合成路线1

The reaction of terephthalic acid (I) with trioxane and oleum at 140-150 C gives 1-oxo-1,3-dihydroisobenzofuran-5-carboxylic acid (II), which is treated with SOCl2 in refluxing toluene to yield the acyl chloride (III). The condensation of (III) with 2-hydroxy-1,1-dimethylethylamine (IV) in the same solvent affords the amide (V), which is cyclized by means of SOCl2 in dichloromethane to provide the oxazoline (VI). The Grignard condensation of (VI) with 4-fluorophenylmagnesium bromide (VII) in THF gives the benzophenone (VIII), which is submitted to a new Grignard condensation with 3-(dimethylamino)propylmagnesium bromide (IX) in the same solvent to yield the diol (X). Finally, this compound is treated with POCl3 or SOCl2 and POCl3 in hot pyridine to afford the target citalopram. Alternatively, the cleavage of the oxazoline ring of (X) with H2SO4 and then with NaOH gives the sodium carboxylate (XI), which is treated with SOCl2 in dichloromethane to yield the corresponding acyl chloride (XII). The reaction of (XII) with dry ammonia in the same solvent affords the carboxamide (XIII), which is finally dehydrated with POCl3 in refluxing acetonitrile to provide the target citalopram.