Xylene, Dibromo

N,N-Dimethylaniline) Dimethylbenzene, see Xylene 1,3-Dimethylbutyl acetate Dimethyl carbamoyl chloride Dimethyl-1,2-dibromo-2,2-dichloroethyl phosphate, see Naled Dimethyl ether N-N-Dimethylethylamine Dimethylethoxy silane Dimethylformamide SK... 

Dimethylbenzene, see Xylene Dimethyl-1,2-dibromo-2-dichloroethyl phosphate, see Dibrom ... 

The procedure described is a modification of the general procedure of Angyal2 for the preparation of aldehydes from benzylamines by the Sommelet reaction. Isophthalaldehyde has been prepared from w-xylene by preparation of the tetrachloro derivative and hydrolysis,3 from isophthaloyl chloride by the Rosenmund reaction,4 from a,a -dibromo-m-xylene by the Sommelet reaction,5 and from isophthaloyl chloride by reduction with lithium tri-Cbutoxyaluminumhydride.6... 

The o-quinodimethanes are very reactive, unstable dienes, which are usually prepared in situ. The cycloaddition under high pressure of the dibromo-o-quinodimethane 91, generated in situ from a,a,a, a -tetrabromo-o-xylene. 

An important feature of the antibiotic chloramphenicol (9) is the presence of the dichloroacetamide function. Inclusion of this amide in a simpler molecule, teclozan (15), leads to a compound with antiamebic activity. Whether this is cause and effect or fortuitous is unclear. The synthesis begins with alkylation of the alkoxide derived from ethanolamine (10) with ethyl iodide to give the aminoether (11). Reaction of a,a -dibromo-p-xylene (12) with 2-nitropropane in the presence of base leads to dialdehyde (13). The reaction probably proceeds by O-alkylation on the nitropropyl anion... 

Low intensity ultrasound has also been applied to the Simmons-Smith cyclopropanation of olefins with zinc-diiodomethane (237). This reaction normally will not occur without activation of mossy Zn with I2 or Li, and was difficult to scale-up due to delayed initiation. Yields upon sonication are nearly quantitative, activation of the Zn is unnecessary, and no delayed exotherms are observed. In reactions with another class of organic dihalides, ultrasonic irradiation of Zn with a,a -dibromo-o-xylene has proved a facile way to generate an o-xylylene-like species [Eq. (49)],... 

When zinc and a,a -dibromo-o-xylene are irradiated with ultrasonic waves at room temperature, synthetically useful quantities of the reactive intermediate, o xylylene, are generated which can be treated in situ with activated olefins to give good yields of cycloaddition products(30). Chew and Ferrier used this methodolgy to generate a-xylylene for the synthesis of optically pure functionalized hexahydroanthracenes(31). The reaction with lithium takes a different course(19). Rather than generate the -xylylene intermediate, ionic species are produced. The two fates of a, a -dibromo-o-xylene are presented in the scheme below ... 

Although 1, -elimination of o xylene polyhalides with sodium iodide, zinc, copper, or iron metal is a fundamental method for the formation of o-xylylene intermediates, it is difficult to carry out the reaction under mild conditions such as at room temperature. o Trimethylsilylmethyl)-benzyltrimethylammonium halides were devised for this purpose and were shown to generate the o-xylylene at room temperature. However, we have successfully generated o-xylylene at room temperature by the reaction of a, 0,-dibromo o-xylene with metallic nickel(51). The Diels-Alder reaction of... 

Reaction of (66) with the difunctional alkylating agent, a,a-dibromo-o-xylene, results in ring closure to produce (67) by bridging the c/s-thiolato functions of (66) as shown in [2.10] (Thompson Busch, 1964). This... 

Reaction of glycosyl thioimidate 79 with aa -dibromo-m-xylene in the presence of NaH as a base and 15-crown-5 as a supporting reagent allowed the intermediate 80 (Scheme 4.88). Treatment of the diol 81 with dibutyltin oxide in dry toluene and then reaction with 80 in the presence of tetrabutylammonium iodide afforded the desired O-linked intermediate 82. Activation of this compound with NIS-TMSOTf afforded 83 in a good yield. Hydrogenolysis followed by acetylation gave the desired disac-... 

The Sandoz company used the dibromoterephthalic acid method. This acid was made from p-xylcnc by brominating it to form 2,5-dibromo-p-xylene and then oxidising this to 2,5-dibromoterephthalic acid. Reaction of one mole of this acid with two moles of an arylamine in the presence of copper(II) acetate gives 2,5-bis(arylamino)terephthalic acid, which can be ring-closed to a linear quinacridone. Unsymmetrical substitution using two different arylamines is possible. 

Dibromo-l,4-xylene or its 2,5-dichloro derivative is obtained by bromination or, correspondingly, chlorination of 1,4-xylene. It is oxidized to form 2,5-dibro-moterephthalic acid or its dichloro derivative 59. Subsequent reaction with aryl-amine, for instance in the presence of copper acetate, affords 2,5-diarylamino-terephthalic acid 60. It is also possible to replace the halogen atoms stepwise by arylamino moieties [11]. Cyclization to form linear trans-quinacridones, as in the above-mentioned method, is achieved by using acidic condensation agents ... 

These products obviously arose from metallation at unsubstituted ring positions in the starting tetrahalobenzene. To force metallation at the carbon-bromine bonds, they used 2,6-dibromo-3,5-difluoro-p-xylene which, with magnesium in THF gave mainly mono-adduct. With butyllithium, only the bis-adduct was obtained (15%). No mention was made of syn/anti isomers of the bis-adducts. 

Terephthaldehyde has been made by the action of lead nitrate on a.a -dichloro- -xylene1 or a,a -dibromo-/>-xylene 2 by... 

Gas chromatography was performed as described previously (10), except that a column temperature of 170°C was used when analyzing for di-tetrabromobenzene, dibromo-toluene and xylene. 

Accumulation in Fish. The accumulation coefficient and excretion half-life of tri- and tetrabromo-benzenes, dibromo-toluene and xylene, are within a range expected on the basis of similar experiments Q ), and are summarized in Table II. 

Similarly, secondary phosphines and a,a -dibromo-m-xylene usually react to give diprotonated ditertiary diphosphines [44-48]. However, in the case of the fluorous secondary phosphine 12-Rfs (Scheme 2, bottom), dialkylation occurred to give the metacyclophane 13-Rfs. As detailed elsewhere [40], extensive efforts to adjust the stoichiometry to favor noncyclized products failed. Fortunately, the reduction of 13-Rfs with IiAlH4 gave some of the target ligand lO-Rfs. 

Another related reaction is the debromination of a,a-dibromo-o-xylenes by sodium aryl tellurolates. The formed o-quinodimethane is allowed to react in situ with dienophiles to... 

The CERCLA Priority List of Hazardous Substances contains many substances released in industry as gaseous hazards and which can be treated biotechnologically (Table 1), including the following chloroform, trichloroethylene, 1,2-dibromoethane, 1,2-dibromo-3-chloropropane, carbontetrachloride, xylenes, dibromochloropropane, toluene, methane, methylene chloride, 1,1-dichloroethene, fow(2-chloroethyl) ether, 1,2-dichloroethane, chlorine, 1,1,2-trichloroethane,... 

Aliphatic and aromatic carboxylic esters are also directly converted, in one step, to oxazolines using amino alcohols. As expected, harsh conditions are required for this transformation. Typically, the reaction is performed in refluxing xylene in the presence of catalytic quantities of a Lewis acid such as dibromo- " or dichloro-dimethylstannane. More recently, lanthanide chloride and samarium chloride have also been reported as useful catalysts for this one-pot transformation in refluxing toluene. Representative examples are shown in Table 8.2 (Scheme 8.2). ... 

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