Enantioselective hydrogenation of itaconic acid and its derivates with sol–gel immobilized Rh/BPPM catalysts

Itaconic acid and some of its derivates were hydrogenated with sol–gel entrapped Rh/BPPM catalysts in methanol solutions. The immobilization process was carried out by different gel building agents: hydrophilic tetramethyl orthosilicate Si(OMe)4 (TMOS) and tetraethyl orthosilicate Si(OEt)4 (TEOS), hydrophobic triethoxyphenylsilane PhSi(OEt)3/TMOS and trimethoxy(octyl)silane OcSi(OMe)3/TMOS. The choice of the silane precursor influences the enantioselectivity and the rate of the reaction because of the hydrophobic interactions between catalyst, gel and substrate. The immobilized catalyst could be recovered and recycled several times under N2-atmosphere. About 90–99% ee were achieved for the hydrogenation of itaconic acid to (S)-(+)-2-methyl succinic acid, and about 14% ee for the hydrogenation of dimethylitaconate to (S)-(+)-2-methyl-succinic acid dimethylester.

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► Sol–gel Rh/BPPM catalysts enable hydrogenation of itaconic acid and derivates.
► Sol–gel entrapment allows the recycling of the catalyst.
► The selected support influences the reaction rate.
► Reaction rate depends on the selected medium.