有機化學問題 LDA

Typical bases such as sodium hydroxide or an alkoxide ion be used to form enolates for alkylation because at equilibrium a large quantity of the hydroxide or alkoxide base is still present .

These strongly nucleophilic bases give side reactions with the alkyl halide or tosylate .

Lithium diisopropylamide (LDA) avoids these side reactions.

Because it is a much stronger base, LDAconverts the ketone entirely to its enolate.

All the LDA is consumed in forming the enolate,leaving the enolate to react without interference from the LDA .

Also,LDA is a very bulky base and thus a poor nucleophile,so it generally does not react with the alkyl halide or tosylate.

(a) write an equation to show how would you prepare LDA?

(b) Predict the product when acetone is treated with LDA then reacts with allyl bromide.