O-alkoxy phenol

Weak Medium 300 15b Alcohols, phenols, and intermolecular hydroxyl to carbonyl bonding <100 10 100-300 50 1.2- Diols, a- and most /3-hydroxy ketones o-chloro and o-alkoxy phenols 1.3- Diols some /3-hydroxy ketones /3-hydroxy amino compounds nitro compounds... 

The stoichiometric factors of inhibition and the rate constants of the ter-penephenols (TP) with isobornyl and isocamphyl substituents were determined by the reaction with peroxy radicals of ethylbenzene. The reactivity was found to decrease for o-alkoxy compared with o-alkyl substituent caused by the intramolecular hydrogen bond formation that is conformed by FTIR-spectroscopy. The inhibitory activity for mixtures of terpene-phenols with 2,6-di-ferf-butyl phenols in the initiated oxidation of ethylbenzene was also studied. In spite of the similar antiradical activities of terpenephenols with isobornyl and isocamphyl sunstituents, the reactivity of phenoxyl radicals formed from them are substantially different that is resulted from the kinetic data for mixtures of terpenephenols with steri-cally hindered phenols. 

O- Alkylation is comparable to A/-alkylation, but since the sodium salts are water-soluble it is most convenient to treat the phenol or naphthol in aqueous caustic solution with dimethyl sulfate or diethyl sulfate. These are comparatively expensive reagents, and therefore, alkoxy groups are introduced at a prior stage by a nucleophilic displacement reaction whenever possible. 

The existence of a protonated oxazolone has been demonstrated indirectly by a simple experiment. When p-nitrophenol was added to an excess of 2-alkoxy-5(4//)-oxazolone in dichloromethane, a yellow color appeared. The color persisted until all the p-nitrophenol had been consumed by the oxazolone. The anion of p-nitro-phenol is yellow. The explanation for the color of the mixture is the presence of the p-nitrophenoxide anion that was generated by abstraction of the proton by the oxazolone. In summary, protonation of the O-acylisourea suppresses the side reaction of oxazolone formation as well as the side reaction of A-acylurea formation and accelerates its consumption by enhancing its reactivity and generating an additional good nucleophile that consumes it. Protonation of the oxazolone suppresses epimerization by preventing its enolization and also increases the rate at which it is consumed.4 68 78 79... 

The chemical diversity of carboxylic acid esters (R-CO-O-R ) originates in both moieties, i.e., the acyl group (R-CO-) and the alkoxy or aryloxy group (-OR7). Thus, the acyl group can be made up of aliphatic or aromatic carboxylic acids, carbamic acids, or carbonic acids, and the -OR7 moiety may be derived from an alcohol, an enol, or a phenol. When a thiol is involved, a thioester R-CO-S-R7 is formed. The model substrates to be discussed in Sect. 7.3 will, thus, be classified according to the chemical nature of the -OR7 (or -SR7) moiety, i.e., the alcohol, phenol, or thiol that is the first product to be released during the hydrolase-catalyzed reaction (see Chapt. 3). Diesters represent substrates of special interest and will be presented separately. 

In contrast to the simple alkoxy radicals, the 0-0 radical is seemingly quite stable against further oxidation by 02. In addition, the odd electron in the 0-O is delocalized by resonance, and can facilitate o- and p-addition of N02 to the benzene ring. The phenolic H—O bond of p-nitrophenol must be formed intermolecularly, whereas an intramolecular H-atom transfer cannot be ruled out for the formation of o-nitrophenol. The detailed mechanism for these final steps is presently unknown. 

A convenient one-step conversion of moderately activated nitroarenes to phenols was achieved in DMSO via nucleophilic nitrite displacement by the anion of an aldoxime.153 TTie resulting O-arylaldox-ime is rapidly cleaved to the phenol derivative under the reaction conditions. The reaction is also applicable to activated fluorides and even to 2-chloropyridine which, at 110 °C, is converted to 2-pyridone in 72% yield.153 A somewhat related process concerns the synthesis, in 82-92% yield, of 4-alkoxybenzoni-triles (45 R = Me, CH2-oxirane, CHrfh, CHMeCTfcMe from O-alkyl-4-nitrobenzaldoximes (44) via hydride-induced elimination of the alkoxide followed by alkoxy denitration (Scheme 17).154... 

The pyrimido-pteridine N-oxide (38) can be used for the photohydroxylation of phenols in acetonitrile solution (Sako et al.). Wan and Wu have reported that irradiation of o-dialkoxybenzenes in aqueous acetonitrile containing sulphuric acid leads to replacement of the alkoxy groups by hydroxyl the mechanism appears to involve protonation of the Si arene to give a o-complex which then undergoes ipso attack by water. Fields has reported that diphenylmaleic anhydride photocyclises readily to the phenanthrene (39), and has corrected an earlier report that the product is a (2+2) dimer. 

Rhodium carboxylates. 13, 266-269 15, 278-280 16, 289-292 17, 298-302 a-Alkoxy esters. Rhodium carbenoids derived from a-diazo esters undergo O-H bond insertion in the reaction with alcohols or phenols. Low to moderate asymmetric induction from chiral esters is observed. ... 

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