PURPOSE: To provide a novel compound having a platelet coagulation-inhibiting action, an anti-arteriosclerosis action and an anti-anginal action.

CONSTITUTION: A compound of formula I (when one of A, B is N, the other is C; R1, R2 are formyl, a dialkylamino; R3, R4 are H, a halogen; dotted line expresses the presence of an aromatic double bond), e.g. 4-chloro-3-formyl-1- dimethylaminoimida [1, 5-a] quinoline. The compound of formula I is obtained by reacting a 2-cyanoquinoline of formula II with Vilsmeier reagent prepared from an N,N-dialkylformaldehyde and a phosphorus oxyhalide. The compound of formula I is useful as an agent for treating circulatory diseases, and is administered at daily a dose of approximately 200-3000 mg once to several times a day for an adult.