Process for the preparation of n,n'-bis(2-hydroxybenzyl)ethylenediamine-n,n'-diacetic acid and its derivatives

A process for the preparation of N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid and its derivatives of general formula I:

• wherein:
• both R have the same meaning and are selected from H, C1-C4alkyl, CH2OH, SO3M, and COOM;
• and
• all M have the same meaning and represent hydrogen atom, Na, K or NH4;
• which comprises:
• reductive amination of glyoxylic acid with a salan compound of general formula (II)
• wherein R have the same meaning as defined for formula (I), by hydrogenation with hydrogen in the presence of a hydrogenation catalyst and an amine proton acceptor in a C1-C3 alkanol or their mixtures, a C1-C3 alkanol/water mixture or in water,
• to obtain the compound of formula (I), wherein M are hydrogen atoms, and
• if desired, converting it further into compound of formula (I), wherein M represent Na, K or NH4 by the treatment with a corresponding base.

A process for the preparation of N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid and its derivatives of general formula I:

• wherein:
• both R have the same meaning and are selected from H, C1-C4alkyl, CH2OH, SO3M, and COOM;
• and
• all M have the same meaning and represent hydrogen atom, Na, K or NH4;
• which comprises:
• a) reaction of ethylenediamine with 2 molar equivalents of a compound of formula (IV)
• wherein R is as defined for formula (I), to obtain a corresponding salen compound of formula (V)
• b) reduction of the salen compound of formula (V) to obtain a compound of formula (II)
• wherein R have the meanings as defined for formula (I),
• c) reductive amination of glyoxylic acid with the compound of formula (II) by hydrogenation with hydrogen in the presence of a hydrogenation catalyst and an amine proton acceptor in a C1-C3 alkanol or their mixtures, a C1-C3 alkanol/water mixture or in water,
• d) if desired, converting it further into compound of formula (I) wherein M represent Na, K or NH4 by the treatment with a corresponding base.

A process for the preparation of N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid derivatives of general formula I:

• wherein
• both R have the same meaning and are selected from C1-C4alkyl;
• and
• all M have the same meaning and represent hydrogen atom, Na, K or NH4;
• which comprises:
• a) reaction of ethylenediamine, a formaldehyde source and a phenol compound of formula (III)
• wherein R is C1-C4alkyl in a molar ratio ethylenediamine:formaldehyde:the phenol compound of about 1:2:2, to obtain a salan compound of general formula (II)
• wherein R have the same meaning as defined above for formula (I), and
• b) reductive amination of glyoxylic acid with the compound of formula (II) by hydrogenation with hydrogen in the presence of a hydrogenation catalyst and an amine proton acceptor in a C1-C3 alkanol or their mixtures, a C1-C3 alkanol/water mixture or in water,
• c) if desired, converting it further into compound of formula (I), wherein M represent Na, K or NH4 by the treatment with a corresponding base.