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strange boc deprotection / carbamoyal chloride synthesis problem

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OrganicDan96:
i'm trying to make a carbamoyal chloride of pyrrolidine-2-nitrile, the literature synthesis involved deprotecting the commercially available boc pyrrolidine nitrile with TFA to give a TFA salt which can easily be dried, this is the treated with 2.1 equiv 2,6-lutidine and 0.4 equiv triphosgene, this however gave the triflouroacetamide not the carbamoyal chloride. so I decided to make the hydrochloride salt instead originally following a literature boc- deprotection procedure which used two phase conc.HCl/Et2O, this worked but the resulting salt was impossible to dry, so i moved on to a deprotection using 2M HCl in Et2O (idea being that no water is present), however it turns out some water was present in the HCl/ether and i could not dry the salt and it did not go to completion. I need  some ideas as how to deprotect the boc amine in strictly anhydrous conditions or dry the hygroscopic salt.

thanks in advance,
Dan

wildfyr:
You can dry any solid with a P2O5 setup. Are you familiar with it?

clarkstill:
You can remove Boc with ZnBr2 in DCM.

Why do you think changing from TFA to HCl salt will solve the problem with forming the trifluoroacetamide rather than the carbamoyl chloride? I can't see how it will affect that step. I know it isn't much fun, but you can phosgene in toluene from Aldrich, which might be a better way to go.

OrganicDan96:

--- Quote from: clarkstill on April 04, 2019, 03:28:49 AM ---You can remove Boc with ZnBr2 in DCM.

TFA to HCl salt will solve the problem with forming the trifluoroacetamide rather than the carbamoyl chloride?

--- End quote ---
I want the carbamoyal chloride, the triflouroacetamide forms by activation of the trofluoroacetate counter ion (maybe forming trifluoro acetyl chloride from phosgene) the hydrochloride salt obviously can't do this.

OrganicDan96:

--- Quote from: clarkstill on April 04, 2019, 03:28:49 AM ---You can remove Boc with ZnBr2 in DCM.


--- End quote ---

that could work

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