Construction of Eight-Membered Carbocycles by Palladium-Catalyzed [4 + 4] Cycloaddition of Vinylallenes

All articles of this category A palladium-catalyzed [4 + 4] cycloaddition reaction is described. A vinylallene having a pendant phenyl or vinyl substituent was treated with a catalytic amount of a palladium(O) complex to afford a symmetrical eight-membered carbocycle. The extended conjugation of the diene unit of an intermediate with the pendant unsaturated substituent is important for the [4 + 4] cycloaddition to occur. [4 + 4] cycloaddition - carbocycles - eight-membered ring - palladium - vinylallenes