From halo sulfonic acid esters

Formation of Alkyl Halides from Esters of Sulfuric and Sulfonic Acids Halo-de-suffonyloxy-substitution, etc. 

In the same way as enantiomerically pure a-halo ketones, a-halo esters have been prepared in high diastereomeric excesses by asymmetric halogenation of silyl ketene acetals generated from chiral esters So, a successfull procedure was first introduced in 1985, by W. Oppolzer (refs. 8,9), using derivatives of camphor-10-sulfonic acid as chiral auxiliaries (Fig. 4). 

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