Dihydrophenazine, from phenazine

With phenyllithium and iodobenzene in tetrahydrofuran in the presence of copper powder, 5,10-diphenyl-5,10-dihydrophenazine is formed from phenazine 5,10-dimethyl-5,10-dihy-drophenazine is obtained in the reaction with iodomethane. ... 

The primary process for the oxidation by O2 - of dihydrophenazine and dihydro-lumiflavin must be analogous to that for PhNHNHPh (Scheme 7-14) to give the anion radicals of phenazine (Phen ) and lumiflavin (Fl ). These in turn react with O2 to give O2 - plus phenazine and lumiflavin, respectively the process is analogous to that for the anion radical of azobenzene (PhN NPh), The oxidation potentials (Ep,a) for PhN NPh, Phen - and Fl - in Me2SO are -1.1 V versus NHE, -0.9 V, and -0.6 V, respectively. Each value is sufficiently negative to reduce O2 to O2 - (-0.5 V versus NHE in Me2SO). Hence, the (O2 )-induced auto-oxidation of PhNHNHPh also is thermodynamically feasible for dihydrophenazine and dihydro-lumiflavin and does occur for these two model substrates of reduced flavoproteins (Table 7-3). Such an auto-oxidation reaction sequence may be relevant to the fractional yield of 02 - from the flavin-mediated activation of 02 ° and the auto-oxidation of xanthine [catalyzed by xanthine oxidase (XO), a flavoprotein]. ... 

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