Efficient and Simple Approaches Towards Direct Oxidative Esterification of Alcohols

The present article describes novel oxidative protocols for direct esterification of alcohols. The protocols involve successful demonstrations of both “cross” and “self” esterification of a wide variety of alcohols. The cross‐esterification proceeds under a simple transition‐metal‐free condition, containing catalytic amounts of TEMPO (2,2,6,6‐tetramethyl‐1‐piperidinyloxy)/TBAB (tetra‐n‐butylammonium bromide) in combination with oxone (potassium peroxo monosulfate) as the oxidant, whereas the self‐esterification is achieved through simple induction of Fe(OAc)2/dipic (dipic=2,6‐pyridinedicarboxylic acid) as the active catalyst under an identical oxidizing environment. One‐pot oxidative esterification: A wide variety of alcohols undergo transition‐metal‐free (in the presence of oxone/2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)/tetra‐n‐butylammonium bromide (TBAB)) selective “cross” esterification in moderate to excellent yields (see Figure). The “self” esterification process has however been achieved in the presence of Fe(OAc)2/2,6‐pyridinedicarboxylic acid (dipic) as the active catalytic species under a similar oxidizing environment.