[CH3:1][C:2]1[CH:3]=[CH:4][C:5]2[O:14][C:9]3=[N:10][CH:11]=[CH:12][CH:13]=[C:8]3[C:7](=[O:15])[C:6]=2[CH:16]=1.[Br:17]N1C(=O)CCC1=O>C(OOC(=O)C1C=CC=CC=1)(=O)C1C=CC=CC=1.C(Cl)(Cl)(Cl)Cl>[Br:17][CH2:1][C:2]1[CH:3]=[CH:4][C:5]2[O:14][C:9]3=[N:10][CH:11]=[CH:12][CH:13]=[C:8]3[C:7](=[O:15])[C:6]=2[CH:16]=1A mixture of 42 g of 7-methyl-5-oxo-5H-[1]benzopyrano[2,3-b]pyridine, 36 g of N-bromosuccinimide, 0.4 g of benzoyl peroxide and 420 ml of carbon tetrachloride is refluxed with stirring under ultraviolet light for 2 hours. The reaction mixture is quickly filtered while it is hot. The crystals are suspended in hot water (about 60°C), and the suspension is thoroughly stirred and filtered again. The crystals are recrystallized from dioxane to give 47.1 g of 7-bromomethyl-5-oxo-5H-[1]benzopyrano[2,3-b]pyridine melting at 211°-212.5°C.
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