The role of zinc activation

Reformatsky reactions have a bad reputation as being difficult to entrain. To the authors experience, however, the reactive donors such as alkyl bromo-acetates do not pose particular problems even under rather conventional conditions. Commercial zinc dust activated by pre-treatment with either iodine of preferentially with cuprous chloride (i.e. Zn(Cu)) readily inserts into these halocarbonyl compound with formation of the corresponding zinc enolates. Protocols 1 and 2 describe prototype examples for Reformatsky reaction in the conventional two-step or Barbier-type set-up, respectively. 

However, zinc activation becomes exceedingly important as soon as less 

Finally, the use of ultrasound to entrain Reformatsky reactions deserves mentioning.37 Since a conventional laboratory cleaning bath is usually sufficiently effective, this easily adaptable method should find wider use in particular for large scale preparations. The same may hold true for the use of sacrificial anodes and/or for Reformatsky-type reactions triggered by electrochemical means.38 

Synthesis of ethyl (bromo) (trimethylsilyl)acetate (Structure 13) 

Caution Bromine is highly irritating and corrosive. Wear gloves and safety goggles and carry out all manipulations in a well-ventilated hood. 

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