N-Phenethyl-4-piperidinone
"N"-Phenethyl-4-piperidinone (NPP) is a derivative of 4-piperidinone with the molecular formula CHNO. It is used as an intermediate in the manufacture of chemicals and pharmaceutical drugs such as fentanyl. Because of its possible use in the illicit manufacture of fentanyl, NPP was placed onto the list of controlled chemicals in the USA in 2007, and possession and sales of this compound are now restricted. Preparation. "N"-Phenethyl-4-piperidinone can be prepared from 4-piperidinone and phenethyl bromide in biphasic conditions with a variety of phase transfer catalysts. Uses. "N"-Phenethyl-4-piperidinone is useful in the synthesis of  pharmaceuticals, primarily fentanyl and its analogs. Paul Janssen (founder of Janssen Pharmaceutica) first synthesized fentanyl in 1960 from NPP. Janssen's synthesis involved reacting "N"-Phenethyl-4-piperidinone with aniline, and then reducing the imine product with sodium borohydride to 4-anilino-N-phenethylpiperidine (ANPP). This product is reacted with propionyl chloride to form fentanyl.