合成路线1

The intermediate 1-(4-fluorophenyl)-1-(3-hydroxypropyl)-1,3-dihydroisobenzofuran-5-carbonitrile (IV) has been obtained by three related ways: 1. The condensation of 1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (I) with 3-(tert-butyldimethylsilyloxy)propyl bromide (II) by means of LDA in THF gives 1-[3-(tert-butyldimethylsilyloxy)propyl]-1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (III), which is deprotected with HCl in methanol to yield the hydroxypropyl intermediate (IV). 2. The condensation of 1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (I) with 3-(benzyloxy)propyl bromide (V) by means of LDA in THF gives 1-[3-(benzyloxy)propyl]-1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (VI), which is deprotected by treatment with 1,4-cyclohexadiene over Pd/C in ethanol to yield the hydroxypropyl intermediate (IV). 3. The condensation of 1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (I) with 3-(tetrahydropyranyloxy)propyl bromide (VII) by means of LDA in THF gives 1-(4-fluorophenyl)-1-[3-(tetrahydropyranyloxy)propyl]-1,3-dihydroisobenzofuran-5-carbonitrile (VIII), which is deprotected with Ts-OH in methanol to yield the hydroxypropyl intermediate (IV). The reaction of the intermediate (IV) with Ts-Cl and TEA in toluene gives the corresponding tosylate (IX), which is finally treated with dimethylamine in hot DMF to afford the target citalopram. The reaction of the intermediate (IV) with Ms-Cl and TEA in THF gives the corresponding mesylate (X), which is finally treated with dimethylamine in hot ethanol/THF to afford the target citalopram. Alternatively, the reaction of mesylate (X) with NaN3 in hot DMF gives the corresponding azido compound (XI), which is hydrogenated with H2 over Pd/C in EtOH to yield the 3-aminopropyl derivative (XII). Finally, this compound is methylated by means of formaldehyde and NaCNBH3 in methanol to provide the target citalopram.