[zhangh]

My substrate ester was reduced to alcohol using DIBAL as redcuing reagent in dry THF.

how to work up  avoiding the formation of the terrible slurry? By the way, my product was amine, it can not be adjusted to acidic condition.

[russellm72]

Ah the old dreaded amines can I ask why you didn't have the amine protected before this step and remove at a later stage?

Normally I use moist ether is get rid of the excess DIBALH then spin down and apply to a plug of silica but in your case you may find the amine complexes to the salts and you have trouble stripping it away but you wont know unless your try.

R.

[Yogi]

To workup a reaction containing x mmol of an agent such as Diisobutyl aluminum hydride (Dibal):

   1. Dilute with ether and cool to 0 oC
   2. Slowly add 0.04x mL water
   3. Add 0.04x mL 15 % aqueous sodium hydroxide
   4. Add 0.1x mL water
   5. Warm to RT and stir 15 min
   6. Add some anhydrous magnesium sulfate
   7. Stir 15 min and filter to remove salts

I got this procedure from this website: http://www.chem.rochester.edu/~nvd/index.html

I encourage people to check it out, it has a lot of useful information.

[movies]

I'd agree that the Fieser & Fieser type workup is probably the best.

Another option is to quench with EtOAc at 0 degrees and then add celite followed by sodium sulfate.  Warm to room temp., dilute with a bit more EA and filter through celite.

Finally, you can also quench with MeOH at -78 degrees, then add a bunch of sodium sulfate decahydrate and celite.  Warm and filter.

[playstyles]

Yogi,

What you posted is the workup for LAH, I have not seen one like this for a DIBAL hydride reduction.

What about the possibilities, as listed in some articles, like adding water or MeOH at -78C?

Can anyone comment on its ease of use?

[playstyles]

Yes also, MeOH addition is usually followed by stirring for hours with ROchelle,s salt (sodium potassium tartrate).. Which can be time consuming.

Does anyone have any good ideas for a -40 and -50 temperature bath respectively?

I find that dry ice with MeOH and water warms too quickly and wont stay at that temperature too long without being babysat.

Also people that posted above mentioned cooling to 0C does that mean you use Dibal above 0C? In what electrophillic reductions would that be performed?