October 18, 2021, 02:13:11 PM
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Topic: DiBAL-H wont reduce Ethylester to ALdehyde  (Read 475 times)

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Offline MuscarineChloride

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DiBAL-H wont reduce Ethylester to ALdehyde
« on: April 21, 2021, 05:21:55 AM »
Hello everyone,

I habe been trying to reproduce a reduction reaction of an ethylester (Benzyl-Ethyllactate) to an aldehyde using DiBAL-H in Ethylether at -78 °C in Dry solvents but have been getting basically no product, the solvents an the glasware are dry and the  DiBAL-H is new. Also no alcohol is present...

Any suggestions why my reduction isnt working? The Literature reports up to 80-90 % isolated yield for the same reaction.

Offline rolnor

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Re: DiBAL-H wont reduce Ethylester to ALdehyde
« Reply #1 on: April 21, 2021, 05:54:18 AM »
Is diethyl ether the solvent used in the reference?

Offline MuscarineChloride

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Re: DiBAL-H wont reduce Ethylester to ALdehyde
« Reply #2 on: April 21, 2021, 06:51:45 AM »
yes diethylether is also the solvent in the refrence

Offline rolnor

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Re: DiBAL-H wont reduce Ethylester to ALdehyde
« Reply #3 on: April 21, 2021, 07:37:50 AM »
Do you have NMR of the starting ester?
Do you monitor the reaction in some way, TLC?

Offline Babcock_Hall

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Re: DiBAL-H wont reduce Ethylester to ALdehyde
« Reply #4 on: April 21, 2021, 04:20:20 PM »
How dry is your starting material?

Offline MuscarineChloride

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Re: DiBAL-H wont reduce Ethylester to ALdehyde
« Reply #5 on: April 22, 2021, 04:08:00 AM »
Yes i have a NMR of the startung ester, it fits the refrence.

I can monitor the reaction by TLC an massspec.

The starting material should be dry, it is dried after the extraction with Na2SO4 and then purifyed on a sillica column, I will dry it a second time and give it an noter try!

Offline rolnor

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Re: DiBAL-H wont reduce Ethylester to ALdehyde
« Reply #6 on: April 22, 2021, 04:16:07 AM »
How does it look on MS?

Offline Babcock_Hall

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Re: DiBAL-H wont reduce Ethylester to ALdehyde
« Reply #7 on: April 22, 2021, 10:16:26 AM »
There are other more experienced synthetic chemists here than I am.  However, I will share my thoughts.  When I first started to use Dibal-H to attempt the reduction of a Weinreb amide, we obtained poor results.  Much later and with a different batch of Dibal-H, we obtained better yield.  It might or might not have been the Dibal-H itself; it could easily have been other aspects of our technique.

Offline wildfyr

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Re: DiBAL-H wont reduce Ethylester to ALdehyde
« Reply #8 on: April 27, 2021, 09:15:32 PM »
Maybe give it a little extra ass kicking by doing at higher temp?

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