Chiral amine-derived

Asymmetric aza Diels-Alder reactions provide a useful route to optically active heterocyclics such as piperidines and tetrahydroquinolines.45 Although successful examples of diastereoselective approaches had been reported as early as 10 years ago,46 only recently have enantioselective reactions been accomplished.47 For example, the reaction of chiral amine-derived aromatic imine 115 with Brassard s diene 116 gives adduct 117 with up to 95% diaster-eoselectivity (Scheme 5-37).48... 

Catalytic enantioselective fluorination has recently emerged. Both organocatalysis and metal catalysis have been successfully developed. Chiral N-F reagents have been prepared or formed in situ starting form a chiral amine derivative and a classical N-F reagent vide supra)P These reagents allow the enantioselective fluorination of... 

A series of chiral amines derived from amino acids has been used the best optical yields have been obtained with phenylalanine derivatives (128) (R1 = CH2C6H5) and tert-leucine tert-butyl ester (129) 146>. 

Although the diastereoselective addition of nucleophiles to imines offers an attractive route to chiral amine derivatives, most chiral nonracemic imines suffer from low reactivity (electrophilicity), resulting in no reaction or competitive reduction with organometallic reagents. Other problems include enolization of aliphatic imines, poor... 

The asymmetric reduction of enamides to produce chiral amine derivatives has also been examined by the Paris Group (52). Subsequent unpublished studies (53) have shown that the degree of asymmetric synthesis is much higher in benzene than it is in ethanol for such systems up to 92% enantiomeric excess was achieved in one case. 

Chiral Amines Derived from Asymmetric Aza- M orita-Baylis-H i I Iman Reaction... 

Chiral Amines Derived fiom Asymmetric Aza Morita Baylis Hillman Reaction... 

Interesting examples of optical resolutions include the use of dicarbonyl-rhodium(i) 3-trifluoroacetyl-(li )-camphorate for g.l.c. separation of chiral olefins and of dimeric nickel(ll) bis-(3-trifluoroacetyl-li -camphorate) for an improved separation of chiral epoxides (cf. Vol. 8, p. 8). The resolution of (i /5)-pantoic acid with chiral amines derived from a- and jS-pinene (Vol. 7, p. 43, ref. 420) may signal their more widespread use. 1,3-Dithian 1-oxide has been resolved. ... 

Spahn, H. Langguth, P. Chiral amines derived from 2-arylpropionic acids novel reagents for the liquid chromatographic (LC) fluorescence assay of optically active carboxylic acid xenobiotics. Pharm.Res., 1990, 7, 1262-1268... 

Some attempts to use aliphatic alcohols as nucleophiles in the enantioselec-tive conjugate addition to enals have been carried out, but with no success with regard to the stereochemical control (Scheme 3.29). For example, the conjugate addition of methanol to several aliphatic enals using axially chiral amines derived from BINOL as catalysts proceeded with enantioselectivities around 50% ee and also a 31c-catalyzed intramolecular reaction leading to the formation of the tetrahydropyrane skeleton has been reported to proceed with 57% ee. 

Chiral amines derived from (S)-proline were used to ring-open azabenzonorbor-nadienes using an achiral [Rh(COD)Cl]2/dppf catalyst (Scheme 10.14) [18]. While only marginal diastereoselectivity was observed the resulting enantiopure diaster-eoisomers could be readily separated and then converted into unique cyclic... 

In 2014, Guan and co-workers reported the direct synthesis of a-chiral tert-butanesulfinylamines from the reaction of racemic alcohols and Ellman s sulfinamide catalyzed by ruthenium (II) pincer catalyst 23 (Eq. 54) [176], providing an effective method for the synthesis of chiral amine derivatives. 

A range of cyclic ketimines (38, X = CH2, O, NR) undergo rhodium-catalysed asymmetric arylation to give gem-diaryl sulfamidates or sulfamides (39) in up to 99% ee. The products can be converted into a-tertiary chiral amine derivatives without loss of enantiomeric purity. 

Later, Eilbracht et al. developed a related enantioselective domino hydroformylation-aldol reaction catalysed by a rhodium complex in combination with a chiral amine derived from L-proline. In this process, the reaction of acetone with vinylbenzene afforded the corresponding chiral p-hydrojgr ketone in 69% yield, a moderate diastereoselectivity of 74% de, and a high enantioselectivity of 93% ee, as shown in Scheme 7.50. ... 

Synthesis of Sulfinamides. The nucleophilic substitution of (l/ ,25, 5/J)-(—)-menthyl (5)-p-toluenesulfinate with LHMDS leads to the synthesis of (S)-(+)-p-toluenesulfinamidem72% yield with complete stereochemical inversion (eq 18). S)- +)-p-Toluenesulfinamide is a versatile intermediate for the preparation of various chiral sulfinimines that are used for the synthesis of chiral amine derivatives via diastereoselective addition of nucleophiles. ... 

In recent years a lot of information related to the use of ionic Uquids as media for organocatalytic reactions catalyzed by chiral amine derivatives has been reported [11,13, 24]. ILs specifically solvate polar enamine or iminium intermediates generated from a carbonyl substrate and a catalyst and significantly polarize nucleophilic or electrophilic compounds that enantioselectively interact with these intermediates (Figure 22.1), leading to a rise in reaction rates, sometimes at the expense of a slight drop in the enantiomeric enrichment of products as compared with similar reactions in organic solvents [12]. 

Other ylides have also been used for cyclopropanation. Ley and coworkers reported effective cyclopropanation using chloroketones and an acrylate ester in the presence of DABCO (Scheme 1.28) [47]. In the reaction, N-ylide 43 or 44 was assumed to be generated as an active reaction intermediate. A chiral amine derived from quini-dine 45 catalyzed asymmetric cyclopropanation to give 46 in 94% ee. 

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