Arenes phenyl group oxidation

The authors propose that the influence of the phenyl group is not an electronic effect, as no product formation is observed with palladium catalysts known to be highly active in disilane systems substituted with electronegative elements. Rather, the phenyl group may allow for precoordination via a w-arene complex, which would accelerate the oxidative addition of an Si-Si bond to platinum, a key step in the proposed catalytic cycle. 

The wide-rim CMPO calix[4]arenes are the most efficient compounds for the extraction of trivalent actinides and lanthanides. They are also the compounds that display the highest selectivity along the lanthanide series, provided that phosphorus atoms are linked to phenyl groups. They also display a higher selectivity than the calixarene-bearing diphosphine oxide, where the phosphorus atom is linked to phenyl units CPo21.176- ... 

Polycyclic aromatic compounds, such as naphthalene and anthracene, are weU known to participate in Diels-Alder and related transformations as these reactions typically result in loss of aromaticity in only one of several arene rings [38]. Such cycloadditions are rarely observed in simpler monocyclic arenes. Several examples of intramolecular [3+2] cycloaddition between an arene and an attached nitrile oxide moiety have been reported [39]. Additionally, 4+2 cycloadditions (also intramolecular) between phenyl groups and attached aUenes have been examined [40]. Allene substrates can be conveniently genwated by base-induced isomerization of alkynyl amides under conditions also suitable for cycloaddition, thweby affording a one-pot method to convert substrates such as 42 to tricyclic products 43 (Schane 15.16) [41]. Elaboration of 43 and structurally related... 

It is proposed that the cleaved methyl or phenyl group in 21 is coupled with arylboronic acid via intermediate 24, and is released as a methyl- or phenyl-arene, respectively. The resultant acylrhodium 25 is then oxidized to 26 by the action of Cul and O2 to undergo additional transmetalation from arylboronic acid. In accordance with the proposed mechanism, the reaction did not proceed at all under a nitrogen atmosphere. 

McCleland has reported that 3-phenylpropan-l-ol [125] and 3-(p-methyl-phenyl)propan-l-ol 99 [126] cyclize to chromans when oxidized by the radical anion SO4, generated by redox decomposition of S20 with Fe. The intermediate arene radical cation 100 is attacked by the nucleophilic hydroxy group. Whereas 1,6-cyclization yields 7-methylchroman 102, 1,5-cyclization with subsequent C-migration leads to the regioisomer 6-methylchroman 105. A dependence of the isomeric ratio and the combined yields to the pH value is determined. While 7-methylchroman 102 is the main product over a wide pH range, 6-methylchroman 105 is only formed at low pH. When the pH is lowered, the combined yields decrease due to the formation of an a-oxidized non-cyclized product. 

When [bis(acyloxy)iodo]arenes have electron-withdrawing groups either in the phenyl ring or in the acyloxy moiety, their oxidizing power increases generally. In a comparative study of the conversion of 1,5-dihydroxy-naphthalene to juglone, the following yields were obtained, under similar conditions [62] ... 

The corresponding hydrido/alkyl (and aryl) complexes v-[RuHR(L-L), ] (L-L = dppe, dppm, dmpe R = Me, Et, Ph) are readily prepared from m-[RuClR(L-L)2] and Li[AlH4]1659 whereas treatment of cis- or tvans-[RuCl2 (dmpe)2 ] with arene radical anions affords d.v-[RuH(f 1-aryl)(dmpe)2] (aryl = phenyl, 2-naphthyl, anthryl, phenanthryl).1389 In solution, these compounds are in tautomeric equilibria with significant concentrations of Ru° complexes (e.g. equation 148) although X-ray analysis for aryl = 2-naphthyl confirms the presence of the six-coordinate Ru" species (373) in the solid state.2459 Some reactions of (373) with various substrates to produce other hydrido complexes are shown in Scheme 74.44>24m Note that the compound of empirical formula [ Ru(dmpe)2 ] obtained by pyrolysis of [RuH(2-np)(dmpe)2] (reaction (iv) Scheme 74) is a binuclear Ru" hydrido complex, resulting from intermolecular oxidative addition of methyl groups to ruthenium.1390... 

It is observed that the presence of a CF3 group at the arene mefa-position leads to a fast reaction likely by increasing the acidity of the ortho C-H bond thus favouring the ruthenacycle intermediate formation. The proposed mechanism, as for direct arylation of phenyl pyridine C-H bonds, involves initial cyclometalation, via carbonate-assisted C-H bond deprotonation, successive oxidative addition of CICO2R or CICONR2 and reductive elimination forming a C-CONu bond. 

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