Hydrazide (II) was prepared by treatment of methyl 3-chloro-4-hydroxybenzoate (I) with hydrazine in refluxing EtOH. Condensation of hydrazide (II) with 4-hydroxynaphthaldehyde (III) in the presence of a catalytic amount of glacial HOAc in DMSO produced the target acyl hydrazone.
Methyl 4-hydroxybenzoate (I) is iodinated by means of iodine monochloride in hot AcOH, producing (II). Displacement of the aryl iodide (II) with CuCN gives nitrile (III). Then, ester group saponification in (III) leads to 3-cyano-4-hydroxybenzoic acid (IV). Coupling of (IV) with tert-butyl carbazate produces the N-Boc hydrazide (V), which is further deprotected to (VI) by treatment with trifluoroacetic acid
Alkylation of 4-hydroxy-3,5-dimethoxybenzaldehyde (VII) with 4-isopropylbenzyl chloride (VIII) affords the benzyloxy benzaldehyde (IX). Then, condensation of aldehyde (IX) with hydrazide (VI) furnishes the target N-acyl hydrazone