Tetrahydrofuran → 3,7-Dibromodibenzo(b,d)thiophene

Participants

Reaction Steps

Into a 1 L 3-necked round-bottomed flask equipted with a reflux condenser, nitrogen inlet, magnetic stirring bar and a heating mantle was place 4.63 g (0.122 mol) of LiAlH4, and 600 mL of dry tetrahydrofuran (THF) (distilled from benzophenone ketyl). To this was added 18.31 g (0.0489 mol) of 3,7-dibromodibenzothiophene-5,5-dioxide. The mixture was stirred overnight at room temperature, then refluxed for 1 hour. To the cooled mixture was added 5 mL H2O, 5 mL of 15% NaOH, followed by 15 mL of water. After stirring for 2 hours at room temperature the coagulated salts were filtered and washed with THF. The combined THF extracts were condensed to give 20 g of crude material. This was taken up into 1.5 L of hot ethanol, filtered and cooled. The yellow precipitate was suction filtered and air dried to give 5.2 g of 3,7-dibromodibenzothiophene: mp 174.5-176. Molecular ions by mass spectroscopy had molecular weights of 340, 342 and 344 (due to different isotopes of Br).

Provenance & Evidence