Retrosynthesis of Esters a-Alkylation

While tertiary (A,A-disubstituted) amides can also undergo a-alkylation using LDA, the most common way to synthesize an amide is by an acyl substitution reaction on a carboxylic acid derivative (R COLG) in which the leaving group 

Amides without any A-alkyl groups (RCONH2) can also be prepared by partial hydration of a nitrile (RC N). Addition of one equivalent of water across the nitrile triple bond results in an enol-like intermediate that tautomer-izes to give a carbonyl. This mechanism is analogous to the hydration of an alkyne to give a ketone product. Since amides can also be hydrolyzed to give carboxylic acids, the nitrile partial hydrolysis reaction conditions are kept relatively mild when the amide product is desired. 

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