P-Dimethoxybenzene

It has been considered that nitric acid was responsible for the oxidation of the nitroso compoimd, but there is recent evidence from the catalysed nitration of p-dimethoxybenzene in carbon tetrachloride that dinitrogen tetroxide is involved ... 

A solution consisting of 27.6 g. (0.2 mole) of p-dimethoxybenzene (Note 6), 4.0 g. of potassium hydroxide, and 400 ml. of methanol is placed in the apparatus. The beaker and contents are cooled with a 0° bath. The solution is electrolyzed with magnetic stirring for 6 hours at a current intensity maintained at 2.0 A (Notes 5, 7). The temperature of the solution varies between 8 and 14°. During this time small amounts of methanol are added from time to time to compensate for evaporation. 

The p-dimethoxybenzene was obtained from Aldrich Chemical Company, Inc. 

Electron-rich aromatic compounds such as durene, p-dimethoxybenzene, mesitylene, anisole, thiophene, and fluorene can be benzoylated or acetylated by the corresponding Af-acylimidazole in trifluoroacetic acid to give the corresponding benzophenone or acetophenone derivative in good yield (Method A). As the actual acylating agent, a mixed anhydride of trifluoroacetic acid and benzoic acid has been proposed 1973... 

Nitration versus oxidative dealkylation with nitrogen dioxides. The reaction of various substituted hydroquinone ethers with nitrogen oxides leads to either oxidation (i.e. 1,4-benzoquinones) or nitration (i.e. nitro-p-dimethoxybenzenes) depending on the reaction conditions239 (equation 84). 

Soma et al. (9) studied the interaction between a Ru - and CuZ -exchanged montmorillonite and p-dimethoxybenzene (DMBO) under desiccating conditions at room temperature. On the basis of Raman, IR, and VIS absorption spectra, they demonstrated that DMOB is stably adsorbed on Cu + and Ru +-exchanged montmorillonites as a radical cation. Oxidation by the metal cation was found to be reversible in the presence of water vapor ... 

Reductive alkene isomerizations can also be induced by photochemical excitation. Geometric isomerization and rearrangement can be observed upon electron transfer sensitization with molecules with inverse electron demand. Thus, a substituted cinnamyl alcohol in the presence of excited p-dimethoxybenzene gave geometric isomerization and rearrangement characteristic of a free allyl cation, eq. 32 (94) ... 

SYNTHESIS To a 300 mL three-neck round-bottom flask set up with a magnetic stirrer and protected with a N2 atmosphere, there was added 75 mL hexane, 3.5 g tetramethylethylenediamine, and 4.2 g p-dimethoxybenzene. The reaction mixture was cooled to 0 °C with an external ice bath, and there was then added 19 mL of 1.6 M butyllithium in hexane. With stirring, the reaction was brought up to room temperature, and there were produced loose, creamy solids. There was then added. 

SYNTHESIS To a well-stirred ice-cold suspension of 2.8 g p-dimethoxybenzene and 3.2 mL N,N,N ,N -tetramethylethylenediamine in 100 mL petroleum ether... 

This is a useful route for the preparation of aldehydes and ketones from alkenes, and is covered in this section. Photosensitized oxidative cleavage of alkenes occurs in reasonable yield using p-dimethoxybenzene in the presence of oxygen (equation 31)157. The products are aldehydes or ketones depending upon substrate structure. 

The most typical example of a radical anion-electrophile combination is the carboxylation of aromatics (Scheme 3 naphthalene [28], phenanthrene, anthracene, pyrene [29] cyclopenta[de/]phenanthrene [30] and, with lower yield, biphenyl [31]) with C02 by irradiation in the presence of donors such as amines or p-dimethoxybenzene (pDMB). A mixture of dihydro derivatives and rearomatized products is usually obtained. 

Diprotonation was observed only in the strongest superacid (I). Apart from the di-O-protonated p-dimethoxybenzene already mentioned, 3,5-dimethylanisole gives a di-C-protonated cation [228]... 

When (253) reacts with phosgene the 1-acyl chloride product (254) can react with amines to give amides (79LA1756X while in a further transfer reaction with ketones the compounds (255) and (256) are produced (Scheme 146) (80H(14)97). Acylation of aromatic hydrocarbons using 1-acylimidazoles in the presence of trifluoracetic acid gives high yields provided that the aryl compounds are electron rich, e.g. p-dimethoxybenzene, thiophene, anisole <80BCJ1638). 

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