Aqueous-phase hydrogenation and hydroformylation reactions catalyzed by a new water-soluble [rhodium]-thioligand complex

Rh(DHTANa) is a new water-soluble catalyst easily obtained by mixing in water the catalytic precursor [Rh(COD)Cl]2 and the dihydrothioctic acid sodium salt (DHTANa). This catalyst showed to be very active in the hydrogenation of unsaturated substrates as 2-cyclohexen-1-one, the biomass-derived furfural and acetophenone. In this last case the catalytic system obtained by using as water-soluble ligand (R)-(DHTANa) afforded (R)-1-phenylethanol with very modest enantioselectivity. Rh(DHTANa) was active also in the aqueous biphase hydroformylation of styrene producing exclusively the two corresponding aldehydes with 80-86% selectivity toward the branched aldehyde 2-phenylpropanal. This new catalytic system was easily recycled in both hydrogenation and hydroformylation processes and no leaching phenomenon was observed.