Oxidative Cyclization of Amino Alcohols: Comparing Gold Nanocluster Photocatalysis with Electrochemical Oxygen Activation Authors

Oxazolidines are valuable five-membered heterocycles with broad applications in medicinal and synthetic chemistry. Herein, we investigate sustainable oxidative cyclization of amino alcohols using molecular oxygen, comparing gold nanocluster photocatalysis with electrochemical activation. Peptide dendron-functionalized gold nanoclusters promoted the cyclization of amino alcohols to oxazolidines in good yield, consistent with an oxygen-mediated pathway involving singlet oxygen and iminium formation. In contrast, electrochemical activation of oxygen under a range of electrode, solvent, electrolyte, current, and flow conditions failed to produce the desired cyclized products and instead resulted predominantly in oxidative degradation to benzaldehyde. Cyclic voltammetry indicated that overoxidation of the amino alcohol may account for the observed degradation. These results demonstrate that the mode of oxygen activation is critical for controlling selectivity in oxidative amino alcohol cyclization and highlight the potential of gold nanocluster photocatalysis as a sustainable approach to oxazolidine synthesis.