Stereochemical Studies of the Hydrogenation with an Asymmetrically Modified Raney Nickel Catalyst. The Hydrogenation of Acetylacetone

The hydrogenation of acetylacetone (I) over asymmetrically modified Raney nickel (MRNi) proceeded, step by step, as follows: acetylacetone (I) 1→ 4-hydroxy-2-pentanone (II) 2→ 2,4-pentanediol (III). It was demonstrated that the optical yield of Step 1 and the diastereomer excess of Step 2 are governed by the ratio of the stereo-differentiating reaction site to the non-stereo-differentiating reaction site on the catalyst. The stereochemistry of each step was also discussed based on the mode of the intermolecular hydrogen bondings between the substrate and tartaric acid adsorbed on the catalyst. RNi modified with a mixture of tartaric acid and NaBr (TA–NaBr–MRNi) gave the best result with respect to both Step 1 and Step 2.