Although Serge Zaretsky defended his PhD thesis and left my lab almost 10 months ago, we still continue our fruitful cooperation. During his graduate stay, Serge was working in the area of macrocyclization reactions driven by amphoteric aziridine aldehydes. Mechanistically, this turned out to be a difficult problem. Right now, this process is straightforward and we make macrocycles rather efficiently, but the reaction itself is still an enigma. My other former PhD student, Ben Rotstein, once likened this macrocyclization to an onion. There are just so many layers and you don’t know where to stop. While we all know that at some point we must stop (hoping all of the findings are consistent with some logic), there is one extra experiment that throws it all down the drain. Convergence is not something we are inherently good at in science. And this is for the better.
In Serge’s case, we got to the bottom of some key selectivity controls. The imidoanhydride species you see below is the most important constituent of this process. We think that this intermediate accounts for the reactivity trends we observe. A paper describing this work just appeared in Chemical Science. I am providing a link as well as a photo of Serge (he’s wearing a light-green shirt) having Jägerbombs after his graduation. We sat down in our group room, raised our drinks, and sincerely thanked Serge for his contributions.