Chemistry of the Alkaline Earth Metal Enolates

Aldehydes, ketones, carboxylic esters, carboxylic amides, imines and N,N-disubstituted hydrazones react as electrophiles at their sp2-hybridized carbon atoms. These compounds also become nucleophiles, if they contain an H atom in the a-position relative to their C O or C N bonds. This is because they can undergo tautomerization to the corresponding enol as seen in Chapter 12. They are also C,H-acidic at this position, i.e., the H atom in the a-position can be removed with a base (Figure 13.1). The deprotonation forms the conjugate bases of these substrates, which are called enolates. The conjugate bases of imines and hydrazones are called aza enolates. The reactions discussed in this chapter all proceed via enolates.