Reaction with a-Haloesters

The Eschenmoser reaction is extremely useful for the conversion of amides into enaminoesters via the thioamide reaction with a-haloesters, and triphenylphosphine mediated sulfide contraction, and we are fortunate that Shiosaki has published a thorough review on this topic [180]. The accompanying scheme shows a typical example for which an organometallic route with a lithium or a zinc enolate was not successful [181]. 

The Reformatsky reaction is one of the representative reactions of zinc being used as a catalysts [12,35-38,41,64—74]. The Reformatsky reaction is that reaction with a-haloesters, carbonyl compounds and zinc that produces )5-hydroxyester as shown in eq. (5.20). The reaction of a-haloesters with zinc yields organozinc compounds (XZnCH2COOR) which are called the Reformatsky reagents. These Reformatsky reagents are the organozinc compounds which are considered to be the intermediates of the Reformatsky reaction. 

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