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Topic: Deprotecting heterocyclic OTBDMS groups  (Read 760 times)

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Offline Babcock_Hall

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Deprotecting heterocyclic OTBDMS groups
« on: September 08, 2023, 08:42:37 AM »
I am planning a three step synthesis, the last step of which is the removal of the TBDMS group from an oxygen at the 5-position of a pyridine (pKa ~ 7). There is a vinyl sulfone group on the ring. Regarding the last step, my searches have not turned up much that is similar (I did find a few references for the protection step). I foresee using TBAF or another source of fluoride ion. My concerns are how to protonate the oxygen given that it is not very basic, and how to remove TBA and any remaining fluoride ions. One possibility is an aqueous wash with citric acid.

We have deprotected TBDMS with TBAF previously and not seen attack on the vinyl sulfone (TFA is not a problem, either)  When I posted this a couple of weeks ago at a different site, some good suggestions came up.  These included using TFA, TBAF with ammonium chloride work-up, CsF, and TetraButylAmmonium difluoroTriphenylsilicate.  I like the TFA idea, but I am not sure whether I should use a stoichiometric amount or an excess.  My plan is to do the first two steps, then try a deprotection on a small portion of this intermediate before committing the whole amount.
The lower pKa of this oxygen makes this situation somewhat different from our previous deprotections.
« Last Edit: September 08, 2023, 11:27:30 AM by Babcock_Hall »

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