A new asymmetric two-center phase-transfercatalyst was designed and a catalyst library containing more than 40 new two-center catalysts was constructed. The catalysts were applied in phase-transferalkylations and Michael additions to afford the corresponding products in up to 93% ee and 82% ee, respectively.
was used in phase-transfer alkylations and Michael additions to afford various opticallyactive α-amino acid equivalents in up to 93% yield. Moreover, dramatic counter anion effects were observed in phase-transfer catalysis (PTC) for the first time, making it possible to further improve reactivity and selectivity. These findings validate the usefulness of three-dimensional fine-tuning of the catalyst
Stereoselectivity of Grignard Reaction in the Presence of Chiral Podands and Crown Ethers
作者:N. G. Luk'yanenko、A. V. Lobach、O. N. Leus
DOI:10.1023/b:rujo.0000034953.76058.e4
日期:2004.2
Reactions of ethylmagnesium bromide with benzaldehyde and acetophenone in toluene proceed stereoselectively in the presence of catalytic amounts of chiral podands and crown ethers. Under catalytic conditions theyield of the corresponding alcohols is nearly quantitative. The optical yield varies in the range 9-86% depending on the catalyst structure.
Enantioselective Syntheses of Aeruginosin 298-A and Its Analogues Using a Catalytic Asymmetric Phase-Transfer Reaction and Epoxidation
We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogues, in which all stereocenters were controlled by a catalytic asymmetric phase-transfer reaction and epoxidation. Furthermore, drastic counteranion effects in phase-transfer catalysis were observed for the first time, making it possible to three-dimensionally fine-tune the catalyst (ketal part, aromatic