Applications of Palladium and Nickel Complexes in Natural Product Synthesis

Applications of Palladium and Nickel Complexes in Natural Product Synthesis 

Several coupling reactions, particularly those involving aryl halides, have been discussed in the chapter devoted to copper (see above). However, Pd(0) and Ni(0) complexes are also efficient reagents for realizing such coupling reactions, a-aryl palladium entities being formed as intermediates. 

Example one key cyclization step in an alnusone synthesis involves such a nickel(O) (or palladium (0)) promoted intramolecular coupling of aryl iodide groups [23]. 

It is noteworthy that the use of Ni or Pd catalyst also limits homocoupling to less than 5% in many classical organometallic-organohalides nucleophilic reactions [24]. 

Palladium catalysed coupling reactions are also effectively applied to vinyl derivatives and thus constitute a particularly convenient access to conjugated diene systems [23bj. 

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