Phenol-tetrahydrofuran complex

The decrease in rate was proportional to the concentration of dioxane in the reaction mixture. An equivalent concentration of p-xylene (whose dielectric constant is similar to that of dioxane) produced a smaller decrease, consistent with simple dilution of the reactants. It was, therefore, hypothesized that dioxane forms an H-bonded molecular complex with phenol, the complexed form of the phenol being unreactive. The data could be accounted for with a 2 1 stoichiometry (phe-nokdioxane). This argument was supported by experiments with tetrahydrofuran, which also decreased the rate, but which required a 1 1 stoichiometry to describe the rate data. 

A plausible pathway is that the aromatisation of the cyclohexadienone 92 by a proton shift is accelerated in the presence of Ac20 under formation of acetate 93. The simultaneously generated acetic acid then cleaves the acetate to form the free phenol 94 (Scheme 44). This effect was observed for the first time during studies towards the total synthesis of the lipid-alternating and anti-atherosclerotic furochromone khellin 99 [64].The furanyl carbene chromium complex 96 was supposed to react with alkoxyalkyne 95 in a benzannulation reaction to give the densely substituted benzofuran derivative 97 (Scheme 45). Upon warming the reaction mixture in tetrahydrofuran to 65 °C the reaction was completed in 4 h, but only a dimerisation product could be isolated. This... 

Combination of silicon hydrides with catalytic amounts of a ruthenium(II) complex in tetrahydrofuran, chloroform or benzene has afforded a new reducing system capable of efficient reduction of a,p-unsatu-rated carboxylic acids, esters, amides, etc. Addition of a weak proton source, such as a sterically hindered phenol significantly increases reaction rates. The ruthenium mixture was found to exhibit the same regioselectivity observed with the above-described palladium systems. 

As previously mentioned, the RP-HPLC of phenolic compounds is carried out with polar eluents. Simple HPLC systems use one pump that pumps a single solvent or, more frequently, a solvent mixture through the column. This is known as isocratic HPLC. More complex gradient systems use more than one pump governed by a computer and pump changing mobile phases that can involve several solvents. Water is usually one of the components in the mixmre the other components most frequently include methanol, acetonitrile, and, more rarely, tetrahydrofuran, etc. The pH of the eluent is always acidic, and this acidity can be attained by the addition of acids such as acetic, formic, phosphoric, trifluoroacetic, and others. The selection of the acid used is dependent on the specific separation problems that need to be solved. 

Several oxovanadium(IV) complexes (141) with ON-donor ligands were prepared from [YOCl2(thf)2] (thf = tetrahydrofuran) and /// /////-substituted phenols to study the electronic effects of para substituents in order to develop better [VCl2(OR)2]-type olefin polymerization catalysts.676 The hyperfine coupling constants, the HOMO-LUMO transitions, and the oxidation potentials were all found to be linearly related to the Hammett a constant of the substituent on the monoanionic aryloxy ring.676... 

With regards to oxidative reactivity, it seems that dicopper(II) end-on peroxo complexes are basic, or nucleophilic, in nature, without oxidizing substrates such as PPha or 2,4-di-tert-butylphenol. Instead, O2 is released and PPhs binds, or deprotonation of the phenol occurs leading to a Cu -hydroperoxide. By contrast, the side-on bound dicopper(II) peroxide and its isoelectronic isomer, the dicopper(III) bis(p-oxo) species, both are electrophilic and have been shown to react with a wide array of substrates, in intramolecular (ligand) oxidations, and intermolecular organic transformations. Our group has extended the oxidative capability of CU2O2 complexes to novel (for copper chemistry) substrates such as tetrahydrofuran and dimethylaniline, which are oxidized to 2-hydroxy-tetrahydrofuran, and methylaniline plus formaldehyde, respectively. 

X-ray crystallographic determinations illustrate a range of complexes exhibiting inclusion of m-xylene, di-methylformamide, tetrahydrofuran. triethylamine, dimeth-ylsulfoxide. or acetone. rThe expansion of the calix[4]arene framework is particula ly suited, however, to europium and uranyl complexation by phenolic oxygens. ... 

KL extracted from OPEFB fiber is insoluble in water. This insoluble property makes it a substance with constricted chemical reactivity which attributes to the complexity inside its structure due to its bulkiness and the reticulation of phenolic groups (Bonini et al., 2003). The newly S5mthesized light brown colored copolymer (LGC) however, showed high solubility in water, methanol, ethanol, tetrahydrofuran (THE), sulfuric acid, hydrochloric acid, DMSO, dimethylformamide (DMF), and acetone. In contrast with KL, LGC is insoluble in chloroform. The grafting reaction improved the solubility of KL therefore, its chemical reactivity has been enhanced and that may attribute to grafted AA homopol5mier chain onto KL backbone via the condensation process, as illustrated in Fig. 4.9. 

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