract Malondianilides 3 derived from dichloro substituted anilines 2 undergo cyclization to afford 4-hydroxy-2 (1H)-quinolones 4 in very good yields using methane sulfonic acid- phosphorus pentoxide as catalyst. 3, 4-Dichloro anilines 5 can be shown to yield two isomers, 7 and 8, whereas 3-substituted anilines 9 afford merely 7-substituted 4-hydroxy-2 (1H)-quinolones 11.
