To a solution of 3-chloro-4-hydroxybenzoic acid hydrazide (2 g, 10.7 mmol) in DMSO (20 mL) was added the above (4-formylnaphth-1-yloxy) acetic acid (3 g, 13 mmol) and a catalytic amount of acetic acid (10 drops). The solution was stirred overnight and diluted with ethyl acetate. The solution was washed with water (3×), brine, and dried over MgSO4. The volume was reduced to approximately 100 mL and placed in an ice-bath. The resulting solid was filtered and washed with cold ethyl acetate to afford {4-[(3-chloro-4-hydroxy-benzoyl)hydrazonomethyl]naphth-1-yloxy}acetic acid.
