Hydrazine hydrate (1:1) → 2'-Fluoro-4-hydroxy-5'-methoxy-[1,1'-biphenyl]-2-carbohydrazide

To a solution of ethyl 2′-fluoro-4-hydroxy-5′-methoxy-[1,1′-biphenyl]-2-carboxylate (1.37 g) in ethanol (15 mL) was added hydrazine monohydrate (4.47 mL), and the mixture was stirred at 95° C. for 46 hr. The reaction mixture was concentrated under reduced pressure and the residue was purified by silica gel column chromatography (ethyl acetate/hexane and then methanol/ethyl acetate) to give the title compound (1.05 g) as a white amorphous solid.