Polymer-Supported Bisacetoxybromate(I) Anion –-An Efficient Co-Oxidant in the TEMPO-Mediated Oxidation of Primary and Secondary Alcohols

A polymer-bound reagent for the efficient oxidation of primary alcohols to aldehydes and secondary alcohols to ketones in the presence of a catalytic amount of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) is described. The oxidation process is particular mild and allows one to prepare aldehydes with α-chirality without racemization. This also includes the synthesis of α-aminoaldehydes. In most cases, work-up of this heavy metal-free oxidation is achieved by simple filtration followed by removal of the solvent. Insight into the role of the bromate(I) anion in the oxidation process was gained from the TEMPO-mediated oxidation of benzaldehyde in the presence of the hypochlorite anion loaded on an anion exchange resin.