Two Useful Reactions of Nonenolizable Carbonyl Compounds

FIGURE 17.56 Cross Cannizzaro reaction using formaldehyde. 

The regiochemistry of alkylation of simple, non-symmetric ketones may be problematic to control, and polyalkylation can be a competing reaction. The most useful strategy is to ensure complete deprotonation of the carbonyl compound using the strong, non-nucleophilic base LDA, followed by inverse addition of the enolate to an excess of the alkylating agent. 

Enamines can be prepared from carbonyl compounds and secondary amines they react with electrophiles with predictable regioselectivity. 

A Reformatskii reagent may be regarded as a zinc enolate and is useful for selectivity in cross condensation reactions. 

Non-enolizable aldehydes and ketones may undergo the benzoin or Cannizzaro reactions. 

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