Stereoselectivity of Asymmetric Michael Addition Reactions Controlled by Chiral Auxiliary

Chiral auxiliary controlled asymmetric reaction is one of the main methods in asymmetric synthesis. Under the control of the various chiral Evans auxiliaries, different Grignard reagents were added asymmetrically to the substrates I by the way of 1,4-Michael addition reaction and a series of Michael addition products 2a similar to 2h have been synthesized. The results showed that the steric hindrance of the chiral auxiliaries and the Grignard reagents was the main factor to influence the stereoselectivity of Micheal addition. When the chiral auxiliaries and the Grignard reagents were aryl-substituted, good yield and high stereoselectivity could be achieved up to 95% de, while the de values were lower than 70% when the substituent groups were alkyl, benzyl or alcyl.