Diamines chiral catalysts

Nucleophilic addition of metal alkyls to carbonyl compounds in the presence of a chiral catalyst has been one of the most extensively explored reactions in asymmetric synthesis. Various chiral amino alcohols as well as diamines with C2 symmetry have been developed as excellent chiral ligands in the enantiose-lective catalytic alkylation of aldehydes with organozincs. Although dialkylzinc compounds are inert to ordinary carbonyl substrates, certain additives can be used to enhance their reactivity. Particularly noteworthy is the finding by Oguni and Omi103 that a small amount of (S)-leucinol catalyzes the reaction of diethylzinc to form (R)-l-phenyl-1 -propanol in 49% ee. This is a case where the... 

For an example of asymmetric Michael addition using a chiral diamine-dipeptide catalyst, see Tsogoeva, S. B. Jagtap, S. B. Synlett 2004, 2624—2626. 

Bifunctional catalysts have proven to be very powerful in asymmetric organic transformations [3], It is proposed that these chiral catalysts possess both Brpnsted base and acid character allowing for activation of both electrophile and nucleophile for enantioselective carbon-carbon bond formation [89], Pioneers Jacobsen, Takemoto, Johnston, Li, Wang and Tsogoeva have illustrated the synthetic utility of the bifunctional catalysts in various organic transformations with a class of cyclohexane-diamine derived catalysts (Fig. 6). In general, these catalysts contain a Brpnsted basic tertiary nitrogen, which activates the substrate for asymmetric catalysis, in conjunction with a Brpnsted acid moiety, such as urea or pyridinium proton. 

Berkessel and co-workers synthesized a library of structurally diverse tertiary amine-functionalized catalyst candidates incorporating a chiral 1,2- or 1,4-diamine chiral backbone [231, 232, 246]. Structure-efficiency studies through sequential modification of the diamine backbone, the tertiary amine functionality, the (thio) urea N-substituents as well as of the amide substituent pattern, exemplarily illustrated a Jacobsen-type 1,2-diamine-based structure (figure 6.24), identified... 

Selectivity in enantiotopos-differentiating acylation and phosphorylation of meso-diols can rival that of enzymes. The organocatalysts employed include chiral phosphines, chiral diamines, chiral DMAP derivatives and peptides identified from combinatorial libraries. The highest selectivity in meso diol desymmetrization has been achieved with a planar-chiral Fu catalyst. It seems the substrate scope of this process is not yet broadly explored. Because of their sequential variability it is to be... 

Asymmetric amplification in the diethylzinc addition to aldehydes has been observed with many (3-amino alcohols as catalyst, presumably because of a reservoir effect similar to that discovered by Noyori et al. Asymmetric amplification has also been found for other classes of chiral catalysts—diamines, diols, titanium complexes, etc. The various examples are collected in Table 1. The... 

Dendrimer-Fixed Chiral Diamine-Based Catalysts. 84... 

A catalytic approach to the synthesis of arylglycines was proposed by Evans and coworkers using enantioselective amination of iV-acy 1 oxazolidinones [54], Metallo-bis(sulfonamide) complexes derived from chiral diamines are potential chiral catalysts. The magnesium-bis(sulfonamide) complex 109 was generated by treating (S,S)-bis(sulfonamide) 108 with dimethylmagnesium in dichloromethane (Scheme 50). 

Similar chiral catalysts 7 were used in the Michael addition of glycine derivatives to acrylic esters to obtain functionalised oc-aminoacids5 here, the guanidines were prepared from chiral amines or diamines in one step but using cyanogen bromide, which is a noxious reagent (Figure 4). 

Mazaleyrat and Cram have used diamines (108) and (109) as chiral catalysts in the enantioselective addition of alkyllithiums to aldehydes (equation 27 Table 29). Optical yields of 23-95% are obtained. " Highest values are associated with the use of larger alkyllithium reagents, as well as with the more steri-cally encumbered catalyst (108). 

The resolving agent is tartaric acid 150 g are dissolved in water in a litre beaker. Then 240 ml of the mixture of isomers of 50 is added at 70 °C followed by 100 mis acetic acid at 90 °C and the solution cooled to 5 °C. The pure salt 51 separates out in 99% yield - that is 99% of all that enantiomer originally present - and with 99% ee. This is almost incredibly good. Though the free trans-diamine 50 can be isolated from this salt, it is air-sensitive and it is better to make the chiral catalyst 52 directly from the salt as shown. The yield is better than 95% and the catalyst 52 can be made in multi-kilogram quantities by this resolution.10... 

The Fu and Vedejs catalysts are excellent and work with a range of substrates but good kinetic resolutions can be achieved even with some very simple chiral diamines. A catalyst derived from proline 21 was used at low temperature and low loading to resolve the secondary alcohol 22 very effectively.13 The use of the proline-derived catalysts has been extended to some primary alcohols.14... 

Dehydrogenative oxidation of secondary alcohols in the presence of acetone is the reverse process of transfer hydrogenation of ketones with 2-propanol [87b, 95b]. Kinetic resolution of racemic secondary alcohols is possible using this process with an appropriate chiral catalyst and suitable reaction conditions. As exemplified in Scheme 45, a variety of racemic aromatic or unsaturated alcohols can be effectively resolved in acetone with a diamine-based Ru(II) complex 42 or 50 [129]. Chiral alcohols with an excellent optical purity are recovered at about... 

Propargylic alcohols The highly cnantioselcctivc aldol reaction of Mukaiyama can also be used to obtain optically active propargylic alcohols by reaction of acetylenic aldehydes with a silyl cnol ether. The most effective chiral catalyst is obtained by a combination of tin(ll) triflatc with a diamine derived from (S)-prolinc, (S)-l-mcthyl-2-(N-naphthylamino)mcthyllpyrrolidinc (1). Thus the reaction of an acetylenic aldehyde... 

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