Hydrochloric Acid → 5-Bromo-1,2,3,4-tetrahydronaphthalen-1-one

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Reaction Conditions

Reaction Steps

To prepare this compound, 1-tetralone (10.2 g, 70 mmol) was added dropwise to a slurry of aluminum trichloride (23.3 g, 175 mmol) heated to 70° C. in a 3-neck flask with an outlet tube connected to a 2 M sodium carbonate solution. The slurry was stirred with a spatula. After the addition of 1-tetralone, the slurry was removed from heat and allowed to cool to room temperature. Bromine (12.3 g, 77 mmol) was added dropwise over 15 minutes. After that addition was complete, the slurry was heated at 80° C. for 10 minutes, then it was poured into a mixture of 200 grams of ice and 25 mL concentrated HCl. The 3-neck flask was rinsed with water and that rinse water was also added to the ice and slurry solution. That solution was extracted twice with ether (200 mL each) and those two extracts were combined. The combined ether extract was washed sequentially with water (50 mL), saturated sodium bicarbonate (25 mL), and brine (100 mL), and then was dried over sodium sulfate, filtered, and concentrated under reduced pressure to afford an oil. The oil was subjected to flash chromatography (12% THF/hexanes), and the resultant product was recrystallized from hexanes to afford 4.4 g (27%) of 5-bromo-3,4-dihydro-2H-naphthalen-1-one. 1H NMR (500 MHz, CDCl3) δ 8.03 (dd, J=7.7, 1.2, 1H), 7.75 (dd, J=7.7, 1.2, 1H), 7.20 (t, J=7.8, 1H), 3.03 (t, J=6.2, 2H), 2.66 (t, J=6.5, 2H), 2.15-2.20 (m, 2H).

Provenance & Evidence