ok, let's do an _Organic Syntheses_ roulette
and the number is...818
I had to go to the third hit to find one that I don't remember doing some earlier time, haha
well it's a curious one. conversion of a phenol to a arylsulfonyl chloride
http://orgsyn.org/demo.aspx?prep=v94p0198
in this case the starting phenol is 4-cyanoguaiacol, the monomethyl ether of catechol only with a -CN group stuck para to the phenolic -OH
the -OH is first converted to -SH through a curious rearrangement, then oxidized to -SO₂Cl
it's the phenol to thiophenol conversion that's the really fascinating step here, because that's not an ordinary sort of aromatic substitution. I think that it can be done with brute-force conditions on simple substrates: one obtains thiophenol from phenol by distilling with phosphorus(V) sulfide, I believe, and the yield is probably low (and the reaction smelly and dangerous)
but here, the phenol is converted to a dimethylthiocarbamate ester with dimethylthiocarbamoyl chloride (cont'd)
well that's a fun one. looks like they're doing this all under nitrogen. probably just as well; some of the intermediates in this whole process must reek like nobody's business. plain unsubstituted thiophenol is famously stinky, being compared to the odor of burning tires, only...stronger. guessing that thiophenol is formed from vulcanized rubbers in combustion
(cont'd) and this ester, on prolonged heating with methanolic potassium hydroxide, rearranges and hydrolyzes to the thiophenol without, somewhat to my surprise, hydrolyzing the cyano group. this reaction has a name, the Newman-Kwart reaction: https://en.wikipedia.org/wiki/Newman%E2%80%93Kwart_rearrangement
then mild oxidation of the thiophenol with 30% hydrogen peroxide and anhydrous zirconium (??) chloride in acetonitrile yields the sulfonyl chloride. I believe there are other protocols for this