Asymmetric Catalysis with Purely Organic Compounds

ASYMMETRIC CATALYSIS WITH PURELY ORGANIC COMPOUNDS... 

Asymmetric Catalysis with Purely Organic Compounds 323... 

ASYMMETRIC catalysis with purely organic compounds... 

Books 1. Ojima, Catalytic Asymmetric Synthesis , VCH, New York, 1993 R. Noyori, Asymmetric Catalysis in Organic Synthesis , John WUey Sons, New York, 1994 T. Hayashi, K. Tomioka, O. Yonemitsu, Asymmetric Synthesis , Kodansha/Gordon and Breach Science Publishers, Tokyo, 1998 J. Seyden-Penne, Chiral AuxUiaries and Ligands in Asymmetric Synthesis , John Wiley Sons, New York, 1995 Recent Reviews M. Shibasaki, H. Sasai, T. Aral, Angew. Chem. 1997, 109, 1290 Angew. Chem., Int. Ed. 1997, 36, 1237 (Asymmetric Catalysis with Heterobimetallic Compounds), S. Koba-yashi, PureAppl Chem. 1998, 70, 1019 (New Types of Lewis Acids Used in Organic Synthesis), K. Mikami, Pure Appl. Chem. 1996, 68, 639 (Asymmetric Catalysis of Carbo-nyl-Ene Reactions and Related Carbon-Carbon Bond Forming Reactions). 

Asymmetric synthesis has emerged as a major preparative method, widely used in organic chemistry and in the total synthesis of natural products, and which is also of interest for industrial chemistry. The importance of enantiomerically pure compounds is connected with the applications in pharmaceutical industries, since very often the biological activity is strongly linked to the absolute configuration. In this article the historical developments of asymmetric synthesis will be briefly presented, as well as the main methods to prepare enantiomerically enriched compounds. Then recent asymmetric synthesis of two classes of compounds will be discussed i) Sulfoxides, chiral at sulfur ii) Ferrocenes with planar chirality. The last part of the article will be devoted to asymmetric catalysis with transition-metal complexes. The cases of asymmetric oxidation of sulfides to sulfoxides and nonlinear effects in asymmetric catalysis will be mainly considered. 

The chirality in the organic compound (even though with small ee) can be converted into almost enantiomerically pure pyrimidyl alkanol by asymmetric auto catalysis with amplification of chirality. 

Enantiomerically pure sulfoxides are important intermediates in organic synthesis (21) and quite a number of pharmaceuticals and other biologically active compounds harbor a chiral sulfoxide unit (22). With respect to oxidation catalysis, enantiomerically enriched sulfoxides can either be accessed by asymmetric sulfoxidation of prochiral thioethers (Scheme 7, path a), or by kinetic resolution of racemic sulfoxides (Scheme 7, path b). For the latter purpose, enantio-specific oxidation of one sulfoxide enantiomer to the sul-fone, followed by separation, is the method of choice. 

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