1-Methoxybenzene, reactions with

Displacement of a tertiary amine from a quaternary (eq. lb) iavolves the attack of a nucleophile on the a-carbon of a quaternary and usually competes with the Hoffman elimination (173). The counterion greatiy iafluences the course of this reaction. For example, the reaction of propyltrimethylammonium ion with hydroxide ion yields 19% methanol and 81% propylene, whereas the reaction with phenoxide ion yields 65% methoxybenzene and 15% propylene (174). 

Similar reactions with 1,4-dihydroxybenzene and para-substituted methoxybenzenes did not produce the expected diaryl tellurium dichlorides1. 

Messmer and Sziman measured the coupling rates of p-methoxybenzene-diazonium tetrafluoroborate with N,N-dimethylaniline, m-toluidine and 1- and 2-naphthylamine in nitrobenzene as solvent. Except for reactions with m-toluidine, the reaction rates were reduced significantly if a deuterium ion had to be displaced instead of a proton. The kinetic isotope effect varied from k /kp = 1.5 for 2,4,6-dj-... 

Silver salts of other acids have been employed in the Prevost reaction, as summarized by Wilson. As a means of preparing frani-glycols, the method seems to us less convenient and more costly than reaction with performic acid and hydrolysis. The presence of free iodine may lead to complications. A methoxybenzene with an olefinic side chain gave a glycol having an iodine substituent para to the methoxyl group. ... 

The reaction of vinyldiazocarbene 17 parallels that observed with methoxybenzenes. Due to the ability of the nitrogen to stabilize a positive charge, only the alkylation product 168 is obtained. Methyl pyrrole-l-carboxylate, however, on reaction with 17 affords the tropane skeleton... 

METHOXYBENZENE (100-66-3) Forms explosive mixture with air (flash point 125°F/51°C oc). Able to form unstable peroxides. Violent reaction with oxidizers, strong acids. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

Ether groups exert their ortho-directing action in the metallation of aromatic rings mainly via their electron-withdrawing inductive effect. Methoxybenzene has been lithiated with BuLi in Et20 or THF. The metallation in the latter solvent can be carried out in a reasonable time (2-3 h at 20 °C), but part of the butyllithium is consumed by reaction with the solvent, unless a considerable excess of anisole is used. The activating influence of two methoxy groups in 1,3-dimethoxybenzene renders the metallation easier. 

Methoxybenzene (10 to 20 % excess) can be potassiated in an essentially similar way subsequent reaction with dimethyl disulfide gives l-methoxy-2-methylthio-benzene in more than 90 % yield. 

Synthesis from methoxybenzene(s) or fluoro or bromo derivatives by reaction with organometallic reagents. 

Reaction with benzoquinone. Apinol tetramethyl ether (1,2,3,4-tetra-methoxybenzene (3) can be prepared readily from hydroquinone (1) as formulated. 

In contrast to the reactions with benzene, the reactions of 4 with 1-methoxybenzene, 1,2-dimethoxybenzene, and 1,2,3-trimethoxy-benzene result in the formation of the alkylation products 65 in... 

Scheme 11.28) presumably has benzoquinone as a ligand. A mixture of regioiso-mers was obtained in the reaction of 117 with arenes such as anisole (Scheme 11.39). It is interesting that the reaction is not particularly sensitive to the effect of substituents at the arene. Thus, a competition experiment of 117 with 1,3-dimethyl-2-nitrobenzene and l,3-dimethyl-2-methoxybenzene gives a 1 1.4 ratio of arylation products, sUghtly favoring reaction with the nitro derivative.

Naphthol AS dyestuffs were invented as early as 1912 by Adolph Winther, August Leopold Laska and Arthur Zitscher of Hoechst AS is the abbreviation of Amid einer Saure (amide of an acid). Naphthol AS dyestuff components are distinguished from the unsubstituted 2-naphthol derivatives by their increased affinity for the dyed substrate and by higher chemical stability in the atmosphere. Nitro-, chloro-, methyl- and methoxybenzene derivatives can serve as aromatic moieties of the amide group. The coupling reaction with the diazo salt takes place in the 1-position. Examples of early important naphthol AS dyestuffs are Gries-heim Red, discovered in 1912, and Indra Red. 

PROBLEM 14.48 Show specific reagent(s) and produces) for the following reactions with anisole (methoxybenzene) ... 

The cationic monomeric complexes Re(CO)4(diimine) formed in the reaction of Eq. (6,39) when L=CO show excited state redox reactions. Reductive quenching experiments of the excited state with substituted methoxybenzenes and with chloride ion leads to an sq)proximate value of 1.5 V being found for the Re(CO)4(di-imine) /Re(CO)4(diimine) excited state potential. Photosubstitution is also observed with these complexes, although a definitive assignment of the photoactive states that lead to these different reactions has not yet been achieved. 

The alpha acids represent a mixture of several homologues and isomers (3). The main component, called humulone, was discovered by Lintner and Schnell in 1904 (4). The purification was described by Wollmer (5), who succeeded in obtaining a crystalline derivative of the alpha acids by reaction with 1,2-diaminobenzene (1,2-phenylenediamine). These 1 1 complexes are fully dissociated in solution (6). After several recrystallizations the humulone complex is isolated in the pure state, while the complexes of the other alpha acids remain in solution. The course of the purification process may be monitored via NMR (7). Acid decomposition of the humulone complex and recrystallization from acetic acid water furnishes very pure humulone (pale-yellow crystals melting point 72°C). Humulone itself has little or no bitter taste. Other crystalline derivatives of the alpha acids have been obtained by complexation with 1,2-diamino-4-methylbenzene, 1,2-diamino-4,5-dimethylbenzene, 2,6-diaminopyridine and 1,2-diamino-4-methoxybenzene (8), while a phenylurethane derivative has also been prepared (9). 

The lifetime of 1,2-methoxybenzene against OH reaction will be only about 3 h, assuming daytime [OH] = 2.5 x 10 molecule cm". Similar rate coefficients for OH reaction with the 1,3- and 1,4-isomers (and thus similar lifetimes for these species)... 

In hydroxylation, quinones are usually obtained since the initial hydroxyl product is further oxidised. Kinetic studies on the hydroxylation of 1,3,5-tri-methoxybenzene with perbenzoic acid gave second-order rate coefficients (Table 29) which remained fairly constant for a wide variation in concentration of aromatic and acid thus indicating that the rate-determining step is bimolecular133. The variation was considered to be within the rather large experimental error for the reaction which was very fast and, therefore, studied at low temperature (—12.4 °C). Since more than one mole of acid per mole of aromatic was eventually consumed, the mechanism was formulated as... 

In 1999, Ikeda et al. reported a new type of sulfur-oxazoline ligands with an axis-fixed or -unfixed biphenyl backbone prepared in good yields by coupling reactions of methoxybenzene derivatives substituted with a chiral oxazoline and a sulfur-containing Grignard reagent. These ligands were subsequently evaluated for the test palladium-catalysed asymmetric allylic alkylation... 

When phenylacetonitrile is converted to its anion in the presence of excess LDA and then allowed to react with 2-bromo-4-methyl-l-methoxybenzene, the product contains both a benzyl and cyano substituent. Propose a mechanism for this reaction. 

Iodination versus chlorination. Three distinct classes of halogenation reactions are observed with various substituted methoxybenzenes and IC1 when carried out under an identical set of conditions, i.e., exclusive iodination, exclusive chlorination, and mixed chlorination and iodination. For example, equimolar mixtures of anisole, 2,5-dimethyl-1,4-dimethoxybenzene and 1,4-dimethoxybenzene and iodine monochloride (kept in the dark) yield p-iodoanisole, chloro-2,5-dimethyl- 1,4-dimethoxybenzene, and a (4 6) mixture of chloro- and iododimethoxybenzene, respectively, in nearly quantitative yields,225 i.e.,... 

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