Br[CH2:2][CH2:3][C:4]1[CH:9]=[CH:8][C:7]([B:10]([OH:12])[OH:11])=[CH:6][CH:5]=1.[N+:13]([C:16]1[NH:17][CH:18]=[CH:19][N:20]=1)([O-:15])=[O:14].C(=O)([O-])[O-].[K+].[K+]>CN(C)C=O>[N+:13]([C:16]1[NH:17][CH:18]=[C:19]([CH2:2][CH2:3][C:4]2[CH:9]=[CH:8][C:7]([B:10]([OH:12])[OH:11])=[CH:6][CH:5]=2)[N:20]=1)([O-:15])=[O:14]4-(2-Bromoethyl)phenyl boronic acid (0.525 g, 2.72 mmol) and 2-nitroimidazole (0.3 g, 2.72 mmol) were heated in dry dimethylformamide (15 ml) in presence of anhydrous potassium carbonate (1.38 g, 10 mmol) under nitrogen with stirring at 60°-70° C. for 48 hours. Dimethylformamide was removed under reduced pressure and the resulting gum was dissolved in a minimum amount of water and acidified with 2N hydrochloric acid. The precipitated solid was filtered off and washed with water. The combined aqueous portion was again extracted with ethyl acetate (5×50 ml). The organic layer was dried, concentrated and combined with the previously precipitated solid and chromatographed (silica gel). Elution with 1:1 ethyl acetate/hexane yielded some unreacted starting bromide (0.1 g); continued elution with 2:1 ethyl acetate/hexane provided the required boronic acid as a pale yellow crystalline solid. The product was recrystallized from tetrahydrofuran/hexane. Yield: 0.25 g (36%), m.p. 229°-231° C., M.S. (M+H)+ 262.
Wird geladen…
