Making alcohols from esters

A carbanion will attack an ester, kicking off RO^-:

Another carbanion will then attack the ketone to produce a stable alkoxide, which becomes an alcohol on acid workup. :

Assuming there is a single type of carbanion used, notice that this results in at least two identical substituents on the product. 

Using this, you should be able to tell what type of organolithium is used for this reaction:

We can also use hydrides as the twice-attacking nucleophile, such as LiAlH₄.

You might reasonably predict that simply using a 2:1 carbanion:ester ratio will give aldehydes or ketones. But this doesn't work - because the aldehyde/ketone is more reactive to nucleophiles than an ester is. So a 2:1 ratio would just cause half of the esters to stay as esters, and half to be converted to alcohols.

But stopping the reaction halfway is achievable by other methods.