Aldehydes, halogenation metal catalyzed

In a series of reactions similar to those described for amino acid complexes, pyruvic acid undergoes metal-catalyzed condensation with aldehydes and also halogenation (Scheme 14). Again, the metal ion presumably functions by accelerating the formation of the methylene carbanion. 

In addition, it is noteworthy that this catalytic system tolerates several functional groups (halogens, esters, and aldehydes) that often pose problems in metal-catalyzed reactions. 

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