Synthesis of spirooxindoles by the catalytic tandem reaction of 2-arylidene-1,3-indanediones with 2-(2-oxoindolin-3-yl)malononitriles

A facile method has been developed for the synthesis of spirooxindoles bearing a 3-oxoisobenzofuran-1(3H)-ylidene motif. The Michael addition-triggered tandem cyclization reaction between 2-arylidene-1,3-indanediones and 2-(2-oxoindolin-3-yl)malononitriles catalyzed by K₂CO₃ afforded the spirooxindole products bearing a 3-oxoisobenzofuran-1(3H)-ylidene motif in good to high yields (up to 95%) with excellent diastereoselectivity (up to >20 : 1 dr). Meanwhile, the gram-scale preparation verified the practicality of this reaction.