Lecture 16 PDF

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Lithium diisopropylamide

strong and sterically hindered base

(weak base)

or any alkoxide base ( tBuOK )

Equilibrium occurs in thermodynamic LDA base is strong enough to deprotonate the ketone completely so we can use equivalents to control the selectivity. If we use slightly less than 1 equiv, then there is alway a small amount of ketone available. If that is the case then the existing enolate in solution can behave as a base and deprotonate the ketone (turning the enolate back into a ketone and the ketone into an enolate). In this case there is an equilibration of enolates and therefore thermodynamic contro With >1 equiv of LDA then all the ketone molecules are deprotonated and there is no possibility for that ketone-toenolate/enolate-to-ketone equilibration.

tBuOK - only thermo....