DE536424C - Process for the preparation of pyridinarsic acids - Google Patents

Description

Process for the preparation of pyridinarsinic acids It is known that one organic halogen compounds by treatment with arsenites in arsinic acids can convict.

The inventors have set themselves the task of arsenic compounds of the Manufacture pyridine series. Experiments have shown that it is possible to use halogen substitution products of pyridine with arsenites to form arsinic acids, which should be done with consideration to the extensive chemical diversity of these heterocyclic starting materials of the previously used aliphatic or aromatic halogen compounds was to be foreseen.

Single and polysubstituted halogen compounds are used as starting materials into consideration. The pyridine compounds can contain halogen atoms, e.g. B. in the 2-, q.-, 6-position and also contained in the 3- and 5-positions. In addition to halogen atoms, the starting materials also other substituents, especially those of an electronegative character and those which have therapeutic effects. As a substituent come z. B. hydroxyl groups, carboxyl groups, complexes or acidic radicals Character, such as B. phenyl, benzoyl, etc., into consideration.

The implementation with z. B. Alkali arsenite can be used at ordinary temperature, possibly with the help of solvents. In some In cases it is advisable to start the reaction by increasing the temperature or by using catalysts, z. B. copper sulfate, or both measures to promote. By transferring the received Arsic acids in salts, e.g. B. by partial or complete neutralization with alkali, one arrives at products which are characterized by a remarkably high level of non-toxicity.

By treating with reducing agents, e.g. B. hydrosulfite, hypophosphorous Acid, bisulfites, electrolysis, arsinic acids can be reduced to lower levels of oxidation transfer, e.g. B. initially in arsine oxides and the latter in arsenic compounds or also directly in arsenic compounds. By oxidation, e.g. B. with hydrogen peroxide, the reduction products can be converted back into the starting materials. the The combined use of reduction and reoxidation provides a convenient cleaning process represent.

The invention enables the production of arsenic compounds which are characterized by a strong bactericidal (trypanocid6 and spirillocide) effect, possess remarkable non-toxicity and great durability.

Examples: i. ii g of 2-oxy-5-iodopyridine become a solution of g, 9 Ferric trioxide in 150 cc of water and 16.8 g of potassium hydroxide are added and added boiled of i g of crystallized copper sulphate for 2 hours. The reaction solution is diluted with 150 cc of water, filtered and saturated with carbonic acid, whereby unchanged starting material precipitates. The filtrate is acidified and made with sodium hypophosphite to the Arsenic compound reduced. This is washed well, slurried in water and oxidized with ice-cooling with 10% hydrogen peroxide solution. The one with animal charcoal decolorized solution is evaporated to crystallize. The 2-oxypyridine-5-arsic acid crystallizes in fine white needles that do not change when heated up to 3oo °, it is easily soluble in alkalis and alkali carbonates, moderately soluble in water, very sparingly or not at all soluble in common organic solvents.

2. i2 g of 2-chloro-5-iodopyridine are dissolved in iooccm: 'methanol and to a solution of 10 g of arsenic trioxide in a mixture of 150 cc of water and 17 g of potassium hydroxide. After adding x g of natural copper, the mixture becomes C for 3 hours boiled on the reflux condenser. After diluting with zoo ccm of water, hydrochloric acid is added neutralized and from unchanged starting material and the again excreted Arsenic acid filtered off. The filtrate is made by adding hypophosphorous Acid and a little hydriodic acid, the 2-chloropyridine-5-arsic acid formed as Arsenic compound deposited. After washing it thoroughly with 100% hydrogen peroxide solution oxidized. After filtration, it is concentrated until crystallization. The connection forms white needles with a melting point of 174 '. It is easily soluble in hot water, Alkali carbonate and alkali lye. 3. 9 g of 2-oxy-5-bromopyridine are dissolved in 25 cc of n-potassium hydroxide solution dissolved and with a solution of 8 g of arsenic trioxide and 13 g of potassium hydroxide in 50 ccm Water with the addition of 1 g of copper sulfate was boiled for 18 to 20 hours on the reflux condenser. It is then acidified, boiled with animal charcoal and filtered to remove any insolubles. In order to separate the 2-oxy-pyridine-5-arsinic acid from the filtrate, the solution, as indicated in Example 2, treated. .

Claims (3)

PATENT CLAIMS: i. Process for the preparation of pyridinarsinic acids, characterized in that 3- or 5-bromine or iodine substitution products of the Pyridines, which are negatively substituted in the 2-position, with arsenites, if appropriate in the presence of catalysts. 2. The method according to claim i, characterized in that that the arsinic acids by partially or completely neutralizing with alkali converted into salts. 3. Embodiment of the method according to claim i and 2, characterized characterized in that the arsinic acids or their alkali metal salts according to those in the benzene series customary methods reduced to the corresponding arsenic oxides or arsenic compounds and these are converted back into the higher degrees of oxidation by oxidation.