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The application of diastereoselective hydrogenation catalyzed by heterogeneous catalysts for the asymmetric synthesis of organic compounds is illustrated in the reduction of several functional groups. In that approach, the chiral information is provided by the prior attachment of a chiral auxiliary to the substrate to be hydrogenated. The optically active hydrogenated product is then disconnected from the chiral auxiliary. Proper choice of the inductor, of the catalyst and of reaction conditions may result in high diastereoselectivities.

Ultrasound radiation has been recently used for the synthesis of mesoporous materials (MSPM). The main advantages are manifested in the short preparation time and thicker walls leading to a more hydrothermally stable structure.1 This preparation method has already been reviewed.2 The discovery of MSP materials led immediately to the development of many experimental methods for the deposition of materials, especially catalytic materials, into the mesopores. Impregnation, thermal spreading, ion adsorption, and the most recent method3 in which colloidal gold solution is premixed with the precursors for the preparation of the MSPM, are among the methods used for the insertion of materials into the mesopores. Sonochemistry was also employed for this purpose. We will outline in this article the use of the sonochemical processes for the insertion of nanomaterials into the pores of MSPM. We will explain how this process is conducted, to what extent the materials are deposited in the pores and what is the mechanis...

The diastereoselective hydrogenation of 2-methyl nicotinic acid covalently bound to proline ester or pyroglutamic ester over supported metallic catalyst yielded moderate diastereoselectivity (26%). The hydrogenation of the corresponding pyridinium salt was studied and similar de's were achieved.

The diastereoselective hydrogenation of o -toluic acid or o -methoxy benzoic acid covalently bound to different chiral auxiliaries was performed on Rh and Ru supported catalysts. The cis- isomers were formed predominantly, with a diastereoselectivity largely influenced by the structure of the chiral inductor and the steric hindrance brought for the preferential adsorption of one face of the aromatic substrate. The effect of the functional group on the proline auxiliary (alcohol or ester groups susceptible to modify the anchoring of the aromatic substrate) was weak. Hydrogenolysis occurred rather extensively with the methoxy benzoic acid and constituted the most important hydrogenation pathway on Rh/C. The presence of the CO group in the pyroglutamic acid methyl ester is a determining factor for obtaining good diastereoselectivity.