Derivatives of N-phosphonomethylglycine

A new class of compounds, prepared by reacting a salt of N-phosphonomethylglycine with a cyclic anhydride, have utility as post-emergent herbicides.

This invention relates to a novel class of organic chemical compounds. More 
particularly, the invention is concerned with novel derivatives of 
N-phosphonomethylglycine obtained by reacting a salt of the glycine with a 
cyclic anhydride. This class of compounds have been found to be useful as 
post-emergent herbicides. 
U.S. Pat. Nos. 3,799,758 and 3,868,407 describe the use of 
N-phosphonomethylglycine, and certain esters, amides and salts thereof, as 
phytotoxicants or herbicides to destroy undesirable plants. A very similar 
class of compounds, also including certain simple N-acyl derivatives, is 
described in U.S. Pat. No. 3,853,530 as useful for the non-lethal 
regulation of the natural growth or development of desirable plants such 
as crops. In addition, U.S. Pat. Nos. 3,888,915, 3,910,969 and 3,933,946 
describe various other N-substituted derivatives of 
N-phosphonomethylglycine for either or both of the above-mentioned uses. 
The particular substituents described are nitroso, phenylsulfonamido and 
hydroxy, respectively. 
The novel compounds of the present invention can be illustrated by the 
formula 
##STR1## 
wherein Y is selected from hydrogen, lower alkyl and alkali metal, each Z 
is selected from hydrogen and alkali metal, and R is selected from 
vinylene, methylvinylene, alkylene having a chain length of 2 to 3 carbon 
atoms between the free valences and a total of up to 8 carbon atoms, the 
monochloro derivatives of such vinylene and alkylene, phenylene, 
carboxyphenylene, 3-nitrophenylene, tolylene, cyclohexenylene 
methylcyclohexenylene, cycloalkylene of 4 to 6 carbon atoms, 
dicarboxycycloalkylene of 4 to 6 ring carbon atoms, 
dicarboxybenzoylphenylene, norbornenylene, norbornylidene, 
N-methylpyrrolylidene, pyridylidene, picolylidene and thienylidene, 
provided that the free valences on the cyclic radicals must be in ortho 
relationship with respect to the ring carbon atoms. As employed herein, 
the term "lower alkyl" connotes the straight and branched chain aliphatic 
hydrocarbon radicals of from 1 to 4 carbon atoms. 
Within the genus of the above formula, preferred compounds for purposes of 
this invention are those wherein R is phenylene, cyclohexenylene or 
alkylene having a chain length of 2 to 3 carbon atoms between the free 
valences and a total of up to 5 carbon atoms. 
As will be described below, one of the reactants employed in preparing 
these novel compounds is a cyclic anhydride. It should be recognized that 
R in the above formula represents the central core of such an anhydride if 
the 
##STR2## 
group is removed. The alkylene radicals represented by R are those wherein 
the chain is obtained from succinic or glutaric anhydride, and they 
include the substituted chains such as those from 3,3-dimethylglutaric, 
2,4-diethylglutaric and 2,2-dipropylsuccinic anhydrides. The cyclic 
radicals represented by R are those wherein the ring is obtained from 
anhydrides such as phthalic, the isomeric tetrahydrophthalics, tri- and 
hemi- mellitic, pyridine-, thiophene- and norbornanedicarboxylic, the 
cycloalkane dicarboxylics and the like. In the specific case where R 
represents tolylene, it should be understood that this includes the rings 
obtained from the isomeric methylphthalic anhydrides and also from 
homophthalic anhydride (the .alpha., 2-tolylene radical). 
It should also be recognized that the cyclic anhydrides which are employed 
as reactants herein include certain dianhydrides such as benzophenone 
tetracarboxylic dianhydride and the cycloaliphatic tetracarboxylic 
dianhydrides. As illustrated in certain of the examples below, reaction 
takes place across one of the anhydride groups while the second anhydride 
group is opened to produce ortho dicarboxy substituents. 
The novel compounds of the present invention are prepared by condensing the 
appropriate cyclic anhydride with a di(alkali metal) salt of 
N-phosphonomethylglycine or with a mono(alkali metal) salt of a lower 
alkyl glycinate. Said salts are obtained by adding alkali metal hydroxide 
to the N-phosphonomethylglycine or glycinate in the conventional manner, 
it being understood that the product of such addition will contain a 
hydroxyl group attached to the phosphorus atom. The anhydride and the salt 
can be employed in about equimolar quantities, although it is preferred to 
employ an excess of said anhydride to assist in completion of the 
reaction. 
This reaction is generally conducted at about room temperature, and cooling 
means can be used if exothermic increases occur. During this reaction the 
pH should be in the range of about 6 to 10, preferably about 7 to 9, and 
this pH range can be readily maintained by periodic additions of alkali as 
needed. 
The product of this reaction is a tri-salt of the formula above (wherein Y 
and each Z are alkali metal) or a glycinate di-salt (wherein Y is lower 
alkyl and each Z is alkali metal). As hereinafter described, said product 
can be used in this form, without isolation or purification, or it can be 
acidified to remove the alkali metal. Acidification or the reaction 
product may be accomplished in some cases by treatment with HCl although 
this procedure can cause partial or complete reversal of the reaction. It 
is much preferred, therefore, to acidify the salt product via ion exchange 
chromatography using an ion exchange resin in the acid form.