Kinetic control with LDA : Proton abstraction takes place at less hindered a -CH position and the reaction is faster and essentially irreversible.
Thermodynamic control with t BuOK : equilibration takes place between the two enolates and the methyl-substituted one, being the more stable, is present in high concentration.
However, when the highly substituted position is strongly sterically hindered, alkylation with t BuOK occurs at the less sterically substituted carbon (Scheme 9).
Scheme 9
1.3.2 Alkylation of Bifunctional Compounds
A C-H bond adjacent to two electron withdrawing groups is more acidic than that adjacent to one electron withdrawing group and the alkylation could be carried out in milder conditions (Scheme 10).
Scheme 10
1.4 Addition of Enolates to Activated Alkenes
Enolates undergo addition to alkenes that are activated by conjugation to carbonyl, ester, nitro and nitril groups (Scheme 11). These reactions are usually referred to as Michael addition.
Scheme 11
Examples:
