SU134679A1 - Method for preparing aryl bromides - Google Patents

Description

There are various ways to get ready for the game. on bromine and pyrolysis obtained rekapiopio: mix.

However, all these methods have significant drawbacks. For example, the first method results in a mixture of flux-separated isomers, as well as di- and polybromo derivatives; the second method is difficult in terms of the preparation of the starting amines and gives low yields; the third method, in addition to multi-stage, gives a relatively low yield (not higher than 50%) and involves the process of isolation and purification of the final product.

In order to increase the yield of the target product, simplify the process and shorten the reaction time, a one-step method is proposed for the preparation of aryl bromides (a and p-bromonaphthalenes, m-bromotoluene, o-bromdiff: 11L), ocHOsaHifbjii on a; Ill.: And the corresponding aromatic hydroxy compound with phosphorus pibromide in a molar ratio of 4: 1 at a temperature of 130-140 °, followed by pyrolytic decomposition of the resulting monobromo tetraaryl phosphate at 250-280 °.

The yield of aryl bromide is 70-95% of theoretical.

Example 1. To 49.5 ml (0.52 mol) of trichromic phosphorus in 100 ml of chloroform with stirring and the temperature of the reaction mixture minus 16-minus 8 ° are added dropwise over 4.5 hours of a solution of 27.7 ml (0 , 54 mole) of bromine in 100 ml of chloroform. 216 g (2 mol) of m-cresol is added dropwise to the precipitated pibromophosphorus precipitate as a yellow precipitate at room temperature, after which the solvent is distilled off and the mixture is heated for approximately

No. 134679-2-2 hours at 130 ° until the release of hydrogen bromide. The reaction mass is subjected to pyrolysis at 280 ° for 0.5 hours. The m-bromotoluene obtained is isolated by distillation. The yield is 59.8 g (70% of the theoretical).

Example 2. To a pibromo-foophor prepared under the conditions of Example 1 (out of 36.7 ml of phosphorus tribromide and 20.5 ml of bromine), 255 g (1.5 chalk) of o-oxydiphenyl were added. After distilling off the chloroform, the reaction mixture is stirred for 3 hours at a temperature of 130-145 ° and subjected to pyrolysis and 280 ° for 20 minutes. 64.6 g of o-bromodifacil are obtained. Output 79% of theoretical.

Example 3. Pibromide phosphorus obtained under the conditions of the example (from 30.4 ml of phosphorus tribromide and 17.4 ml of bromine) and 173 g (1.2 mol) (S-naphthol is stirred for an hour at a temperature of 145 °, and then subjected to pyrolysis for 15 minutes at 250 °.

58.2 g of p-bromonaphthalene were isolated by vacuum pyrolysis. Yield 93.5% of theoretical.

Example 4. Pibromide phosphorus (prepared by brominating 52.7 ml of phosphorus tribromide s 100 ml of methylene chloride with a solution of 33.3 ml of bromine in 100 ml of methylene chloride) and 320 g (2.22 mol) of an afthol are heated with stirring and at a temperature of 137- 139 ° for 2 hours. The resulting reaction mass is subjected to pyrolysis at 235 for 15 minutes. The yield of α-bromonaphthalene is 100 g (87% of theoretical).

Subject invention

A process for the preparation of aryl bromides, for example a-and p-bromonaphthalenes, m-bromotoluene, o-bromobiphenyl, from the corresponding, their phenols and phosphorus pentophorus, characterized in that, in order to simplify the process and increase the yield of products, the aromatic oxo compound is heated with fibrous phosphorus 2-4 hours at a molar ratio of reagents 4: 1, a temperature of 130-140 °, followed by pyrolysis of the reaction mass at 250-280 ° for 15-30 minutes.