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NotesH2 (1170 ml) had ceased. The catalyst was removed by filtration (Filter-Cel) and washed with fresh ethanol. The combined filtrates were cautiously neutralized with saturated NaHCOs and concentrated at reduced pressure to ca. 200 ml. This residue was diluted with benzene, washed with H20, and dried (Na2S04). Solvent removal gave a light yellow solid which was filtered through silica gel with 7:3 benzene-ether to give 15.4 g of light tan solid. Crystallization from CH2Cl2-ether gave 11.72 g (71.3%) of dione 2b as fine white needles, sintered at 171°, mp 173-175°. The analytical sample was prepared by a second crystallization from CH2Cl2-ether of similarly prepared material: mp 170.5-174°; uv max (C2H5OH) 222 nm (e 4750); ir (CHCls) 1740 (C-17 C=0), 1714 (C-5 C=0), and 1638 cm-1 (isoxazole);[a] 25d +122.0°(c 0.895, CHCls); mass spectrum (70 eV) m/e 329 (M+) and 110 (base peak); nmr (CDCls) 0.99 (s, 3, C-18 CHS), 2.20 (s, 3), and 2.37 ppm (s, 3, 2 isoxazole CH3); ORD (dioxane) [o+so +560°, [a]2$2 ±0°, [a]244 -938°( sh), [a]276 -2276°( min), [a)295 ±0°, and [ ] 7 +2926°(max).

In conclusion, the ring bromination of kojic acid derivatives takes place at the 6 position, but the reaction occurs only when the 5-hydroxyl is free. Experimental SectionBromination of Chlorokojic Acid (2) with NBS. A mixture of 1.54 g of 2, 1.8 g of NBS, and 10 ml of CeHe was refluxed for 1 hr and was concentrated under vacuum.The residue was washed with water and recrystallized twice from absolute C2H5OH to yield 0.49 g of 3: mp 162-163°; positive Feds; ir (Nujol) 3150, 1580 cm-1.Bromination of Kojic Acid Monoacetate (9) with NBS. The same procedure was used with 0.197 g of 9, and yielded 0.217 g of 11 after recrystallization from CCI4, mp 131-133°, ir (Nujol) 3350, 1740, 1640 cm-1.

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