66130-41-4Relevant articles and documents
Asymmetric hydrogenation of indene carboxylic acids: Stereochemistry of hydrogen addition
Borszeky,Mallat,Baiker
, p. 4781 - 4789 (2007/10/03)
The stereochemistry of hydrogen addition to α,β-unsaturated carboxylic acids was studied by means of hydrogenation of indene carboxylic acids and their derivatives. Experiments were carried out over Pd/Al2O3 in the presence and absence of cinchonidine as a chiral modifier. In all cases hydrogenation occurred via bottom side syn addition of two hydrogen atoms to the chemisorbed substrate. Formation of trans isomers, up to 72%, was observed due to C=C bond isomerization in the substrate, and to adsorption and hydrogenation of the unsaturated molecule in a sterically unfavourable position. Adsorption in 'upside down' position was promoted by N-bases. Hydrogenation of 3-methylindene-2-carboxylic acid provided up to 45% ee. Due to the high activity of Pd in C=C bond migration, a good ee can be achieved only when isomerization is negligible. (C) 2000 Elsevier Science Ltd.