Method and intermediates for preparing high purity 3,3'-azo-bis-(6-hydroxy benzoic acid)
AssigneePharmacia Corporation
InventorsKarl H. Agback, Alf S. Nygren
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Abstract
A method of preparing 3,3'-azo-bis-(6-hydroxy benzoic acid) of formula I ##STR1## and salts thereof in at least 98% purity for treating inflammatory intestinal diseases. According to the invention a compound II ##STR2## is diazotized, and the diazonium salt obtained is coupled with a compound III ##STR3## The formed intermediate IV, which is also comprised by the invention, ##STR4## is hydrolized in alkaline medium to form the compound I. R.sub.1, R.sub.2 and R.sub.3 signify lower alkyl, R.sub.2 also possibly substituted phenyl.
Claims16
A method of preparing 3,3'-azo-bis-(6-hydroxy benzoic acid) of formula I ##STR10## or salts thereof, comprising the steps of:
- diazotizing a compound of formula II or a salt thereof ##STR11## wherein R.sub.1 is lower alkyl and R.sub.2 is lower alkyl, phenyl or alkyl substituted phenyl, coupling the diazonium salt obtained in alkaline aqueous solution to a compound of formula III ##STR12## wherein R.sub.3 is hydrogen or lower alkyl, to form a compound of formula IV ##STR13## wherein R.sub.1, R.sub.2 and R.sub.3 are as indicated above, and hydrolizing in alkaline medium the compound of formula IV, and isolating the compound of formula I or a salt thereof.
3,3'-azo-bis-(6-hydroxy benzoic acid) or salts thereof of at least 98% purity pharmaceutically acceptable purity.
Dependencies are inferred from the claim text.