0
$\begingroup$

I am aware that esters can be selectively hydrolysed depending on the type of alkyl group present e.g. Me ester vs t-butyl ester, the latter is reactive to acidic conditions and not basic because of its inability to form tetrahedral intermediate. But what reagent could I use to carry out the following transformation?

enter image description here

I see it is the O-C bond that breaks, so it is acyl cleavage (Ac). Acidic conditions would destroy my Me ester as would basic, so how can I get around this? Could a big bulky base, say LDA, take it down a B(Ac)2 route (generate CO2?)

| improve this question | |
$\endgroup$
5
$\begingroup$

If you use methanol as a solvent and add a suitable base, you should end up with the correct product, since any MeOH attacking the protecting group you want to keep will simply re-form the methyl ester, whereas the acetate will cleave to give the unprotected alcohol.

You could potentially also achieve this using sodium methoxide/methanol to speed the reaction up, but standard potassium carbonate/methanol is usually just fine.

enter image description here

| improve this answer | |
$\endgroup$
  • $\begingroup$ this makes sense as it would reversibly add/leave. how does cleavage take place mechanistically? Is it attack of methanol at the carbonyl then leaving group is the "rest of the ester" $\endgroup$ – gamma1 May 27 '17 at 18:00
  • $\begingroup$ Pretty much. Standard addition elimination mechanism $\endgroup$ – NotEvans. May 27 '17 at 18:17
2
$\begingroup$

You could try refluxing in NaOMe/MeOH. The presence of methanol would preserve the methyl ester, while transesterification would produce methyl acetate as a by-product.

| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.