The growing demand for opioid antagonists necessitates the development of more efficient and affordable synthetic routes. The most challenging step in the preparation of these essential medicines is the selective N-demethylation of a 14-hydroxy opioid precursor to the corresponding nor-opioid, which is followed by N-alkylation of the resulting secondary amine. This process is carried out on large scales using stoichiometric amounts of hazardous chemicals like cyanogen bromide or chloroformates. We have developed a mild, reagent- and catalyst-free procedure for the N-demethylation step, based on the anodic oxidation of the tertiary amine. The ensuing iminium cation rapidly undergoes cyclization with the 14-hydroxy group, or acyl transfer from its acetylated derivative, resulting in intermediates that can be readily hydrolyzed to the target nor-opioids. The electrochemical method provides excellent yields and has successfully been transferred to a flow electrolysis cell, thus enabling the potential scale-up of this synthetic strategy.