Recently Developed Organometallic Complexes of Zn, Cu(Zn, Li), Fe, Ru and Less-used Ions. Use in Selective 1,2-or 1,4-Additions, Transfer Hydrogenations, Aldol Reactions and Diels-Alder Reactions

Abstract

This review introduces the broad general topic of asymmetric organic synthetic reactions and reagents. Reagents containing both frequently used metallic ions, e.g. Zn ++ , Cu +(++) and Ru ++ , and rarely used ions, such as Ag + , employed in the construction of designed chiral centers, are updated here. Enantioselective 1,2-additions and 1,4-conjugate additions, transfer hydrogenations, and diasteroselective aldol reaction are discussed. The selectivities induced by chiral β-, δor γ-chiral amino alcohols, chiral diols, chiral binaphthyl derivatives, chiral P,N-containing auxiliaries, and other ligands used to prepare chiral metallic complexes, were compared in each reaction system. The use of two or more metallic ions with a single chiral ligand has now become a more popular strategy to catalyze chiral-center-controlled processes. For example, only diethylzinc was used in enantioselective additions to aldehydes in early studies. Recently, the combination of Et 2 Zn and Cu ++ in the selective additions has been used to achieve high ee% values and yields. Finally, quantum calculations have been used to obtain kinetic data to predict a reactions ee% values. For example, the calculated ∆G cal. values have a strong relationship with the obtained ∆G fit values which have the direct linkage with the ee% values. EntryActivator ee (%) at 0 °°°°C (config.) ee (%) at -45 °°°°C (config.)

Synthesis and Application of New, Optically Active Compounds as Catalysts and Ligands in Enantioselective Reactions

“…Enantioselective addition of organozinc reagents to aldehydes is one of the most important synthetic methods for the preparation of enantioenriched secondary alcohols, [11,12] which are key intermediates in the preparation of valuable chiral biologically active compounds [13]. Therefore this reaction was choosen as a test of the efficiency of our new-found atropisomeric amino alcohol ligands.…”

Large-scale ruthenium- and enzyme-catalyzed dynamic kinetic resolution of (rac)-1-phenylethanol

“…Chiral alcohols are important synthetic intermediates and are structural elements in biologically active compounds and natural products. [ 1 - 4 ] A few methods have been developed for the enantioselective synthesis of chiral alcohols including catalytic asymmetric hydrogenation [ 5 - 14 ] and enantioselective hydride addition [ 15 , 16 ] of prochiral ketones, asymmetric dialkylzinc addition to aldehydes, [ 17 , 18 ] and asymmetric aldol reactions. [ 19 - 23 ] Biocatalysts have also been successfully employed in the enantioselective reduction of ketones.…”