2.4- Dihydroxy-5-bromobenzoic acid

Thirty grams of purified 2,4-dihydroxy-5-bromobenzoic acid is refluxed for twenty-four hours with 375 cc. of water, and the resulting solution is filtered, cooled, and extracted with a 400-cc. and a 200-cc. portion of ether. The ether is removed by evaporation, and the 4-bromoresorcinol is dried on a steam bath. The yield of product melting at 100-102° (Note 2) is 22-22.5 g. (90-92 per cent of the theoretical amount). 

Strains of Pseudomonas putida are very versatile in metabolizing aromatic compounds, particularly to the corresponding 1,2-dihydro-l,2-diols. The hydroxylating enzyme of the P. putida mutant is not strongly substrate specific and alkyl, aryl and halogen functionalities are usually readily tolerated380. Thus, 4-bromobenzoic acid (1, R = Br) is converted to a. v-4-bro-mo-5,6-dihydroxy-l, 3-cyclohexadiene-l-carboxylic acid (2, R = Br) in 80% yield with 98% cc (determined by chiral NMR shift experiments on the 4-nitrobenzyl ester) 375. The absolute stereochemistry, (5R,6R), was determined by a single crystal X-ray analysis. 

Methoxy-6-bromobenzoic acid and phloroglucine boiled 1 min. in 1 N NaOH, containing a little CuS04 —d-methoxyA -dihydroxy-dibenzo-a-pyrone. Y 70%. (F. e. with lower yields s. E. Lederer and J. Polonsky, Bl. 1948, 831.)... 

A mixture of 2-hydroxy-3-methoxy-6-bromobenzoic acid, anhydrous AIGI3, and dry benzene refluxed 6 hrs. while additional AICI3 is added after 4 hrs. 2,3-dihydroxy-6-bromobenzoic acid. Y 90.4%. Ghem. 25, 721 (1960). 

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