Aldehydes a-halo

Diastereoselective halogenations using removable chiral auxiliaries have been the purpose of recent significant developments. a-Halo aldehydes, a-halo ketones and a-halo carboxylic acid derivatives are very useful precursors involved for total syntheses of pharmaceutical drugs and phytochemicals. In most cases, the biological activity is associated with one of the two enantiomers. So, diastereoselective halogenation of carbonyl compounds and carboxylic acid derivatives has attracted considerable attention in recent years, as a tool for the production of enantiomerically pure substances. The numerous examples of diastereoselective halogenation of compounds with non removable chiral adjuvants are outside the scope of this review. 

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