Heterogeneous Enantioselective Catalysis with Chiral Encoded Mesoporous Pt−Ir Films Supported on Ni Foam

Abstract

The development of heterogeneous catalysts for asymmetric synthesis is one of the most challenging topics in chemistry, as it allows obtaining enantiomerically pure compounds. Recently, metal layers incorporating molecular chiral cavities, obtained by electroreduction of a metal source in the simultaneous presence of a non‐ionic surfactant and asymmetric molecules, have been proposed for a wide range of applications, including enantioselective electroanalysis and electrosynthesis, as well as chiral separation. In contrast to this previous work, solely based on electrochemical phenomena, herein we designed and employed nanostructured chiral encoded Pt−Ir alloys, supported on high surface area nickel foams, as heterogeneous catalysts for the asymmetric hydrogenation of aromatic ketones. Fine‐tuning the experimental conditions allows achieving very high enantioselectivity (>80%), combined with improved catalyst stability.

Highly Enantioselective Synthesis of Pharmaceuticals at Chiral‐Encoded Metal Surfaces

“…The signal related to hydrogen adsorption and desorption on the PtÀ Ir surface is observed in the potential range from À 0.25 to 0.20 V, while the characteristic Pt oxidation and PtO reduction occurs from 0.80 to 0.90 V and 0.30 to 0.5 V, respectively. [15,22,25,32] As shown in Figure S3, compared with flat Pt deposited on Ni foam, the ECSA of the as-prepared mesoporous PtÀ Ir film is increasing significantly, with values of 270, 283 and 78 cm 2 for non-imprinted PtÀ Ir film, l-EP imprinted PtÀ Ir film and flat Pt, respectively. These observations confirm the successful integration of mesoporous features into the chiral imprinted PtÀ Ir alloy films.…”

“…In particular, chiral‐encoded Pt−Ir alloys have been successfully employed as electrocatalysts with an excellent enantioselectivity (>90 %) and high stability [22] . Chiral imprinted mesoporous Pt−Ir alloys can also be used as heterogenous catalysts for the selective synthesis of the enantiomers of a chiral model compound, PE, through the hydrogenation of the corresponding prochiral precursor (acetophenone) with up to 85 % ee [25] . However, this type of strategy has not been tested yet for the heterogeneous catalysis of reactions leading to real and, by definition, more complex pharmaceutical compounds [25] …”

“…[22] Chiral imprinted mesoporous PtÀ Ir alloys can also be used as heterogenous catalysts for the selective synthesis of the enantiomers of a chiral model compound, PE, through the hydrogenation of the corresponding prochiral precursor (acetophenone) with up to 85 % ee. [25] However, this type of strategy has not been tested yet for the heterogeneous catalysis of reactions leading to real and, by definition, more complex pharmaceutical compounds. [25] In this context, it is therefore challenging to study and validate the use of chiral imprinted metals as simple heterogeneous catalysts for the production of chiral pharmaceutical compounds.…”

Electrochemiluminescent enantioselective detection with chiral-imprinted mesoporous metal surfaces

“…10 They combine the advantages of the mesoporosity, providing a high active surface area and improved mass transport, 11 with enantioselective adsorption on surfaces. 12 To extend the scope of this strategy, noble and non-noble metals, such as platinum (Pt) 10 and nickel (Ni) 13 or alloyed platinum–iridium (Pt–Ir), 14 have been investigated. These nanostructured surfaces could be used as electrodes for three major aspects of chiral technologies: asymmetric synthesis, 10 c – e ,13,14 chiral separation, 15 and enantioselective analysis.…”

“…12 To extend the scope of this strategy, noble and non-noble metals, such as platinum (Pt) 10 and nickel (Ni) 13 or alloyed platinum–iridium (Pt–Ir), 14 have been investigated. These nanostructured surfaces could be used as electrodes for three major aspects of chiral technologies: asymmetric synthesis, 10 c – e ,13,14 chiral separation, 15 and enantioselective analysis. 10 a , b ,16 Most importantly, when an alloy is used instead of a monometallic matrix, a significantly improved stability of the chiral features has been observed, 14 a making these surfaces interesting candidates for the asymmetric synthesis of chiral compounds via both electrocatalysis, 14 a and heterogeneous chemical catalysis.…”