Immobilization of a Modified Tethered Rhodium(III)‐p‐Toluenesulfonyl‐1,2‐diphenylethylenediamine Catalyst on Soluble and Solid Polymeric Supports and Successful Application to Asymmetric Transfer Hydrogenation of Ketones

Abstract

Catalyst immobilization through covalent attachment onto a support is one strategy to provide recyclable systems. Here, soluble and surface-functionalized solid polymers were used as supports for a modified tethered rhodiumAThe supported catalysts were applied to the asymmetric transfer hydrogenation of phenyl ketones in aqueous solution of sodium formate. High ee values (up to 99%) and good activities were achieved. It was discovered that the solid polymersupported catalyst could be recycled at least four times without a significant decrease of the activity when a mixture of sodium formate and formic acid was used as the hydrogen source. This catalytic system provides a promising approach towards an ecologically and economically rational production of enantioenriched building blocks.

The Golden Age of Transfer Hydrogenation

“…Immobilization of tethered rhodium(III)-p-toluenesulfonyl-1,2-diphenylethylenediamine complex onto hPG was easily achieved through covalent attachment, and the formed metallorganic supported catalyst 217 provided excellent catalytic performances in terms of activity and enantioselectivity in ATH of aromatic ketones with formate (Scheme 86). 652 With 217 as catalyst, several alcohols were synthesized with 100% conversions and as high as 99% ee values. In addition, the catalyst was recoverable by ultrafiltration.…”

Regeneration of the NADH Cofactor by a Rhodium Complex Immobilized on Multi-Walled Carbon Nanotubes

“…29 A welldesigned synthesis method has been reported, which describes a tethered rhodium hydrogenation catalyst on soluble polymers and solid polymeric chips. 30 Hollmann and coworkers evaluated the application of this recyclable catalyst for NADH regeneration, but the modified Rh catalyst (modified for immobilization) showed a decrease in catalytic activity by one order of magnitude. 31 The immobilization of rhodium complexes on polymer backbones is able to alleviate damage of the rhodium complex from enzymes and other chemicals, while making catalyst recycling possible.…”

“…The use of a polymer network to immobilize rhodium catalysts hinders mass transfer of cofactor through polymer layers and can limit the rate of electron transfer of rhodium complex near the electrode surface. [28][29][30][31] In these circumstances, a porous polymer is preferred and the thickness of the polymer layer should be carefully controlled.Besides polymers, carbonaceous materials such as graphene 32,33 and carbon nanotubes [34][35][36] are also catalyst supports and are widely used in various fields. The π-π stacking effect is an effective strategy to immobilize catalysts whereby aromatic moieties are attached to the catalysts, which can then strongly adsorb onto carbon nanotubes.…”

“…The use of a polymer network to immobilize rhodium catalysts hinders mass transfer of cofactor through polymer layers and can limit the rate of electron transfer of rhodium complex near the electrode surface. [28][29][30][31] In these circumstances, a porous polymer is preferred and the thickness of the polymer layer should be carefully controlled.…”

Polymer-immobilized chiral catalysts

“…The polymeric chiral diamine ligand was treated with Cu(OAc) 2 The complex of block copolymer α-methoxypoly(ethylene glycol)-β-poly((S)-glutamic acid) Soluble and surface-functionalized solid polymers were also used as supports for a modified tethered Rh(III)-TsDPEN complex 109 ( Figure 2). 59 The polymeric catalysts were applied to the ATH of phenyl ketones in an aqueous solution of sodium formate. High enantioselectivities (up to 99%) and good activity were achieved.…”