Halogenation enantioselectivity

Enantioselective halogenation is a powerful transformation, directly installing an efficient leaving group. Thomas Leckta of Johns Hopkins University has shown (7. Am. Chem. Soc. 2004,126, 4245) that benzoylquinine 11 catalyzes the a-chlorination of ketenes derived from acid chlorides such as 10, to give 12 in high . 

The structural and stereochemical aspects of the enantioselective halogenation of 1,3-dicarbonyl compounds catalysed by Ti(TADDOLato) complexes have been report- ed.158 The observed absolute configuration at the fluorinated stereogenic centre has... 

Fig. 1 Selection model for enantioselective halogenation of an (R,R)-TADDOLate-Ti catalyst...

Fig. 3 Dimeric and monomeric palladium complexes for enantioselective halogenation. (5)-BINAP ligands and (5)-Segphos-ligand...

Scheme 14 Enantioselective halogenation reactions with different chiral ligand/metal combinations...

An enantioselective halogenation reaction of silyl enolates mediated by ZrCU with chiral halogen source was reported (Equation 14) [19]. Dichloromalonate ester (43) was employed for the reaction as a halogen source. 

Despite the elegancy of the approaches toward a catalytic enantioselective enolate amination, one has to be aware that a certain restriction is evident from the substitution pattern at the nitrogen in the amination products that seems to be rather special than general. Another challenging problem among the oxidative transformations of enolates is the catalytic enantioselective halogenation. Efforts... 

The first, highly diastereo- and enantioselective halogenative cyclisation of phosphoramidic acids (93) in the presence of AT-iodosuccinimide and the chiral Bronsted acid (94) has been developed by Johnston and co-workers. A unique feature of this catalysed reaction was stereocontrol at carbon and phosphoms chiral centers, leading to cyclic P-chiral phosphoramidates (95) (Scheme 28). Synthesis of enantioenriched epo)q allylamines (96) from phosphoramidate (95) has also been reported (Scheme 29). ... 

Ibrahim H, Togni A. Enantioselective halogenations reactions. Chem. Commun. 2004 (10) 1147-1155. 

Brings M, Bolm C. Enantioselective halogenations of 3-oxo esters catalyzed by a chiral sulfoximine-copper complex. Eur. J. Org. Chem. 2009 (24) 4085-4090. 

STEREOSELECTIVE SYNTHESIS OE HALOGENATED NATURAL PRODUCTS TABLE 43.2. Enantioselective Halogenation of (J-Ketoesters... 

RECENT PROGRESS IN ENANTIOSELECTIVE BROMINATION, CHLORINATION, AND lODINATION 1335 TABLE 43.3. Enantioselective Halogenation of 3-Ketoesters... 

TABLE 43.5. Enantioselective Halogenation of Other Carbonyl Compounds... 

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