Hydrogen Bromide → 3,9-Dibromo-5,7-dihydrodibenzo[c,e]oxepine

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Reaction Steps

HBr (11 mL, 97 mmol) was added to a THF (10 mL) solution of (4,4′-dibromobiphenyl-2,2′-diyl)dimethanol (for preparation, see: Tetrahedron Letters 2004, 45, 2801; 1.3 g, 3.49 mmol), and the mixture was refluxed for six hours and then allowed to cool to ambient temperature. Most of the organic component was removed with a rotervap, and the residue was extracted with CH2Cl2 (10 mL, 3×). The combined organic phase was dried (MgSO4), filtered, and concentrated in vacuo to afford a brown oil, which when dissolved in 5 mL acetone and allowed to stand at ambient condition for 1 h afforded a precipitate. Filtration and drying in vacuo afforded 3,9-dibromo-5,7-dihydrodibenzo[c,e]oxepine as a white solid (0.628 g, 51% yield). 1H NMR (DMSO-d6, δ=2.5, 500 MHz): 4.23-4.29 (m, 4H), 7.53-7.60 (m, 2H), 7.74 (dd, J=7.9, 2.1, 2H) 7.79 (d, J=2.1, 2H).

Provenance & Evidence