Ir-catalyzed tandem hydroformylation-transfer hydrogenation of olefins with (trans-/cis-)formic acid as hydrogen source in presence of 1,10-phenanthroline

The one-pot tandem hydroformylation-reduction to synthesize alcohols from olefins is in great demand but suffering from low yields, poor selectivity and harsh condition. Herein, 1,10-phenanthroline (L1) modified Ir-catalyst proved to exhibit multiple catalysis in terms of FA dehydrogenation, hydroformylation of olefins, and transfer hydrogenation of aldehydes to accomplish the tandem hydroformylation-transfer hydrogenation of olefins with formic acid (FA) as hydrogen source, as the result of 52–70% yields for the target alcohols and the corresponding formate esters (obtained upon esterification of the alcohol with FA). In this sequence, only the use of FA with trans- and cis-conformers could fulfill the reduction of aldehydes to the alcohols through transfer hydrogenation as well as greatly depress hydrogenation of the olefin, which universally occurred in the high pressured gaseous H2. Both the in situ FT-IR spectroscopic analysis and the DFT-calculations verified that, over L1-[Ir(COD)Cl]2 catalyst, cis-FA serving as the hydride-ligand was responsible for the efficient dehydrogenation of FA to release H2 along with CO2, and trans-FA serving as the carbonyl O-containing ligand corresponded to the transfer hydrogenation of the aldehydes to the alcohols under the same catalytic conditions.