T. Máthé

(-)-Dihydro-apovincaminic acid ethyl ester, preparation and use as a chiral modifier in enantioselective heterogeneous catalytic hydrogenations

Abstract The preparation, characterisation and use of (−)-dihydro-apovincaminic acid ethyl ester as a chiral modifier in heterogeneous catalytic asymmetric hydrogenations is reported. The epimeric compositions were determined using NMR and HPLC methods and circular dichroism spectroscopy was used to detect the interaction between the chiral modifier and the substrate.

Enantioselective hydrogenation of acetophenone in the presence of S-proline

Abstract Enantioselective heterogeneous catalytic hydrogenation of acetophenone in the presence of S -proline was investigated. The effect of various catalytically active metals, reaction temperature and amount of catalyst on optical purity was studied. The correlation between optical yield and conversion, concentration of the reactants, different pretreatment methods and additives was also investigated.

Enantioselecttve hydrogenation of isophorone

Abstract The effects of catalyst, pH, hydrogen pressure and intensity of agitation in the enantioselective hydrogenation of isophorone were discussed. The changes in chemical and optical yield of the saturated ketone as functions of conversion and of the water content of the solvent have also been investigated. An iminium salt hydrogenation intermediate has been identified.

A new chiral auxiliary in enantioselective hydrogenations: (−)-dihydrovinpocetine. Part I. Hydrogenation of isophorone

Abstract A vinca-type synthetic alkaloid: (−)-dihydrovinpocetine is a promising chiral auxiliary in the enantioselective hydrogenation of the prochiral Cue5fbC bond of isophorone. Various catalytic metals and supports have been screened. The effect of acidic additives is described. The highest optical yield (38%) is obtained with a Pd black catalyst. Mechanistic considerations and comparison with the known Pt/cinchona system have been made.

Comparison of chiral modifiers in the Pd catalysed hydrogenation of phenylcinnamic acid and isophorone

Abstract The asymmetric induction of (−)-dihydroapovincaminic acid ethyl ester [(−)-DHVIN] and cinchonidine employed as chiral modifiers was compared in the Pd catalysed hydrogenation of the Cue605C double bonds of phenylcinnamic acid and isophorone. The differences in their effect and behaviour were attributed to the difference in the interaction between the modifier and the reactant and to their different basicity.

Enantioselective hydrogenation of ethyl pyruvate and isophorone over modified Pt and Pd catalysts

The present study aimed at revealing the mode of enantiodifferentiation in the asymmetric hydrogenation of ethyl pyruvate and isophorone over platinum and palladium catalysts. The effect of adding the modifier after an initial phase of racemic hydrogenation and the combined use of different vinca and cinchona type modifiers, on enantioselectivity and activity were studied. A mechanistic rationale is proposed to account for the experimental observations.

New chiral auxiliaries in enantioselective heterogeneous catalytic hydrogenations: (-) and (+)-dihydro-apovincaminic acid. Comparison with (-)- dihydro-apovincaminic acid ethyl ester. III

Abstract The preparation, characterisation, use and comparison with (−)-dihydro-apovincaminic acid ethyl ester of (−) and (+)-dihydro-apovincaminic acid as chiral modifier in heterogeneous catalytic asymmetric hydrogenations are reported. The epimeric compositions were determined using NMR and HPLC methods.

Effect of carbon support properties on enantioselective hydrogenation of isophorone over palladium catalysts modified with (-)-dihydroapovincaminic acid ethyl ester

The support-effect was investigated in the enantioselective hydrogenation of isophorone over Pd catalysts prepared on different carbon supports. Carbon supports with different specific surface area and activated carbons with different surface chemistry were used. The Pd catalysts, obtained by different reduction methods of the catalyst precursor, had different dispersion. The low dispersion was advantageous for the high enantioselectivity and the different supports had influence on the ee due to their different specific surface area and surface chemistry.

Hydrogenation of pyrrole derivatives I. Hydrogenations over palladium

Abstract The heterogeneous catalytic hydrogenation of 1-methyl-2-pyrrole ethanol resulted in 1-methyl-2-pyrrolidine ethanol, an important and valuable pharmaceutical intermediate. In non-acidic medium, with carbon supported palladium catalyst, applying solvent mixtures and mild reaction conditions (6 bar, 80°C) high conversion and selectivity were obtained. This hydrogenation is part of a newly developed and industrially feasible synthesis.

Hydrogenation of pyrrole derivatives. II. Hydrogenations over supported noble metal catalysts

Abstract The heterogeneous catalytic hydrogenation of 1-methyl-2-pyrroleethanol resulted in 1-methyl-2-pyrrolidineethanol, an important and valuable pharmaceutical intermediate. Various noble metal catalysts on different supports have been screened. The best results were achieved with a carbon supported rhodium catalyst, in non-acidic medium, under mild reaction conditions (6 bar, room temperature). Ruthenium on carbon also showed high activity in this hydrogenation.