Prolinate Salts as Catalysts for α-Aminoxylation of Aldehyde and Associated Mechanistic Insights

Potassium and tetrabutylammonium prolinate salts are efficient catalysts in the α-aminoxylation reaction of aldehydes and nitrosobenzene, to afford synthetically useful chiral α-aminoxylated aldehydes in nearly enantiomerically pure form. This is the first reaction in which prolinate is more reactive and enantioselective than proline. Because of its higher reactivity, the catalyst loading can be reduced. A reaction mechanism involving the activation of nitrosobenzene through N-protonation of a hydrogen-bonded water molecule is proposed.