“…For more than half a century, pericyclic reactions—reactions that proceed via a single, concerted transition state allowing a cyclic overlap of π and/or σ orbitals—have played a central role in advancing our fundamental understanding of cycloadditions, 1 sigmatropic shifts, 2 group transfer reactions, 2 electrocyclization, 3 and cheletropic reactions. 4,5 The mechanistical understanding of pericyclic reactions has impacted electronic structure and chemical bonding theory 2 as well as preparative organic chemistry on the industrial scale (Scheme 1).…”