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US 2003/0191320 A1Published application
Process for the preparation of bis-benzazolyl compounds
OwnerVictor Paul Eliu, Julia Hauserinventors
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OwnerVictor Paul Eliu, Julia Hauserinventors
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The present invention provides a process for the preparation of a compound of formula (I) wherein Y represents —O—, —S— or —N(R2)—, R2 being hydrogen, C1-C10alkyl or aralkyl; Z represents a 2,5-furanyl, 2,5-thiophenyl, 4,4′-stilbenyl or a 1,2-ethyleny residue and R1 represents hydrogen, halogen, C1-C10alkoxyl, cyano, COOM or SO3M, M being hydrogen or an alkaline or alkaline earth metal, characterized by reacting a compound of formula (II) with a dicarboxylic acid of formula (III): HOOC-Z-COOH, or an ester thererof, Y, Z and R1 being as previously defined, in N-methylpyrrolidone or N,N-dimethylacetamide, in the presence of an acidic catalyst and, optionally, in the presence of a secondary solvent capable of removing water from the reaction mixture, which are useful as optical whitening agents for natural and synthetic materials.
A process for the preparation of a compound of the formula
Dependencies are inferred from the claim text.
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Condensed with carbocyclic rings or ring systems: having two or more ring systems containing condensed 1,3-oxazole rings
Benzimidazoles; Hydrogenated benzimidazoles: two benzimidazolyl-2 radicals linked together directly or via a hydrocarbon or substituted…
Having two or more ring systems containing condensed 1,3-oxazole rings: linked in positions 2 and 2' by chains containing six-membered aromatic…
With only hydrocarbon or substituted hydrocarbon radicals attached in position 2: with aromatic rings or ring systems directly attached in position 2
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The present invention relates to a process for the preparation of bis-benzazolyl compounds which are useful as optical whitening agents for natural and synthetic materials.
Various methods for the preparation of such compounds are known.
Thus, for example, U.S. Pat. No. 4,508,903 describes the preparation of 4,4′-bis.benzoxazol-, benzthiazol- and benzimidazol-2-ylstilbenes by dimerisation of the corresponding p-chloromethylphenylbenzazoles. However, such methods suffer from the disadvantage that the preparation of the intermediates involves several reaction steps, subsequently rendering poor overall yields.
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250 g of N-methylpyrrolidone are charged to a reaction vessel and 82 g of 98% stilbene-4,4′-dicarboxylic acid, followed by 75 g of 99% 2-aminophenol, 10 g of boric acid and 30 g of xylene are added with stirring. The apparatus, equipped with a Dean and Stark water trap, is evacuated and the vacuum released with nitrogen. The light yellow suspension is heated to 195° C. and stirred at this temperature for 18 hours, during which time 23-25 ml of water and approximately 25 g of xylene are distilled off through the water trap. The reaction mixture is cooled to 20° C. and stirring continued for 1 hour at this temperature. The yellow suspension is filtered, washed with 100 g of N-methylpyrrolidone to give 350 g of a brown solution which may be used as solvent for a further charge and then with three 80 g portions of water. The resulting press-cake is dried under a vacuum of 50 mbar at 100° C. to yield 120 g of the compound of formula (101) as a yellow solid, characterized by a UV absorption maximum λmax at 368 nm with an extinction coefficient ε of 71000.
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