Oxidative Coupling of Coumarins by Blue‐LED‐Driven <i>in situ</i> Activation of Horseradish Peroxidase in a Two‐Liquid‐Phase System

A blue-LED-driven two-liquid-phase system has been set up for the in situ activation of horseradish peroxidase avoiding use hydrogen peroxide and drawbacks related to enzyme denaturation undesired radical side-reactions. The photobiocatalytic was applied oxidative coupling natural synthetic coumarins bicoumarins, allowing obtain homodimers only one step, tedious protecting groups. Two C-2 symmetric bicoumarins derived from scopoletin were synthesized first time. UV-visible spectrophotometry analysis confirmed radical-free oxidation green solvent 2-methyltetrahydrofuran corresponding hydroperoxide, which turn oxidizes ferric heme ferryl intermediate, triggering reaction.