Palladium and nickel catalysed reactions

Radical cyclization reactions can be carried out by treating an unsaturated alkyl iodide or bromide with Et2Zn in the presence of palladium(II) or nickel(II) complexes.28 Under these conditions, an intermediate Pd(0) or Ni(0) complex is formed which initiates a radical chain reaction providing a new cyclized zinc cyclopentylmethyl derivative which can be trapped with various electrophiles in the presence of a copper catalyst. A related cyclization can be 

Copper-mediated addition of a functionalized alkylzinc iodide to an acid chloride preparation of 4-oxocyclohexyl 5-phenyl-5-oxopentanoate2 

Caution Carry out all procedures in a well-ventilated hood, and wear disposable vinyl or latex gloves and chemical-resistant safety goggles. 

Weigh the zinc dust into the first three-necked flask, add THF (2 mL), and flush the flask with argon. 

Add the 1,2-dibromoethane and heat gently with a heat gun to gently boil the THF. Allow to cool to rt. Repeat this heating-cooling process four more times. 

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Palladium and nickel catalysed reactions of organozinc compounds... 

Many of the palladium- and nickel-catalysed reactions of alkenyl-aluminium or -zirconium compounds which fail or give low yields of cross-coupled products can be promoted to give the desired product in high yield by the addition of catalytic amounts of zinc chloride. " Trisubstituted olefins (40), for example, can be synthesized in good yield (ca. 70%) from the metal complex (38) in the presence of a palladium or nickel phosphine complex and zinc chloride. This reaction is particularly attactive for the one-pot synthesis of natural products containing... 

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