Patents by Inventor Wolfgang Dannenberg

Wolfgang Dannenberg has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 4302614
    Abstract: 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.
    Type: Grant
    Filed: February 11, 1980
    Date of Patent: November 24, 1981
    Assignee: Riedel-de Haen Aktiengesellschaft
    Inventors: Wolfgang Dannenberg, Walter Heyer, Theo Doldissen, Manfred Zimmermann
  • Patent number: 4285884
    Abstract: 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.
    Type: Grant
    Filed: November 1, 1978
    Date of Patent: August 25, 1981
    Assignee: Riedel-de Haen Aktiengesellschaft
    Inventors: Wolfgang Dannenberg, Horst Schmand
  • Patent number: 4233456
    Abstract: 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.
    Type: Grant
    Filed: August 28, 1978
    Date of Patent: November 11, 1980
    Assignee: Riedel-de Haen Aktiengesellschaft
    Inventors: Horst Schmand, Wolfgang Dannenberg