Condensation of 4-fluorophenol (I) with 4-fluorobenzaldehyde (II) by heating with K2CO3 in N,N-dimethylacetamide provides 4-(4-fluorophenoxy)benzaldehyde (III), which is finally converted into the target product by reaction with semicarbazide hydrochloride (IV) and NaOAc in the refluxing mixture EtOH/H2O.