Highly Enantioselective Michael Addition of Malonate Derivatives to Enones Catalyzed by an N,N′-Dioxide-Scandium(III) Complex

A highly enantioselective Michael addition of malonate derivatives to chalcone derivatives catalyzed by L-Ramipril acid derived N,N'-dioxide-scandium (III) complex was reported. The experiment included use of L-Ramipril acid derived N,N'-dioxide L1-nickle(II) complex to catalyze the asymmetric Michael addition of diethyl malonate to chalcone in EtOH at 35°C. The results show that 4 Å molecular sieves when added as additives result in an improved reactivity and a 95% yield without loss of enantioselectivity. Diisopropyl malonate is found to be an excellent Michael donor than the reaction accomplished in 15hr in 98% yield with 99% ee. The results also show that the electronic nature or the position of the substituents at the aromatic rings of R2 or 3 has little influence on the enantioselectivity.