4,4-bis-(carboxyphenylsulfonyl)diphenyl ethers, process for their preparation and their use

摘要

Novel aromatic carboxylic acids are represented by the general formula [V]: wherein R₁ is hydrogen or a carboxyl group, and R₂ and R₃, which may be the same or different, are hydrogen, a lower alkyl group containing from 1 to 5 carbon atoms or a carboxyl group; and n is the number of substituents other than hydrogen and is an integer of from 0 to 4; Preferably R₁ is hydrogen. The carboxylic acids may be used in producing useful polymers such as polyesters, polyamides and polyimides. The carboxylic acids may be made by a process which comprises the step of oxidizing a compound represented by the general formula [IV]: wherein R₄ is hydrogen or a methyl group; R₅ and R₆, which may be the same or different, are hydrogen or a lower alkyl group containing from 1 to 5 carbon atoms; and n is the number of substituents other than hydrogen and is an integer of from 0 to 4, with molecular oxygen in a liquid phase in an aliphatic carboxylic acid solvent in the presence of a cobalt-manganese-bromine catalyst.