Hypervalent iodine(III)/Et4N+Br− combination in water for green and racemization-free aqueous oxidation of alcohols

We have found that the use of the PhI(OAc)2/Et4N+Br− combination in water can significantly enhance its oxidation ability and oxidize a wide range of alcohols 1 to carbonyl compounds 2 in good to excellent yields. This clean aqueous oxidation method shows no detectable racemization processes, and even an enolizable ketone 2m could be obtained in an optically pure form from the corresponding chiral alcohol 1m. Utilization of the recyclable reagent 3 as a more practical alternative to PhI(OAc)2 is also successful in these reactions.