[CH3:1][O:2][C:3]([C:5]1[N:10]=[CH:9][C:8]2[N:11]=[C:12]([C:14]3[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=3)[O:13][C:7]=2[C:6]=1[OH:20])=[O:4].[Br:21]N1C(=O)CCC1=O.C(OOC(=O)C1C=CC=CC=1)(=O)C1C=CC=CC=1>C1C=CC=CC=1>[CH3:1][O:2][C:3]([C:5]1[N:10]=[C:9]([Br:21])[C:8]2[N:11]=[C:12]([C:14]3[CH:15]=[CH:16][CH:17]=[CH:18][CH:19]=3)[O:13][C:7]=2[C:6]=1[OH:20])=[O:4]A suspension of 7-hydroxy-2-phenyl-oxazolo[4,5-c]pyridine-6-carboxylic acid methyl ester (3.57 g, 13.2 mmol; example 1d), N-bromosuccinimide (2.47 g, 13.9 mmol), and benzoyl peroxide (320 mg, 1.32 mmol) in 43 mL of benzene was heated at reflux temperature for 5 hours. The reaction mixture was washed successively with saturated sodium bicarbonate, brine, saturated ammonium chloride solution, and brine. The organic solution was dried, filtered, and concentrated. The residue was purified by flash chromatography eluting from silica gel with a gradient of 0-25% methanol in methylene chloride to give 2.81 g of the title compound as a light yellow solid. MS: (+) m/z 348.9, 350.9 (M+1, 79Br/81Br).
Wird geladen…
