1036381-91-5

7341-96-0

79099-07-3

1036381-91-5

To a stirred solution of N-Boc-4-piperidone (35.6 g, 178.89 mmol) in chloroform (260 mL) was slowly added pyrrolidine (19 mL, 223.61 mmol) dropwise over a period of 1 hour at room temperature. The reaction mixture was continued to be stirred at room temperature for 1 hour before propargylamide (16 g, 223.61 mmol) was added. Subsequently, the reaction mixture was subjected to reflux in a Dean-Stark device for 16 hours. After completion of the reaction, the mixture was cooled and filtered. The filtrate was ground with toluene and filtered again. The filtrate was concentrated under reduced pressure to give a red to brown viscous liquid. The crude product was purified by fast column chromatography (silica gel, eluent 98:2 chloroform/methanol) to yield tert-butyl 2-oxo-1,2,7,8-tetrahydro-1,6-naphthyridine-6(5H)-carboxylate (4.01 g, 51.8% yield) as a brown oil.