Process for preparing phosphorus-containing dicarboxylic acids

Abstract

The present invention relates to a process for preparing of phosphorus-containing dicarboxylic acids of the formula (I) ##STR1## where R.sup.1 and R.sup.2 are identical or different and are each a straight-chain or branched alkyl radical having from 1 to 8 carbon atoms, a cycloaliphatic radical having 5 or 6 carbon atoms in the ring, an unsubstituted or substituted aryl radical having from 6 to 10 carbon atoms, or R.sup.1 and R.sup.2 form, with inclusion of the phosphorus atom, a ring having from 5 to 8 members, and m and n are each, independently of one another 0 or 1, by reacting a compound of the formula (II) ##STR2## where R.sup.1, R.sup.2 and m are as defined above, with fumaric acid, maleic acid or itaconic acid in the presence of a saturated aliphatic monocarboxylic acid having a total of from 1 to 5 carbon atoms as solvent at from 100.degree. to 200.degree. C. under atmospheric pressure or superatmospheric pressure.

Dependencies are inferred from the claim text.