Synthesis of chloroquine from 4-amino-7-chloroquinoline
My intuition tells me that the nitrogen in the ring is more nucleophilic than the exocyclic amine. A quick-and-dirty electrostatic potential calculation using B88LYP/6-31G(d) on the PM3 geometry shows a large electron density (blue and violet) on the ring nitrogen and lower density (yellow) on the exocyclic amine:



Are there conditions that might work? Yes. Should you try it, if you need that molecule? Yes. Will it be difficult? Yes.