Syntheses and Applications of (Thio)Urea-Containing Chiral Quaternary Ammonium Salt Catalysts
作者:Johanna Novacek、Mario Waser
DOI:10.1002/ejoc.201301594
日期:2014.2
bifunctional (thio)urea-containingquaternaryammonium salts based on easily obtainable chiral backbones. Among the different classes of catalysts that were successfully synthesized, those based on trans-1,2-cyclohexane diamine were found to be the most powerful for the asymmetric α-fluorination of β-keto esters. Selectivities up to 93:7 could be obtained by using only 2 mol-% of the optimized catalyst. The
Development of Planar Chiral Iodoarenes Based on [2.2]Paracyclophane and Their Application in Catalytic Enantioselective Fluorination of β-Ketoesters
作者:Yang Wang、Hang Yuan、Hongfei Lu、Wen-Hua Zheng
DOI:10.1021/acs.orglett.8b00711
日期:2018.5.4
The design and synthesis of novel planar chiral iodoarenes based on [2.2]paracyclophane is reported. A process of highly enantioselective oxidative fluorination of a β-ketoester with 3HF–Et3N as a nucleophilic fluoride source mediated by these new hypervalent iodine catalysts has been developed. This represents the first highly enantioselective reaction catalyzed by planar chiral hypervalent iodine
The squaramide moiety has proven to be a powerful hydrogen-bonding donor in organocatalysis, but chiral phase-transfer catalysts bearing the squaramide motif have not been reported so far. Reported herein is this kind of catalyst and their catalytic performance in the asymmetric fluorination of beta-keto esters.