Aldol reactions basic principles

Scheme 28 Basic principle of the hydroformylation/aldol reaction...

The basic principles of the mechanism of this Lewis-base-catalyzed aldol reaction have already been described in Section 6.2.1.1. With regard to the course of the enantio- and diastereoselective formation of aldol adducts with two stereogenic centers, it is proposed that synthesis of anti-products proceeds via a chair-like transition structure. A distinctive feature of the cationic transition state complex is a hexacoordinated silicon atom bearing two chiral phosphoramide molecules as ligands (Scheme 6.30). 

Mechanism and transition states The basic principles of the proline-catalyzed direct aldol reaction are summarized in Section 6.2.1.1 [93, 94a], The preferred diastereo- and enantioselectivity were explained in terms of the potential transition states for the aldol reaction using hydroxyacetone shown in Scheme 6.38 [93], Thus, re-facial attack of the aldehyde at the si face of hydroxyacetone leads to the... 

Aldol addition of acetone (Figure 7) is an imponani reaction in industry, since it yields diacetone alcohol (DAA) [234] used, for instance, as a soivcni for cellulose. Moreover, it can provide us with some infonnation on the basicity of the tested solids. In principle, both acid... 

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