Cross-Coupling of Cyclobutenone N-Tosylhydrazones with Organohalides: Access to Conjugated Enynes and Enallenes via a Strained Allylpalladium Intermediate

A palladium-catalyzed cross-coupling reaction of cyclobutenone N-tosylhadrazones with organohalides is disclosed. The protocol involves the generation of a strained allylpalladium intermediate from readily available starting materials through palladium carbene migratory insertion, which undergoes electrocyclic ring opening and β-hydride elimination for the production of conjugated enynes and enallenes. The broad substrate scope, good to excellent yields, and tunable product diversity make the protocol potentially useful in organic synthesis.