I have not tried this new reaction out, but it could be a real convenience, in several ways, for synthetic organic chemists. The authors, from Texas A&M, had previously reported an air-driven catalytic route to iodine (III) oxidants, and now they extend that work all the way up to iodine (V). The key is generation of an iodine (III) species that then disproportionates, sending some of it back down and some of it up to the +5 oxidation state, with the whole process driven by stirring in air. That may not make your pulse run any faster if you’re not an organic chemist, but many bench chemists will read that and say “Hey, does this mean that they have a catalytic Dess-Martin reagent?”
Well, they might. A whole range of oxidations are reported, and the reactions are characteristic of what you’d get with the actual Dess-Martin. Unfortunately, I don’t see the transformation I always used to break out that reagent for – trifluoromethyl secondary alcohol to trifluoromethyl ketone. You can tell that I worked on protease inhibitors for a while – that group is a classic serine protease inhibitor warhead, since the electrophilic ketone would rather be a ketal or hemiketal, all things considered, and if you stick it down into an active site it’ll tie up the serine residue for quite a while. At any rate, Dess-Martin is in many cases the sovereign remedy for that oxidation, and it would be good to see if this system can do it as well.
Why does one care? Well, the Dess-Martin reagent is quite useful (it’ll do oxidations on sensitive frameworks that other reagents will tear up), but it’s a problematic beast. It has gone in and out of commercial availability over the years, because an intermediate in its preparation is most definitely explosive if mishandled. I’ve made the stuff myself (back when I was making those trifluoromethyl ketones), and I did not enjoy the process. Particularly since (at that stage in the development of the synthetic route to the reagent) the last step tended to just up and fail on you, which meant that you had passed through the Valley of the Explosive Intermediate only to have all your effort for naught. I went through that, too. Improved routes have been developed, but no one does even those cheerfully.
And I have seen an explosion during the preparation, some years ago in a nearby lab, and it’s a very fortunate thing that no one was injured. There was plenty of shattered Pyrex and plenty of smoke hanging in the air, for sure. The problem is that when people make the stuff, they generally make a good-sized batch so they never have to do it again, so the bang is correspondingly bigger when things go wrong. Mind you, I had a 100g commercial bottle of the stuff right next door in my freezer, so these guys didn’t even have to be making the reagent in the first place: always check the compound inventory system, folks.
That happens less often these days. The new routes really are better, which has allowed the reagent to become an article of commerce again (I see that Sigma-Aldrich lists up to 250g bottles, albeit for nearly $2000) but the fact remains that the final reagent itself is also a rather energetic material. It would definitely be nicer if it appeared only catalytically, a statement that probably applies to all these high-oxidation-state iodine reagents. And if you can run that catalytic cycle off ambient oxygen, so much the better. I hope that this paper does the trick!