1 Introduction The Diels–Alder reaction [1] is a cornerstone in organic chemistry being of outstanding industrial importance for basic chemicals (such as production of cyclohexene from steam-cracker products ethylene and butadiene) [2], high relevance for life sciences molecules, with preferred formation from electron-deficient dienophiles and electron-rich dienes (Review: [3]; for selected conceptually novel applications of Diels–Alder reactions, see: [4-7]), and characterized by a reaction...
