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Topic: From TFA salt to HCl salt  (Read 3751 times)

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Offline Nescafe

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From TFA salt to HCl salt
« on: April 13, 2015, 01:19:23 PM »
Hi all,

I currently have my product stirring in water and I am sure my free amine is probably coordinated to TFA. I was wondering, what is the best way to make the HCl salt and crash my stuff out? I am planning to evaporate the water (Product is very soluble so work up will be a headache), the reconstitute in 4.0M HCl dioxane and then crash the salt out?

Any suggestions? Unfortunately the need for water to make the compound seems to be necessary so I can not avoid having it there.

Thanks,

Nescafe. 

Offline TheUnassuming

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Re: From TFA salt to HCl salt
« Reply #1 on: April 13, 2015, 02:29:11 PM »
Is the freebase soluble in organics? 
Typically to exchange ions/make the HCl salt I make the freebase, extract the amine with organic from the aqueous layer, then bubble in HCl and filter off my product as the HCl salt. 
When in doubt, avoid the Stille coupling.

Offline Nescafe

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Re: From TFA salt to HCl salt
« Reply #2 on: April 14, 2015, 09:12:53 AM »
I would like to try this, I am curious, how do you bubble in HCl gas?

Offline TheUnassuming

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Re: From TFA salt to HCl salt
« Reply #3 on: April 14, 2015, 09:47:58 AM »
The best way is with a tank of HCl gas.
You can generate HCl gas on demand in smaller amounts by dripping conc. HCl into conc. sulfuric acid or by dripping conc. HCl onto NaCl as well.  The gas produced isn't "dry" but you can bubble the gas through sulfuric acid first to help dry it out.
When in doubt, avoid the Stille coupling.

Offline tomek

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Re: From TFA salt to HCl salt
« Reply #4 on: April 15, 2015, 08:41:48 AM »
I highly recommend using anhydrous CaCl2 and concentrated HCl. HCl produced this way is dry enough for many purposes. I usually do it in a suction flask which is stoppered and side neck is connected through tubing to a Pasteur pipette (this can clog sometimes at the tip so it might be a good idea to chop it off first). I swirl the flask in one hand and hold the pipette in the other hand dipping it in ethereal solution of amine. Here's a paper describing this: http://pubs.acs.org/doi/abs/10.1021/ed072p1139

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