Process for the preparation of 2-phosphonobutane-1,2,4-tricarboxylic acids and their alkaline metal salts

摘要

- Prepn. of 2-phosphonobutan-1,2,4-tricarboxylic acid (I) or its alkali metal salts involves (1) reacting dialkyl phosphite (II) with dialkyl ethen-1,2-dicarboxylate (III) in 1:(1-1.1), pref. 1:(1.03-1.07) molar ratio in the presence of alkali metal (m)ethylate to tetraalkyl phosphonosuccinate (IV); (2) reacting (IV) with 0.9-1.1, pref. 1-1.07 mole alkyl acrylate (V) in the presence of an alkali metal (m)ethylate as catalyst, with addn. of MeOH or EtOH, giving pentaalkyl 2-phosphonobutan-1,2,4-tricarboxylate (V); and (3) acid hydrolysis of (V) to (I) at 100-150, pref. 105-130 degrees C, pref. using (I) as catalyst. The intermediates (IV) and (VI) are used in the next step without a working up or purificn. stage. In (II), (III) and (V), alkyl = Me or Et. The novelty is that, in step (2), (IV) and (V) are reacted batchwise at -20 to +50, pref. 0 to +25 degrees C with a residence time of over 500, pref. over 700 min in the presence of 1-2, pref. ca. 1.5 mole MeOH or EtOH and 5-50, pref. 10-40 mmole alkali metal (m)ethylate w.r.t. 1 mole (I).