LDA and Kinetic Enolates

LDA and Kinetic Enolates - UCLA Chemistry 30C LDA and...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
UCLA Chemistry 30C LDA and Kinetic Enolate Chemistry Deprotonation of aldehydes, ketones, esters, and amides with hydroxide or alkoxide bases can lead to problems with the regiochemistry of reaction or with over-reaction. That is because these thermodynamic bases only generate small concentrations of the enolate and the reaction product must then be exposed to base also. O O + NaOH + H 2 o Na pKa = 20 pKa = 16 Strong bases, with a conjugate acid much less acidic than the substrates being deprotonated, deprotonate substrates without any reversibility. Such reactivity provides control over reaction regioselectivity and can limit overreaction. Enolates are formed quantitatively and then react with electrophiles completely. LDA, lithium diisopropylamide, is a common strong base that is also sterically hindered to prevent nucleophilic reactions. In the example below, the pKa difference of 17 will guarantee that the reaction is not reversible. Reactions are performed in aprotic polar solvents such as THF.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 2

LDA and Kinetic Enolates - UCLA Chemistry 30C LDA and...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online