THE NEW PROCESS FOR PRODUCING N-PHENYL-N-(4-PIPERIDINYL) AMIDE DERIVATIVES SUCH AS REMIFENTANIL AND CARFENTANIL

Disclosed is a process for the preparation of the compound of formula (I): which comprises reacting a compound of formula (II): with acylating agent of formula (IV) in the presence of orthoester of formula (III) in an aprotic solvent: The process may be used for synthesizing derivatives of fentanyl. Specifically set out are pathways for synthesizing remifentanil and carfentanil. The disclosed process require fewer steps and produce a greater yield of products than methods reported in the prior art.