Resorcinol 2,4-dibromo

The 2,4-dihydroxy-3,5-dibromobenzoic acid invariably present is in this way converted into the very soluble 2,4-dibromo-resorcinol and removed. The monobromo acid is decarboxylated much more slowly. 

It should be noted that NBS can cause nuclear bromination when that reaction occurs readily. In the absence of a catalyst it can brominate the nucleus of condensed aromatic compounds such as naphthalene, anthracene, and phenanthrene,399 veratrole, the dimethyl ethers of resorcinol and hydro-quinone,389 and pyrogallol trimethyl ether.390 Pyrocatechol and 2 moles of NBS afford 4,5-dibromopyrocatechol resorcinol and 3 moles of NBS afford 2,4,6-tribromoresorcinol 391,392 and anthranilic or o- or/ -hydroxybenzoic acid with 2 moles of NBS afford the 4,5- or 3,5-dibromo derivatives.391-393 However, nuclear bromination of benzene and toluene is effected by NBS only if equimolar amounts of A1C13, ZnCl2, FeCl3, or H2S04 are added. 

Also obtained by Friedel-Crafts acylation of 2,4-dibromo-resorcinol with phenylacetyl chloride in nitrobenzene in the presence of alumininm chloride, first at r.t. overnight, then heating on a steam bath for 4 h (44%) [5176]. 

To confirm that the electron density of 7-oxygen plays a role in suppression of COX-2 transcriptional activity, resacetophenone was brominated to reduce die electron density. As shown in Figure 5, 3,5-dibromo-2,4-dihydroxyacetophenone (BHAP) has a lower electron density for oxygens at positions 2 and 4 in the resorcinol moiety than resacetophenone. BHAP suppressed COX-2 transcriptional activity in a dose-dependent manner, and was 6.8-times more potent than resacetophenone 11). 

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