Diastereo- and Enantioselective Synthesis of Functionalized Cyclopentenes Containing a Quaternary Chiral Center via a Thiosquaramide-Catalyzed Cascade Michael–Henry Reaction

An efficient method for the highly diastereoselective
synthesis
of chiral quaternary center-containing cyclopentenes via a cinchona
alkaloid-derived thiosquaramide VIII-catalyzed tandem
Michael–Henry reaction of phenacylmalononitriles and nitroolefins
was deleveloped. Meanwhile, up to 98% of enantioselectivity was observed.
A mechanism involving thiosqaramide-catalyzed asymmetric Michael addition
and assisted E2 elimination was proposed based on experimental data
and preliminary theoretical analysis (Hartree–Fock calculations).