Reaction and transport co-intensification enhanced continuous flow electrocatalytic aminoxyl-mediated oxidation of sterol intermediates by 3D porous framework electrode

Abstract

Electrocatalytic aminoxyl-mediated oxidation has attracted great attention for pharmaceutical synthesis. However, the low current density leads to sluggish reaction kinetics in traditional batch reactors. Herein, a continuous-flow electrolyzer with a three-dimensional graphite felt filled in serpentine channel (3D GF@SCE) was designed for electrocatalytic aminoxyl-mediated oxidation of steroid carbonyl intermediates, which can achieve an outstanding performance of high selectivity of 98%, and high space–time yield of 7.79 kg/(m3·h). Notably, an unprecedented turnover frequency (TOF) of 7196 h−1 was achieved, which was approximately 9-fold higher than that of the batch reactor, and almost represents the best performance for electrocatalytic aminoxyl-mediated oxidation of alcohols. The reaction and transport co-intensification of the continuous-flow electrocatalytic aminoxyl-mediated oxidation strategy presented herein reduced activation and concentration polarization, thereby inducing favorable reaction kinetics, and provides a promising alternative method for controlling the selectivity and overcoming the limitations of mass transfer for active pharmaceutical ingredients synthesis.