Chiral lanthanoid complexes, asymmetric

Chiral Lanthanoid Complexes, Asymmetric Catalysis with (Shibasaki and Sasai). .. 22 201... 

Shibasaki M., Sasai H. Asymmetric Catalysis With Chiral Lanthanoid Complexes... 

Shibasaki, M., Asymmetric Catalysis with Chiral Lanthanoid Complexes, 22, 201. 

Asymmetric Catalysis with Chiral Lanthanoid Complexes... 

IV. Previous examples of asymmetric catalysis with chiral lanthanoid complexes... 

C. Catalytic, asymmetric reduction of ketones with a chiral lanthanoid complex... 

The third part of this chapter reviews previously described catalytic asymmetric reactions that can be promoted by chiral lanthanoid complexes. Transformations such as Diels-Alder reactions, Mukaiyama aldol reactions, several types of reductions, Michael addition reactions, hydrosilylations, and hydroaminations proceed under asymmetric catalysis in the presence of chiral lanthanoid complexes. 

IV. PREVIOUS EXAMPLES OF ASYMMETRIC CATALYSIS WITH CHIRAL LANTHANOID COMPLEXES... 

As discussed in Section III J, in general, catalytic asymmetric aldol reactions have been studied using enol silyl ethers, enol methyl ethers, or ketene silyl acetals as a starting material. So far several types of chiral catalysis have been reported.75-85 The chiral lanthanoid complex prepared from Ln(OTf)3 and a chiral sulfonamide ligand was effective in promoting an asymmetric Mukaiyama aldol reaction with a ketene silyl acetal.86 The preparation of the catalyst and a representative reaction are shown in Figure 45. 

A chiral lanthanoid complex, which was prepared similarly to La-(/ )-17,7 23 is an effective catalyst for asymmetric reduction of ketones.102 With 10 mol % of the catalyst, borane reduction of ketones proceeds very smoothly to give alcohols in up to 62% ee (Figure 48). 

Scheme 1. The first catalytic asymmetric nitroaldol reaction catalyzed by chiral lanthanoid complexes.

Catalytic asymmetric epoxidations are one of the most important asymmetric processes [1]. In addition to previous successful achievements of other groups with allylic alcohols [50,51] and unfunctionalized olefins [52-55], the first efficient catalytic asymmetric epoxidation of a variety of enones with broad generality has been developed when using chiral lanthanoid complexes [56]. 

Shibasaki M, Grdger H (1999) Chiral Heterobimetallic Lanthanoid Complexes Highly Efficient Multifunctional Catalysts for the Asymmetric Formation of C-C, C-O and C-P Bonds. 2 199-232... 

Asymmetric Mukaiyama aldol reactions have also been performed in the presence of Lewis-acid lanthanoid complexes combined with a chiral sulfonamide ligand. Similar enantioselectivities of about 40% ee were obtained for all... 

Groger, H., Saida, Y., Sasai, H., Yamaguchi, K., Martens, J., and Shibasaki, M., A new and highly efficient asymmetric route to cyclic a-amino phosphonates the first catalytic enantioselective hydrophosphonylation of cyclic imines catalyzed by chiral heterobimetallic lanthanoid complexes, /. Am. Chem. Soc., 120, 3089, 1998. 

A series of trivalent lanthanoid complexes, scandium, and ytterbium tris-(R)-(-)-1,1 -binaphthyl-2,2 -diyl phosphonate, have been introduced as new chiral and stable Lewis acids for the asymmetric hetero Diels-Alder reaction of Danishefsky s diene and aldehydes. 2,6-Lutidine was found to be an effective additive to improve the enantioselectivity up to 89% ee [66] (Eq. 8A.42). 

Asymmetric catalytic addition of dialkylphosphites to a C=0 double bond is a powerful method, and probably the most general and widely applied, for formation of optically active a-hydroxy phosphonates [258], The basic principle of this reaction is shown in Scheme 6.108. Several types of catalyst have been found to be useful. The transition-metal-catalyzed asymmetric hydrophosphonylation using chiral titanium or lanthanoid complexes was developed by several groups [259, 260], The most efficient type of chiral catalyst so far is a heterobimetallic complex consisting... 

The first part of this chapter describes recent advances in the use of novel, chiral, alkali metal free-lanthanoid-BINOL derivative complexes for a variety of efficient, catalytic, asymmetric reactions. For example, using a catalytic amount of chiral Ln-BINOL derivative complexes, asymmetric Michael reactions and asymmetric epoxidations of enones proceed in a highly enantioselective manner. 

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