| 20110021781 | Method for the Preparation of Fentanyl - The invention provides a method for the preparation of fentanyl comprising: (a) reacting 4-piperidone hydrochloride (NPP) with aniline in presence of reducing environment to produce 4-anilinopiperidine (4-ANPP), (b) reacting the 4-ANPP as obtained from step (a) with phenethyl halide under reflux conditions in highly alkaline medium to give 4-anilino-N-phenethylpiperidine, and (c) converting the 4-anilino-N-phenethylpiperidine to fentanyl by reacting with propionyl chloride in presence of halogenated hydrocarbons, then isolating fentanyl by solvent extraction and purifying by crystallization from petroleum ether at a temperature ranging from 60-80° C. | 01-27-2011 |
