Sulfuric Acid → 3-Bromo-5,7,8,9-tetrahydro-6H-benzo[7]annulen-6-one

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Reaction Steps

To a solution of 3-amino-6,7,8,9-tetrahydro-5H-benzocyclohepten-6-one (9.42 g) in a mixture of acetic acid (1.85 ml), conc. sulfuric acid (9.24 ml) and water (24.56 ml) was added portionwise a solution of sodium nitrate (4.08 g) in water (6.00 ml) with ice salt bath cooling and the whole was stirred for 1 hour. The solution was added to a solution of cuprous bromide (10.02 g) and sodium bromide (9.40 g) in a mixture of 47% hydrobromic acid (27.72 ml) and water (61.52 ml) at 75° C. and the whole was stirred for 0.5 hour. After cooling, ice water (100 ml) and chloroform (200 ml) were added to the mixture. The insoluble material was filtered off. The organic layer was separated and the aqueous layer was extracted with chloroform. The combined organic layer was washed with brine, dried over anhydrous sodium sulfate, and treated with active carbon (0.65 g). The solution was evaporated in vacuo and the residue was purified by column chromatography on silica gel with toluene as an eluent to give 3-bromo-6,7,8,9-tetrahydro-5H-benzocyclohepten-6-one (6.34 g).

Provenance & Evidence