Transformations of Strained Three‐Membered Rings a Common, Yet Overlooked, Motif in Heavy‐Atom Tunneling Reactions

Quantum mechanical tunneling has long been recognized as an important phenomenon when considering transformations dominated by a lightweight hydrogen atom. Tunneling of heavier atoms like carbon, initially dismissed as negligible, has seen a quickly increasing number of computationally predicted and/or experimentally confirmed examples over the last decade, thus highlighting its importance for a wide variety of reactions. However, no common structural motif has been pointed out within these seemingly unconnected examples, strongly limiting the predictability of the impact of heavy‐atom tunneling on a given reaction. This Concept article will provide this perspective and showcase how the recognition of the formation and cleavage of three‐membered rings as common motif can inform the prediction of and research into heavy‐atom tunneling reactions.