Pd-catalyzed asymmetric (6+2) dipolar cyclization for medium-sized spirooxindoles†

Chiral spirooxindoles are privileged scaffolds in bioactive molecules, yet efficient strategies for their functionalization—especially for medium-sized spirocycles—remain scarce. We report a Pd-catalyzed asymmetric (6+2) dipolar cyclization between vinyloxetanes and 3-diazoquinoline-2,4-diones, which allows the synthesis of enantioenriched spirooxindoles with eight-membered lactones under mild conditions. This method provides 22 examples with high yields and enantioselectivities (up to 90% yield and 98% ee), facilitated by a tailored chiral phosphine ligand and in situ photogenerated ketene dipolarophiles.