Process for the synthesis of 2,5-dihydroxyterephthalic acid

Abstract

2,5-dihydroxyterephthalic acid is produced in high yields and high purity from 2,5-dihaloterephthalic acid by contact with a copper source and a ligand that coordinates to copper under basic conditions.

Description

technical field [0001] The present invention relates to the preparation of hydroxybenzoates which are valuable for a variety of uses, for example as intermediates or as monomers for the preparation of polymers. Background technique [0002] Hydroxybenzoic acid compounds can be used as intermediates to make many valuable materials, including pharmaceuticals and compounds with crop protection effects, and as monomers to make polymers. In particular, 2,5-dihydroxyterephthalic acid (Formula I, "DHTA") is a synthetic high-strength fiber made, for example, of poly[(1,4-dihydrodiimidazo[4,5-b:4 ', 5'-e]pyridine-2,6-diyl)(2,5-dihydroxy-1,4-phenylene)] useful monomers for fibers. [0003] [0004] Various methods for the preparation of 2,5-dihydroxyterephthalic acid and other hydroxybenzoates are known. Marzin in "Journal fuer Praktische Chemie", 1933, 13, 103-106 proposed the synthesis of 2,5-dibromoterephthalic acid (formula II, "DBTA") in the presence of copper powder - Dihy...

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Problems solved by technology

[0009] The various prior art processes for the preparation of hydroxybenzoic acids are characterized by long reaction times and limited conversions, leading to a significant drop in productivity, or need to be carried out under pressure and / or at elevated temperatures (typically 140 to 250°C) for reasonable rates and productivity

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