Benzene methoxy-substituted

Production of cellulose esters from aromatic acids has not been commercialized because of unfavorable economics. These esters are usually prepared from highly reactive regenerated cellulose, and their physical properties do not differ markedly from cellulose esters prepared from the more readily available aHphatic acids. Benzoate esters have been prepared from regenerated cellulose with benzoyl chloride in pyridine—nitrobenzene (27) or benzene (28). These benzoate esters are soluble in common organic solvents such as acetone or chloroform. Benzoate esters, as well as the nitrochloro-, and methoxy-substituted benzoates, have been prepared from cellulose with the appropriate aromatic acid and chloroacetic anhydride as the impelling agent and magnesium perchlorate as the catalyst (29). 

In contrast to the dihalogens, there are only a few spectral studies of complex formation of halocarbon acceptors in solution. Indeed, the appearance of new absorption bands is observed in the tetrabromomethane solutions with diazabicyclooctene [49,50] and with halide anions [5]. The formation of tetrachloromethane complexes with aromatic donors has been suggested without definitive spectral characterization [51,52]. Moreover, recent spectral measurements of the intermolecular interactions of CBr4 or CHBr3 with alkyl-, amino- and methoxy-substituted benzenes and polycyclic aromatic donors reveal the appearance of new absorption bands only in the case of the strongest donors, viz. Act = 380 nm with tetramethyl-p-phenylendiamine (TMPD) and Act = 300 nm with 9,10-dimethoxy-l,4 5,8-... 

In summary, the sulfonylureas are new herbicides which exhibit activity at extremely low rates of application and show very low mammalian toxicity. Exceptionally high activity is shown by compounds containing a benzene ring substituted in the ortho position, an unsubstituted sulfonylurea bridge, and a pyrimidine or triazine heterocycle substituted with methyl or methoxy groups. 

Figure 10. Plots of log feel vs the oxidation peak potentials of methyl- and methoxy-substituted benzenes ( x) for the fluorescence quenching of flavin analogs (la,2a-c) by the quenchers in the absence (O) and presence of O.lOmol dm-3 Mg(C10J2 ( ) or Zn(C10J2 (3) in MeCN. Numbers refer to the quenchers (e.g., 1 = MeC6H5, 14 = p-(MeO)2C6H4) [154],...

In practice, extrapolations of p fR in water have usually used the older acidity function based method, for example, for trityl,61,62 benzhydryl,63 or cyclopropenyl (6) cations.66,67 These older data include studies of protonation of aromatic molecules, such as pKSi = —1.70 for the azulenium ion 3,59 and Kresge s extensive measurements of the protonation of hydroxy- and methoxy-substituted benzenes.68 Some of these data have been replotted as p fR or pKa against XQ with only minor changes in values.25,52 However, for more unstable carbocations such as 2,4,6-trimethylbenzyl, there is a long extrapolation from concentrated acid solutions to water and the discrepancy is greater use of an acidity function in this case gives pA 2° = —17.5,61 compared with —16.3 (and m = 1.8) based on X0. Indeed because of limitations to the acidity of concentrated solutions of perchloric or sulfuric acid pICs of more weakly nucleophilic carbocations are not accessible from equilibrium measurements in these media. 

For phenol one can compare the effects of hydroxy and methoxy substituents. Scheme 19 shows effects of O-methyl substitution on pATas for protonation of a benzene ring containing one, two, and three hydroxy substituents. The pK s for di- and trihydroxy-substituted and methoxy-substituted benzenes were measured directly by Kresge et al.68 Again the stabilities of the hydroxy-substituted cations in water are consistently greater than methoxy. The importance of solvation in controlling these effects is demonstrated by the inversion of relative pK s of trihydroxy and trimethoxy benzene in concentrated solutions of perchloric acid.68 Thus the difference in p/fas is matched by a... 

Additional manipulations of the benzene ring, as illustrated in Scheme 3.118, include halogen substitution at the 2 -position [232,240], as well as methyl and methoxy substitution [240],... 

Figs. 24-27. The relationship between the reaction constant and log (fc/fcH) for the Hammett side-chain reactions of (24) p-methoxy substituted benzenes (25) p-methyl substituted benzenes (26) yj-fluoro substituted benzenes and (27) p-ehloro substituted benzenes. (Reproduced by permission from Brown and Stock, J. Am. Chem. Soc. 84, 3298 (1962).)... 

The example depicted below indicates preferential cleavage of the electron-rich enol ether double bond over the trisubstituted one by the electrophilic ozone. Thus, Birch reduction of methoxy-substituted benzenes followed by ozonolysis of the resultant enol ethers provides a powerful route to functionally substituted (Z)... 

Homolytic C—S bond fission occurs in compounds such as 267. This process yields the 1,4-dihydroxy benzene in yields as high as 60%. Desulphurization of the thio ethers 268 results on irradiation. This only occurs when hydroxy groups or the corresponding methoxy-substituted compounds are used. ... 

The usual method of synthesis of methoxy substituted benzaldehyde derivatives is by formylation of the methoxy substituted benzene derivatives. The formylation is generally effected by acid catalysed electrophilic substitution reactions like the Vils-meyer-Haack reaction. When resorcinol dimethylether is formylated under these conditions, the product obtained is the derivative (2) and not (7). 

The effect of substituents on the regiochemistry of the intramolecular meta photocycloaddition of the l-(3-butenyl)indanes (49)-(54) has been examined by Keese and coworkers.In the methoxy-substituted compounds (49)-(51) meta addition of the side chain alkene occurs across the 1,5-positions of the benzene ring while for (52)-(54) addition occurs across the 1,3-positions. 

G. Hizal, Y. Yagci, and W. Schnabel, Charge-transfer complexes of pyridinium ions and methyl-substituted and methoxy-substituted benzenes as photoinitiators for the cationic polymerization of cyclohexene oxide and related-compounds. Polymer 1994, 35(11), 2428-2431. 

SOLUTION TO 18b The methyl substituent donates electrons inductively into the benzene ring, but donates electrons to a lesser extent than does the resonance-donating methoxy suhstituent. Therefore, the rate of hydrolysis of the methyl-suhstituted ester is slower than the rate of hydrolysis of the unsubstituted ester, but faster than the rate of hydrolysis of the methoxy-substituted ester. 

Iodine in combination with [bis(acyloxy)iodo]arenes is a classical reagent combination for the oxidative iodination of aromatic and heteroaromatic compounds [99], A typical iodination procedure involves the treatment of electron-rich arenes with the PhI(OAc)2-iodine system in a mixture of acetic acid and acetic anhydride in the presence of catalytic amounts of concentrated sulfuric acid at room temperature for 15 min [100,101]. A solvent-free, solid state oxidative halogenation of arenes using PhI(OAc)2 as the oxidant has been reported [102]. Alkanes can be directly iodinated by the reaction with the PhI(OAc)2-iodine system in the presence of f-butanol under photochemical or thermal conditions [103]. Several other iodine(in) oxidants, including recyclable hypervalent iodine reagents (Chapter 5), have been used as reagents for oxidative iodination of arenes [104-107]. For example, a mixture of iodine and [bis(trifluoroacetoxy)iodo]benzene in acetonitrile or methanol iodinates the aromatic ring of methoxy substituted alkyl aryl ketones to afford the products of electrophilic mono-iodination in 68-86% yield [107]. 

Likewise, the oxidative dearomatization ofpara-methoxy substituted N-protected anilines 288 using (diace-toxyiodo)benzene in the presence of methanol gives p-quinone monoimide ketals 289 (Scheme 3.120) [358]. If the oxidation of aniline derivatives is performed in the presence of water, the final isolated products are the respective / -benzoquinones or p-benzoquinone monoketals resulting from the hydrolysis of initially formed monoimide ketals 289 [358,359]. 

Preparation of Benzyl Chlorides. A 5.0 g sample (0.015-0.025 mol) of methoxy substituted benzyl alcohol in 100 mL benzene was added to a 250 mL round bottom flask. With constant stirring, 3.0 ml (1-1.5 mol relative to the benzyl alcohol) thionyl chloride was added dropwise over a period of 30 min. The reaction mixture was refluxed, and then transferred into a 500 ml beaker containing 200 ml 10% sodium hydroxide solution. The solution was extracted with ethyl ether. The combined organic layers were washed with 10% sodium carbonate solution followed by saturated brine, then dried with anhydrous sodium sulfate, and concentrated to give the crude product. Finally, column chromatography eluted with benzene afforded the spectroscopically pure benzyl chloride as a white solid in a yield of 50%-70%. Structures and purity were confirmed by GC/MS and NMR. 

Wang, R. L. Moshurchak, L. M. Lamanna, W. M. BuUnski, M. Dahn, J. R., A Combined Computational/Experimental Study on Tert butyl- and Methoxy-Substituted Benzene Derivatives as Redox Shuttles for Lithium-Ion CeUs. J. Electrochem. Soc. 2008, 155, A66-A73. 

A solvent effect on the rate of the rearrangement was also determined (Scheme 11.21). The significance of the solvent effect depended on the position of the methoxy substituent. For the 6-methoxy-substituted allyl vinyl ether 9c, the rearrangement proceeded 68 times faster in methanol-d4 than in benzene-dg. 

---