Recent Advances in the Annulation of Benzofuran‐Derived Azadienes for the Synthesis of Benzofuran‐Containing Heterocycles

N , O ‐containing heterocycles are widely recognized for their importance in biologically active molecules, making the development of efficient and selective synthetic strategies for their construction a longstanding focus in modern organic chemistry. Among the various available building blocks, benzofuran‐derived azadienes (BDAs) have emerged as highly versatile synthons for the efficient assembly of benzofuran‐containing heterocycles through a broad range of annulation reactions. BDAs can operate flexibly as either four‐atom synthons in diverse [4 + n] annulation processes or as two‐atom synthons in [2 + n] annulations, thereby enabling the rapid generation of structurally complex molecular architectures. This review summarizes recent advances in both racemic and asymmetric transformations of BDAs, with an emphasis on their application in the synthesis of a wide array of benzofuran‐fused and spirocyclic heterocycles mediated by metal catalysis and organocatalysis.