[esona]

Hi everyone,

I'm working on the fluorination of sulfonamide-linked alcohols using reagents like DAST and Fluolead.

My target product is the mono-fluorinated derivative (–CH₂F):


However, I also observe the trifluorinated byproduct (–CF₃):


I’ve been trying to separate the two using flash column chromatography on silica, but they are very close in polarity  on TLC (Hexane/Ethyl Acetate)

Has anyone had success separating –CH₂F vs. –CF₃ derivatives?
Any tips on solvent systems or additives would be really appreciated!

Thanks in advance!

[rolnor]

Its easier and gives a purer product if you sulphonate the corresponding amines instead

https://www.sigmaaldrich.com/SE/en/product/aldrich/cds011723?msockid=3dfdc393625665b327c1d6cb63d96407

[MOTOBALL]

I worked in carbohydrate chemistry, and when I was setting up for column chromatography on silica gel I would use TLC to adjust the mobile phase.

If EtOAc/Hexane (3:1) gave two spots close together at Rf ~ 0.5 - 0.9, I would drop the EtOAc to say, about 1:3 and run TLC in this for 3-4 times (allow plate to air-dry between each run). This would usually just pull the product(s) above the base-line and give better resolution of similar products on the column.

Good luck, and if you go this route please let us know how it worked for you.