Enantioselective Michael Addition: An Experimental Introduction to Asymmetric Synthesis
We adapted a classical asymmetric Michael addition for a 1-day experimental session (6-8 hrs) for third or fourth-year undergraduate students. The experiment follows up three steps : synthesis of a chiral Lewis Acid, LiAl(BINOL)2, then its use as a catalyst in the Michael addition of diethyl malonate on cyclopentenone, followed by purification through column chromatography on silica gel. The desired product can be fully characterized by 1D and 2D NMR experiments and IR spectroscopy. The enantiomeric excess can be determined by polarimetry and 1H NMR using chiral lanthanide shift reagent Eu(hfc)3.