Process for preparing N-phosphonomethylglycinonitrile or derivat

Details Process for preparing N-phosphonomethylglycinonitrile or derivat Process for preparing N-phosphonomethylglycinonitrile or derivat

1995-10-05

1997-02-25

McKane, Joseph

Organic compounds -- part of the class 532-570 series

Organic compounds

Phosphorus esters

562 17, C07F 938, C07F 940

Patent

active

056060939

DESCRIPTION:

BRIEF SUMMARY
This application was filed under 35 USC 371 and is a continuation of PCT International Application No. PCT/GB94/0051, which was filed on Mar. 15, 1994.
The present invention relates to a process for the manufacture of N-phosphonomethylglycinonitrile or salts and esters thereof.
N-phosphonomethylglycinonitrile is a known compound, useful as a herbicide. It may also be converted by hydrolysis into the commercially important herbicide N-phosphonomethylglycine.
N-phosphonomethylglycinonitrile is described for example in U.S. Pat. No. 4,221,583. An alternative process for the manufacture of N-phosphonomethylglycine via the intermediate formation of N-phosphonomethylglycinonitrile is described in U.S. Pat. No. 3,923,877 whilst a related process which is also believed to proceed via N-phosphonomethylglycinonitrile as an intermediate is described in U.S. Pat. No. 4,415,503.
A process for the preparation of a diaryl ester of N-phosphonomethylglycinonitrile is disclosed in U.S. Pat. No. 4,083,898, and in EP-A-0068732 there is disclosed a process for the manufacture of monoesters and diesters of N-alkyl-substituted amino methyl phosphonic acid using a trisubstituted hexahydro-1,3,5-triazine as starting material.
We have now found that the action of a trialkylphosphite phosphonating agent on methyleneaminoacetonitrile trimer in the presence of an acid and an inert solvent provides an improved process which is well adapted to manufacture on a commercial scale and which provides excellent yields of N-phosphonomethylglycinonitrile in the form of a salt of its alkyl ester containing an exceptionally low level of impurities.
According to the present invention there is provided a process for the manufacture of an acid salt of an alkyl ester of N-phosphonomethylglycinonitrile which comprises reacting methyleneaminoacetonitrile trimer with a trialkylphosphite under anhydrous conditions and in the presence of an anhydrous acid and an inert solvent in which the methyleneaminoacetonitrile trimer starting material is at least partially soluble and the acid salt of the alkyl ester of N-phosphonomethylglycinonitrile product is substantially insoluble and thereafter recovering the precipitated acid salt of the alkyl ester of N-phosphonomethylglycinonitrile.
The description methyleneaminoacetonitrile trimer as used herein refers to the compound of formula as shown in Scheme 1 which illustrates the process of the present invention. In Scheme 1, the groups R in the trialkylphosphite (II) represent C.sub.1-7 alkyl groups and preferably C.sub.1-5 alkyl groups and the trialkylphosphite is thus preferably a tri (C.sub.1-7 alkyl)phosphite or a tri(C.sub.1-5 alkyl)phosphite.
The trialkylphosphite is preferably trimethylphosphite, triethylphosphite or tributylphosphite. Trimethylphosphite is a readily available phosphonating agent which is thus a particularly effective feedstock for the commercial manufacture of N-phosphonomethylglycinonitrile. Higher alkyl phosphites such as tributylphosphite and tripentylphosphite may provide advantages in terms of commercial production of product as indicated in more detail below.
Suitable anhydrous acids which can be used in the process of the present invention and which will form an insoluble salt of the alkyl ester of N-phosphonomethylglycinonitrile product will occur to those skilled in the art. Hydrogen halides are especially suitable for use in the process of the present invention. Hydrogen chloride in particular is an effective and readily available anhydrous acid.
The solvent should be inert in the sense that it is not significantly attacked under the reaction conditions, and in particular the solvent should be stable against attack by the trialkylphosphite. Suitable inert solvents in which the methyleneaminoacetonitrile trimer starting material is at least partially soluble and the acid salt of the alkyl ester of N-phosphonomethylglycinonitrile product is substantially insoluble will occur to those skilled in the art. It is to be understood that the methyleneaminoacetonitrile trimer starting mater

REFERENCES:
patent: 3923877 (1975-12-01), Barton
patent: 4083898 (1978-04-01), Dutra
patent: 4415503 (1983-11-01), Robbins

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