Method for preparation of salts of n-phosphonomethylglycine

Abstract

Disclosed is a method for the preparation of salts of N-phosphonomethylglycine which comprises the steps of (a) reacting hydantoin or a 3-substituted hydantoin, a compound of the formula ##STR1## wherein R is selected from the group consisting of hydrogen, alkyl having from 1 to 10 carbon atoms, aryl having from 6 to 12 carbon atoms, alkylcarbonyl wherein the alkyl group has from 1 to 10 carbon atoms, and arylcarbonyl wherein the aryl group has from 6 to 12 carbon atoms, with paraformaldehyde in the presence of a low molecular weight carboxylic acid at a temperature and for a sufficient period of time to produce a mixture of intermediate products, including the 1-hydroxymethyl derivative of the starting hydantoin; (b) converting said 1-hydroxymethyl derivative to the 1-phosphonomethyl derivative by thereafter adding to the reaction mixture either (i) a substituted phosphorus compound selected from the group consisting of phosphorus trichloride, and phosphorus tribromide; or (ii) adding to the reaction mixture phosphorous acid and a anhydride selected from the group consisting acetic anhydride, propionic anhydride, butyric anhydride, or mixture thereof, and continuing said reaction at a temperature and for a sufficient period of time to cause completion of the reaction to form the 1-phosphonomethyl derivative; and (c) hydrolyzing the 1-phosphonomethylhydantoin product thus formed with a base selected from the group consisting of alkali metal or alkaline earth hydroxide, to produce a salt of N-phosphonomethylglycine.