ENANTIOSELECTIVE HYDROGENATION OF 2-METHYL-2-PENTENOIC ACID OVER CINCHONIDINE-MODIFIED PD ALUMINA/

A chiral alkanoic acid was prepared with up to 52% excess of the (S) e nantiomer by hydrogenating alpha,beta-unsaturated carboxylic acid with a cinchonidine-Pd/Al2O3 catalyst system. Favourable conditions are: h igh surface hydrogen concentration (greater than or equal to 60 bar hy drogen pressure, low catalyst concentration and apolar solvents), near ambient temperature and a cinchonidine/reactant molar ratio of at lea st 0.4 mol%. It is proposed that high hydrogen solubility and the pres ence of 2-methyl-2-pentenoic acid reactant as dimers are advantageous for enantiodifferentiation.