Xylylene Dibromide

In 1972, Vogtle and Zuber condensed 1,2-dibromomethylbenzene (xylylene dibromide) with another xylylene unit, 1,2-dihydroxymethylbenzene. The result was formation of the macrocyclic tetraether (40% yield, mp 194°) shown in Eq. (3.19). The... 

Caution This reaction should be carried out in a good hood because hydrogen is evolved and o-xylylene dibromide is a powerful lachrymator (Note 6). 

A solution of 52.8 g. (0.20 mole) of o-xylylene dibromide (Note 6) in 300 ml. of purified dimethylformamide is added dropwise with stirring at such a rate as to maintain a temperature of 60-70° (Note 7). Subsequently the reaction mixture is stirred at room temperature for 3 hours and then poured into 600 ml. of ice water in a 2-1. Erlenmeyer flask. After standing at room temperature overnight the product is collected by suction filtration, pressed on the funnel, and washed twice with 100-ml. portions of water. The crude product is air-dried on filter paper for 2-3 hours and is then dissolved in 1.21. of boiling 95% ethanol. The solution is filtered through a heated funnel, and the filtrate is refrigerated overnight. The crystals are collected on a Buchner funnel and washed on the funnel with 100 ml. of cold 95% ethanol. The product is dried over phosphorus pentoxide in a vacuum desiccator. The yield of white crystals of 2-(% tolylsulf onyl)-dihydroisoindole is 41-46 g. (75-84%), m.p. 174-175° (dec.). 

Precautions to be observed in handling o xylylene dibromide are described in Org. Syntheses, Coll. Vol. 4, 984 (1963). The dibromide was purchased from Eastman Organic Chemicals, recrystallized from 95% ethanol (3 ml./g.), and dried over potassium hydroxide in a vacuum desiccator, m.p. 89-91°. 

TolyIsulfonyl)dihydroisoindole has been prepared by alkylation of /Moluenesulfonamide with o-xylylene dibromide in the presence of sodium methoxide in ethanol.2 3... 

Ji-Toldaldehyde, 2-bromo-, 46,13 />-ToJuenesult onamide, alkylation with o-xylylene dibromide, 47, 111 -Toluenesulfonvlbromide, 45, 88 -Toluenesulfonyl chloride m prepara tion of methvl isocyanide, 46,... 

Convenient routes to several new sterically crowded chelating diphosphines have been described.48-50 Thus, e.g., m-xylylene dibromide, on treatment with di-t-butylphosphine, affords a bisphosphonium salt, which on treatment with a weak base affords the diphosphine (58).48... 

Caution This preparation should be conducted in a hood, and rubber gloves should be worn, to avoid exposure to bromine as well as the by-product o-xylylene dibromide which is a lachrymator and skin irritant. 

Caution o-Xylylene dibromide is a powerful and persistent lachrymator. The preparation and all subsequent handling of this substance should, therefore, be carried out in an efficient hood with adequate protection by rubber gloves. A gas mask should be at hand for emergency. All apparatus coming in contact with the dibromide should be immersed in alcoholic alkali contained in a large crock with a lid. A period of 24 hours is sufficient for decontamination. Waste substances stick as filter paper and corks usually require several days of such soaking before they can be safely discarded. 

The preparation and properties of 2-substituted isoarsindolines (28) have been examined in some detail. They are prepared from o-xylylene dibromide (32) by the reactions shown in Scheme 8 (50JCS1917). Isoarsindolines have many of the properties of stable tertiary arsines and form arsine oxides, methopicrates and methiodides. With concentrated nitric acid the intermediate arsine oxide is polar enough to react further to give the water soluble hydroxynitrate (33). With boiling hydriodic acid, 2-iodoisoarsindoline (34) is formed. This... 

When the 2-methyIisoarsindoline (28 R = Me) is quaternized with an o-xylylene dibromide, a spiroisoarsindolinum salt (35) is formed (45JCS30). The unsubstituted salt (35 R = H) is symmetrical about the heteroatom, but the 5-chloro substituted salt (35 R = Cl) should possess molecular dissymmetry and would be expected to exhibit optical activity. Attempts to resolve this material with optically active anions were not, however, successful (47JCS662). 

The parent compound (5) may be prepared by heating o-xylylene dibromide (a,a -dibromo-o-xylene) with sodium or potassium sulfide, usually in aqueous ethanol (see Table I for references), or by reducing phthalic thioanhydride (Section VII, B) with aluminum hydride or diborane 20 the former procedure has been used to prepare a number of derivatives of 5 (Table I). Disodium o-xylylenedimercaptide (6) can be isolated from the reaction between o-xylylene dibromide and... 

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