Dimethylformamide → 4-(6-Bromonaphth-2-ylthio)phthalic acid

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Reaction Steps

Triethylamine (3.1 ml) was added dropwise to a stirred mixture of 5-bromophthalic anhydride (5-bromo-1,3-dihydro-2-benzofuran-1,3-dione; 4.54 g), 6-bromo-2-naphthalenethiol (European Patent Application No. 0409413, Example 19; 5.25 g) and DMF (50 ml) and the mixture was stirred at ambient temperature for 10 minutes. The mixture was heated at 60° C. for 1 hour and then stirred at ambient temperature for 16 hours. The solvent was evaporated and the residue was suspended in methanol (60 ml). The mixture was basified by the addition of 2M aqueous sodium hydroxide solution and the mixture was heated to reflux for 1 hour. The mixture was cooled ambient temperature and partitioned between water (300 ml) and diethyl ether. The aqueous layer was acidified by the addition of concentrated hydrochloric acid and extracted with ethyl acetate (2×100 ml). The combined extracts were washed with water and with brine, dried (MgSO4) and evaporated. The residue was triturated under diethyl ether to give 4-(6-bromonaphth-2-ylthio)phthalic acid (6 g, 74%) as a pale yellow solid;

Provenance & Evidence