Ligand-Controlled, Palladium-Catalyzed Asymmetric [4+4] and [2+4] Cycloadditions.

Ligand-controlled, palladium-catalyzed asymmetric [4+4] and [2+4] cycloaddition reactions of benzofuran-derived azadienes have been developed. Taking advantage of chiral P,N-ligand (S,Rp)-PPFA, we obtained a variety of benzofuro[2,3-c][1,5] oxazocines in good yields with excellent enantioselectivities via [4+4] cycloaddition reactions. Employing chiral P,P-ligand (S)-Cl-MeO-BIPHEP, the chemo- and regioselectivities were switched to synthesize tetrahydropyran-fused spirocyclic compounds in good efficiency via [2+4] cycloaddition reactions.