Organocatalytic Asymmetric Formal [4+2] Cycloaddition for the Synthesis of Spiro[4-cyclohexanone-1,3′-oxindoline] Derivatives in High Optical Purity

A bifunctional organocatalytic asymmetric formal [4 + 2] cycloaddition reaction of Nazarov reagents and methyleneindolinones afforded spiro[4-cyclohexanone-1,3'-oxindoline] derivatives with excellent enantioselectivity (up to 98% ee).