Hell-Vollhardt-Zelinsky reaction

When the polyene chain is extended from the ends towards the centre, acetic acid (9) is used as starting material. In a two-step, one-pot procedure, this can be converted into ethyl bromoacetate (10) by reaction with phosphorus tribromide and bromine in a Hell-Vollhardt-Zelinsky reaction [20,41], yielding the bromoacetyl bromide, which is subsequently quenched by adding ethanol, to give the labelled ethyl bromoacetate (W) in a yield of 86% [42]. Ethyl bromoacetate (10) is also available commercially in labelled form, but its preparation from acetic acid is an economically attractive alternative. 

Hell-Vollhardt-Zelinsky reaction is used to prepare a-haloacid halides. 

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