Azomethine Ylide Cycloadditions with ThioClickFerrophos Ligands

Significance

Chiral pyrrolidines play an important role as synthetic intermediates and organocatalysts. These heterocycles can be accessed rapidly by a 1,3-dipolar cycloaddition between azomethine ylides and electron-deficient alkenes, such as unsaturated esters, vinyl sulfones, and ­nitroalkenes. In addition to enantioselectivity, the control of endo versus exo selectivity is crucial. Utilizing their previously prepared ThioClickFerrophos ligands (M. Kato et al. Eur. J. Org. Chem. 2009, 5232), the authors have developed the first endo-selective dipolar cycloaddition between acyclic α,β-unsaturated ketones and azomethine ylides.