The Cyano‐Diels–Alder Reaction: From Nitrile Activation to Functional Molecular Architectures

The cyano‐Diels–Alder (c‐DA) reaction represents an interesting yet underexplored variation of the classical DA reaction, hampered by the intrinsically poor dienophilic character of the nitrile group. In recent years, significant progress has been made in overcoming this limitation through rational activation strategies, including conjugation of the nitrile with strong electron‐withdrawing substituents, intramolecular preorganization, Lewis acid coordination and the use of highly electron‐deficient multicyano frameworks. This concept article highlights how these approaches have transformed the c‐DA reaction from a poorly explored transformation into a valuable synthetic tool for the preparation of N ‐heterocycles and structurally complex polycyclic architectures. Particular attention is devoted to multicyano systems such as tetracyanobutadiene‐ and tetracyanoquinodimethane‐derived scaffolds, in which cyano activation, molecular topology and cascade reactivity cooperate to unlock efficient intramolecular c‐DA cycloadditions, leading to multifunctional chromophores. Altogether, the evolution of the c‐DA reaction illustrates how a traditionally reluctant nitrile dienophile can be harnessed through molecular design to access increasingly sophisticated molecular architectures.