Biaryls oxidative coupling, organometallic

Reactions involving electrophilic substitution of hydrogen in arenes are known for both nontransition [Hg(II), Tl(III), Pb(IV)] and transition metals [Au(III), Pd(II), Pt(IV)] [49]. Pd(II)-catalyzed acetoxylation involves arene activation via formation of an organometallic aryl-Pd c-complex followed by oxidative addition of oxidant and reductive elimination to restore Pd(II) and release the product [11, 50]. Without oxidant, coupling reactions predominate, suggesting arylpalladium(IV) and arylpalladium(II) intermediates in the routes leading to aryl acetates and biaryls, respectively (Scheme 14.10). 

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