J. K. Laha, K. S. Satyanarayana Tummalapalli., A. Gupta
FULL PAPER
General Procedure for the Synthesis of Phenazines: In a screw-
capped vial that was equipped with a rubber septum, a mixture of
the o-phenylenediamine (0.5 mmol), the 1,2-dibromobenzene
(0.5 mmol), Pd(OAc)2 (11 mg, 0.05 mmol), S-Phos (20.5 mg,
0.05 mmol), and Cs2CO3 (537 mg, 1.65 mmol) in toluene (2 mL)
was purged with argon for approximately 10 min and then heated
at 110 °C for 16 h under argon. The reaction mixture was cooled
to room temperature and then diluted with an excess amount of
ethyl acetate. The obtained suspension was filtered through a Celite
bed, and the filtrate was concentrated under reduced pressure. The
residue was purified by column chromatography on silica gel (pe-
troleum ether/ethyl acetate, 4:1 to 3:2) to give the phenazine.
13C NMR (100 MHz, CDCl3): δ = 166.5, 153.3, 152.7, 144.1,143.7,
143.2, 140.6, 132.0, 130.4, 129.1, 128.3, 103.3, 103.1, 102.9,
52.6 ppm. HRMS: calcd. for C15H11N2O4 [M + H]+ 283.0719;
found 283.0710. IR (KBr): ν = 2318, 1725, 1635, 1446, 1275, 1260,
˜
1082, 764, 749 cm–1.
Phenazine-2-carbonitrile (8):[22] Yellow solid; m.p. 212–214 °C. 1H
NMR (400 MHz, CDCl3): δ = 8.67 (d, J = 1.3 Hz, 1 H), 8.34 (d,
J = 8.9 Hz, 1 H), 8.25–8.29 (m, 2 H); 7.90–7.97 (m, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 144.6, 144.4, 143.8, 141.8, 136.6,
132.4, 131.8, 131.5, 130.0, 129.8, 129.6, 118.0, 113.8 ppm. HRMS:
calcd. for C13H8N3 [M + H]+ 206.0718; found 206.0709. IR (KBr):
ν = 1635, 1446, 1275, 1260, 1083, 1020, 764, 750 cm–1.
˜
N1-(2-Bromophenyl)benzene-1,2-diamine [1(i)]:[20] Pale yellow li-
7-Methoxyphenazine-2-carbonitrile (9): Yellow solid; m.p. 190–
194 °C. 1H NMR (400 MHz, CDCl3): δ = 8.58 (d, J = 1.2 Hz, 1
H), 8.31 (d, J = 8.8 Hz, 1 H), 8.12 (d, J = 9.5 Hz, 1 H), 7.86 (dd,
J = 8.8, 1.6 Hz, 1 H), 7.61 (dd, J = 9.5, 2.7 Hz, 1 H), 7.41 (d, J =
2.6 Hz, 1 H), 4.07 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 162.3, 146.2, 142.3, 142.2, 141.8, 135.6, 131.4, 130.8, 128.7, 128.4,
118.2, 113.6, 104.4, 56.1 ppm. HRMS: calcd. for C14H10N3O [M +
H]+ 236.0824; found 236.0818.
1
quid. H NMR (400 MHz, CDCl3): δ = 7.50 (dd, J = 7.9, 1.3 Hz,
1 H), 7.10 (m, 3 H), 6.84 (dd, J = 7.8, 1.2 Hz, 1 H), 6.79 (dt, J =
7.5, 1.3 Hz, 1 H), 6.67 (dt, J = 7.8, 1.4 Hz, 1 H), 6.58 (dd, J = 8.1,
1.4 Hz, 1 H), 5.73 (s, 1 H), 3.83 (s, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 143.1, 143.0, 132.5, 128.3, 127.1, 127.0, 126.6, 119.5,
119.0, 116.0, 114.2, 110.2 ppm. HRMS: calcd. for C12H12BrN2 [M
+ H]+ 263.0184; found 263.0180. IR (Nujol): ν = 3456, 3375, 1275,
˜
1260, 764, 749 cm–1.
8-Methoxyphenazine-2-carbonitrile (10): Yellow solid; m.p. 251–
253 °C. 1H NMR (400 MHz, CDCl3): δ = 8.64 (d, J = 1.2 Hz, 1
H), 8.26 (d, J = 8.9 Hz, 1 H), 8.13 (d, J = 9.5 Hz, 1 H), 7.91 (dd,
J = 8.9, 1.76 Hz, 1 H), 7.60 (dd, J = 9.5, 2.7 Hz, 1 H), 7.42 (d, J
= 2.6 Hz, 1 H), 4.07 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 162.8, 146.5, 143.9, 142.0, 140.3, 136.5, 131.1, 130.6, 129.9,
128.1, 118.3, 112.1, 104.3, 56.1 ppm. HRMS: calcd. for C14H10N3O
[M + H]+ 236.0824; found 236.0812.
2-Methoxyphenazine (2):[11b] Yellow solid; m.p. 123–125 °C. 1H
NMR (400 MHz, CDCl3): δ = 8.21 (d, J = 8.4 Hz, 1 H), 8.17 (d,
J = 9.5 Hz, 1 H), 8.10 (d, J = 9.5 Hz, 1 H), 7.74–7.84 (m, 2 H),
7.51 (dd, J = 9.5, 2.7 Hz, 1 H), 7.41 (d, J = 2.7 Hz, 1 H), 4.02 (s,
3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 161.3, 145.0, 143.3,
141.9, 140.7, 130.6, 130.4, 129.6, 129.0, 128.8, 126.4, 104.4,
55.9 ppm. HRMS: calcd. for C13H11N2O [M + H]+ 211.0871;
found 211.0871.
Methyl 7-Cyanophenazine-2-carboxylate (11):[22] Yellow solid; m.p.
Methyl Phenazine-2-carboxylate (3):[21] Dark brown solid; m.p.
152–154 °C. 1H NMR (400 MHz, CDCl3): δ = 9.03 (d, J = 1.6 Hz,
1 H), 8.42 (dd, J = 9.0, 1.6 Hz, 1 H), 8.27–8.32 (m, 3 H), 7.88–7.94
(m, 2 H), 4.07 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
166.2, 144.7, 144.3, 144.1, 142.5, 133.0, 131.7, 131.6, 131.0, 130.0,
129.9, 129.7, 129.3, 52.7 ppm. HRMS: calcd. for C14H11N2O2 [M
1
242–245 °C. H NMR (400 MHz, CDCl3): δ = 9.03 (s, 1 H), 8.72
(d, J = 9.1 Hz, 1 H), 8.48 (d, J = 8.8 Hz, 1 H), 8.35–8.42 (m, 2 H),
7.98 (d, J = 8.8 Hz, 1 H), 4.08 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 145.5, 143.8, 142.7, 136.7, 133.3, 133.1, 132.9, 131.8,
131.6, 131.1, 130.7, 130.6, 130.3, 130.1, 52.9 ppm. HRMS: calcd.
for C15H10N3O2 [M + H]+ 264.0773; found 264.0763. IR (KBr): ν
˜
+ H]+ 239.0821; found 239.0815. IR (KBr): ν = 1725, 1617, 1275,
˜
= 1725, 1621, 1446, 1275, 1260, 1083, 1020, 764, 750 cm–1.
1260, 764, 749 cm–1.
Pyrido[2,3-b]quinoxaline (12):[24] Dark brown solid; m.p. 145–
147 °C. 1H NMR (400 MHz, CDCl3): δ = 9.37 (dd, J = 3.8, 1.9 Hz,
1 H), 8.62 (dd, J = 8.6, 1.9 Hz, 1 H), 8.39 (dd, J = 6.6, 3.4 Hz, 1
H), 8.29 (dd, J = 6.6, 3.4 Hz, 1 H), 7.91–7.95 (m, 2 H), 7.79 (dd,
J = 8.6, 3.8 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
156.5, 149.5, 145.0, 144.2, 139.1, 138.5, 131.6, 131.4, 130.3, 129.4,
125.5 ppm. HRMS: calcd. for C11H8N3 [M + H]+ 182.0718; found
182.0718.
2-(Trifluoromethyl)phenazine (4): Pale yellow solid; m.p. 170–
172 °C. H NMR (400 MHz, CDCl3): δ = 8.61 (s, 1 H), 8.39 (d, J
1
= 9.1 Hz, 1 H), 8.27–8.30 (m, 2 H), 7.98 (dd, J = 9.1, 1.9 Hz, 1 H),
7.90–7.96 (m, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 144.5,
144.2, 143.7, 142.0, 132, 131.7, 131.6, 131.3, 131.2, 129.9, 129.8,
128.1, 128.0, 125.5, 124.9 (q, J = 275 Hz) ppm. HRMS: calcd. for
C13H8F3N2 [M + H]+ 249.0640; found 249.0631.
[1,3]Dioxolo[4,5-b]phenazine (5): Pale brown solid; m.p. 170–171 °C.
1H NMR (400 MHz, CDCl3): δ = 8.13 (dd, J = 10, 2.6 Hz, 2 H),
7.75 (dd, J = 9.32, 2.6 Hz, 2 H), 7.39 (s, 2 H), 6.22 (s, 2 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 152.2, 142.8, 141.6, 129.2, 128.8,
103.2, 102.6 ppm. HRMS: calcd. for C13H9N2O2 [M + H]+
225.0664; found 225.0662.
3-(Trifluoromethyl)pyrido[2,3-b]quinoxaline (13): Yellow solid; m.p.
115–117 °C. 1H NMR (400 MHz, CDCl3): δ = 9.52 (d, J = 2.4 Hz,
1 H), 8.93 (d, J = 1.2 Hz, 1 H), 8.31–8.44 (m, 2 H), 7.99–8.04 (m,
2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 151.5, 150.0, 146.0,
145.0, 137.0, 136.9, 136.8, 133.0, 132.4, 130.4, 129.7, 128.9, 127.6,
127.5, 127.3, 126.3, 124.1 (q, J = 275 Hz), 121.4, 119.5, 117.4 ppm.
HRMS: calcd. for C12H7F3N3 [M + H]+ 250.0592; found 250.0589.
7-Methoxy-[1,3]dioxolo[4,5-b]phenazine (6): Pale yellow solid; m.p.
252–254 °C. 1H NMR (400 MHz, CDCl3): δ = 7.99 (d, J = 9.3 Hz,
1 H), 7.41 (dd, J = 9.3, 2.7 Hz, 1 H), 7.33–7.36 (m, 3 H), 6.19 (s,
2 H), 3.99 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 160.4,
152.1, 151.0, 143.1, 142.6, 140.8, 138.5, 129.8, 124.2, 104.6, 103.4,
102.9, 102.4, 55.7 ppm. HRMS: calcd. for C14H11N2O3 [M + H]+
255.0770; found 255.0760.
Pyrido[3,4-b]quinoxaline (14): Yellow solid; m.p. 171–173 °C. 1H
NMR (400 MHz, CDCl3): δ = 9.81 (s, 1 H), 8.85 (d, J = 6.1 Hz, 1
H), 8.35 (d, J = 8.5 Hz, 1 H), 8.29 (d, J = 8.0 Hz, 1 H), 8.08 (d, J
= 6.1 Hz, 1 H), 7.92–8.01 (m, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 156.7, 146.2, 145.6, 144.5, 144.3, 138.1, 132.9, 131.4,
130.5, 129.7, 121.1 ppm. HRMS: calcd. for C11H8N3 [M + H]+
182.0718; found 182.0707.
Methyl [1,3]Dioxolo[4,5-b]phenazine-7-carboxylate (7): Brown solid;
m.p. 239–241 °C. 1H NMR (400 MHz, CDCl3): δ = 8.88 (d, J =
1.5 Hz, 1 H), 8.31 (dd, J = 8.9, 1.7 Hz, 1 H), 8.16 (d, J = 4.7 Hz,
1 H), 7.41 (s, 1 H), 7.40 (s, 1 H), 6.26 (s, 2 H), 4.03 (s, 3 H) ppm.
[1,3]Dioxolo[4,5-g]pyrido[3,4-b]quinoxaline (15): Tan solid; m.p.
1
287–290 °C. H NMR (400 MHz, CDCl3): δ = 9.63 (s, 1 H), 8.76
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Eur. J. Org. Chem. 2013, 8330–8335