Recyclable copper-catalyzed ambient aerobic oxidation of primary alcohols to aldehydes in water using water-soluble PEG-functionalized pyridine triazole as ligand

A water-soluble PEG-PyTa ligand, conveniently derived from commercially available reagents via a simple synthetic approach, could efficiently promote copper/2, 2, 6, 6-tetramethyl piperidine-1-oxyl (TEMPO)-catalyzed aerobic oxidation of primary alcohols to aldehydes in water under room temperature. A number of primary benzylic, allylic alcohols and heteroaryl methanols were selectively converted into their corresponding aldehydes with excellent yields. The oxidation products could be isolated by simple extraction, and the residual aqueous phase containing the catalyst Cu(OTf)2/PEG-PyTa could be reused at least 7 times.