by a siloxy amino acid lithium salt

Abstract—Siloxy amino acid lithium salt, O-tert-butyldiphenylsilyl L-serine lithium salt, was found to be an effective catalyst for the asymmetric Michael addition reaction of malonates to enones. Organocatalysis has come to be recognized as an important synthetic methodology for constructing an enantiomeric carbon center in organic synthesis.1 In organocatalysis based on the formation of iminiums or enamines from carbonyl compounds with optically active amines, secondary amines, especially L-proline and its derivatives, have generally been employed as catalysts. Within common natural amino acids, however, only a few secondary amino acids are available, while more than 20 types of primary amino acids are readily obtainable from a commercial source. Although the use of primary amines as asymmetric catalysts is quite primitive, several successful works have been published in recent years.2 The Michael addition of malonates to ,-unsaturated carbonyl compounds is one of the most important carbon-carbon bond formation reactions, and many catalytic asymmetric syntheses have been achieved by using amine catalysts,3 quaternary ammonium catalysts,4 thiourea catalysts5 and metal complex catalysts.6 Zhao and Yan