Dimethylformamide → 4-[(4-Methylpiperazin-1-yl)methyl]benzoyl chloride--hydrogen chloride (1/2)

A mixture of 4-(4-methylpiperazin-1-ylmethyl)benzoic acid dihydrochloride (50 g), thionyl chloride (200 ml) and N,N-dimethylformamide (12.5 ml) was refluxed for 20 hours. After completion of reaction, the reaction mass was distilled out completely under vacuum to give residue which was diluted with dichloromethane (100 ml). Solid thus precipitated was filtered and washed to give 4-(4-methylpiperazin-1-ylmethyl)benzoyl chloride dihydrochloride. To a mixture of 4-Methyl-N-(4-pyridin-3-yl-pyridin-2-yl)benzene-1,3-diamine (20 g) in dichloromethane (500 ml), potassium carbonate (80 g) was added and stirred for 30 minutes. 4-(4-methylpiperazin-1-ylmethyl)benzoyl chloride dihydrochloride (prepared above) was added to the reaction mass at 0-5° C. and refluxed for 10 hours. After completion of reaction, reaction mass was quenched with dilute hydrochloric acid (420 ml) up to pH 1.0-3.0 and layers were separated. Aqueous layer was washed with dichloromethane, diluted with tetrahydrofuran (120 ml) and basified up to pH 8.0-8.5 with 10% sodium hydroxide solution (200 ml). Solid thus precipitated was filtered, washed with sodium hydroxide solution and demineralised water to give title compound having amine intermediate: 39.7 ppm).