Preparation of high purity thiabendazole
AssigneeE. I. Du Pont de Nemours and Company
InventorsLynn E. Applegate, Carl A. Renner
Life of this patent
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Abstract
Process for preparing 2-(4'-thiazolyl)-benzimidazole (generic name: thiabendazole) by the acid-catalyzed condensation of o-phenylenediamine and 4-cyanothiazole using as a solvent polar organic compounds in which the reactants, catalysts and impurities are soluble, and the product, thiabendazole, is substantially insoluble.
Claims12
A process for preparing thiabendazole which comprises reacting 4-cyanothiazole with (a) o-phenylenediamine in the presence of an acid catalyst, or (b) a protonic acid salt of o-phenylenediamine, at a temperature in the range between 85.degree. and 145.degree. C. in a liquid polar organic compound for a time sufficient to effect the desired conversion to thiabendazole, and recovering thiabendazole from the reaction mass;
- said polar organic compound being a liquid in which thiabendazole is substantially insoluble, and 4-cyanothiazole, said catalyst, o-phenylenediamine, and protonic acid salts of o-phenylenediamine, are soluble, and being selected from alkanols containing 3 to 8 carbon atoms, alkanediols containing 2 to 8 carbon atoms, alkane polyethers containing 4 to 10 carbon atoms and 2 to 4 oxygen oxygen atoms, and alkoxyalkanols having 1 to 8 carbon atoms in the alkoxy group and 1 to 8 carbon atoms in the alkanol portion of the molecule.
A process for preparing thiabendazole comprising:
- (a) contacting o-phenylenediamine with an acid catalyst in a polar organic solvent;
- (b) reacting the reaction mixture at its boiling point with 4-cyanothiazole at a mole ratio of o-phenylenediamine to 4-cyanothiazole in the range between 1:0.9 and 1:1.1 for a time sufficient to effect the desired conversion to thiabendazole;
- (c) isolating precipitated thiabendazole from the mother liquor which comprises solubilized impurities;
- (d) washing said solid thiabendazole with an additional quantity of said polar organic solvent and then with water, thereby obtaining a white solid of high purity, and (e) recycling said polar organic solvent wash and recovered mother liquor to said reactor;
- said polar organic compound being a liquid in which thiabendazole is substantially insoluble and o-phenylenediamine, protonic acid salts of o-phenylenediamine, 4-cyanothiazole and said catalyst are soluble, and being selected from alkanols containing 3 to 8 carbon atoms, alkanediols containing 2 to 8 carbon atoms, alkane polyethers containing 4 to 10 carbon atoms and 2 to 4 oxygen oxygen atoms, and alkoxyalkanols having 1 to 8 carbon atoms in the alkoxy group and 1 to 8 carbon atoms in the alkanol portion of the molecule.
Dependencies are inferred from the claim text.