Cinchona-based squaramide-catalysed cascade aza-Michael-Michael addition: enantioselective construction of functionalized spirooxindole tetrahydroquinolines.

An efficient enantioselective cascade aza-Michael-Michael addition reaction catalysed by a chiral bifunctional tertiary amine-squaramide catalyst has been developed. This cascade reaction proceeded well under mild conditions, furnishing highly functionalized spirooxindole tetrahydroquinolines with three contiguous stereocenters in excellent yields with excellent diastereoselectivities (>25:1 dr) and high enantioselectivities (up to 94% ee).