Oxidative Substitution Reactions

Ni(02)(CNBu )2] reacts with a variety of compounds and the reactions which are outlined in Scheme 5 can be classified as either atom transfer redox reactions, atom transfer oxidation reactions, oxidative substitution reactions or metal assisted peroxidation reactions. An i.r. study of [Ni( 02)(CNBu )2]... 

In a different study, anthracene, phenanthrene, perylene 93 (Fig. 31), and 2,7-di-tert-butylpyrene underwent regioselective oxidative-substitution reactions with iodine(III) sulfonate reagents in dichloromethane to give the corresponding aryl sulfonate esters. The use of [hydroxy(tosyloxy)iodo]benzene, in conjunction with trimethylsilyl isothiocyanate, led to thiocyanation of the PAH nucleus. 

Finally, it should be mentioned that all the oxidative substitution reactions of aromatics discussed above are stoichiometric processes. Rather expensive reagents are employed, and the processes would not generally be suitable for syntheses on the industrial scale. They do, however, provide simple, attractive routes for bench-scale syntheses for a wide variety of substituted arenes283 284 that are difficult to prepare by other methods. Moreover, electrochemical regeneration of the oxidant could provide for the use of catalytic amounts of expensive metal oxidants. 

In some cases, 2H or 4H adducts are isolable intermediates of substitution or oxidative substitution reactions (see below). 

Tcne (E° = 0.22 V) and [Co(CNMe)5] + (E° = 0.10 V) give high yields of [Co(CNMe)4(f/2-tcne)]+ by an oxidative substitution reaction involving initial one-electron transfer the intermediate, [tcne]-, was detected by flow ESR spectroscopy (202). The dication [Co(CNPh)5]2+ is isolable as a perchlorate salt (203), but solutions of the blue MeNC analog give red crystals of dimeric [Co2(CNMe)10][ClO4]4 (204). No doubt the monomer-dimer equilibrium interfered with the electrochemical study of [Co(CNMe)5]2 + in water (205). 

Homocoupling and Oxidative Substitution Reactions of Aromatic Compounds... 

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