IE48126B1 - Process for the preparazion of herbicidally active compounds containing phosphorus-carbon-nitrogen bond - Google Patents

Description

The present invention relates to a process for the preparation of compounds containing phosphorus-carbonnitrogen bonds particularly N-phosphono-methyl-glycine and derivatives thereof, latter compounds being known in plant protection as herbicidally active compounds.

The compounds containing phosphorus-carbon-nitrogen bond have been widely used in plant protection due to a wide spectrum of herbicidai activity. The herbicidai activity is accompanied by low residual activity, i.e. the active ingredient decomposes relatively readily in the soil.

Several synthetic methods have been disclosed in the prior art for the preparation of phosphorus-carbon-nitrogen bond containing compounds, preferably N-phosphono-methylglycine and derivatives thereof.

According to U.S. Patent Specification No. 2 635 112 compounds having phosphorus-carbon-nitrogen bond are prepared by reacting a primary or secondary amine with an aldehyde or ketone and phosphorous acid dialkyl ester. When using phosphorous acid dialkyl ester, the formation of the ester, isolation thereof and the following hydrolysis are long processes, the formed active ingredient resists acids and bases and the isolation of the product is thus complicated.

A further disadvantage of the use of phosphorous acid dialkyl ester is, that its use requires special supervision due to its toxicity. - 3 In Belgian Patent Specification No. 774 349 a phosphoruscarbon- nitrogen bond containing compound, i.e. N-phosphonomethyl glycine is prepared by reacting chloromethylphosphonic acid with an amine, i.e. glycine. The reactivity of chloromethylphosphonic acid is however rather weak and thus the reaction has to be carried out under vigorous circumstances, and thus the formation of by-products cannot be avoided.

According to West German Patent Specification No. 355 351 a ring amine, such as tricyano-methyl-hexahydrotriazine is reacted with phosphorous acid diester in the presence of a catalyst in order to obtain an ester of Nphosphono-methyl-glycino-nitrile, which is then hydrolysed in a second step to give N-phosphono-methyl-glycine. This process shows again the disadvantage of the complicated preparation of the phosphorous diester and of the treatment of the starting material i.e. the tricyano-triazine derivatives.

All the above processes and other disclosed processes use phosphorous acid or derivative thereof as a reactant.

Due to the hydrolysis of the o-phosphorous acid there is a possibility of formation of by-products in all processes spoiling the quality of the desired end-product, and reducing the attainable yield.

The compounds containing phosphorus-carbon-nitrogen bonds are generally prepared in a concentrated mineral acid medium, the corrosion danger is increased, the reaction parameters have to be strictly maintained in order to obtain reproduceable end-products and the reaction is very slow.

The process of the present invention eliminates the disadvantages of the known processes and comprises the preparation of compounds containing phosphorus-carbon48126 - 4 nitrogen bond, preferably N-phosphono-methyl-glycine and derivatives thereof, optionally directly in a pure form by a simple synthesis.

The present invention provides a process for the preparation of compounds containing phosphorus-carbon-nitrogen-bond of the general formula I II I1 P—C—N (I) OH R„ wherein and R£ are identical or different and stand for hydrogen or organic radical, at least one of and R^ being hydrogen, R^ and R^ are identical or different and stand for hydrogen, hydroxy or an organic radical - which comprises reacting a phosphorus trihalide with ammonia, a water-soluble ammonium salt, a primary or a secondary amine in the presence of at least 10 moles of water per mole of phosphorus tri15 halide, subsequently reacting with an aldehyde and recovering the product by reducing the reaction volume or by adding a water-miscible solvent to the reaction mixture.

According to a particularly preferable embodiment of the process of the invention as starting material a secondary amine is used, thus substantially no by-product is obtained in the end-product. In addition to a primary and a secondary amine, ammonia may also be used as a reactant. Primary or secondary amines are preferably selected from amino carboxylic acids, or amino-dicarboxylic acids, in particular monoethyl25 amine, dimethylamine or N-alkyl derivatives of glycine, such as sarcosine.

As phosphorus trihalide phosphorus trichloride is preferred. The system is adjusted to be saturated with hydro• 48126 - 5 chloric acid under given reaction circumstances, The desired end-product is recovered from the reaction mixture hy reducing the reaction volume or by feeding in a watermiscible organic solvent.

Suitable reactants are aldehydes, such as formaldehyde, acetaldehyde, capronaldehyde, benzaldehyde, 2-bromoacetaldehyde and similar compounds. Generally an aldehyde containing not more than 30 carbon atoms is used as a reactant. If a primary or secondary amine is replaced by ammonia, this may be aqueous ammonia, or a soluble ammonium salt, such as ammonium chloride, ammonium acetate, ammonium bromide, ammonium phosphate, or some other ammonium salt.

The product obtained according to the invention crystallizes readily, is chemically homogeneous and neither its NMR nor its IR spectra show any contamination. The yield amounts to more than 90%, and the ratio of the compounds containing PCN-bond in the formed product is above 98%.

The process may be used preferably for the preparation of all known compounds containing a phosphorus-carbonnitrogen bond.

The process according to the invention shows the following advantages: 1. The undesired by-products formed due to the decomposition of orthophosphoric acid and the heteropolyacid may be eliminated. 2. It is unnecessary to add acid during the reaction as the acid concentration of the reaction mixture may be controlled by adding water. - 6 3. The reaction may be influenced in direct ratio to the reaction temperature, the optimal reaction conditions may be used, and thus both the yield and the quality of the product may be improved. 4. One may obtain a chemically homogeneous, pure product. The compounds containing a phosphorus-carbonnitrogen bond are not contaminated with by-products which are chemically similar to the desired products. This is of great significance as the plant physiological activity of the homologous compounds is rather different and by producing a pure product, a selective activity may be achieved instead of a wide spectrum herbicidal activity.

The further details of the invention are illustrated by the following Examples.

Example 1 To a flask equipped with a stirrer 300 ml water are added, and under stirring 137 g of phosphorus trichloride are added and to the solution of raised temperature 75 g of 50% aqueous glycine solution is added. The reaction mixture is heated to boiling point under steady stirring and after 30 minutes 200 g of 37% aqueous formaldehyde solution are slowly added. After the reaction the water is distilled off. The obtained syrup is dissolved in hot ethanol. The ethanol solution is cooled, whereafter a crystalline product is precipitated, containing N-carboxymethyl-N,N-bis(methylene phosphonic acid) of purity 97%. Point of decomposition: 210°C, Yield: 93%. The ratio of water to phosphorus trichloride is 18.6.

Example 2 To a flask equipped with a thermometer, stirrer and • 48126 - 7 reflux 125 ml of water are added. Under stirring and cooling 51.7 g of phosphorus-trichloride are added and the temperature is maintained below 40°C. When the addition of the phosphorus trichloride is terminated 50 g of imino-diacetic acid is added to the mixture and heated to boiling. The mixture is heated under reflux and 119 g of 38% aqueous formaldehyde are added within 45 minutes. When the formaldehyde is added, the mixture is boiled for 3 hours 2/3 of the water is distilled off, the solution is diluted with ethanol and the mixture is allowed to stand under cooling, the precipitated crystals are filtered, washed with ethanol and water, and dried.

Very pure Ν,Ν-bis(carboxy-methyl)-N-methylene phosphonic acid is obtained decomposing at 208°C. Yield: 95%. The ratio H2O/PC13 is 29.1, 114 g of N-phosphono-methyl-glycine, prepared as described above, are added to a flask and 150 ml of water are added. To the mixture 50 g of concentrated sulfuric acid is added and the mixture is heated under stirring to 90°C. 260 g 30% aqueous hydrogen peroxide solution is added at the same temperature within 3 hours. When the hydrogen peroxide is added the temperature is maintained at 90°C for a further 3 hours.

When the reaction is completed, part of the water is distilled off and the residue is diluted with ethanol and cooled, N-phosphono-methyl-glycine is precipitated in the form of crystals under cooling and dried after washing. The product is of a purity of 98%, decomposing at 23O°C. Yield: 95%.

Example 3 To a flask equipped with a stirred and reflux 175 ml - 8 of water added and under stirring 69 g of phosphorus trichloride are added. 44.5 g of N-methy1-glycine is further added. Under stirring 188.4 g 38% aqueous formaldehyde solution is added, maintaining the reaction mixture in boiling. When the addition is completed the mixture is boiled for 2 hours and evaporated to half volume. After adding ethanol and cooling the precipitated crystalline product is washed with water and dried. The obtained N-carboxymethyl-N-methyl-N-methylene phosphonic acid is of a purity of 97%. Yield: 90%. The ratio of H2O/PC13 is 32.2.

Example 4 To a flask equipped with a stirrer, and reflux filled with 525 ml of water 206 g of phosphorus trichloride are added under stirring so that the temperature does not exceed 40°C. 27 g of ammonium chloride are then added, heated to boiling and 565 g of 38% aqueous formaldehyde solution is then added and it is boiled for 1 hour. When the reaction is completed the mixture is cooled to room temperature and the precipitated crystalline substance is filtered from the solution. The obtained amino trimethylenephosphonic acid is of a purity: 97%. The ratio H^O/PCl^ is 32.4.

Claims (7)

1. CLAIMS:1. A process for the preparation of compounds containing phosphorus-carbon-nitrogen-bonds of the general formula I 0 R. HO—P—C—N R, '3 I I \ OH R 2 R 4 wherein R^ and R 2 are identical or different and stand for hydrogen or organic radical, at least one of R^ and R^ being hydrogen, R 3 and R^ are identical or different and stand for hydrogen, hydroxy or an organic radical - which comprises reacting a phosphorus trihalide with ammonia, a water-soluble ammonium salt, a primary or a secondary amine in the presence of at least 10 moles of water per mole of phosphorus trihalide, subsequently reacting with an aldehyde and recovering the product by reducing the reaction volume or by adding a water-miscible solvent to the reaction mixture.

2. A process as claimed in claim 1 which comprises using an amino carboxylic acid, an amino dicarboxylic acid, or an N-alkyl derivative of glycine.

3. A process as claimed in claim 2, wherein the amine is monoethylamine, dimethylamine or N-methyl-glyoine,

4. A process as claimed in any one of the preceding claims which comprises using as a phosphorus trihalide, phosphorus trichloride and adjusting the reaction mixture to be saturated by hydrochloric acid.

5. A process as claimed in any one of the preceding claims which comprises using as an aldehyde, formaldehyde, acetaldehyde, capronaldehyde, benzaldehyde, or 2-broroo-acetaldehyde. 4812θ - 10

6. A process as claimed in claim 1, substantially as hereinbefore described in any one of the Examples.

7. A compound having a phosphorus-carbon-nitrogen bond produced by a process as claimed in any one of claims 1 to