Chiral enolate addition

To further exemplify the dependence of the stereochemical course of chiral enolate additions catalyzed by phosphoramides, a detailed survey of additions to aldehydes using chiral p-hydroxyenolate 17 and 10 mol % of la was performed. Unlike additions of 15, diastereoselectivities of the resultant aldol products using 17 could be switched depending upon the configuration of the phosphoramide employed (eq 7, Table 6). 

The recognition of chiral carbonyl compounds, especially the substrates having a chiral stereogenic center at the a-carbon, have been a main subject of research for long time [81], since Curtin [82] and Cram [83] initially proposed a structural model for the diastereoselective addition to these molecules. There are in-depth studies related to this subject including chiral enolate addition, i.e., double asymmetric synthesis [84]. In this section, therefore, some other impressive topics of current interest are discussed briefly. 

Asymmetric Michael addition of chiral enolates to nltroalkenes provides a useful method for the preparation of biologically important compotmds. The Michael addition of doubly deprotonated, optically active fi-hydroxycarboxylates to nltroalkenes proceeds v/ith high dias-tereoselecdvity to give fityr/iro-hydroxynitroesters fEq, 4,58, ... 

Volume E 21 D.1.3.4.2. Addition of Chiral Enolates to Achiral Carbonyl Compounds... 

Further examples of additions of chiral enolates to chiral carbonyl compounds are listed in Table 2. 

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