Cinchona-promoted asymmetric compounds

In 2007, Connon and McCooey developed highly efficient, asymmetric syn-selective addition reactions of enolizable carbonyl compounds to nitroolefins by adopting the enamine catalysis approach [48]. The 9-epi-amino cinchona alkaloid derivative (160,9 -epi-DHQDA) as an aminocatalyst promoted the addition ofa variety... 

Cinchona alkaloids are readily available natural chiral compounds and have a long history to be utilized as organocatalysts in asymmetric catalysis [3, 4]. They are multifunctional, tunable, and more importantly, they could promote a diversity of reactions through different catalytic mechanisms, which make them privileged catalysts in organocatalysis. In this chapter, the applications of cinchona alkaloids and their derivatives for asymmetric cydoaddition reactions after 2000, especially for the construction of a variety of five- and six-membered cyclic compounds, are discussed. 

Zhang et al. investigated the asymmetric 1,3-dipolar cycloaddition of tert-butyl 2-(diphenylmethyleneamino)acetate and nitroalkenes promoted by bifunctional thiourea compounds derived from cinchona alkaloids, affording chiral pyrrolidine derivatives 13 with multisubstitutions. Catalyst lm delivered the best results in terms of catalytic activity, diastereoselectivity and enantioselectivity. Nevertheless, only moderate ee values could be obtained while the diastereoselectivities were generally good (Scheme 10.18) [22]. 

The hetero [2+2] cycloaddition reaction is a synthetically important reaction for the construction of 4-membered heterocyclic compounds. As far as the catalytic asymmetric reaction is concerned, however, only the cycloaddition between ketenes and aldehydes has been reported. The thus synthesized chiral oxetan-2-ones are employed as monomer precursors for the biologically degradable co-polyesters and also as chiral building blocks for natural product synthesis. Two types of catalysts. Cinchona alkaloids and a chiral Lewis acid, are known to promote this reaction. 

S.2.4.3. oL,p-Unsaturated Ketones as Acceptors. The earliest studies on the organocatalytic asymmetric Michael reactions were reported by the group headed by Wynberg [1,83]. The authors found that natural cinchona alkaloids could effectively promote the Michael addition of 1,3-dicarbonyl compounds to a,(3-unsaturated enones. In 2003, Jprgensen and co-workers [84] developed the first highly... 

In these cases, the polymer was used as an asymmetric support to induce the formation of optically pure product (cf. Worster et al., 1979). Few reports of the use of polymer-bound asymmetric reagents seem to exist in the literature. In this application, the reagent is used either to promote the asymmetric coupling of two groups or to add a group to a compound in an asymmetric manner. By far the largest number of applications have been those in which the polymer-bound asymmetric centers act as catalysts. Asymmetric catalysts, based on either amino acids or cinchona alkaloids, have been used to catalyze the Michael reaction in an... 

Cinchona-based primary amine catalysis in the asymmetric functionalization of carbonyl compounds has been reviewed and their modularly designed thioamide 0 derivatives have been applied successfully to direct cross-aldol reactions between aldehydes and ketones, reactions of activated carbonyl compounds (isatins) with acetylphosphonate as the enol precursor, and C( 1) functionalization of 1,3-dicarbonyl compounds by aldehydes and ketones. Cross-aldol addition to C(3) of isatins by the methyl group of 4-aryl-tra 5 -cf, -unsaturated methyl ketones has also been promoted... 

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