The Diels–Alder (DA) cycloaddition reaction has the ability to significantly increase molecular complexity regioselectively and stereospecifically in a single synthetic step. In this review it is discussed how the activation strain model of chemical reactivity reveals the physical factors that determine the course of Diels–Alder reactivity using recent, representative examples that cover a wide range of issues, such as the “endo-rule”, reactivity trends emerging from systematic variation in the reactants′ strain, and cycloaddition reactions involving relevant species in materials science (i.e., fullerenes, polycyclic aromatic hy
drocarbons and nanotubes). More information can be found in the Focus Review by
Fern&
aacute;ndez and Bickelhaupt on
page 3297 in Issue 23, 2016 (DOI:
10.1002/asia.201601203).