Chapter 21: Ester Enolates

Common Bases used to prepare enolates
 

• The most common bases for preparing enolates are shown below:

• General points to remember:
• Hydroxide will cause hydrolysis of esters
• Alkoxide basses should match the alcohol part of an ester to avoid transesterification
• NaH and LDA are usually used in tetrahydrofuran (THF) as the solvent (like many organometallic reagents)
• NaH and LDA are strong bases.
• Important things about LDA:
• Strong base but poor nucleophile (too sterically hindered)
• LDA is very good for making enolates of esters, aldehydes and ketones since it can give essentially 100% (quantitative conversion) to the enolate
• This allows the enolate to be alkylated or acylated with less chance of self-condensation reactions.

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© Dr. Ian Hunt, Department of Chemistry