Organocatalyzed cascade aza-Michael/Michael addition for the asymmetric construction of highly functionalized spiropyrazolone tetrahydroquinolines

An organocatalyzed diastereo- and enantioselective cascade aza-Michael/Michael addition of 2-tosylaminoenones to unsaturated pyrazolones has been developed to afford novel chiral spiropyrazolone tetrahydroquinolines containing three contiguous stereocenters. This cascade reaction proceeded well with 2 mol% chiral bifunctional tertiary amine squaramide catalyst to give the desired products in excellent yields (up to 99%) with excellent diastereoselectivity (up to > 25:1 diastereomeric ratio) and high enantioselectivity (up to 91% enantiomeric excess).