A solution of ammonium 2-[[1-(4-pyridinyl)piperidin-4-ylmethyl]amino]pyridine-3-carboxylate (400 mg, 1.28 mmol) in methylene chloride (5 mL) was treated with thionyl chloride (0.112 mL, 1.54 mmol) and the mixture was heated at reflux. After 3 h, the mixture was cooled and then treated dropwise with a solution of 2-amino-6-chlorobenzothiazole (284 mg, 1.54 mmol) in pyridine (5 mL). After 1 h, the mixture was concentrated in the presence of silica gel. The residue was purified by column chromatography (SiO2: 1 to 4% [2 N ammonia in methanol]:chloroform) followed by recrystallization from methanol to yield 68 mg (11%) of the title compound.
