Active zinc preparation and reactivity

Early preparations of active zinc utilized the potassium or sodium metal reduction of anhydrous zinc salts in refluxing THF or DME (Protocol l).3,8 These highly divided zinc powders displayed high reactivity towards organic halides in oxidative addition. Alkyl iodides and bromides reacted with the zinc powders at room temperature. Even aryl bromides and iodides would react to form the corresponding arylzinc iodides or bromides at refluxing 

Active zinc prepared from the potassium reduction of zinc chloride 

Caution Carry out all procedures in a well-ventilated hood, and wear disposable 

Using a drybox or a glove bag with an argon or nitrogen atmosphere, charge an oven-dried, two-necked, round-bottomed flask (100 mL), contain- 

Remove the apparatus from the drybox or glove bag, and connect it to a vacuum/argon or nitrogen manifold. Before opening the stopcock to the inert atmosphere from the manifold, evacuate the system (5 min) and refill with argon or nitrogen (1 min) in three cycles. 

---