Oxygen reaction with phenanthrene

Dioxocin 206 (X = CH=CH) was also obtained from the hydroperoxide-substituted phenanthrene-fused oxepine 281 upon reaction with stoichiometric amount of benzaldehyde or acetone and TFA. The formation of the dioxocin goes through the elimination of MeOH and consequent intramolecular cyclization of the oxygen on the stabilized carbocation (Scheme 55) <1998J(P1)3053>. 

Cyclization with subsequent oxidation leading to aromatic systems other than phenanthrene has also been effected, Eqs. (180)-(183). The formation of carbazole from diphenyl amine, Eq. (183), is of special interest since it appears to differ mechanistically from the other reactions. The rate of disappearance of the T state of diphenyl amine and the rate of appearance of a transient were measured using flash spectroscopic techniques, and it was concluded that the precursor of the transient is the diphenyl amine triplet state. The transient, which may possess structure (XXXIII), can yield carbazole by two routes reaction with oxygen or ejection of hydrogen. The latter process is without precedent in solution photochemistry. 

Weak to moderate chemiluminescence has been reported from a large number of other Hquid-phase oxidation reactions (1,128,136). The Hst includes reactions of carbenes with oxygen (137), phenanthrene quinone with oxygen in alkaline ethanol (138), coumarin derivatives with hydrogen peroxide in acetic acid (139), nitriles with alkaline hydrogen peroxide (140), and reactions that produce electron-accepting radicals such as HO in the presence of carbonate ions (141). In the latter, exemplified by the reaction of h on(II) with H2O2 and KHCO, the carbonate radical anion is probably a key intermediate and may account for many observations of weak chemiluminescence in oxidation reactions. 

Kojima and co-workers also examined the photo-oxidation of stilbenes in zeolite Y [150]. The presence of O2 in the stilbene-NaY sample led to a red-shifting of the tail end of the diffuse reflectance spectrum and was assigned to the charge-transfer complex with O2. Upon excitation at 313/366 nm, both cis- and /ra .v-stilbene undergo photo-oxygenation to form benzaldehyde. Phenanthrene, the expected product from the ]2 -f 4] cycloaddition reaction of excited m-stilbene, was also formed. The details of the mechanism leading to benzaldehyde and phenanthrene... 

The reaction of phosphorous acid with pivaloyl chloride in pyridine has been studied three eq. of pivaloyl chloride gave the triacyl phosphite (152). Thiophos-phinltes or monothiophosphites (153) rearrange spontaneously to the thiophosphoryl isomer (154) in the presence of oxygen. The rearrangement was inhibited by the addition of radical inhibitors. Irradiation of a mixture of naphthalene or phenanthrene and trialkyl phosphites in the presence of 1,3-dicyanobenzene gave several isomeric monophosphonates. ... 

The phenanthrene acts as a sensitizer generating the singlet oxygen that in turn reacts with the ground-state molecule resulting in the oxidative transformations. This type of reaction has also been demonstrated in the photooxidation of anthracene associated with particulate organic matter. At this point, however, it is not clear why the reaction rates vary between sUica gel and alumina. 

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