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
We demonstrated the cobalt-catalyzed asymmetric α-fluorination and α-chlorination of β-ketoesters. Both reactions were achieved using a catalytic amount of Co(acac)2 with (R,R)-Jacobsen’s salen ligand; α-fluorinated or α-chlorinated products were thus obtained with a good enentioselectivity.
New fluorinating reagents - I. The first enantioselective fluorination reaction
作者:Edmond Differding、Robert W. Lang
DOI:10.1016/s0040-4039(00)82271-6
日期:——
Crystalline, optically pure N-fluoro sultams (−)-3 and (+)-5 are the first examples of enantioselective fluorinatingreagents. Thus unprecedented enantiomeric excesses up to 70% are observed when various prochiral metal enolates are fluorinated by using these newreagents.
SPANamine derivatives in the catalytic asymmetric α-fluorination of β-keto esters
作者:Olivier Jacquet、Nicolas D. Clément、Zoraida Freixa、Aurora Ruiz、Carmen Claver、Piet W.N.M. van Leeuwen
DOI:10.1016/j.tetasy.2011.08.023
日期:2011.7
The use of C-2-symmetric enantiopure nitrogen ligands in the asymmetric catalytic alpha-fluorination of beta-ketoesters is described. SPANamine 1 in the presence of nickel salts gives up to 63% ee in the fluorination of tert-butyl 2-oxocyclopentanecarboxylate with N-fluorosuccinimide (NFSI). The same enantioselectivity is obtained when SPANamine 1 is used as an organocatalyst, although the reaction is much slower. (C) 2011 Elsevier Ltd. All rights reserved.