Bromo-2,3-dimethylbenzene

A mixture of 106 g. (1.0 mole) of o-xylene and 107 ml. of concentrated sulfuric acid is stirred and heated on a steam bath for 1.5 hours, and the resulting solution is dissolved in 1.5 1. of water. A solution of 473 g. of hydrated barium hydroxide in 750 ml. of water is added, and the resulting neutral solution is filtered hot and cooled to 50-60°. To this is added a solution of 192 g. (1.20 moles) of bromine and 200 g. of barium bromide in 700 ml. of water. (Hood.) The mixture is held at 50-60° for 15 hours, after which it is cooled and the precipitated barium bromo-o-xylenesulfonate removed by filtration, washed with water, and dried. The yield of the salt (somewhat impure) is 63%. 

A mixture of 231 g. of the above barium salt and 300 ml. of sulfuric acid (sp. gr. 1.67) is distilled with superheated steam (inlet steam temperature at 200-220° and exit steam at 150-160°). The oily layer of the distillate is separated, washed with water, dried, and distilled twice through a 1-m. packed fractionating column to give 40 g. of o-xylene and 149 g. of l-bromo-2,3-dimethylbenzene, b.p. 210.5-212.5°. This is a 42% yield calculated on the barium salt. 

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Bromo-2,3-dimethylbenzene 1,2,4-Trinitrobenzene 1 -Ethenyl-3-ethyl-5-ethynylbenzene... 

Bromo 1 3 dimethylbenzene is inert to nucleophilic aromatic substitution on treatment with sodium amide in liquid ammonia It is recovered unchanged even after extended contact with the reagent Suggest an explanation for this lack of reactivity... 

The present method of preparation of 4,4 -dimethyl-l,l -biphenyl is that described by McKillop, Elsom, and Taylor 15 It has the particular advantages of high yield and manipulative simplicity and is, moreover, applicable to the synthesis of a variety of symmetrically substituted biaryls 3,3 - and 4,4 -Disubstituted and 3,3, 4,4 -tetrasubstituted 1,1 -biphenyls are readily piepared, but the reaction fails when applied to the synthesis of 2,2 -disubstituted-l,T biphenyls The submitters have effected the following conversions by the above procedure (starting aromatic bromide, product biphenyl, % yield) bromobenzene, biphenyl, 85,1 -bromo-4-methoxybenzene, 4,4 -dimethoxy-l, 1 -biphenyl, 99, 1 bromo 3 methylbenzene, 3,3 dimethyl-1,l -biphenyl, 85 4-bromo-l,2-dimethylbenzene, 3,3, 4,4 -tetramethyl-l,l -biphenyl, 76, l-bromo-4-chlorobenzene, 4,4 -dichloro-l,l -biphenyl, 73, l-bromo-4-fluorobenzene, 4,4 -difluoro-l,l -biphenyl, 73... 

Magnesium turnings (freshly activated) (13.42 g, 552 mmol) l-Bromo-3,5-dimethylbenzene (68.10g, 368mmol) Phosphorus trichloride (11.26g, 82.0 mmol)... 

To a 1 L three-necked round-bottomed flask with condenser, under a N2 atmosphere, containing 40mLTHL and Mg turnings (13.42 g, 552mmol) 1-bromo-3,5-dimethylbenzene (13.62g, 73.6 mmol) was added with stirring at a rate such... 

A related series of oligophenylenevinylene dimers 50a-d was prepared by Ma and coworkers and compared with the corresponding linear counterparts [74, 75]. The synthetic strategy towards 50a-d is summarized in Scheme 3.24 and involves the dimerization of l-bromo-2,5-dimethylbenzene in a Yamamoto-type cou-... 

Propose a route for the synthesis of l-bromo-2,4-dimethylbenzene from benzene. 

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