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Topic: diazotation in non aquaeous solvents?  (Read 5153 times)

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Offline kriggy

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diazotation in non aquaeous solvents?
« on: April 25, 2015, 06:53:55 AM »
Hi there, Im doing an reaction sequence of diazotation and then forming diazosulfonate  (is it called that way?) R-N=N-SO3- using Na2SO3. The problem is that my starting material is very insoluble in water so the reaction doesnt proceed or I get only low yields with recovery of starting material (in the same mixture so further purification is needed).
Ive tried dissolving my SM in CH3CN but after adding HCl it precipitated again :/
Is something like DMSO usable for diazotations? Im not sure but I think that most organic solvents will not dissolve NaNO2 and / or Na2SO3 that is used after the diazotation.

Thanks for help

Offline opsomath

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Re: diazotation in non aquaeous solvents?
« Reply #1 on: April 25, 2015, 08:52:33 AM »
I often use acetic acid as the solvent for the organic compound. Here's an example...we should have a Synthetic Page up for this sort of thing soon. It's ok to have some precipitate, the reaction is often a bit slushy.

https://docs.google.com/document/d/1eRmpeFrQAkupuAXPCjaVanfR6WKAJlrs2IWzKGZ0hVE/edit?usp=sharing

Offline Dan

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Re: diazotation in non aquaeous solvents?
« Reply #2 on: April 25, 2015, 08:55:08 AM »
What about a mixture of water and MeCN?

Can you use tButyl nitrite instead of HCl/NaNO2 for the diazotization? I've used that before for Sandmeyer reactions in the past.
My research: Google Scholar and Researchgate

Offline pgk

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Re: diazotation in non aquaeous solvents?
« Reply #3 on: April 25, 2015, 12:19:13 PM »
1). SANDMEYER TYPE REACTION IN DIMETHYL SULFOXIDE
Organic Preparations and Procedures, 1(4], 221-224, (1969)
http://www.tandfonline.com/doi/abs/10.1080/00304946909458386?journalCode=uopp19#
2). What about a mixture of water and DMSO?

Offline kriggy

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Re: diazotation in non aquaeous solvents?
« Reply #4 on: April 25, 2015, 05:02:25 PM »
Opsomath: I was thinking about it but sodium sulfite is not stable in acidic enviroment so I would need to use more molar amounts of sulfite thatn acetic acid and that would be huge amounts. It might be worth trying. Im following published procedure and I get some precipitate when replicating their work from ARKIVOC 2011 (ii) 127-136 bunt im trying to make a compound 3 (and then 4) where R=Cl.

Dan: I tried mixture (to be exact, dissolve in MeCN and then add water) but the SM precipitated anyway. I dont have my lab notebook with me but as far as I remember, the MeCN and water mixture gave me about 20% conversion and 5% other impurities, the rest is starting material so it might be way to go but I have no idea how to further improve it. I didnt try tButylNitrite, Im not sure if we have it in a lab but thats good idea. Is it soluble in organic solvents?

pgk: thans for article, I´ll read it as soon as I can

Offline Dan

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Re: diazotation in non aquaeous solvents?
« Reply #5 on: April 26, 2015, 08:53:07 AM »
Yes tBu nitrite is organic soluble (and presumably insoluble in water). I used it for some Sandmeyer reactions in MeCN a while back. It might be a strategy worth investigating but I don't know if it will necessarily transfer to your reaction.
My research: Google Scholar and Researchgate

Offline kriggy

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Re: diazotation in non aquaeous solvents?
« Reply #6 on: April 26, 2015, 01:05:29 PM »
Thanks, I will look into this option :)


Offline opsomath

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Re: diazotation in non aquaeous solvents?
« Reply #7 on: April 26, 2015, 09:49:56 PM »
There's also nitrosonium tetrafluoroborate, which AFAIK can be used directly in some organic solvents. It's commercially available but has to be handled under nitrogen (I used a glove box). I don't have a prep on-hand though.

It has the advantage that it comes with a counterion included, so that you don't have to add BF3 or anything which could presumably screw with your sulfite nucleophile.

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