Acetic Acid → 7H-Naphtho(1,2,3-ij)(2,7)naphthyridin-7-one

Dimethylformamide dimethyl acetal (1.50 mL, 11.34 mmol, Aldrich) was added to a solution of cleistopholine, (1.95 g, 8.73 mmol) in dimethylformamide (5 mL). The mixture was then heated for 30 minutes by submerging the reaction vessel into an oil bath preheated to 120° C. At this point, ammonium chloride (4.5 g) and glacial acetic acid (15 mL) were added to the reaction and the heating (120° C.) continued for an additional 30 minutes. After allowing to cool, the reaction was poured onto water (200 mL) and partitioned with methylene chloride (5×100 mL). The combined organic phases were washed with saturated sodium bicarbonate solution (3×100 mL), water (3×100 mL), dried over potassium carbonate, and concentrated to dryness. The residual dark brown solids were chromatographed on silica gel (4×70 cm column, Merck 230-400 mesh) while eluting with ethyl acetate. Concentration of the appropriate column fractions provided pure sampangine (1.60 g, 79%), mp 220-222 (lit. mp 216°-218° C.). IR 1670, 1615, 1590, 1400, 1380, 1320, 1275, 1225, 760, 725 cm−1; 1H and 13C NMR (see Tables I and II).

1. temperatureThe mixture was then heated for 30 minutes
2. custompreheated to 120° C
3. temperatureto cool
4. additionthe reaction was poured onto water (200 mL)
5. custompartitioned with methylene chloride (5×100 mL)
6. washThe combined organic phases were washed with saturated sodium bicarbonate solution (3×100 mL), water (3×100 mL)
7. dry with materialdried over potassium carbonate
8. concentrationconcentrated to dryness
9. customThe residual dark brown solids were chromatographed on silica gel (4×70 cm column, Merck 230-400 mesh)
10. washwhile eluting with ethyl acetate

ORD record

ord-177fc6ab6aaa4ac8b62976e2e3902374

Source dataset

uspto-grants-2005_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06844353B2