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Gamez, A.; Köhler, Jochem U.; Bradley, John S.

doi:10.1023/a:1019078727850

Cited by 38 publications

(20 citation statements)

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“…It is worth pointing out that multiple studies have indicated that cinchona adsorption actually requires preconditioning of the surface with hydrogen [46][47][48][49][50][51], and that such preconditioning may help cinchona protonation [43]. In general, good solvents, where the adsorption equilibria for cinchona are shifted toward the liquid phase, have proven to be better for the chiral promotion of hydrogenation catalytic reactions [52][53][54][55][56][57]. Fig.…”

Section: Adsorption On Metal Surfacesmentioning

confidence: 99%

The Physico-chemical Properties of Cinchona Alkaloids Responsible for their Unique Performance in Chiral Catalysis

Mink

Olsen

et al. 2008

Top Catal

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The physico-chemical properties of cinchona alkaloids have been characterized in connection to their use for catalytic enantioselective conversions. Adding to the previous identification of their active site at the nitrogen atom in the quinuclidine ring and the chiral environment provided by the carbon centers of the neighboring alcohol linker, an argument is made here for the importance of the adoption of certain rotational conformations by those cinchona alkaloids in optimizing their chiral promotion. Because catalysis with cinchona alkaloids involves a liquid phase, there is a dynamic conformation isomerization process controlled by a number of factors having to do with the exact structure of the cinchona as well as with the nature of the solvent used and, in the case of heterogeneous catalysis, the presence of a solid surface. Solvents of intermediate polarity have been found to be the best for dissolving the cinchona, for establishing rapid adsorption equilibria with metal surfaces, and for promoting chiral catalysis. Protonation also leads to a dramatic change in performance, locking the cinchona molecule in a specific conformation held in place by the counter anion of the acid used, and modifying the chemical and biological activity of the system. Comparative studies with several cinchona indicate that molecular groups attached to peripheral positions also exert a great influence on the conformational and adsorption behavior of these molecules.

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Section: Adsorption On Metal Surfacesmentioning

confidence: 99%

The Physico-chemical Properties of Cinchona Alkaloids Responsible for their Unique Performance in Chiral Catalysis

Mink

Olsen

et al. 2008

Top Catal

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“…Benzyl amine (19) was used for the asymmetric allylic amination of 4 (Scheme 3). Only those ligands that showed some activity in the AAA were selected in this reaction (Table 3).…”

Section: Asymmetric Allylic Aminationmentioning

confidence: 99%

Organic Carbonates as Alternative Solvents for Palladium‐Catalyzed Substitution Reactions

et al. 2008

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Organic carbonates, such as propylene carbonate, butylene carbonate, and diethyl carbonate, were tested in the Pd-catalyzed asymmetric allylic substitution reactions of rac-1,3-diphenyl-3-acetoxy-prop-1-ene with dimethyl malonate or benzylamine as nucleophiles. Bidentate diphosphanes were used as chiral ligands. The application of monodentate phosphanes capable of self-assembling with the metal was likewise tested. In the substitution reaction with dimethyl malonate, enantioselectivities up to 98% were achieved. In the amination reaction, the chiral product was obtained with up to 83% ee. The results confirm that these "green solvents" can be advantageously used for this catalytic transformation as an alternative to those solvents usually employed which run some risk of being harmful to the environment.

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“…Other approaches include the use of Michaelis-Menten-type expressions [13]. This method was shown to be pragmatic in describing solvent effects in ethyl pyruvate hydrogenation by discriminating a lumped reaction term from one relating to adsorption.…”

Section: Kinetic Modelling Of Solvent Effects In the Literaturementioning

confidence: 99%

A kinetic analysis methodology to elucidate the roles of metal, support and solvent for the hydrogenation of 4-phenyl-2-butanone over Pt/TiO2

Wilkinson

McManus

Daly

et al. 2015

Journal of Catalysis

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a b s t r a c tThe rate and, more importantly, selectivity (ketone vs aromatic ring) of the hydrogenation of 4-phenyl-2-butanone over a Pt/TiO 2 catalyst have been shown to vary with solvent. In this study, a fundamental kinetic model for this multi-phase reaction has been developed incorporating statistical analysis methods to strengthen the foundations of mechanistically sound kinetic models.A 2-site model was determined to be most appropriate, describing aromatic hydrogenation (postulated to be over a platinum site) and ketone hydrogenation (postulated to be at the platinum-titania interface). Solvent choice has little impact on the ketone hydrogenation rate constant but strongly impacts aromatic hydrogenation due to solvent-catalyst interaction. Reaction selectivity is also correlated to a fitted product adsorption constant parameter. The kinetic analysis method shown has demonstrated the role of solvents in influencing reactant adsorption and reaction selectivity.

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Cited by 38 publications

References 0 publications

The Physico-chemical Properties of Cinchona Alkaloids Responsible for their Unique Performance in Chiral Catalysis

The Physico-chemical Properties of Cinchona Alkaloids Responsible for their Unique Performance in Chiral Catalysis

Organic Carbonates as Alternative Solvents for Palladium‐Catalyzed Substitution Reactions

A kinetic analysis methodology to elucidate the roles of metal, support and solvent for the hydrogenation of 4-phenyl-2-butanone over Pt/TiO2

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