Reduction of esters to aldehydes using DIBAL
Description: Esters can be reduced to aldehydes with diisobutylaluminum hydride (DIBAL), a bulky source of hydride ion.
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Hello James, can you also explain why step 2 (1,2 addition) doesn’t occur between DIBALH and aldehydes?
Hi Shuo – it *does* occur with aldehydes, but not with the tetrahedral intermediate in Step 3.
The reason that esters can be reduced to the aldehyde stage is that the tetrahedral intermediate (drawn in step 3) is *stable* at -78° and does not react further with DIBAL-H. So long as the temperature is kept low, the tetrahedral intermediate will not break down to the aldehyde stage through elimination.
If the solution is warmed, 1,2-elimination of the tetrahedral intermediate will occur, liberating the aldehyde, and the aldehyde will then be reduced.
Hey, will lithium tri-tert-butoxyaluminum hydride work here, as well, or just for the acid halides? If not, why the selectivity?
Thanks in advance!
Yep – it will also reduce aldehydes. That’s why it’s important to use only 1 equivalent when reducing acid halides, otherwise you get full reduction to the alcohol.
what’s the meaning of Me on this diagram?
Me means “methyl”, or CH3
please tell me how 3 or 4 molecule of DIBAL are used to reduction of alkyl ester
give me detailed mechanism