The limitations of Combes reaction were reinvestigated. 4-(p-Chloroanilino)-3-penten-2-one (III), hitherto believed to be insusceptible to cyclodehydration in sulfuric acid, reacted at a higher temperature to give 2, 4-dimethyl-6-chloroquinoline (IV). 4-Anilino-3-buten-2-one (V),