The Enantioface-differentiating (Asymmetric) Hydrogenation of the C=O Double Bond with Modified Raney Nickel. XXXVI. The Development of Modified Nickel Catalysts with High Enantioface-differentiating Abilities

Abstract

Various types of modified nickel catalysts were prepared and their enantioface-differentiating (asymmetric) abilities were examined. It was found that the presence of aluminum or related metal compounds in the catalyst was unfavorable for the effective enantioface-differentiating catalyst. The modification with a solution containing tartaric acid and inorganic salt gave a high enantioface-differentiating ability to Raney nickel and reduced nickel catalyst. Among the modified nickel catalysts examined, the Raney nickel modified with tartaric acid and sodium bromide gave the best result with respect to the hydrogenation activity and enantioface-differentiating ability (optical yield 88%). NaBr adsorbed on Raney nickel was found to inhibit the nonenantioface-differentiating hydrogenation.

The Chiral Switch of (S)-Metolachlor: A Personal Account of an Industrial Odyssey in Asymmetric Catalysis

“…The best catalyst already gave 99% ee [14] but the highest ton×s were a relatively modest 2300. [4] For the hydrogenation of CO groups the most active catalysts were modified heterogeneous catalysts: Ni-tartrate for b-keto esters [15] and Pt-cinchona catalysts for a-keto esters [5] with best ee×s up to 85%. Some soluble Rh diphosphine catalysts were also reported to give ee×s up to 95% but without any data on activity.…”

Enantio-differentiating hydrogenation of methyl acetoacetate over reduced nickel catalysts pre-modified in methanol

“…Conversion was determined by GLC analyses (5% Thermon 1000 on Chromosorb W at 383 K). The specific optical rotation [a] D of the optically pure (R)-methyl 3-hydroxybutyrate is½a 20 D ¼ À22:95 (neat) [8]. When the purity of the methyl 3-hydroxybutyrate after distillation was less than 100% (in the case of the low conversion), the e.d.a.…”

“…of this catalyst reaches 80-98% [4][5] for b-ketoesters and 72-85% for 2-alkanones [6]. The catalyst has been prepared by the pre-modification of a Ni catalyst in an aqueous modification solution [7][8][9][10][11][12][13]. That is, an activated Ni catalyst, such as Raney Ni, supported Ni, Ni powder prepared by the reduction of Ni oxide (reduced Ni), or fine Ni powder, is soaked in an aqueous solution of tartaric acid and NaBr (pH of the solution is adjusted to 3.2 by NaOH solution) at 373 K for 1 h. Although the modification of Raney Ni in an aqueous solution attained a high e.d.a., the durability of the e.d.a.…”

“…That is, an activated Ni catalyst, such as Raney Ni, supported Ni, Ni powder prepared by the reduction of Ni oxide (reduced Ni), or fine Ni powder, is soaked in an aqueous solution of tartaric acid and NaBr (pH of the solution is adjusted to 3.2 by NaOH solution) at 373 K for 1 h. Although the modification of Raney Ni in an aqueous solution attained a high e.d.a., the durability of the e.d.a. is very low [4] and the modification produces an aqueous waste containing Ni ions [8].…”

Study of the properties of nickel oxide and nickel as precursors for the tartaric acid-NaBr-modified nickel catalyst

“…One is a pre-modification and the other is an in-situ modification. The premodification is a conventional method for preparing the modified nickel catalyst, i.e., the activated nickel is modified in an aqueous solution of tartaric acid and NaBr at pH 3.2 and 373 K [5]. The in-situ modification method has been recently applied to the preparation of a modified nickel catalyst [6].…”