Boron tribromide → 5-Carbamoyl-4-hydroxy-1-chlorocarbazole

Participants

Reaction Steps

A solution of 0.66 g of 9-benzyl-5-carbamoyl-4-methoxy-1-chlorocarbazole in 40 ml of dichloromethane was cooled in an ice bath treated dropwise with 14 ml of 1.0 M boron tribromide solution in dichloromethane. The reaction was allowed to warm to room temperature slowly over 2 hours and then quenched by pouring into ice and then adding 50 ml of 1 N HCl. The mixture was extracted with dichloromethane (3×200 ml) and the extracts were washed with brine, dried with magnesium sulfate and concentrated. The aqueous layers exhibited a precipitate and was then extracted twice with ethyl acetate, washed with brine, dried with magnesium sulfate and concentrated to afford 0.287 g of the subtitle compound. The first residue was chromatographed on silica gel using 0.5% methanol in dichloromethane to afford another 93 mg of the subtitle compound. (total yield 80%) ESIMS m/e 259 (M+−1) NMR (300 MHz, d6-DMSO): δ11.79 (s, 1H); 10.76 (s, 1H); 8.87 (br s, 1H); 8.41 (br s, 1H); 7.77 (t, J=4.6, 1H); 7.48 (d, J=4.2, 2H); 7.34 (d, J=8.5, 1H); 6.54 (d, J=8.5, 1H).

Provenance & Evidence