Several η2-coordinated anisole complexes were treated with various Michael acceptors in thepresence of a Lewis or Brønsted acid to generate stable 4H-anisolium complexes. These reactions werefound to proceed with high stereochemical control with predictable outcomes, provided that the moderateacid (NH2Ph2)OTf was used and the complex was dissolved in an acidic solution. The stereochemistry isshown to originate from an unexpectedly high preference for one coordination diastereomer of the anisolecomplex in the solid state and a Diels−Alder like transition state for the Michael reaction.