Cross-Coupling/Cyclization Reactions of Two Different Allenic Moieties

The allene moiety represents an excellent building block for allene cross‐coupling cyclization reactions, affording heterocyclic skeletons in a single step. This strategy is of particular interest when two different allene derivatives are involved in a series of metal‐catalyzed cross‐coupling heterocyclization processes. This Concept article is focused on the Pd‐catalyzed union of two different allenic moieties, with cyclization of at least one of them by intramolecular cyclometalation. These new, versatile, and highly effective transformations are complex multistep processes leading to potential privileged structures that could find wide applications in related medicinal chemistry. Simple and practical: The heterocyclization, palladium‐catalyzed cross‐coupling reaction of two different allene moieties (see scheme) is a selective and powerful method for the direct synthesis of functionalized heterocycles of biological interest, namely, butenolides, furanimines, and 2,5‐dihydrofuran derivatives.