Ene-Allenes: Access from Dialkynes by an Intramolecular anti-Carbopalladation Cascade.

Herein, an intramolecular palladium-catalyzed cascade reaction is reported consisting of both formal anti-carbopalladation and syn-carbopalladation of internal alkynes. This process leads to two new carbon-carbon bonds across the first double bond formed. The cascade is terminated by β-hydride elimination from the emerging vinyl Pd(II) complex. As a result, di-, tri-, and tetrasubstituted ene-allenes embedded in an oligo(hetero)cyclic ring system are synthesized in yields of up to 73%.