Process for preparing 2-arylbenzimidazole-5-sulfonic acids
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United States of America Patent
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Dec 5, 1995
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app pub date -
Oct 1, 1993
filing date -
Feb 4, 1992
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Abstract
The invention relates to an improved process for preparing 2-arylbenzimidazole-5-sulfonic acids of the formula I, ##STR1## in which Ar is unsubstituted phenyl or phenyl substituted by one or more C.sub.1 -C.sub.6 alkyl or alkoxy groups and m is 1, 2 or 3, wherein o-phenylenediamine is reacted in the presence of sulfuric acid at between room temperature and 250.degree. C. with a benzoic acid derivative of the formula II Ar(--X).sub.m II in which Ar and m are as above, and X is COO-alkyl, where alkyl is n-alkyl having from 1 to 6 C atoms, COOH, COCl, COBr or CN, and new arylbenzimidazole acids of the formula Ia ##STR2##
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