The demethylation of 4-amino-5-chloro-N-[2-(diethylamino)ethyl]-2-methoxybenzamide (I) with EtS-Na in hot DMF gives the hydroxy compound (II), which is acylated with 3-chloro-2-butanone (III) by means of K2CO3 and NaI in DMF to yield 4-amino-5-chloro-N-[2-(diethylamino)ethyl]-2-(1-methyl-2-oxopropoxy)benzamide (IV). Finally, this compound is treated with HCl to furnish the target hydrochloride. Alternatively, the alkylation of the hydroxy compound (II) can also be performed by reaction of (II) with tetrabutylammonium bisulfate and NaOH to give the tetrabutylammonium phenolate (V), which is alkylated with the chlorobutanone (III) to give (IV).
A new synthesis for [14C]-labeled batanopride has been described: The starting material is 4-amino-2-hydroxybenzoic acid labeled with [14C] at the carboxy group (I). The methylation of (I) in the usual way gives 4-amino-2-methoxybenzoic acid methyl ester (II), which is treated with acetic anhydride to yield the corresponding acetamido derivative (III). Chlorination of (III) with Cl2 in acetic acid affords 4-acetamido-5-chloro-2-methoxybenzoic acid methyl ester (IV), which is hydrolyzed with aqueous NaOH to 4-amino-5-chloro-2-methoxybenzoic acid (V). The condensation of (V) with 2-(diethylamino)ethylamine (VI) by means of triethylamine and isobutyl chloroformate in THF gives the corresponding amide (VII), which is demethylated with sodium ethanethiolate in DMF to yield the phenolate (VIII). The condensation of (VIII) with 3-chloro-2-butanone (IX) in DMF affords batanopride free base (X), which is finally treated with HCl in acetone - water.