Ni-catalysed C-O Bond Activation of Phenol or Enol Derivatives

1 Ni-catalysed C-O Bond Activation of Phenol or Enol Derivatives 

In this reaction relatively strong Ar-O bond is selectively activated in the presence of a more reactive carbonyl C-O bond. Theoretical studies show that oxidative addition of ArO-Ac to Ni(0) is more facile than oxidative addition of Ar-OAc to Ni(0), which is consistent with the bond dissociation energies of the two C-O bonds as shown in structure 26. However, the former process is reversible, and the oxidative addition product does not transme-talate easily, whereas the latter process is irreversible, and its oxidative addition species transmetalates more readily. These results lead to the final product selectivity.  

Other nickel-catalyst systems were also demonstrated to catalyse amina-tion of phenol derivatives, such as Ni(COD)2/SIPr-catalysed amination of aiyl carbamates, Ni(COD)2/dppf-catalysed amination of aryl sulfamates, and (dppf)Ni(o-tolyl)Cl-catalysed amination of aiyl sulfamates, mesylates, and triflates/  

Fiffure 14.6 Proposed mechanism for Ni-catalysed reduction of aryl methyl ether 

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