An Easy, Convenient, and Safe Process for the Synthesis of Lofexidine Hydrochloride

A very efficient, cost-effective, and easily scalable process for the synthesis of lofexidine hydrochloride (1), an alpha 2-adrenergic receptor agonist used for treating opioid withdrawal is presented. Process development allows the preparation of lofexidine hydrochloride (1) through a one-pot amidation/imidazoline ring formation reaction, starting from ethyl 2-(2,6-dichlorophenoxy)propionate (13) and ethylenediamine (5) by the action of titanium isopropoxide. The required intermediate ethyl 2-(2,6-dichlorophenoxy)propionate (13) can efficiently be obtained through O-alkylation of 2,6-dichlorophenol (2) with ethyl 2-chloropropionate (12) using potassium carbonate as an acid-scavenger agent.