Alkylation of Carboxylic Acids to Form Ketones

A general synthesis of ketones involves the reaction of a carboxylic acid with two 20-14 equivalents of an organolithium reagent. This reaction was discussed in Section 18-9. 

The first equivalent of the organolithium reagent simply deprotonates the acid. The second equivalent adds to the carbonyl to give a stable dianion. Hydrolysis of the dianion (by adding water) gives the hydrate of a ketone. Because the ketone is formed in a separate hydrolysis step (rather than in the presence of the organolithium reagent), overalkylation is not observed. 

Propose a mechanism for conversion of the dianion to the ketone under mildly acidic conditions. 

Show how the following ketones might be synthesized from the indicated acids, using any 

---

Mechanism 20-3 Esterification Using Diazomethane 966 20-12 Condensation ofAcids with Amines Direct Synthesis of Amides 966 20-13 Reduction of Carboxylic Acids 967 20-14 Alkylation of Carboxylic Acids to Form Ketones 968 20-15 Synthesis and Use of Acid Chlorides 969... 

---