CS246045B1 - Bromination agent and method of its preparation - Google Patents

Abstract

The present invention relates to a brominating agent allyl-bromination-type, which is 5,5'-cyclohexylethylethylene. The reagent is prepared by dissolving 5 ^ 5 * - -cycloipentamethylnihihydantoin in solution sodium or potassium hydroxide; temperature -15 to +15 ° C.

Description

The present invention relates to a brominating agent and to a process for its preparation. The reagent is used to perform aillylthio-type bromination.

Allyl accumulation is a free-radical chain reaction occurring in a heterogeneous system and on the crystal surface of a brominating agent at which a bromine atom enters the olefin molecule at a position adjacent to the double bond. The mechanism of this reaction is a substitution, i.e. the bromine radical substitutes a hydrogen atom on. the carbon atom adjacent to the double bond and enters into its position to form a hydrogen bromide molecule. In this respect, the chemical composition and physical properties of the brominating agent used have a great influence on the course and results of the reaction.

The first bulk reagent designed and used for this type of reaction was N-bromosuccinimide, which has optimal reaction properties, as was later confirmed by a large number of papers on this subject. However, since the starting material for the preparation of N-bromosuccinimide, succinic acid, is not always a readily available raw material for industrial purposes, other brominating agents with similar properties have also been sought. N-bromophthalimide and N-tolylsuccinimide, N-bromobenzjamide, N-bromo-3-mitrobenzamide, N-bromo-3,5-dinitrobenzamide, N-bromoacetamide, N, N-dibromurethane, N-bromoiminoethyl carbonate, bromine, tertiary butyl hypochlorite and bromate, pyridine dibromide, 2,4,6-trichloro-6-bromo-1,4-cyclohexadiene-3-one and 2,4,6,6-tetrabromo-1,4-cyclohexadiene-3- he, N-chloro-p-toluenesulfamide, N, N-dibromobenzenesulfamide, N-broimsaccharin, 3-bromo-4,4-dimethyloxazolidin-2-one.

The only known case of industrial use of any of the above reagents is Soviet technology, which uses 1,3-dibromo-5,5‘-dimethyl-hydantoline. This substance is relatively readily available industrially, since the starting material 5,5‘-dimethylhydantoin is prepared by the reaction of acetone, ammonium bicarbonate and sodium cyanide on the basis of the Bucherer-Berg synthesis.

In the preparation of this material, ammonium bicarbonate remains, which must be washed well from the finished product, since it otherwise interferes with the course of the next reaction step. The disadvantage is that perfect washing of 5,5‘-dimethylhydantoline is associated with considerable product losses and is not always perfectly successful, as the ammonium salts are crystallized directly in the product. As a consequence of the presence of ammonium salts in dimethylhydantoin, the yield and quality of dibromodimethylhydantoin are reduced, which is reflected in the allyl accumulation yield and yield.

These disadvantages are overcome by the brominating agent of the present invention, which is 2,4-dibroim-5,5im-cyclopentamethylenehydantoin.

A method for preparing a brominating agent is to dissolve 5,5‘-cyclopentainethylenhydantoin in a solution of sodium or potassium hydroxide at a concentration of 0.5 to 10% by weight in a 2 to 2.5 molar excess at a temperature of -15 to +15 ° C.

Advantages of the agent of the invention are substantially less water solubility and less ability to bind undesired ammonium salts to the crystalline structure. The starting material 5,5 cykl-cyclopentamethylenehydantoin is readily available, the starting material is cyclohexanone, also relatively readily available. The brominating ability of the novel reagent is very good and shows similar yields and quality when used in allyl brominations. N-bromosuccinimide.

In order that the invention may be more fully understood, the following examples are provided.

Example 1

167 kg of ammonium bicarbonate and 50 kg of sodium cyanide are dissolved in 850 l of distilled water. 93 kg of cyclohexanone are then introduced into the solution. The cloudy reaction solution was heated to 60 ° C for 2 hours and stirred at 70 ° C for a further 2 hours. Ammonia gas is excreted throughout the reaction time and the product 5,5‘-cyclopentamethylenehydantoin is gradually excreted as a white crystalline precipitate. The reaction mixture is then cooled with water to 15-20 degrees Celsius and the precipitated product is filtered off. The filter cake is washed as necessary with about 5x to 10x distilled water. The product after drying weighs 150 kg, which corresponds to a yield of 94% of theory. 336 kg of 5,5‘-cyclopentamethylenehydantoin are dispersed in 3500 liters of water and the suspension is cooled to + 5 ° C. Thereafter, 280 L of 40% NaOH is slowly added thereto so that the temperature does not exceed +10 ° C. The resulting solution is then cooled to -5 ° C and 205 liters of bromine are metered into it over about 30 minutes with vigorous cooling.

After bromine dispensing, the pH of the suspension must be about 6 to 8, preferably neutral, or the pH may be adjusted with a small amount of sodium hydroxide solution as necessary. The thick yellowish suspension was then stirred for about 1 hour at 0 ° C, then filtered and washed with water. The product was dried at 60 ° C for 16 hours. The yield is 635 kg of a yellowish, very fine powder with a content of at least 99.0% by weight and above with a particle content of less than 2. 10 ^-6 m 57%, particles smaller than 5.10 ^-6 m 83.4% and finally with particles larger than 10.10 ^-6 m 5.6%.

Example 2

49 kg of cholesterol benzoate were dissolved in 650 L of n-hexane, then 2 kg of magnesium oxide and 0.1 kg of dry dibenzoyl peroxide were added. Finally, 20 kg of 5,5-cyclopentamethylene-2,4-dibromohydantoin sieved

346045 on 0.8 mm mesh and the solution was heated to boiling n-hexane for 20 minutes. After the reaction time, the suspension was filtered off and the filter cake washed with n-hexane. The filtrate and wash were combined and distilled off all n-hexane. The light yellow residue of 5,5‘-cyclopentamethylene-Z-dibromohydantoin was dissolved by the addition of 75 L of p-xylene and 14 L of 2,4,6-collidine was added to the solution. This solution was stirred at 40 ° C for 30 minutes, and then it was soaked in a solution of 21 L of 2,4,6-collidine in 100 L of p-xylene boiling at 138 ° C over 15 minutes. The reaction mixture was kept under boiling for 1 hour, then cooled to stupňů0 ° C, filtered, the cake washed with 60 L of p-xylene at 60 ° C, and the combined filtrates and washings were evaporated to dryness.

200 L of acetone was added to the distillation residue and the solution was cooled to -10 ° C with stirring for 16 hours. The resulting suspension was. then filtered, washed with 50 L of cooled acetone and dried. The yield of 7-dehydrocbolesterol benzoate was 35.2 kg and had a composition of 74.8% by weight of chiOlesto-5,7-dien-3-ol benzoate, 17.7% by weight of cholesto-4,6-dien-3-ol benzoate and 6% by weight. 5% by weight of benzoate cholesterol, corresponding to a yield of 54% of theory.

Claims (2)

First ^and 5,5'-cyclopropyl ntametylén 2,4-dibromo, hyd- or 0.5 to 10% by weight of 2.0 to 2.5 Antoine. molar excess at -15 to +15 2. Process for the preparation of 5,5'-cyclopentamethyl degrees Celsius and to the thus prepared noslene-2,4-dibroimhydantoin from 5,5'-cyclopenta-flux, bromine is metered in 4 to 5 molar methylenehydantoin dissolved in a solution of hydro-excess at temperature to -15 to +15 ° C. sodium or potassium xidium