Bad odor is often the biggest barrier between some interesting reactivity and scientists. Of course, toxicity is also a challenge, but lethal molecules can be tamed in trained hands. Odor, on the other hand, is pervasive. This tends to stop many reactions from reaching the mainstream of chemistry. It’s rather sad, especially with such versatile reagents as organosulfur compounds. We don’t even need to go that far: dirt cheap elemental sulfur is rich enough in what it can do for you.
This brings me to the main subject of tonight’s post: the Willgerodt-Kindler reaction, one of the more bizarre and ill-understood processes at the fringes of organic chemistry. Despite what’s written about this fascinating process, you won’t find a definitive account describing the mechanism of the reaction. Some hints do appear from time to time. Below you see the reaction itself on the left. In the box on the right I am presenting a curious result obtained by Hartung and colleagues (the reaction medium – Dimsulf – is awesome). This is considered to be as close as we get to isolating the relevant intermediate of the Willgerodt-Kindler reaction. All of this is rather confusing, but my friend Professor Carsten Bolm did a nice overview of the reaction not too long ago (the last link).
http://scripts.iucr.org/cgi-bin/paper?bx0590
http://pubs.rsc.org/en/Content/ArticleLanding/2013/CS/c3cs60154d