The present disclosure generally related to an improved process for the preparation of various piperidine derivatives. More particularly, the present disclosure related to an improved process for preparing sufentanil base (1) and related compounds, which advantageously utilizes more cost effective and/or less hazardous reagents, including a dispersion comprising between about 50% and about 70% by weight (based on the total weight of the dispersion) of an alkali metal hydride, such as sodium hydride, as well as eliminates the need for expensive and/or time consuming purification techniques.