I think we all know about the significance of triazoles, which are readily accessible via [3+2] dipolar cycloaddition between organic azides and variously substituted alkynes. These aromatic heterocycles have found a myriad of applications, immortalized in what we now know as the click chemistry. Are there any 6-membered analogs derived from azides? This is the question I asked myself earlier today. These molecules would correspond to 1,2,3-triazines. As it turns out, there is a pretty nice method by which organic azides produce this sort of heterocycle. Below you see an example that involves triphenylphosphine that acts upon the molecule of an azido ketone. The role of triphenylphosphine in this Staudinger-like reaction is to “mop up” an oxygen atom that is produced upon attack of the terminal azide nitrogen at the carbonyl carbon. In this process, the organic azide acts as a nucleophile. The other notable case where an azide partakes in a polar mechanism is the so-called Aube-Schmidt process, although two nitrogen atoms are ultimately extruded as gas in that sequence. In the triazine case below, all nitrogen atoms stay put. It is not easy to see a concerted cycloaddition reaction that would deliver a 1,2,3-triazine from the corresponding azide, which is why I really like the condensation route shown.