The oxidation of alcohols to afford carbonyl compounds is one of the most important transformations in synthetic organic chemistry. When these oxidations are achieved through a dehydrogenation mechanism, oxidants or hydrogen acceptors are not needed and hydrogen is released. The alcohol acceptorless dehydrogenation (AAD) protocol is therefore advantageous from environmental and atom-economy viewpoints.[1] Here we will present a family of iridium(III) complexes bearing N-heterocyclic carbene (NHC) ligands that contain nitrogen or oxygen functionalized tethers. This type of bifunctional iridium complexes, having an alcohol-functionalized NHC (complex 1), has already shown an extraordinary activity in the N-alkylation of amines with alcohols under base-free conditions.[2] Encouraged by these previous catalytic results and based on mechanistic investigations,[3] we have now synthesized a second generation of bifunctional Cp*IrNHC complexes analogous to complex 1. Their catalytic activity in the acceptorless dehydrogenation of alcohols and mechanistic aspects of the oxidation reaction will be presented. [1] Gunanathan, C., Milstein, D., Science, 341, 6143. [2] Bartoszewicz, A., Marcos, R., Sahoo, S., Ken Inge, A., Zou, X., Martin-Matute, B., Chem.Eur.J., 2012,18,14510-14519. [3] Bartoszewicz, A., González Miera, G., Marcos, R., Norrby, P.O., Martin-Matute, B., ACS Catal., 2015, 5, 3704–3716.

Acceptorless alcohol dehydrogenation catalyzed by a bifunctional Ir-NHC catalyst

251st National Meeting (2016)

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