Methods For Preparing Fentanyl And Fentanyl Intermediates

Abstract

A method and an intermediate are provided for preparing fentanyl. Aniline and 1-phenylethyl-4-piperidone are reacted with a borane complex, in a lower C1-C4 alcoholic solvent, in the presence of an alkanoic acid. The reaction mixture is then treated with a hydrohalic acid to precipitate 4-anilino-N-phenethyl-4-piperidine (ANPP) as the bis-hydrohalide salt in high yield and purity. This ANPP salt may be directly treated with propionyl halide to produce fentanyl, or the ANPP salt may be converted to the free base of ANPP and similarly treated with propionyl halide to produce fentanyl.

Dependencies are inferred from the claim text.