Diethylcarbamoyl chloride → N,N-Diethyl-N'-[2-[6-(4-oxo-4H-1,3-benzothiazin-2-yl)-2-pyridyl]ethyl]urea

A mixture of 2-[6-(2-aminoethyl)-2-pyridyl]-4H-1,3-benzothiazine-4-one trifluoroacetic acid salt (0.40 g, 1.0 mmol), potassium carbonate (0.41 g, 3.0 mmol) and acetonitrile (20 ml) was stirred at room temperature for 20 minutes. Successively N,N-diethylcarbamoyl chloride (0.54 g, 4.0 mmol) was added to the mixture, and the mixture was stirred at room temperature for 4 hrs. The precipitates were filtered, and the filtrate was concentrated. The residue was subjected to a silica gel column chromatography. The fractions eluted with chloroform-ethanol (30:1, v/v) were collected, concentrated and recrystallized from ethanol-hexane to give the titled compound (0.12 g, 31%) as white crystals.