Benzenes alkoxylation

Mayo [138] proposed that PIP degradation occurs as a result of unstable alkoxyl radicals formed in oxidized polymer. Tobolsky [139] cleared that the degradation rate vs in experiments on PIP oxidation in a benzene solution is proportional to the initiation rate vs Vi. 

Alkoxyl radicals react with phenols extremely rapidly. The rate constants of the reactions of tert-butoxyl radicals with some phenols in benzene are given below (Y is the /(-substituent in the phenol molecule) [43,44],... 

Substituting the benzene ring with a double bond, Pd-catalyzed intramolecular alkoxylation of alkyne 122 also proceeded via an alkenyl palladium complex to form furan 123 instead of a benzofurans [99, 100]. In addition, 3-hydroxyalkylbenzo[fc]furans was prepared by Bishop et al via a Pd-catalyzed heteroannulation of silyl-protected alkynols with 2-iodophenol in a fashion akin to the Larock indole synthesis, [101]. 

The AgBp4 method was extended to cyclizations onto the alkoxyl side chain. Novel heterocycles A-acyl-3,4-dihydro-lP -2,l-benzoxazines (25) and A-acyl-4,5-dihydro-l//,3//-2,1-benzoxazepines (26) were synthesized by the treatment of open-chain A-chloro-A-(2-phenylethyloxy)- and A-chloro-A-(3-phenylpropyloxy)amides (24, n = 2, 3) with silver tetrafluoroborate in benzene (Scheme 2). Optimal yields of 25 were ultimately obtained with AgBp4 in ether or TPIP. ... 

Phenols having a variety of substituents including alkyl, alkoxyl, aryl, amino, and carbalkoxyl have been successfully converted to the desired product in good yield. The only limitation yet found is in the hydrogenolysis of the halogen-carbon bond. Thus y -chlorophenol was converted to benzene using this procedure. 

Alkoxylation in the benzene ring of quinazolines and quinazolinones is readily achieved in the presence of an ortho-nitro group, and even in the absence of a nitro group, displacement of fluorine is still quite facile. Examples of haloquinazolines to have been alkoxylated include 5-chloro-8-nitro-4(3//)-quinazolinone 187 <2005BMC5613>, 7-chloro-6-nitro-4(377)-quinazolinone 188 <1996JME267>, 4-arylamino-7-fluoro-6-nitroquinazolines 189... 

Only the head-to-tail adducts were obtained in the [2+2] photoaddition of 4-hydroxy-l-phenyl[l,8]naphthyridin-2(l//)-one with various alkenes in methanol (Scheme 3). The photolysis of the hypoiodites generated by the in situ reaction of the cycloadducts with excess mercury(ll) oxide-iodine reagent in benzene induced a regioselective scission of the non-ring junction bond of the alkoxyl radical to give substituted 3,9-dihydro-9-phenylyfuro[2,3- ][l,8]naphthyridin-4(2//)-one and/or 3,5-dihydro-5-phenylfuro[3,2-f][l,8]naphthyridin-4-(2//)-ones <1996T6125>. 

Depending on the oxidation conditions, benzene and its substituted derivatives, and polycyclic aromatic hydrocarbons may be converted to phenols and quinones. Alkoxylation and acyloxylation are also possible. Addition reactions may afford dihydrodiols, epoxides, and endoperoxides. 

Highly selective formation of phenyl acetate was observed in the oxidation of benzene with palladium promoted by heteropoly acids.694 Lead tatraacetate, in contrast, usually produces acetoxylated aromatics in low yields due to side reac-tions. Electrochemical acetoxylation of benzene and its derivatives and alkoxylation of polycyclic aromatics789 790 are also possible. Thermal or photochemical decomposition of diacyl peroxides, when carried out in the presence of polycyclic aromatic compounds, results in ring acyloxylation.688 The less reactive... 

The photolysis of organic nitrites of appropriate constitution and conformation in solvents such as benzene or acetonitrile transforms them into A-nitroso alcohols via the sequence (1) a homolytic fission of the O-N bond of their nitrosoxy group (2) an intramolecular d-hydrogen abstraction of the resulting alkoxyl radicals to generate a d-carbon radical and (3) formation of d-nitroso alcohols by combining of the d-carbon radical with the generated nitric oxide. The nitroso alcohols are isolated as d-hydroxyimino alcohols as a result of spontaneous thermal isomerization or as nitroso-dimers [1] (Scheme 1). This transformation has been named the Barton reaction [2, 3],... 

Analogous alkoxy-adducts are obtained with alkoxylated benzenes or pyri-dines (Table 9)89. 

This synthesis is applicable to many aromatic compounds, including alkoxyl or N,N dimethylamino derivatives of benzene and naphthalene, naphthols, indole, and certain reactive hydrocarbons, namely, anthra-cene, 1,2-benzanthracene, 3,4-benzpyrene, ° and pyrene. The high-melting polynuclear hydrocarbons react best in the presence of a solvent, such as o-dichlorobenzene. For example, a solution of anthracene, methyl formanilide, and phosphorus oxychloride in o-dichlorobenzene is heated 1 hour at 90-95° then an aqueous solution of sodium acetate is added, and the solvent and N-methylaniline are removed by steam distillation. The solid residue is readily purified to yield 9-anthraldehyde (84%). With liquid or low-melting compounds a solvent is not required. 

A review of chemiluminescent and bioluminescent methods in analytical chemistry has been given by Kricka and Thorpe. A two-phase flow cell for chemiluminescence and bioluminescencc has been designed by Mullin and Seitz. The chemiluminescence mechanisms of cyclic hydrazides, such as luminol, have been extensively analysed. " Fluorescence quantum yields of some phenyl and phenylethynyl aromatic compounds in peroxylate systems have been determined in benzene. Excited triplet states from dismutation of geminate alkoxyl radical pairs are involved in chemiluminescence from hyponitrite esters. Ruorophor-labelled compounds can be determined by a method based on peroxyoxalate-induced chemiluminescence. Fluorescence and phosphorescence spectra of firefly have been used to identify the multiplicity of the emitting species. " The chemiluminescence and e.s.r. of plasma-irradiated saccharides and the relationship between lyoluminescence and radical reaction rate constants have also been investigated. Electroluminescence from poly(vinylcarbazole) films has been reported in a series of four... 

Thallous alkoxides exist as tetramers in benzene solution, and an X-ray study of (T10CH3)4 shows a tetrahedral arrangement of the metal atoms as in the idealized structure shown above, but the alkoxyl groups were not located. In such molecules T1 forms pyramidal bonds, with valence group (2, 6). 

The resulting phenoxonium ion 15, cited in Scheme 2, is attacked by a variety of nucleophiles to yield three cyclohexadienones (64, 65 and 66), as shown in Scheme 12, where X, X, Y and Z are suitable functional groups such as hydrogen atom, alkyl, aryl, alkoxyl and/or hydroxyl group. Usually, these three compounds are competitively formed depending upon the substituents and their locations on the benzene ring. In the... 

The most popular Pd-catalyzed method for the production of furans and benzofurans involves reactions of alkynols. Acyclic alkynols are converted into furans, while benzene substituted alkynols are transformed into benzofurans. The use of this strategy is widespread for the synthesis of benzofurans however, it is occasionally used for the syntheses of furans. For example, intramolecular alkoxylation of alkyne 189 proceeds via an alkenylpalladium complex and subsequent carbonylation to form furan 190 [156, 157]. In addition, 3 -hydroxyalkyl-benzo[/)J furans were prepared by Bishop et al. via a Pd-catalyzed heteroannulation of silyl-protected alkynols with 2-iodophenol in a fashion akin to the Larock indole synthesis [158]. In a related series of experiments, Qing demonstrated that alkynes 191 could be efficiently converted into furans 192 [159]. 

Benzene-containing alkynols are frequently used to prepare a variety of benzofuran products. 2-Phenylbenzofuran 206 is readily available from reaction of o-bromophenol and phenylacetylene [163], The mechanism of this reaction involves a spontaneous cyclization via the intramolecular alkoxylation of alkyne 204 (the coupling adduct of o-bromophenol and phenyl acetylene) to yield bcnzofiirylpalladium complex 205 and, finally, 2-phenylbenzofuran 206 [164]. 

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