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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Monoamine on March 21, 2021, 05:45:00 PM

Title: Amine protecting groups
Post by: Monoamine on March 21, 2021, 05:45:00 PM

Hi, so I have a compound which contains both OH and tertiary amine. Basically I am hoping to homologate the OH to a methoxy group by a Williamson ether synthesis, The problem is that this would also alkylate the amine, producing ammonium cations. Naturally I would prefer to avoid this

I attached a schematic with the proposed synthesis. If anyone would be willing to share what the right protective group mighty be here, and how the are added and removed again. I would be very grateful to know.

Cheers.

Ps: Suppose you want to go the other way around, and cleave the methoxy into a OH group. Could you apply the same procedure, where instead you use HBr to cleave the ether? (again by protecting the amine?

Title: Re: Amine protecting groups
Post by: chenbeier on March 21, 2021, 07:26:16 PM

Why not use the opposit. Use instead of the Aminephenol the Bromine compound and alkylate with Methylate sodium CH₃O- Na⁺
Or reduce he acetic ester of the Aminephenol by  with Triethylsilan Bor triflouride ether

Title: Re: Amine protecting groups
Post by: Babcock_Hall on March 22, 2021, 02:11:25 PM

Can you think of any protecting groups?

Title: Re: Amine protecting groups
Post by: wildfyr on March 22, 2021, 08:36:38 PM

Honestly, methyl iodide, methylate both spots, then in the presence of a decent nucleophile and a little heat, the desired molecule is basically a leaving group.

For instance, if you stir the dimethylated compound with a large excess of KCl, the chloride will attack a methyl on the amine via SN2 and you'll produce some methyl chloride and the desired product.