isolation of reaction products from the hydrolytic kinetic resolution (HKR) of terminal epoxides catalysed by cobaltcomplexes of salen ligands, the extension of the original fluorous biphasic approach to this reaction is far from being a trivial exercise. The nature of the counter anion has a dramatic effect on the catalytic activity of heavily fluorinated chiral (salen) cobalt(III) complexes. Excellent
尽管轻氟技术的应用有助于将反应产物与Salen配体钴配合物催化的末端环氧化物的水解动力学拆分(HKR)分离,但将原始的氟双相方法扩展到该反应绝非易事。抗衡阴离子的性质对重度氟化的手性(salen)钴(III)配合物的催化活性具有显着影响。当引入氟代阴离子时,在1,2-己烯氧化物的氟双相HKR中具有出色的对映选择性(C 8 F 17 COO的ee含量高达99%)–反应速率甚至更高在无氟系统中观察到。
Asymmetric Catalytic Synthesis of α-Aryloxy Alcohols: Kinetic Resolution of Terminal Epoxides via Highly Enantioselective Ring-Opening with Phenols
作者:Joseph M. Ready、Eric N. Jacobsen
DOI:10.1021/ja9910917
日期:1999.6.1
terminal epoxides with catalyst 3b4 (Scheme 1, Nu ) OH) suggested that (salen)Co(III) complexes might also serve as effective catalysts for the enantioselective addition of phenols to epoxides. This strategy has proven successful, and we report here the first examples of kinetic resolution of epoxides with phenols, with the isolation of 1-aryloxy 2-alcohols (1) in high ee’s and yields. Reaction of 2.2
Jacobsen’s cobalt-salen complex was covalently immobilized on polymer carriers that are part of different technical setups (polymer powder, composite Raschig rings, PASSflow microreactors) and employed for the enantioselective ring opening of terminal epoxides with water and phenols. The polymer-supported catalysts showed good activity and stereoselectivity and could be used repeatedly after a simple reactivation protocol in both batch as well as continuous-flow modes.
Highly active oligomeric Co(salen) catalysts for the asymmetric synthesis of α-aryloxy or α-alkoxy alcohols via kinetic resolution of terminal epoxides
作者:Xunjin Zhu、Krishnan Venkatasubbaiah、Marcus Weck、Christopher W. Jones
DOI:10.1016/j.molcata.2010.06.015
日期:2010.8.17
alcohols. The catalyst is compared to other dimeric, oligomeric and monomeric Co(salen) complexes including a pimelate-linked macrocyclic Co(salen) catalyst and a dimeric Co(salen) catalyst referred to as a bisalen. The catalysts that contain multiple Co(salen) units within a single molecular framework allow for substantial decreases in catalyst loading compared with the monomeric catalyst. The cyclooctene-based
Polymer-Supported Chiral Co(Salen) Complexes: Synthetic Applications and Mechanistic Investigations in the Hydrolytic Kinetic Resolution of Terminal Epoxides
作者:D. Allen Annis、Eric N. Jacobsen
DOI:10.1021/ja984410n
日期:1999.5.1
corresponding immobilized cobalt derivatives are shown to be efficient and highly enantioselective catalysts for the hydrolytickineticresolution (HKR) of terminal epoxides. These systems provide practical solutions to certain technical difficulties associated with the isolation of reaction products from the HKR. Removal of the supported catalyst by filtration and repeated recycling is demonstrated with no loss