The central role of heterocycles in modern chemical synthesis cannot be overestimated. Last week, I had a chance to appreciate the role of some of the fathers of modern approaches to heterocycle use and construction. As part of a trip to Germany (superbly organized by Professor Herbert Mayr) I visited the Ludwigs Maximilian University in Munich. The highlight of this trip was a meeting with the two gentlemen featured on the picture below. On my right hand side is Professor Wolfgang Steglich, the discoverer of DMAP (among many other things), while on my left side is Professor Rolf Huisgen. As the founder of dipolar cycloaddition chemistry, Professor Huisgen needs no introduction and I really want to wish him a happy 96th birthday, which will be celebrated on June 13.
My host, Professor Mayr (a former PhD student of Huisgen), continues to push the boundaries of chemical reactivity. I already mentioned his work in the past and I am glad that he continues to educate the chemistry community on how one can predict selective reactions between various functional groups. With the help of my students, we will soon be collaborating with Professor Mayr to better understand the reactivity trends of our own molecules. The Mayr scale has served as the go-to tool in teaching organic reactivity. The following contribution features what I call “the real rule of 5” and I enjoy discussing it with my students.