Quinisocaine (INN) or dimethisoquin (BAN and USAN) is a topical anesthetic used as an antipruritic.

Reduction of the nitro group via catalytic hydrogenation leads to the amine, CID:158569430 (4).

This cyclises spontaneously to the lactam so that the product isolated from the reaction mixture is in fact the isoquinoline derivative, CID:154188092 (7).

Phosphorus oxychloride converts the oxygen function to the corresponding chloride via the enol forms 3-butyl-1-chloroisoquinoline [87-06-9] (9).

Displacement of halogen with the sodium salt from 2-dimethylaminoethanol (10) affords dimethisoquin (11).