NHC-Iridium-Catalyzed Deoxygenative Coupling of Primary Alcohols Producing Alkanes Directly: Synergistic Hydrogenation with Sodium Formate Generated in Situ

The
direct conversion of alcohols into long-chain alkanes is an
attractive but extremely challenging approach for biomass upgrading.
Here, we describe the highly selective deoxygenative coupling of aryl
ethanols with primary alcohols to produce alkanes, using a bis-N-heterocyclic
carbene iridium (bis-NHC-Ir) complex as the catalyst. Up to quantitative
yields and selectivity with a broad substrate scope are attained in
both homo- and cross-coupling reactions. Mechanistic studies reveal
that the further synergistic hydrogenation of the alkene intermediates
by the formate generated in situ in the presence of bis-NHC-Ir is
crucial for alkane production.