Enantioselective [3+2] Cycloaddition of Azomethine Ylides and α,β-Unsaturated Aldehydes

Significance

Vicario and co-workers present the first organocatalytic enantioselective [3+2] cycloaddition between α,β-unsaturated aldehydes and azomethine ylides. In all the reactions only the single endo isomer 3 was obtained by using commercially available α,α-diphenylprolinol 4 as a ca­talyst. The addition of water increased the yield significantly. This method can deal with linear and branched aliphatic aldehydes as well as with aldehydes containing an aryl or heteroaryl group in the β-position. However, two electron-withdrawing groups on imine 1 are necessary to observe the cycloaddition product 3. The unstable aldehyde products were reduced to the corresponding alcohols.