Phenols arenes

To support a polystyrene onto the upper rim of ca-lix[4]arene (phenolic-O- of calix[4]arene) and 25,26,27-tribenzoyloxy-28-hydroxy, calix[4]arene was treated with chloromethylated polystyrene in the presence of K2CO3 (Scheme 7). Polymeric calix[4]arene (3a) thus obtained was hydrolyzed in the benzoyl groups prior to use for the extraction process. 

Aryl-A3-iodanes bearing an electron-deficient alkyl ligand such as aryl(sul-fonylmethyl)-A3-iodanes (Section 3.2.7) and aryl(perfluoroalkyl)-A3-iodanes are relatively stable. A series of (perfluoroalkyl)phenyl-A3-iodanes 96 were synthesized in good yields by treating bis(trifluoroacetoxy)-A3-iodanes with benzene in the presence of triflic acid [47]. The AModanes 96 transfer the perfluoroalkyl groups to a variety of nucleophiles with reductive elimination of iodobenzene. The nucleophiles involve Grignard reagents, alkyllithiums, enolate anions, alkenes, alkynes, trimethylsilyl enol ethers, arenes, phenols, and thiols. In these reactions, the AModane 96 serves as a source of the perfluoroalkyl cation and, in... 

Compared with the starting arenes, phenols are more reactive toward the hydroxyl radical, resulting in overoxidation to quinones and decreasing selectivity and yield of the reaction. Physical separation of products from the starting materials by means of a biphasic reaction mixture can be successfully used in this case [15], Yields as high as 80% (based on benzene) have been reported with cetyl-... 

Hydroxylations of electron-rich arenes (phenols and hydroxyarenes) can be achieved catalytically with (P-P)Pt(CF3)X and H202 (where P-P is dppe and X is (CH2C12)C104) [31]. The ortho- and para-isomers are formed, with ortho substitution preferred. The authors propose that the higher yields of ortho-hydroxylated products are a manifestation of catalyst pre-coordination. 

The effect of rf coordination on the arenes was studied in the context of the phe-nol-ketodiene equilibrium . It was shown that this equilibrium for the free ligands favors heavily the phenol tautomer vide supra) whereas for the complexes [Os(NH3)5-2,3- -arene)] + (arene = phenol 2-, 3-, 4-methylphenol 3,4-dimethylphenol) the corresponding equilibrium constants approach unity (20 °C). The conversion of phenol 67 into the 2,4-cyclohexadien-l-one 68 was kinetically favored over the formation of the 2,5-isomer 69, although the latter is the thermodynamically favored product (equation 26). It was assumed that osmium rehybridizes the C(5) and C(6) atoms to form a metallocy-clopropane. This removes much of the resonance energy and therefore destabilizes the enohc form of the free hgand. The free energies of ketonization (25 °C) for the /j -phenol complex in comparison with free phenol are shown in equations 27 and 28 . 

Friedel-Crafts reaction. Active arenes (phenols, aryl ethers, aryl sulhdes,...) are alkylated by A-tosyl aldimines (and benzylamines) such that 1,1-diarylalkanes result, with promotion by Bi2(S04)3-Me3SiCl. ... 

Conversion of phenols to arenes. Phenolic hydroxyl groups can be replaced by hydrogen by a two-step procedure ... 

The electronic nature of the organic halide is important. For reactions with electron-poor alkenes, best yields and rates are obtained with electron-poor arenes. Phenolic halides, for instance, can be so electron rich, that they give no products. They must first be converted into a less electron rich derivative, such as an acetate, as in a short synthesis of Plicatin B 5.23 from p-iodophenol 5.21 (Scheme 5.6). ... 

As an illustration, crude benzene extracts of test materials (e.g., carbonaceous shale samples) can be preseparated by TLC into neutral polynuclear aromatic hydrocarbons (PAHs) and polar compounds (e.g., heterocyclic nitrogen compounds, aza-arenes, phenols) and other nonpolar hydrocarbons. This type of separation can be accomplished with a silica-gel plate in a onedimensional run with, for example, benzene-cyclohexane. Plates are air-dried and observed under UV light. Saturated hydrocarbons run with the solvent to... 

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