Water tolerant base free Copper (I) catalyst for the selective aerobic oxidation of primary alcohols
Emi Lagerspets, Donatella Abba, Joseph W. Sharratt, Aleksi Eronen, Timo Repo
Abstract
We report here a base free copper(I) catalyst for the selective aerobic oxidation of primary alcohols to their corresponding aldehydes and various diols to their corresponding lactones or lactols. In the presence of the in situ generated Cu(I)-catalyst with 2,2′-dipyridylamine (dpa) as a ligand and 2,2,6,6-tetramethylpiperdine-N-oxyl (TEMPO) as a persistent radical, the oxidation reaction proceeds under true aerobic conditions, at ambient temperature, utilizing air as the oxidant and without added base. High catalytic activity without over oxidation was achieved for numerous primary alcohols (aliphatic, allylic, benzylic and diols) with different substitution patterns. The catalyst's stability is unique among reported Cu(I)-catalysts. It is not moisture or air sensitive, and is capable of e.g. oxidizing aliphatic and benzyl alcohols in a water/acetonitrile solution in moderate or in quantitative yield (> 99%) in 3 h.