Oxidation cubane system

A convenient synthesis of a cubane system, in which the cyclobutadiene transfer reaction plays a key role, was reported by Pettit et al. (Scheme 11). By the oxidative decomposition of cyclobutadiene-iron tricarbonyl 56 with Ce + ion in the presence of a dienophile, a molecule of cyclobutadiene can be transferred from the iron to the dienophile. Decomposition of 56 in the presence of 2,5-dibromobenzoquinone 57 yielded the Diels-Alder adduct 58 with e do-configuration. Irradiation of 58 in benzene with a high-pressure Hg lamp afforded the bishomocubane derivative 59, which gave cubane-1,3-dicarboxylic acid 60 (80%) by treatment of 59 with aqueous KOH at 100°C. 

The electrochemical results described above indicate that unlike in the cases of other cobalt-catalyzed oxidation processes where the Co /Co redox couple is invariably involved [19b,38], in the present case where cubane clusters of the general formula Co4(p3-0)4( J,-02-CR)4(L)4 are to be employed as catalysts for the air/02 or TBHP oxidation of alkylaromatics, alcohols, etc., we have a catalytic system wherein the oxidation states of cobalt cycle between +3 and +4. The kinetic inertness of Co(lll) coupled with the inadequately explored reactivity of Co(lV) thus make the catalysts based on C04O4 cubanes quite interesting [36]. We shall now discuss the resulting materials prepared by supporting the cubane-like cobalt(lll)-oxo clusters discussed above in this section by following the chemical route in which the carboxylate anion derived from CMS-CH2CH2CO2H binds the in situ or preformed cobalt(III)-oxo tetramers at elevated temperatures. 

Linkage isomerizations, osmium, 37 335-339 Linked cubane clusters, Fe—S proteins, biological implications, 38 55-56 Linked macrocyclic ring systems, 45 75 dinuclear systems, 45 89-95 triaza ring systems, 45 76-87 Li—N—Li linkages, 37 100-101 Lipoxygenase, inhibitors, 36 41 Liquid-liquid extraction of metal ions, 9 1-80 with acidic P-based extractants, 9 34-48 with acidic P-based extractants dinuclear, 9 47-48 mononuclear, 9 34-47 with amines and amine oxides, 9 49-56 complexes in, 9 68-71 countercurrent extraction method, 9 15-25... 

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