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

Pd⁰-catalyzed [3+2] cycloaddition reaction between spirovinylcyclopropyl-2-oxindole and coumarin/bioisosteres is demonstrated. The simple combination of bpy/EtOH differentially influenced the yield up to 97% and diastereoselectivity up to > 99:1 of the target 3-spirocyclopentane-2-oxidole scaffolds. The scale up reaction, synthetic transformations, and asymmetric annulation reactions with BiOx ligand unfold the limitations of this strategy.

Abstract

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.

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