Chiral amine catalysts halogenations

The excellent enantioselectivity and wide scope of the CBS reduction have motivated researchers to make new chiral auxiliaries [3]. Figure 1 depicts examples of in situ prepared and preformed catalyst systems reported since 1997. Most of these amino-alcohol-derived catalysts were used for the reduction of a-halogenated ketones and/or for the double reduction of diketones [16-28]. Sulfonamides [29,30], phosphinamides [31], phosphoramides [32], and amine oxides [33] derived from chiral amino alcohols were also applied. The reduction of aromatic ketones with a chiral 1,2-diamine [34] and an a-hydroxythiol [35] gave good optical yields. Acetophenone was reduced with borane-THF in the presence of a chiral phosphoramidite with an optical yield of 96% [36]. 

Cross-coupling carboamination reactions between allenes and 2-haloaniline derivatives or halogenated allylic amines have also been employed for the generation of substituted indolines, and use of an appropriate chiral catalyst for these transformations leads to formation of enantioenriched products [52]. For example, Larock has described the synthesis of indoline 56 via the Pd-catalyzed reaction of aryl iodide 54... 

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