Riedel-De Haen Aktiengesellschaft

Wolfgang Dannenberg

Horst Schmand

Walter Heyer

Manfred Zimmermann

Theo Doldissen

2,2-Bis[4-(2,3-dibromopropoxy)-3,5-dibromophenyl]-propane (BDDP) has the structural formula ##STR1## This bisphenol-A derivative is prepared by reaction of 2,2-bis[4-hydroxy-3,5-dibromophenyl]-propane with an allyl halide and subsequent bromination of the diallyl ether obtained. In the first reaction step, a lower aliphatic alcohol is used as solvent, and in the second reaction step an aromatic halogenated hydrocarbon. The reaction product is then precipitated by excess alcohol, and separated. The BDDP is obtained in the form of granules and is suitable for application as flameproofing agent.

2,2-Bis[4-(2,3-dibromopropoxy)-3,5-dibromophenyl]-propane process

In a process for resolving racemic DL-.alpha.-aminocarboxylic acids the said acids are reacted in an inert solvent with an aromatic o-hydroxy aldehyde to obtain an azomethine derivative which is reacted in the same stage with an optically active amine base to give a salt. The diastereomeric salt obtained is separated and the respective optically active .alpha.-aminocarboxylic acid is obtained therefrom by an acid treatment. By this process aliphatic and aromatic .alpha.-amino-carboxylic acids can be resolved, especially p-hydroxyphenyl glycine.

Process for resolution of racemic DL-.alpha.-aminocarboxylic acids

Optically active 2-amino-2-phenylacetic acid of the formula ##STR1## in which R.sub.1, R.sub.2 and R.sub.3, which are identical or different, denote hydrogen, halogen, hydroxy, alkyl, acyl, or alkoxy, is prepared by asymmetrical transformation of a corresponding DL-aminophenylacetonitrile with L(+)-tartaric acid. To this end the corresponding DL-2-amino-2-phenyl-acetonitrile is reacted with approximately equimolar amounts of L(+)-tartaric acid in the presence of at least one alkanol having from 1 to 5 carbon atoms and/or at least one carbonyl compound at a temperature of from 0.degree. to 50.degree. C. and the mixture is stirred for 2 to 120 hours at the indicated temperature. The crystallized transformation product is separated, hydrolyzed by treatment with an acid and the desired product is isolated.

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Wolfgang Dannenberg