This report presents a structure-guided approach for the optimization of VANOL-derived imidodiphosphorimidates as catalysts for the halonium-ion-induced spiroketalization reaction. Fine tuning of the catalyst active site, alongside enhanced acidity, were required to achieve high catalytic activity for the spiroketalization reaction. A wide range of substrates were well tolerated yielding halogenated spiroketals in high yields, diastereoselectivities, and enantioselectivities.