Asymmetric transfer hydrogenation of prochiral ketones in aqueous media with chiral water‐soluble and heterogenized bifunctional catalysts of the RhCp*‐type ligand

Abstract

Asymmetric transfer hydrogenation (ATH) of prochiral aromatic ketones was carried out with a water-soluble complex of Rh(III)Cp* and mononitrobenzenesulfonamide bidentate ligand (1R,2R)-N-(2-aminocyclohexyl)-4-nitrobenzenesulfonamide 1 derived from chiral cyclohexane-1,2-diamine. Aqueous sodium formate was used as the hydride source. The reaction afforded the chiral alcohols in good enantioselectivities (79-93%) and yields (>99%). The modified monosulfonamide ligand was also covalently immobilized on solid phase such as silica, resin, and mesoporous SBA-15 silica and then explored as a catalyst with Rh(III)Cp* in the ATH of acetophenone.

Synthesis of New Chiral Monosulfonamides Prepared from (11R,12R)-11,12-Diamino-9,10-dihydro-9,10-ethanoanthracene and their Use as Ligands for Asymmetric Catalysis

“…The transition state for ATH of aromatic ketones is show in (Figure 3). In our previous study [21,22] we found that the dihedral angle N-C-C-N is critical in obtaining maximum overlap, in order to get good yields and enantioselectivities. The dihedral angle calculations were carried out by B3LYP density functional level of theory, using a cc-pVDZ basis set calculations.…”

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

“…The ATH of aromatic ketones was carried out satisfactorily in aqueous medium with the same rhodium catalyst and the ligand 175 with low catalyst loading and sodium formate as the hydrogen source, giving the expected alcohols in general with high yields and enantioselectivities. 141 Specially active in aqueous medium is the bifunctionalized catalyst 176 formed from flower-like mesoporous silica and the rhodium complex generated from [RhCl 2 Cp*] 2 and a TsDPEN fragment, and used in the ATH of different phenones with sodium formate as the reducing agent. 142 The two polymeric ionic ligands 177 143 and 178 144 with CRu as metal complex were successfully used in the ATH of aromatic ketones in water and with sodium formate as the hydrogen source.…”