Palladium-Catalyzed\nStrain-Enabled [2π + 2σ]\nCycloadditions of Vinyl Bicyclo[1.1.0]butanes with Methyleneindolinones

A palladium-catalyzed\n[2π + 2σ] cycloaddition\nof vinyl\nbicyclo[1.1.0]butanes with methyleneindolinones has been developed.\nThe reaction enables the construction of spirobicyclo[2.1.1]hexanes\nbearing an all-carbon quaternary center in moderate to good yields\nwith excellent diastereoselectivities. This method features a broad\nsubstrate scope with good functional group compatibility. The practical\nutility of this protocol was further demonstrated by gram-scale synthesis\nand postsynthetic transformations of desired product.