Highly Enantioselective δ-protonation And Formal [3+3] Annulation Promoted By N-Heterocyclic Carbene

For a long time,the asymmetric construction of the quaternary carbon center and the remote asymmetric hydrogenation reaction have been the research hotspots and difficulties in the field of organic synthesis.In this research work,it was found that when nitrogen heterocyclic carbene interacts with α(11)β-γ(11)δ-unsaturated aldehyde,the reaction system can be controlled by adding an oxidant,and two different reaction results can be obtained.In the presence of oxidant,nitrogen heterocyclic carbene catalyzes α(11)β-γ(11)δ-unsaturated aldehyde to obtain α(11)β-γ(11)δ-unsaturated acylazole intermediate,in which the carbonyl carbons of theb-position and the δ-position are electrophilic.In this research work,the chemoselective control of the α(11)β-γ(11)δ-unsaturated aldehyde β-site can be well achieved,and the enamine-like[3+3] cyclization reaction can be achieved.Efficient asymmetric construction of dihydropyridone compounds with quaternary carbon center(the ee value of all products is above 99%);When no oxidant is added to the reaction system,α(11)β-γ(11)δ-unsaturated aldehyde interacts with nitrogen heterocyclic carbene to form a homoenol diene intermediate,the carbonyl carbon β-position and δ-position of the intermediate both showed nucleophilicity.This research work shows that its δ-position can capture a proton preferentially,thus realizing the control of the remote asymmetric hydrogenation of its δ-position,and at the same time,it also realizes the high efficiency of the dihydropyridone compound containing two chiral centers.Symmetric construction(the ee value of all products is above 95%).