[Sulfinator]

Hello all, I have a question regarding removal of lutidine from a reaction. I am using 2,6-lutidine as a base in a sulfinylation of an alcohol and I would like to remove it by washing or chromatography.  At this point, I don't know enough about sulfinate esters to know whether or not they are labile during chromatography. In a test reaction with neopentyl alcohol, a sulfuric acid wash step removed the lutidine.  However, my alcohol has an acid-labile protecting group elsewhere in the molecule, so this step would not work.  When I have run sulfonylation reactions with triethylamine as a  base in the past, I have used bicarbonate washes to remove the excess triethylamine successfully.  However, bicarbonate did not remove the lutidine in our test reaction, based in H-1 NMR.  Someone suggested that a copper sulfate wash can remove pyridine, and that it might work with lutidine also. Does anyone have any suggestions as to the removal of this base? Any input is appreciated, thank you.

[movies]

I've heard that the copper sulfate wash works great, but I haven't actually done it myself.  Lots of people in my lab have used it with success though.

You might also try aqueous sodium citrate.  I have used that to remove triethylamine hydrochloride with great results.  I'm not certain that it would work with lutidine though.

[Babcock_Hall]

We are trying to find a way to remove collidine.  We used copper sulfate to remove lutidine one time many years ago, but I don't remember who gave us the idea.  We found one thread at Research Gate about using copper sulfate to remove pyridine, and they noted that there was a color change.  Does anyone have a good reference or some practical tips to share?
https://www.researchgate.net/post/What_is_best_method_to_remove_pyridine_from_a_reaction_mixture

[wildfyr]

I've had some general success with using copper to remove amines, especially pyridine. I think its worth just trying the wash in a scint vial with an aliquot amount and checking the purity by NMR.

[Babcock_Hall]

I did not see your comment until just now, but I think trying it on a small scale makes sense.  When my student tried it on the whole reaction, a precipitate formed.  I am not sure what precipitated out.

[wildfyr]

Just to be clear, by copper, I mean copper sulfate aqueous solution, not the Cu(0) metal 

[rolnor]

If the lutidine is free base, would not freeze-drying remove it? Not so high boilingpoint.

[Babcock_Hall]

For this reaction we used collidine, but perhaps if we run it again, we can substitute in lutidine.  Thank you; I would not have thought of freeze drying.

[Optimist]

In my opinion it CuSO4 will also work for  lutidine, Just try with small quantity before going on large scale.

[wildfyr]

I'm not 100% sure but I think CuSO4 works for amines generally... I feel like I got triethylamine off using it one time.