A Glycerol‐Based Deep Eutectic Solvent as Natural Medium and Organic Reductant for Homocoupling of (Hetero)Aryl Chlorides: a Green Route to 2,2’‐Bipyridine and Biaryl Scaffolds

A glycerol‐based Deep Eutectic Solvent (DES) enables the Pd‐catalyzed activation of (hetero)arylchlorides and promotes the formation of 2,2’‐bipiyridines and biaryls through an Ullmann‐type homocoupling in smooth experimental conditions (80 °C) with Ca(OH)2 as a green base and Pd/C as heterogeneous catalyst. Noteworthy, the coupling does not need the addition of external reducing agents, like metals, since the glycerol present in the DES acts as a safe and green organic reductant. The heterogeneous catalytic system (DES‐Pd/C) showed to be easily recyclable and has been applied to the sustainable synthesis of the Abametapir drug. The catalytic activity of Pd/C has been exploited in a glycerol‐based Deep Eutectic Solvent for the activation of chloro(hetero)arenes in mild reaction conditions. The Ullman‐type coupling does not need any external reductant and affords valuable biaryls and 2,2’‐bipyridines in moderate to excellent yields. The method has been applied to the sustainable synthesis of the Abametapir drug.