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

摘要

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 beta-, delta- or gamma-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 aldchydes in early studies. Recently, the combination of Et2Zn 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 Delta G(cal). values have a strong relationship with the obtained Delta G(fit) values which have the direct linkage with the ee% values.