Platinum functionalized Chiral Polyamides: Efficient Heterogeneous Catalyst for Solvent Free Asymmetric Hydrogenation of Ethyl 2‐oxo‐4‐phenylbutanoate

Abstract

The present study highlights platinum nanoparticles incorporated chiral polyamide for asymmetric hydrogenation of carbonyl group. Chiral polyamides are synthesized from chiral monomers, camphoric dichloride and achiral diamine monomers by interfacial condensation reaction. This chiral polyamide supports have helical structure with molecular chirality. The polyamide helices provide chiral environment to platinum nanoparticles that transfer to substrate during catalytic hydrogenation. The chemical and optical selectivity increases with dispersion of platinum nanoparticles on chiral polyamide which act like isolated single atomic catalytic centers. The distribution of nanoparticles depends on spacer used in amine monomer unit. The catalytically active single atom nanoparticles have preferentially Pt (111) planes and exhibit excellent selectivity up to 10 cycles (TOF > 5400 h À1 and > 99.9% ee) in asymmetric hydrogenation reaction of ethyl 2-oxo-4-phenylbutanoate under solvent free condition.[a] P.

Preparation and Chiral Applications of Optically Active Polyamides

“…Sharma et al described the preparation of chiral polyamides by interfacial polycondensation reaction of chiral camphoric dichloride and various diamines. [52] Platinum (Pt) nanoparticles (NPs) were subsequently incorporated into the chiral polyamide for asymmetric hydrogenation of ethyl 2-hydroxy-4phenylbutanoate. In this work, chiral camphoric dichloride was prepared from camphoric acid and thionyl chloride because the dichloride was more suitable for the reaction with diamines under ambient conditions.…”

“…[84] As discussed in Section 2, some chiral polyamides can adopt a helical conformation. [22,51,52,54,55] For example, Park et al reported an interesting strategy for the synthesis of helical nylons and polyphthalamides with one-handed spiral morphologies. [51] That is, a chiral reaction field based on N*-LC was used for the chiral interfacial polycondensation.…”

“…[103] Sharma et al prepared chiral polyamide catalysts by incorporating Pt NPs into chiral polyamide and demonstrated their use as heterogeneous catalysts in the asymmetric hydrogenation reaction. [52] The chirality transfer took place from helical polymer support to product via Pt NPs. It was found that the chemical and optical selectivity increases with dispersion of Pt NPs on chiral polyamide, resulting in highly isolated Pt NPs acted like single atom catalyst.…”

“…Possible interactions between Pt, chiral polyamide, and substrate. Reproduced with permission [52]. Copyright 2017, Wiley-VCH GmbH.…”

One-Pot Synthesis of d-Phenylalanine-Functionalized Multiwalled Carbon Nanotubes: A Metal-Free Chiral Material for the Asymmetric Electroreduction of Aromatic Ketones

“…The racemic product was obtained in the absence of the chiral inducer (Table 1, entry 2), which indicated the importance of the inducer in the chiralinduction process. The chiral inducer is crucial to provide a chiral atmosphere in asymmetric reduction, 27 resulting in high enantioselectivity with a high asymmetric inducer concentration around the cathode. The ee values obtained from the D-PHE-MWCNTs (Table 1, entries 3−6) were markedly higher than those of p-MWCNTs (Table 1, entry 1), indicating that the functionalized MWCNTs cathodes were more beneficial as heterogeneous materials.…”