Dehydrogenation of glycerol to dihydroxyacetone catalyzed by iridium complexes with P–N ligands

The chemoselective dehydrogenation of glycerol was catalyzed by organoiridium derivatives of the type [HIr(cod)L] (cod = 1,5-cyclooctadiene; L = Prn-N(CH2CH2PPh2)2, Et2NCH2CH2N(CH2CH2PPh2)2, o-Me2NC6H4PPh2) using hydrogen acceptors such as acetophenone, cyclohexanone, styrene and benzaldehyde. The catalytic reactions were performed in the absence of a basic cocatalyst in order to avoid decomposition of the desired product, i.e. dihydroxyacetone. Acceptor-less dehydrogenation was also observed either in the absence of a hydrogen acceptor, or as a parallel route, when the reaction was performed in the presence of acetophenone.