ORDER
REPRINTS
5,10-DIOXYPHENAZINE-2-CARBOXYLIC ACID
2333
CH2Cl2, washed with a saturated solution of K2CO3 and then with H2O.
The organic layer was evaporated and the resulting precipitate was washed
with ligroin to yield 564 mg (86%) of 6 as an orange solid. The product was
pure enough to be used in the next step without further purification. An
analytical sample was obtained by flash chromatography (70 : 30 cyclohex-
ane/AcOEt). m.p.130ꢁC. IR (KBr): 1728, 1349, 1271, 1227 cmꢃ1. H-NMR
1
(CDCl3): d 2.50 (m, 2H, H7 and H8), 2.76 (m, 2H, H7 and H8), 3.96 (s, 3H,
CH3), 5.80 (m, 2H, H6 and H9), 8.37 (dd, 1H, J3-4 ¼ 9 Hz, J3-1 ¼ 2 Hz, H3),
8.63 (d, 1H, J4-3 ¼ 9 Hz, H4), 9.22 (d, 1H, J1-3 ¼ 2 Hz, H1). MS (CI/NH3) m/z
433 [MH]þ, 417 [MH-O]þ. Anal. Calcd. for C14H12Br2N2O4, 0.5 H2O: C,
38.12; H, 2.97; N, 6.35. Found: C, 38.37; H, 2.88; N, 6.18.
Methyl 5,10-dioxyphenazine-2-carboxylate 7
To a solution of 6 (250 mg, 0.579 mmol) in CH3OH (25 mL) was added
t-BuOK (1.06 g, 9.48 mmol) at 0ꢁC. The reaction mixture was maintained at
0ꢁC for 1 h. The mixture was acidified to pH 1 with a 1 N HCl solution,
diluted with H2O and extracted with AcOEt. The organic layer was washed
with H2O, dried over Na2SO4, filtered and evaporated. Addition of ligroin
followed by filtration afforded a crude product which was purified by flash
chromatography (70 : 30 ligroin/AcOEt) to give 125 mg (80%) of 7 as a red
solid. m.p. 177ꢁC (dec.). IR (KBr): 1724, 1354, 1284, 1094 cmꢃ1. H-NMR
1
(CDCl3): d 3.97 (s, 3H, CH3), 7.80 (m, 2H, H7 and H8), 8.31 (dd, 1H,
J3-4 ¼ 7 Hz, J3-1 ¼ 2 Hz, H3), 8.65 (m, 3H, H4, H6 and H9), 9.33 (d, 1H,
J1-3 ¼ 2 Hz, H1). MS (CI/NH3) m/z 288 [MþNH4]þ, 271 [MH]þ, 255
[MH-O]þ, 239 [MH-2O]þ. Anal. Calcd. for C14H10N2O4: C, 62.22; H,
3.73; N, 10.37. Found: C, 62.03; H, 3.85; N, 10.04.
5,10-Dioxyphenazine-2-carboxylic acid 8
To a suspension of ester 7 (350 mg, 1.30 mmol) in CH3OH (80 mL) was
added a solution of sodium hydroxide (520 mg, 13.0 mmol) in H2O (80 mL).
The resulting suspension was refluxed for 10 min. After cooling, the reaction
mixture was acidified to pH 2 with a 6 N HCl solution. The resulting pre-
cipitate was filtered off, washed with H2O, and then dried to give 309 mg
(93%) of 8 as an orange solid. m.p. 280ꢁC [lit.1 m.p. 280ꢁC (C2H5OH)]. IR
(KBr): 3105-2360 (br), 1705, 1348, 1278, 1070, 765 cmꢃ1. 1H-NMR (DMSO-
d6): d 8.00 (m, 2H, H7 and H8), 8.30 (dd, 1H, J3-4 ¼ 9 Hz, J3-1 ¼ 2 Hz, H3),
8.60 (m, 3H, H4, H6 and H9), 9.00 (d, 1H, J1-3 ¼ 2 Hz, H1), 13.8 (s, 1H,
COOH).