Regioselective and diastereodivergent organocatalytic asymmetric vinylogous Michael addition

Abstract

Regioselective and diastereodivergent asymmetric vinylogous Michael addition (AVMA) between β-substituted-cyclohexenones and nitroalkenes via dienamine activation under complementary chiral aminocatalysts was reported. γ-Regioselective AVMA of β-alkyl-cyclohex-2-enones via a linear exo-dienamine mechanism and γ′-regioselective functionalization of β-substituted-cyclohex-3-enones via a cyclic extended endo-dienamine mechanism were reported in satisfactory yields with high enantio- and diastereoselectivities. DFT calculations reasonably explained that the diastereoselectivity of the reactions at the γ- and γ′-positions is achieved by regulating the orientation of the nitroalkenes through the hydrogen-bonding interaction and steric hindrance effect. Furthermore, the four different configurations of the γ- and γ′-adducts were diversified to the corresponding enantioenriched spirocyclic ketones and cis-2-decalones with multiple chiral centers.