Asymmetric synthesis of poly-substituted spirocyclohexane oxindole via a squaramide catalyzed cascade Michael-Michael-aldol sequence

A squaramide-catalyzed Michael-Michael-aldol cascade sequence of three readily accessible substrates (1,3-dicarbonyl compound, nitroalkene and methyleneindolinone) was developed. The reactions led to a series of enantioenriched spirocyclohexane oxindoles bearing six contiguous stereocenters in good yields (up to 85%) and with excellent stereoselectivities (>20 : 1 dr, >99% ee).