Lewis-base asymmetric organocatalysis

Rueping, M., Sunden, H., Hubener, L., Sugiono, E. (2012). Asymmetric oxidative Lewis base catalysis-unifying iminium and enamine organocatalysis with oxidations. Chemical Communications (Cambridge), 48, 2201-2203. 

Science of Synthesis Asymmetric Organocatalysis 1, Lewis Base and Acid Catalysts, ed. B. List, Georg Thieme Verlag, 2012. 

Lewis base or nucleophilic catalysis by chiral amines, amine or phosphine iV-oxides, sulfides, and phosphines has been intensively exploited in asymmetric organocatalysis [122]. Representative catalysts are shown in Figure 2.27. 

Several ways how (asymmetric) organocatalysis can be classified have been reported [14]. One general strategy is a classification according to Lewis acids/Lewis bases and Brpnsted acids/Brpnsted bases with the general simphfied activation modes depicted in Scheme 6.16. 

In 1981, Hiemstra and Wynberg reported a thorough investigation of the cinchona alkaloid-catalyzed addition of thiols to a,p-unsaturated enones [24] (Scheme 6.30). Mechanistic studies revealed that the free OH group is ctu-cial in this reaction and thus cinchona alkaloids most likely act as bifunctional catalysts herein. This report may now be considered as one of the major breakthroughs in asymmetric organocatalysis and has inspired a lot of further research toward the development of asymmetric Lewis or Brpnsted base catalysts. 

L, and Shi, Z.H. (2010) Adv. Synth. Catal., 352, 243-279. For a manual see List, B. (ed.) (2012) Asymmetric Organocatalysis 1. Lewis Base and Acid Catalysts, Thieme, Stuttgart (1) For a further manual see Maruoka, K. (ed.) (2012) Asymmetric Organocatalysis 2. Erpnsted Base and Acid Catalysts, and Additional Topics, Thieme, Stuttgart. 

Keywords Aldol, Direct, Ketone, Asymmetric catalysis, Enantioselective reaction, Diastereo-selectivity, 1,2-Diol, Aldehyde, Enamine, Lewis acid, Bronsted base, Organocatalysis, Bimetal-... 

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