Inverse Electron Demand HDA of 2-Alkenoyl N-Oxides

Significance

In related studies Evans and Jørgensen have reported that chiral BOX-Cu(II) complexes efficiently promote inverse electron demand HDA reactions of α,β-unsaturated acyl phosphonates and esters with electron-rich al­kenes. In the present work, the authors apply this system to related reactions of vinyl ethers and 2-alkenoylpyridine N-oxides to obtain dihydropyran derivates in excellent yields and enantioselectivities. Additionally, various vinyl ethers, N-vinyllactams, and vinylsulfides were compatible under the reaction conditions. Conducting the reaction at low temperatures (-20 to -40 ˚C) was crucial for obtaining high selectivities as higher temperatures resulted in a large diminution in ee values.