合成路线1

Condensation of 2'-fluoroacetophenone (I) with 4-methoxybenzaldehyde (II) under acidic conditions afforded chalcone (III). This was subsequently demethylated with boron tribromide to yield the 4-hydroxy chalcone (IV). Alternatively, chalcone (IV) was also obtained by condensation of 2'-fluoroacetophenone (I) with 4-hydroxybenzaldehyde (V). Reaction of chalcone (IV) with 2-(dimethylamino)ethoxyamine dihydrochloride (VI) produced the corresponding oxime as a mixture of syn target compound and anti (VIII) isomers. The title syn isomer was isolated by fractional extraction at increasing pH values or, alternatively, by recrystallization as the corresponding hemifumarate salt. Optionally, the undesired anti compound (VIII) was isomerized by acidic treatment to produce a 45:55 mixture of target compound and (VIII).