The Syntheses of Bis-Guanidium Salts and Their Applications in Asymmetric Mukaiyama Type SN2 Alkylation Reactions
In this study, we designed and successfully synthesized a new type of phase-transfer catalysts with full alkylated guanidiums as functional centers and applied these catalysts in asymmetric catalysis of 1,4-dicarbonyl compounds via Mukaiyama type SN2 alkylation reactions. Firstly, a series of bis-guanidium salts were synthesized from commercially available and cheap chiral sources in 4 to 5 steps. For most of the derivatives, the overall yields were good. Synthetic problems were met when the catalysts were highly sterically hindered or strong electron withdrawing. Then, these chiral bis-guanidium salts were tested in asymmetric Mukaiyama type SN2 alkylation reactions as phase-transfer catalysts. Up to 86% ee was obtained, and for most of the substrates, the yields were good. Two catalytic systems were studied, and each of them had their advantages and disadvantages. At the last of this work, suggestions to further improvement were proposed and detailed experimental procedures were provided.
asymmetric phase transfer reaction, bis-guanidium salts, Mukaiyama alkylation reaction
Networked Digital Library of Theses and Dissertations