Phenoxy cation

Phenoxy cations (35) electrochemicaUy generated from phenols (34) react with olefins to afford two types of bicycKc compounds (36) and (37), depending on the substituents (X, Y, Z), the solvent used for electrolysis, and the structure of the olefin (Scheme 13) [72]. 

Fig. 50 Stereoselective intramolecular addition of anodically generated phenoxy cations [257-259],...

Aromatic Nitro Compounds The molecular ion peak of aromatic nitro compounds (odd number for one N atom) is strong. Prominent peaks result from elimination of an N02 radical (M - 46, the base peak in nitrobenzene), and of a neutral NO molecule with rearrangement to form the phenoxy cation (M - 30) ... 

Accordingly, an overall second-order rate law is expected at constant pH (first order in phenol and in Cr(VT)), and there will be a complex dependence on acidity varying between kinetic order 0 and 2. In addition, the k2 (two-electron transfer) pathway should be the main route at higher acidities, with predominance of the products derived from the phenoxy cation, X2. 

Therefore, the role that the ferrocenium group plays in the in vitro cytotoxicity appears to be that of an intramolecular electron acceptor. The inertness of the non-phenolic compound 7 to pyridine in this model system shows that a phenolic group is necessary for the reaction to take place. Likewise, for the unconjugated 20a-c, chemical reduction of the Fe(III) atoms was not observed suggesting that the electron transfer process occurs through a coupling in the molecular Ti-system. Thus, as soon as an adequate base is available, a substantially fast intramolecular electron transfer may occur, thereby leading to the oxidation of the phenolic moiety made easier because of its displacement by the reaction of the phenoxy cation with the pyridine base [153-155]. 

For other names, such as phenoxonium ions, aryloxonium ions, phenoxy cations etc. see Ref. 201 >... 

Anodically generated phenoxy cations, o-quinones, and o-quinone methides react with olefins to give bicyclic and tricyclic annelated compounds stereoselectively [359-366]. 

Phenoxenium ion—see Phenoxy cation Phenoxy cation 273-277, 289 Phenoxyl radicals 15, 129, 131-139, 310, 638, 865, 1017-1019, 1098, 1100 add-base equilibria of 1132-1135 comparison with isoelectronic radicals 1127... 

The research on the reaction mechanism of the oxidative polycondensation of 2,6-dimethylphenol (DMP) was also continued in the years around 1990. In several publications a Dutch research group reported on kinetic studies dedicated to the 02-promo ted polycondensation of DMP catalyzed by copper tetramethyl 1,2-diamino-ethane complexes [233-236] or by copper complexes of imidazole [237,238]. The speculative mechanistic scheme was based on dimeric copper complexes such as (147a) which were assumed to incorporate a DMP anion (147b) which was oxidized to yield a phenoxy cation and to coordinate another DMP molecule (148a). The growing step was then assumed to consist of a nucleophilic substitution at the phenoxy cation (149) with liberation of a reduced dimeric copper complex (148b). This complex was believed to be... 

Here, the excited triplet ketone abstracts a hydrogen atom from the phenol to give a phenoxy cation-radical. This latter species is further oxidized by the ketyl radical to the resonance-stabilized ylide. The protonated ketone then collapses to regenerate ketone and give the acid, HX,. It is noteworthy that in contrast to the photosensitization of dialkylphenacylsulfonium salts which involves reduction of the onium salts, the above process results in the oxidation of the sulfonium salt. Although formally Scheme 12 is an oxidation, photosensitization closely resembles the non-photosensitized process with respect to the products which are formed, i.e., an ylide and a Bronsted acid. Hence, in this case, photosensitized photolysis is a reversible process and addition of monomers to pre-irradiated solutions does not result in polymerization. 

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