Inverse-Electron-Demand Diels-Alder Reactions of N-(Heteroarylsulfonyl)-1-aza-1,3-dienes Catalyzed by Chiral Lewis Acids

摘要

The feasibility of using chiral Lewis acids as catalysts to promote the inverse-electron-demand Diels-Alder reactions of 1-azadienes with vinyl ethers has been demonstrated. Two catalyst systems were identified for this reaction, both relying on the presence of a coordinating 2-pyridylsulfonyl or 8-quinolylsulfonyl group at the imine nitrogen of the 1-azadiene. The combination of a 8-quinolylsulfonyl moiety and nickel(II)/DBFOX-Ph proved to be highly efficient, allowing the synthesis of substituted piperidine derivatives in good yields, excellent endo selectivity, and enantio-selectivities typically in the range of 77 to 92% ee.