Palladium‐Catalyzed [2+1] Cycloadditions Affording Vinylidenecyclopropanes as Precursors of 7‐Membered Carbocycles

Abstract

Abstract Palladium(II) acetate in association with secondary phosphine oxides provides an efficient catalytic system for [2+1] cycloadditions starting from oxanorbornene derivatives and tertiary propargyl esters giving rise to vinylidenecyclopropanes. This reaction is specific to bidentate phosphinito–phosphinous acid ligands generated from secondary phosphine oxides. The [2+1] cycloaddition was found broad in scope with a high tolerance to various functional groups. Moreover, vinylidenecyclopropanes were straightforwardly converted into oxabicyclo[3.2.1]oct‐2‐ene derivatives through a palladium‐catalyzed ring‐expansion. Finally, the oxa bridge cleavage of oxatricyclic compounds yields functionalized 7‐membered carbocycles. magnified image