Phenylene‐Coated Magnetic Nanoparticles that Boost Aqueous Asymmetric Transfer Hydrogenation Reactions

Abstract

Phenylene-coated organorhodium-functionalized magnetic nanoparticles are developed through co-condensation of chiral 4-(trimethoxysilyl)ethyl)phenylsulfonyl-1,2-diphenylethylene-diamine and 1,4-bis(triethyoxysilyl)benzene onto Fe3O4 followed complexation with [{Cp*RhCl2}2]. This magnetic catalyst exhibits excellent catalytic activity and high enantioselectivity in asymmetric transfer hydrogenation in aqueous medium. Such activity is attributed to the high hydrophobicity and the confined nature of the chiral organorhodium catalyst. The magnetic catalyst can be easily recovered by using a small external magnet and it can be reused for at least 10 times without loss of its catalytic activity. This characteristic makes it an attractive catalyst for environmentally friendly organic syntheses.

Magnetic nanoparticle supports for asymmetric catalysts

“…Very recently, the same research group prepared the same Rh-catalyst from hydrophobic phenylene coated Fe 3 O 4 nanoparticles. 40 The significant advantages of this phenylenecoated Rh-functionalized MNP with respect to SiO 2 -coated MNPs are: significant reduction of reaction times (0.5-5 h vs. 8 h), lower catalyst loading (1 vs. 2 mol%), no need of phase transfer catalyst, conversions almost always quantitative and a higher ee range (86-96%, R-isomer).…”

“…It is worth noting that the authors always mentioned (S,S)-TsDPEN in all the papers, [38][39][40] but they represent it as the (R,R)-isomer. Thus, the configuration depicted in Scheme 2 is opposite to that reported by Liu, since I assumed the text to be correct and not the schemes.…”

Selective Reduction of Carbonyl Compounds via (Asymmetric) Transfer Hydrogenation on Heterogeneous Catalysts

“…Phenylene-coated organorhodium-functionalized magnetic nanoparticles were synthesized, characterized and used successfully in ATHs of aromatic ketones in the aqueous phase (Scheme 19). 78 The co-condensation of chiral 4-(trimethoxysilyl)ethylphenylsulfonyl-1,2-diphenylethylene-diamine and 1,4bis(triethoxysilyl)benzene onto Fe 3 O 4 followed complexation with [{Cp*RhCl 2 } 2 ], which led to a highly active (>99% conversion), selective (up to 96% ee) and reusable system (at least ten times without loss of catalytic activity). The increased catalytic activity was credited to the high hydrophobicity and to the well-confined nature of the chiral organorhodium catalyst (Scheme 19).…”

“…The increased catalytic activity was credited to the high hydrophobicity and to the well-confined nature of the chiral organorhodium catalyst (Scheme 19). 78 Core-shell structures represent one of the most interesting constructions of bimetallic (or multimetallic) nanoparticles. This type of structure can be considered as a…”

Recyclable helical poly(phenylacetylene)‐supported catalyst for asymmetric aldol reaction in aqueous media

“…In addition, water is a very valuable reaction media from the viewpoints of eco ‐friend and saving cost. The chemical reactions that could proceed in aqueous media have been an attractive field due to its great potential in bio‐system and green chemistry . Therefore, developing new bioinspired catalytic systems that use eco ‐friendly catalysts under mild conditions becomes an exciting area of research …”