text: Enantioselective cycloaddition of azomethine ylides using chiral catalysts was first described in a seminal work by Allway and Grigg in 1991. This powerful method was further developed by Jørgensen and Zhang. These reactions generally use zinc, silver, copper, nickel, and calcium complexes.
  Using chiral phosphine catalysts, enantiomerically pure spiroindolinones can be synthesized. The method described by Gong, et al. leads to an unexpected regiochemical outcome that does not follow electronic effects. This is attributed to favorable pi stacking with the catalyst.