December 11, 2019, 08:26:53 AM
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Topic: Deprotection of Boc in the presence of TBDPS  (Read 486 times)

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Offline OrganicDan96

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Deprotection of Boc in the presence of TBDPS
« on: July 24, 2019, 03:45:32 PM »
I am designing a synthesis which is a variant of an existing synthesis with an important difference. so I need an alcohol protecting group that is stable to deprotection of Boc (TFA) and the deprotection of a benzyl group (H2, Pd/C) so the best bet i could find is TBDPS which according to greens protecting groups is fairly stable to acid. so would TBDPS be stable to the deprotection of Boc?

any protecting group must come of in a very mild way with biproducts that are easy to separate.
« Last Edit: July 24, 2019, 04:33:47 PM by OrganicDan96 »

Offline rolnor

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Re: Deprotection of Boc in the presence of TBDPS
« Reply #1 on: July 24, 2019, 06:03:42 PM »
I think its OK if you monitor the reaction and neutralize as soon as the Boc is gone, with TFA this reaction is very fast.

Offline wildfyr

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Re: Deprotection of Boc in the presence of TBDPS
« Reply #2 on: July 24, 2019, 08:44:04 PM »

any protecting group must come of in a very mild way with biproducts that are easy to separate.

So we all wish

Offline rolnor

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Re: Deprotection of Boc in the presence of TBDPS
« Reply #3 on: July 25, 2019, 06:59:09 AM »
If you use TBAF to remove the silyl group the mixture becomes very basic, if you have problem with that you can use pyridine*HF but then you will have a little acidic conditions.

Offline wildfyr

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Re: Deprotection of Boc in the presence of TBDPS
« Reply #4 on: July 25, 2019, 09:06:59 AM »
I think the silyl will come off in almost any fluoride conditions. Can likely use use MeCN and KF, which is about neutral.

Offline rolnor

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Re: Deprotection of Boc in the presence of TBDPS
« Reply #5 on: July 25, 2019, 10:05:03 AM »
When you cleave the Si-OR bond with fluoride a RO- ion is created, this is basic. Normaly there is some water in TBAF so the RO- is protonated and OH- is formed. It is probably possible to have neutral conditions if a apropriate proton source is present.

Offline OrganicDan96

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Re: Deprotection of Boc in the presence of TBDPS
« Reply #6 on: July 25, 2019, 01:41:09 PM »
i think it will be ok, my molecule doesn't contain any particularly sensitive functional groups but it is right at the end of a long synthesis so material will be valuable.

Offline wildfyr

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Re: Deprotection of Boc in the presence of TBDPS
« Reply #7 on: July 25, 2019, 05:41:42 PM »
What about KFHF then?

Offline rolnor

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Re: Deprotection of Boc in the presence of TBDPS
« Reply #8 on: July 25, 2019, 07:31:05 PM »
Yes, I think that would work, maybe together with TBAF?

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