[Urbanium]

Is anyone aware of a TLC dip which does not oxidise the "oxidisable" spots on the plate (KMnO₄, Goofy etc.), but instead acts as a reducing agent?

[Dan]

Goofy

I had to google that. Where does the name come from? I've always known it as CAM...

I found a recipe for 0.1% morin in MeOH (source). Presumably morin is an antioxidant, so the mechanism would be reductive... I've never used it.

[Babcock_Hall]

What compound or class of compounds are you trying to visualize?

[Urbanium]

The compound has two alkyls and few of sulfurs and oxygens between, like an alternating ether-thioether system. For some reason I can't oxidise it, but since the whole compound is a dimer with an S-S bond in the middle, I was thinking of reductive cleavage on the TLC plate.

[Babcock_Hall]

Once reduced, you can use a TLC spray based on Ellman's reagent.  Thioethers?  IIRC we once tried a method that we found referenced in a paper coauthored by Isaac Asimov.  I think it used azide, but I don't believe that we had great success with it.

[kriggy]

The compound has two alkyls and few of sulfurs and oxygens between, like an alternating ether-thioether system. For some reason I can't oxidise it, but since the whole compound is a dimer with an S-S bond in the middle, I was thinking of reductive cleavage on the TLC plate.

Maybe hydrogen peroxide? we learned that thioethers can be easily oxidized to sulfoxides or sulfones

[Babcock_Hall]

G. E. Howard and J. Baldry, Analyst 94 July 1969, pp. 589-593
These authors use chloramine T for thioethers and perhaps disulfides.  I don't recall having tried this myself.  The azide method I mentioned used iodine, and it came from Chargaff's lab in 1948.  We did not have much luck with it, but we did not try very hard.

[Babcock_Hall]

Acta Chemica Scandinavica 1960 14:1980-1984.  Stig Akerfeldt used 1% CuCl₂ in 50% ethanol containing 5% ammonia as a spray reagent to produce black spots for cysteamine S-phosphate on paper.  It also reacts with thiophosphate, but I am not sure how other compounds would behave.

Erratum
In regards to my previous message, I had a look at the 1969 paper by Howard and Baldry.  They did not use chloramine T for TLC detection; it was a reagent.

[Babcock_Hall]

A test thioether stained nicely with basic permanganate.