[nox]

See attached scheme below

I tried making the sulfone using the sulfonyl chloride instead of the sulfonyl fluoride as they did in the patent, all I ended up was 3 spots on TLC, 2 of them extremely faint, and one every strong baseline spot. After an aqueous workup all I fished out was 10% of that extremely polar stuff, and by NMR it looks pretty cruddy so I've no clue what it could be. Doesn't dissolve at all in chloroform, goes into DMSO with some difficulty, and apparently likes water a lot.

My question is, should I even bother retrying this reaction with the sulfonyl fluoride instead? I honestly can't see a huge difference in the reactivity between the two, but I'd like to think perhaps there's a reason why the patent authors took an extra step to make the sulfonyl fluoride (they gave the prep for that) rather than use the sulfonyl chloride directly.

If all else fails, I guess I could just do a C-S coupling followed by peroxide oxidation of the sulfide.

[Dan]

Fluorine and chlorine are very different beasts. The leaving group ability of fluoride is far less than chloride - so the sulfonyl chloride is going to be much more reactive, and from the sounds of it may be prone to side reactions. Personally, I would give the fluoride a shot - unless the coupling-oxidation route you mention is known and has a few advantages (shorter, cheaper, less toxic etc.).

[OC pro]

This will not work with sulfonyl chlorides! A quick look into literature should have shown that (I think you missed it?).
Arenesulfonyl fluorides and grignards give the desired sulfones in fair yields. You definitely have to make the fluoride. The method using KHF2 in water works usually fine.

I strongly recommend reading the seminal publication for arenesulfone synthesis: Frye et al. JOC 1994, 57 (2), 697–701.

[nox]

Yeah I was wondering why there were no lit preps on making sulfones from sulfonyl chlorides, I guess now I have my answer.

But I'm curious, what kinds of side rxns would the sulfonyl chloride undergo? I just find it odd that I did not obtain any of the expected product. Also judging by how incredibly polar the major product was, I have a sneaking suspicion the sulfonyl chloride somehow de-chlorinated to give the sulfinic acid. Which would explain why the yield was so crap even with repeated extractions, and that it refused to go into chloroform.

[Honclbrif]

I have a sneaking suspicion the sulfonyl chloride somehow de-chlorinated to give the sulfinic acid.

I've also had that happen when I attacked a sulfonyl chloride with an enolate. Wasn't what I intended to do at all, just happened to have a proton with an unexpectedly low pKa.

[nox]

Tried it with the sulfonyl fluoride -- spot to spot, quantitative yield, NMR of crude pristine so no column needed.

What a lovely Christmas present, I love sulfonyl fluorides now.  

Getting my hands on the sulfonyl fluoride was a bit of a pain though, since the patent procedure I used only gave 65% conversion. Re-subjecting the 65% stuff to patent conditions but with twice the xs of KF and 18-crown-6 gave full conversion overnight