Dibromoterephthalic acid

The Sandoz company used the dibromoterephthalic acid method. This acid was made from p-xylcnc by brominating it to form 2,5-dibromo-p-xylene and then oxidising this to 2,5-dibromoterephthalic acid. Reaction of one mole of this acid with two moles of an arylamine in the presence of copper(II) acetate gives 2,5-bis(arylamino)terephthalic acid, which can be ring-closed to a linear quinacridone. Unsymmetrical substitution using two different arylamines is possible. 

Nuclear halogen often makes oxidation more difficult it protects alkyl groups against attack. Thus oxidation of 4-chloro-m-xylene and 2,5-dibromo-p-xylene by chromic acid proceeds only as far as 4-chloro-w-toluic and 2,5-dibromo-p-toluic acid, respectively 401 the latter requires alkaline permanganate for conversion into the dibromoterephthalic acid.402... 

Chardonnens and Salamin also synthesized a number of substituted [l,2-h]IF diones, which were typically made in the same fashion as the [l,2-a]IF diones described earlier (Scheme 3) [43]. For example, treatment of 2,5-dibromoterephthalic acid (32) with thionyl chloride and subsequent Friedel-Crafts acylation with 33a-d provided 34a-d (Scheme 8). Intramolecular arylation at elevated temperatures furnished IF-diones 35a-d in 20-28% yield. This technique has also been successfully applied to asymmetric 1,3,4-trisubstituted diones as well as 2,3,8,9-tetrasubstituted diones [42]. 

Friedman modification of the Rosenmund-v. Braun nitrile synthesis. A mixture of 2,5-dibromoterephthalic acid, GuGN, and dimethylformamide heated slowly with stirring to reflux, after 1 hr. poured into a soln. of FeGlg in aq. HGl, and warmed 10 min. at 60° to decompose the complex pyromelitimide. Y ... 

Aliphatic acid chlorides may be similarly a-chlorinated by heating them with a mixture of chlorosulfonic acid, chlorine, an antioxidant, oxygen and TCNQ at 100-120 °C (see Chapter 5, p 171). Terephthalic acid 3 can be converted into 2,5-dibromoterephthalic acid 4 by heating with bromine in chlorosulfonic acid in the presence of iodine catalyst at 40-80 °C (Equation 2). The 2,5-dibromo compound 4 is used as an intermediate in the production of flame-retardant polymers. 

A modification of the synthesis of the tetrarylindenofluorenes 186 shown in Scheme 86 has been used to prepare ladder-type pentaphenylenes (Scheme 88) [283]. The dibromoterephthalate was coupled with two equivalents of a flu-orene boronate instead of a benzene boronic acid to give a pentaphenylene 188. Reaction with an aryl lithium, followed by ring closure with boron trifluoride, gave the ladder-type pentamers 189, which were brominated to prepare dibromomonomers that were then polymerised using nickel(O). 

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