The bifunctional quinine-catalyzed stepwise (3 + 2) cycloaddition for the enantioselective construction of spirooxindole-fused cyclopenta[c] chromen-4-ones is developed. The reactions of 3homoacylcoumarins and alkylidene oxindole electrophiles generate aforementioned spirooxindolechromenone adducts bearing five contiguous stereocenters, of which one is the spiro all-carbon quaternary stereocenter in high yields (up to 99%) with excellent stereoselectivities (up to > 20:1 dr and 99% ee). This methodology was investigated for three different alkylidene oxindole electrophiles and could also be practically demonstrated on a gram scale. Mechanistic investigations revealed that the (3 + 2) cycloaddition for the enantioselective synthesis of spirooxindole-fused cyclopenta[c]chromen-4-ones is proceeding via a stepwise reaction pathway.

A stereoselective concerted (3+2) cycloaddition is demonstrated from 3-homoacyl coumarins and alkylidene indandiones, resulting in fused spirocyclopentanes bearing four contiguous stereocenters.

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