CS195418B1 - Process for preparing N-phosphonomethylglycine - Google Patents

Abstract

The invention relates to a new and improved process for the production of N-phosphonomethylglycine

Description

The invention relates to a new and improved process for the preparation of N-phosphonomethylglycine.

The monosodium and monodimethylammonium salt of N-phosphonomethylglycine is a known broad-spectrum post-emergence herbicidal herbicide which, at a dose of 1 to 2 kg / ha, is effective in alfalfa, maize, orchards, crop and industrial plants etc. against various monolithic, annual and perennial weeds / agropyron repens, sorgum halepense, cynodon dactylon, cyperus spp ,, festuca arudinacea, taraxacum officiale, etc./.

The compound is non-toxic (LD50 in rats is 9,800 mg / kg p.o.), degrades rapidly in the soil and can also be used well in alternate cultures [Baird D. D. et al. Why. Annu. Calif. Weed Conf. 1972,

24, 94-102; CA. 1 97 2, 77_, 97609]. Monoisopropylammonium salt has been shown to be more effective against dactylis glomerata, agropyron repens, and taraxacum officiale in maize / closed growing system / than Paraquat / Peters R. A., et al., Proc. N.E. Weed Sci-Soc. 1797 3, 27, 1-6; CA. 1973, £ 7,106,886].

The following methods are described in the literature for the preparation of N-phosphonomethylglycine:

Phosphonomethylation of glycine (e.g. chloromethylphosphonic acid or its esters), addition of phosphonates to azomethines or oxidation of N-phosphonomethylglycine (Belgian Patent No. 774,349).

According to Dutch Laid-Open No. 7,303,948, N-phosphonomethylglycine is produced by desacetylation of N, N'-carboxymethylaminomethylphosphonic acid with a strong acid.

It has been found that N-phosphonomethylglycine can be produced in good yield and in a very pure state by

II

STEED

CHn. = O ^X N ^X

I /

PH _ -

STEED

II ^ OR o

(1) wherein R represents a hydrogen atom or a C 1 -C 4 alkyl group, hydrolyzes the halo gene with hydrogen at the boiling point of the reaction mixture.

Bis-N, N '- (O, O ^- dialkylphosphonomethyl) diketopiperazines can be used as starting materials of the formula I, in particular bis-N, N' - (O, O 'diethylphosphonomethyl) diacetopiperazine. Hydrochloric acids are preferably used as hydrohalic acids.

The hydrolysis of the bis, N, N ^- (O, O) -dialkylphosphorylmethyl) diketopiperazines can preferably be carried out with 64% hydrobromic acid at the boiling point of the reaction mixture. The reaction time is preferably 6 to 8 hours.

The hydrolysis of the bis-N, N '- (phosphonomethyl) diacetopiperazine is preferably carried out with 52% aqueous hydrobromic acid at the boiling point of the reaction mixture for 8 hours.

The N-phosphonomethylglycine obtained can be isolated in a known manner. Preferably, the reaction mixture is evaporated and the residual crude product is purified by recrystallization, preferably from alcohol.

The starting materials of the formula I are novel compounds whose conversion to N-phosphonomethylglycine by hydrolysis is the object of the invention.

Compounds of formula (I) wherein R is hydrogen or C1-C4alkyl are prepared by producing bis-N for the preparation of compounds of formula (I) wherein R is C1-C4alkyl. The N '- (chloromethyl) diketopiperazine is reacted with a trialkyl phosphite of formula II wherein R is C 1 -C 4 alkyl, or a diketopiperazine disodium salt is reacted to produce compounds of formula I wherein R is hydrogen. with chloromethylphosphonic acid.

According to a first variant of the process, an excess of tri alkyl phosphite (II) in an inert organic solvent is added to a solution of bis-N, N '- (chloromethyl) dike top iperazine in an inert organic solvent. The by-product alkyl chloride is removed from the reaction mixture by gentle heating. The reaction time is 16 to 20 hours.

In a second variant, the diketopiperazine disodium salt is preferably prepared freshly prior to the reaction and added to a solution of chloromethylphosphonic acid in an organic solvent. The by-product sodium chloride is washed with methanol from the product. Preferably, benzene or xylene may be used as the inert solvent.

The production of starting materials is described in the following literature: bis-N, N '- (chloromethyl1) -diketopiperazine in Helv. Chim. Acta, 678, (1922); chloromethylphosphonic acid in Helv. Chim. Acta 32, 1175 (1949).

Further details of the process according to the invention follow from the following examples without limiting the scope of protection thereto.

Example 1

12.8 g (0.066 mol) of bis-N, N * - (chloromethyl) diketopiperazine are suspended in 200 ml of xylene and a solution of 62.4 ml (60.45 g) is added dropwise; 0.39 moles of triethylphosphite in 10 ml of xylene. The mixture was gradually heated to 110 ° C to give a clear solution. At the start of heating, the gas evolution is rapid and subsides during the reaction. Heating takes about 16 to 18 hours to complete the evolution »or gas leakage. Then the solvent is removed from the mixture by vacuum distillation / oil bath temperature 160 ° C, vapor temperature 80 ° C under pressure

SUBJECT

The excess triethylphosphonate was used. The residual oil was dissolved in about three times the amount of water and purified by filtration, then the solution was evaporated in vacuo. 23.9 g (95 Z) of bis-N, N '- (diethylphosphonomet 1) diketopine perazine are obtained as an oil.

On standing, the oil crystallizes, m.p. 35-38 ° C.

Analysis:

Calcd .: CZ = 40.58; HZ = 6.81; NZ = 6.76; PZ «14.95.

Found: CZ = 40.78; HZ = 7.20; NZ = 6.81; PZ - 14.4.

Example 2

0.46 g (0.02 mol) sodium metal in 20 ml absolute ethanol was added to 1.3 g (0.01 mol) diketopiperazine and stirred vigorously. The suspension obtained is evaporated to dryness in vacuo and the residue is added to 2.28 g (0.02 mol) of chloromethylphosphonic acid dissolved in 60 ml of anhydrous benzene. The mixture thus obtained is kept at boiling point for 1 hour and then evaporated to dryness. The solid residue obtained is taken up in cold 200 ml of methanol and the insoluble material is filtered off. 2.55 g of vis-N, N '- (phosphonomet 1) diketopiperazine (76.1 Z) are obtained. The amorphous substance turns into needles at a temperature between 248-255 ° C, melts at 308-311 ° C with decomposition and browning.

Example 3

22.5 g / 0.0543 moles / bis-N, N * - / 0,0'-diets lf os phonome 1 / dike top ipe is heated under reflux with 180 ml of 68N hydrogen bromide for 8 hours at reflux. The solution obtained is cold filtered, then evaporated under 10.7 to 12 kPa (oil bath temperature 137 to 140 ° C). 60 ml of anhydrous ethanol are added to the obtained crystalline mass and mixed well. The precipitated crystals are filtered, washed with 30 ml of anhydrous ethanol and dried. 14.1 g of N-phosphonomethylglycine are obtained. Yield 76.5%, mp 224-225 ° C (dec.).

Analysis:

Calcd .: CZ = 21.30; HZ = 4.42; NZ = 8.28. Found; CZ = 21.24; HZ = 5.11; NZ = 8.35. Example 4

3.26 g (0.01 mol) of bis-N, N '- (phosphonometyl) diketopiperazine was heated to boiling in 14 ml of 52N hydrogen bromide for 6 hours. The solution obtained is evaporated to dryness under a pressure of 10 to 12 kPa and the solid residue is taken up in 50 ml of anhydrous ethanol, then filtered and dried.

2.58 g of N-phosphonomethylglycine are obtained, yield 72 Z, m.p. 225 DEG-227 DEG C. (with decomposition).

Analysis:

Calcd .: CZ = 21.30; H 2 = 4.72; NZ = 8.28. Found: CZ = 21.27; H 2 = 4.72; NZ = 8.08.

Claims (6)

1. A method for producing N-phosphonomethylglycine, characterized in that the compound of general formula I, ’ O CH 2 ^P \ STEED STEED 0; / ^N \ CH ^h 2 ^c \ _n / ^{c=0 CH} 2- ^P <f ² 11^ STEED OR where R represents a hydrogen atom or an alkyl group with 1 to 4 carbon atoms, is hydrolyzed with aqueous hydrohalic acid at the boiling point of the reaction mixture. 2. The method according to item 1, characterized in that N,N'-/0,0'-dialkylphosphonomethyl/diketopiperazine, preferably bis-N,N'-/0,0*-diethylphosphonomethyl/diketopiperazine, is used as the starting material of the general formula I. 3. The method according to item 1, characterized in that bis-N,N'-/phosphonomethyl/diketopiperazine is used as the starting material of the general formula I. 4. The method according to items 1 to 3, characterized in /1/ that hydrobromic acid is used as the hydrohalic acid. 5. The method according to items 1, 2 and 4, characterized in that the hydrolysis is carried out with 64% aqueous hydrobromic acid by heating the reaction mixture to the boiling temperature for 6 to 8 hours, 6. The method according to items 1, 3 and 4, characterized in that the hydrolysis is carried out with 52% hydrobromic acid by heating the reaction mixture to boiling temperature for 8 hours.