Palladium-Catalyzed Formal [3+2] Cycloadditions to Access Spirocyclopentane-2-oxindole Fused Chromanones, Quinolinones, and Thiochromones.

Pd0-catalyzed straight forward [3+2] cycloaddition reaction between spirovinylcyclopropyl-2-oxindole and coumarin/bioisosteres is demonstrated. The resultant products spirooxindolyl-cyclopentane[c]chromanones and structural analogues are obtained in up to 97% yields and > 99:1 dr. The target spirooxindole-cyclopentane architectures with four contiguous stereocenters with high diastereocontrol is differentially influenced by inexpensive 2,2'-bipyridyl ligand and greener solvent EtOH. The resultant functionalized spirooxindole-cyclopentane[c]chromanone and analogues are featured in natural and bioactive molecules, which serves to bridge the ambition of synthetic and medicinal endeavors. Broad substrate scope, scale-up, synthetic transformations, and asymmetric annulation reactions with BiOx ligand unfold the limitations of this strategy.