4-(Benzothiazol-2-ylamino)-piperidine-1-carboxylic acid ethyl ester → N-(Piperidin-4-yl)-1,3-benzothiazol-2-amine

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A solution of 4-(benzothiazol-2-ylamino)-piperidine-1-carboxylic acid ethyl ester (3.70 g, 12.0 mmol) in hydrobromic acid 48% in water (20 mL) was heated to reflux. After 18 h hydrobromic acid was removed under reduced pressure and the crude solid dissolved by vigorous stirring in hot methanol (50 mL). The obtained solution was cooled to −20° C. by which a precipitate formed that was removed by filtration. The organic phase was concentrated under reduced pressure, 4 N NaOH (100 mL) added and the solution extracted with dichloromethane (3×100 mL). The combined organic phases were dried over MgSO4 to yield after evaporation of the solvent 1.7 g (61%) of the title compound which was used directly in the following step. 1H NMR (300 MHz, DMSO): δ 1.19-1.39 (m, 2H), 1.90-2.00 (m, 2H), 2.92-2.97 (m, 2H), 3.72-3.79 (m, 2H), 6.99 (t, J=8.2 Hz, 1H), 7.20 (t, J=8.2 Hz, 1H), 7.37 (d, J=7.6 Hz, 1H), 7.65 (d, J=7.2 Hz, 1H), 7.95 (d, J=7.2 Hz, 1H). MS (ISP): 233.9 [M+H]+.

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