Aerobic DDQ-Catalyzed Reactions Using NO. Cocatalysts

High-potential quinones, such as DDQ and chloranil, are important stoichiometric reagents in organic synthesis with notable applications in the oxidative functionalization of activated C-H bonds and dehydrogenation to form (hetero)arenes [1]. These reactions can be rendered catalytic in quinone by using certain transition metal salts, anodic oxidation, or molecular oxygen to regenerate the quinone in situ. 

The direct aerobic reoxidation of DDQH2 to DDQ is not thermodynamically feasible due to the high potential of DDQ versus the 2e-reduction of Oj to H2O2. 

Aerobic Quinone-Catalyzed Reactions Using Other Cocatalysts 

Alternative cocatalysts, such as [Fe(pc)]20 (pc = phthalocyanine) and AIBN, have also been reported for catalytic aerobic DDQ oxidation reactions, though these have seen less widespread application than NO [28]. Aerobic quinone-catalyzed dehydrogenation reactions using less oxidizing quinones, such as chloranil, have been reported using polymer-incarcerated noble metal catalysts reported by Kobayashi and colleagues [29, 30]. 

In addition to their value as synthetic reagents, quinones also play an essential redox role within biological systems, such as in photosynthetic and mitochondrial electron transport chains and as aerobic enzyme cofactors [31]. This concept was exploited for synthetic applications as early as 1960, when Moiseev found 

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