AbstractChlorination of 1‐substituted 3‐formyl‐4‐hydroxy‐2‐quinolones (1a,b) with phosphorylchloride leads to 4‐chloro‐3‐dichloromethylquinolones (2), which can be hydrolyzed to 4‐chloro‐3‐formyl‐quinolones (4). From the anilinomethylene quinolinediones (3), at low temperatures the formylquinolones4can be obtained directly, whereas at high temperatures cleavage of the tautomeric azomethine moiety followed by subsequent ring closure to the naphthyridines (7) takes place. With 1‐unsubstituted 3‐formyl‐4‐hydroxy‐2‐quinolones (1d) either the 3‐dichloromethylquinolone (2d) or the 2,4‐dichloro‐3‐dichloro‐methylquinoline (10) is obtained depending on the reaction conditions. Similar results are obtained with the 1‐unsubstituted anilinomethylene compounds (3). Attempts to obtain the 3‐formyl‐2,4‐dichloroquinoline (11) were unsuccessful because in all experiments