Electrophilic Attack by Organopalladium Species

Various nucleophiles attack coordinated alkenes. Typically attack of the OH anion on ethylene coordinated to Pd(II), as shown by 57, takes place in the Wacker process to afford acetaldehyde [43]. Also, the COD complex of PdCU 58 was 

Recently Pd-catalyzed reactions of aryl halides, which can be formally understood as electrophilic attacks by arylpalladium halides 65, are rapidly emerging. Arylation of cyclohexanone to afford 2-phenylcyclohexanone (66) (see Chapter 3.7.1) and formation of arylamines 67 (see Chapter 3.7.2) are typical examples. One explanation of intramolecular attack on an aromatic ring in 68 to form biaryl 70 is electrophilic attack of 69 on an aromatic ring, although the mechanism may not be so simple. A detailed discussion is given in Chapter 3.3. 

Recently Yamamoto reported Pd-catalyzed intramolecular nucleophilic addition of the arylpalladium bromide 72 formed from 71 to ketone to give the alcohol 73 using PCy3 as a ligand and an excess of 1-hexanol. This is the first example of a Pd-catalyzed Grignard-type reaction [46], 

8 Termination of Pd-Catalyzed or -Promoted Reactions and a Catalytic Cycle 

Grignard reactions proceed via oxidative addition and insertion. The reaction product 75 is isolated after hydrolysis of the insertion product 74 with dilute aqueous HCl, giving MgCl2, and it is practically impossible to reduce the generated Mg(II) 

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