Process for the preparation of N-substituted glycine acids or glycine esters and the use of the process for indigo synthesis
AssigneeDSM Chemie Linz GmbH
InventorCarlo Kos
Life of this patent
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Abstract
Process for the preparation of an N-substituted glycine ester or an N-substituted glycine acid by reaction of a glyoxylic acid ester half-acetal (hemiacetal) or glyoxylic acid half-acetal (hemiacetal) with an amine and hydrogenation of the intermediate product formed by this reaction, and the use of the process in a process for the preparation of indoxyl and indigo derivatives by cyclization of an N-arylglycine ester, prepared by the above process, in a molten alkali metal carbonate or alkaline earth metal carbonate with or without addition of an alkali metal amide, and if appropriate oxidation of the indoxyl derivative formed by this reaction to give the corresponding indigo derivative.
Claims10
A process for the preparation of an N-substituted glycine ester or an N-substituted glycine acid of the formula
- R.sub.1 R.sub.2 N--CH.sub.2 --COOR I
- in which R is hydrogen or a straight-chain or branched alkyl group having 1 to 10 C atoms and R.sub.1 and R.sub.2 independently of one another are hydrogen, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group where R.sub.1 and R.sub.2 are not simultaneously hydrogen, which comprises reacting a glyoxylic acid ester half-acetal or glyoxylic acid half-acetal (hemiacetal) of the formula
- R.sub.3 (OH)CH--COOR II
- in which R has the abovementioned meaning and R.sub.3 is an alkyl group having 1 to 4 C atoms, with an amine of the formula
- R.sub.1 R.sub.2 NH III
- in which R.sub.1 and R.sub.2 have the abovementioned meaning, in a diluent at temperatures from 0.degree. C. up to the reflux temperature of the diluent used, and treating the resulting intermediate product with hydrogen under pressure in the presence of a hydrogenation catalyst and a diluent, the N-substituted glycine ester or the N-substituted glycine acid of the formula I being formed, and, if desired, isolating this from the reaction mixture and if appropriate converting it into a salt or, in the case of the glycine ester, into the free acid.
Dependencies are inferred from the claim text.