clemi2310 - 8-8-2016 at 07:29
Hello everyone,
I am encountering a serious issue regarding the hydrolysis of an hindered ester.
The initial reaction that works is the BOC substrate in NaOH 10N at 120°C under microwave (see picture), quite harsh conditions but I manage to get
the acid after 4 hours.
With the aim of simplifying my synthetic pathway, I wanted to hydrolyse in the same way the substrate already substituted (see picture second line).
The reaction occurs but do not go till completion... I don't know why there is such a change between the boc version and the aromatic one.;.
I also tried the methyl ester instead of the ethyl as it should be more reactive, but it remains the same.
I tried conditions of a paper involving LiCl in DMF (anhydrous hydrolysis) but it didn't work.
My options now, are try to displace the equilibrium, test for other conditions (I saw thins with Toluene at 150°C and KOH under microwaves, or tBuOK
in DMSO....)
I would like to know you suggestions if you can help me
Thanks by advance
Clémence
zed - 8-8-2016 at 13:32
Dunno. Might try KOH or LiOH.
Might also try a co-solvent. You would like to hydrolyse that ester. But, your first obstacle might be the water insolubility of your substrate.
It is probable someone here, knows a lot more about this, than I do.
[Edited on 8-8-2016 by zed]
Praxichys - 9-8-2016 at 05:22
You might try an appropriate phase transfer catalyst. I can't imagine this substance having appreciable solubility in 10N NaOH.
I would be worried about using tBuOK - you'd end up with a Williamson ether.
AvBaeyer - 9-8-2016 at 17:45
I suggest you try lithium hydroxide in THF with a small amount of water. This often works for hydrophobic esters such as yours. Heating under pressure
may be necessary if hydrolysis at reflux does not work.
AvB