Process for the preparation of N-phosphonomethylglycine

Abstract

The present invention relates to a process for the preparation of N-phosphonomethylglycine by reacting a hexahydrotriazine derivative with a triacyl phosphite. The process gives N-phosphonomethylglycine in high yield and in a simple and inexpensive manner.

We claim:  
     
         1 . A process for the preparation of N-phosphonomethylglycine, wherein 
 a) a hexahydrotriazine derivative of the formula II                        in which X is CN, COOZ, CONR 1 R 2  or CH 2 OY,    Y is H or a radical which is readily exchangable for H,    Z is H, an alkali metal, alkaline earth metal, C 1 -C 18 -alkyl or aryl, which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl,    R 1  and R 2  can be identical or different and are H or C 1 -C 4 -alkyl,    is reacted with a triacyl phosphite of the formula III   P(OCOR 3 ) 3   (III)   in which the radicals R 3 , which can be identical or different, are C 1 -C 18 -alkyl or aryl which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl, and      b) the product obtained is hydrolyzed, and, if X is CH 2 OY, oxidized.    
     
     
         2 . A process as claimed in  claim 1 , wherein reaction of the hexahydrotriazine derivative of the formula II with the triacyl phosphite of the formula III gives a compound of the formula I  
       
         
           
           
               
               
           
         
       
       in which R 3  and X have the meanings stated in  claim 1 .  
     
     
         3 . A process for the preparation of a phosphono compound of the formula I  
       
         
           
           
               
               
           
         
         in which the radicals R 3 , which can be identical or different, are C 1 -C 18 -alkyl or aryl which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl, and  
         X us CN, COOZ, CONR 1 R 2  or CH 2 OY,  
         Y is H or a radical which is readily exchangeable for H;  
         Z is H, an alkali metal, alkaline earth metal, C 1 -C 18 -akyl or aryl, which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl;  
         R 1  and R 2 , which can be identical or different, are H or C 1 -C 4 -alkyl, in which a hexahydrotriazine derivative of the formula II  
         
           
             
             
                 
                 
             
           
         
          is reacted with a triacyl phosphite of the formula III 
         P(OCOR 3 ) 3   (III) 
          in which R 3  and X are as defined above.  
       
     
     
         4 . A process as claimed in any of the preceding claims, wherein X is CN or COOZ.  
     
     
         5 . A process as claimed in any of the preceding claims, wherein R 3  is phenyl which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl, or is CH 3 .  
     
     
         6 . A process as claimed in any of the preceding claims, wherein step (a) is carried out in an organic solvent.  
     
     
         7 . A process as claimed in  claim 6 , wherein the solvent used is dioxane or tetrahydrofuran.  
     
     
         8 . A process as claimed in  claim 6 , wherein a chlorinated organic solvent is used.  
     
     
         9 . A process as claimed in  claim 8 , wherein 1,2-dichloroethane is used as solvent.  
     
     
         10 . A process as claimed in any of the preceding claims, wherein the compounds of the formulae II and III in employed in essentially equivalent amounts.  
     
     
         11 . A process as claimed in any of the preceding claims, wherein the compound of the formula III is prepared by reacting a carboxylic acid of the formula IV 
       R 3 COOH  (IV), 
       in which R 3  has the meanings stated in  claim 1  or a salt thereof with a phosphorus trihalide.  
     
     
         12 . A process as claimed in  claim 11 , wherein an alkali metal salt or the ammonium salt of the carboxylic acid of the formula IV is reacted with the phosphorus halide.  
     
     
         13 . A process as claimed in  claim 11 , wherein the carboxylic acid of the formula IV is reacted with the phosphorus halide in the presence of an amine.  
     
     
         14 . A process as claimed in  claim 11 , wherein the carboxylic acid of the formula IV is reacted with the phosphorus halide in the absence of a base.  
     
     
         15 . A process as claimed in any of  claims 11  to  14 , wherein the reaction is carried out in an inert organic solvent which is selected from among the aromatic or aliphatic hydrocarbons and chlorinated hydrocarbons.  
     
     
         16 . A process as claimed in  claim 15 , wherein the solvent is recovered after the reaction and recycled.  
     
     
         17 . A process as claimed in any of claims  1 ,  2  or  4  to  9 , wherein the compound of the formula I is hydrolyzed with an aqueous acid.  
     
     
         18 . A process as claimed in  claim 17 , wherein the hydrolysis is carried out in a two-phase system.  
     
     
         19 . A process as claimed in  claim 18 , wherein the phosphono-methylglycine is precipitated from the aqueous phase by bringing the pH to a value of in the range of 0.5 to 2.0.  
     
     
         20 . A process as claimed in  claim 19 , wherein the phosphono-methylglycine is precipitated in the presence of a solvent which is miscible with water.  
     
     
         21 . A phosphono compound of the formula I  
       
         
           
           
               
               
           
         
         in which the radicals R 3 , which can be identical or different, are C 1 -C 18 -alkyl or aryl which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl, and  
         X is CN, COOZ, CONR 1 R 2  or CH 2 OY,  
         Y is H or a radical which is readily exchangeable for H;  
         Z is H, an alkali metal, alkaline earth metal, C 1 -C 18 -akyl or aryl, which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl;  
         R 1  and R 2 , which can be identical or different, are H or C 1 -C 4 -alkyl, or a salt thereof.  
       
     
     
         22 . A compound as claimed in  claim 21 , wherein R 3  is phenyl which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl, or is methyl.  
     
     
         23 . A compound as claimed in  claim 21  or  22 , wherein X is CN or COOZ, wherein Z is H, alkali metal or C 1 -C 18 -alkyl.  
     
     
         24 . A compound as claimed in  claim 21  of the formula  
       
         
           
           
               
               
           
         
       
     
     
         25 . An intermediate obtainable by reacting a hexahydrotriazine derivative of the formula II  
       
         
           
           
               
               
           
         
         in which X is CN, COOZ, CONR 1 R 2  or CH 2 OY,  
         Y is H or a radical which is readily exchangeable for H;  
         Z is H, an alkali metal, alkaline earth metal, C 1 -C 18 -alkyl or aryl, which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl;  
         R 1  and R 2  can be identical or different and are H or C 1 -C 4 -alkyl,  
         is reacted with a triacyl phosphite of the formula III 
         P(OCOR 3 ) 3   (III) 
          in which the radicals R 3 , which can be identical or different, are C 1 -C 18 -alkyl or aryl which is unsubstituted or substituted by C 1 -C 4 -alkyl, NO 2  or OC 1 -C 4 -alkyl.