Hell-Vollard-Zelinski reaction conditions

The mediods discussed so far are iq>(dicable to aldehydes, ketones, esters and lactones. The a-haloge-nation of acids has received relatively little attention, alAough the traditional Hell-Vollard-Zelinski conditions are adequate in most instances (equation 2). Alternative ctmditions have been developed, however, in which the acyl halide may be halogenat using NBS. Quenching the reaction with alcohols or amines offers the opportunity of forming carboxylate derivatives. 

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