Asymmetric transfer hydrogenation fluorinated

SCHEME 30.36. Asymmetric transfer hydrogenation of rac-188 under DKR in the synthesis of fluorine-containing analogs of a/JH-bacterial sanfetrinem and LK-157. 

Combination of the Hantzsch ester mediated transfer hydrogenation together with chlorine (116) or fluorine (117) electrophiles allows for the formal addition of HCl or HF aaoss a double bond in a catalytic asymmetric manner (Scheme 48) [178], Within this paper the reactions were further refined by the use of two cycle-specific secondary amines which effectively operated independently within the same reaction mixture. Impressively, this allowed access to either diastereoisomer of the product depending upon the absolute configuration of the catalyst used in the second step of the sequence. 

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