Scheme 1. Unsymmetric 5,10-Diaryldihydrophenazine
Table 1. Synthesis of Unsymmetrically Substituted
5,10-Diaryl-5,10-dihydrophenazines
Synthesis
Ar2, X (method, solvent, T (°C),
yield
(%)
1
Ar1
time (h))
1a Ph
p-tolyl, Br
(A, o-xylene, reflux, 3)
p-anisyl, Br
(A, o-xylene, reflux, 3)
p-(dimethoxymethyl)phenyl, Br
(A, o-xylene, reflux, 3)
p-formylphenyl (from 1c)
p-cyanophenyl, Br
79
55
74
1b Ph
1c Ph
unsymmetrical diaryldihydrophenazines, the in situ prepara-
tion of 5-aryl-5,10-dihydrophenazine is a key step. Applica-
tion to EL devices is also reported for some of the
derivatives.
1d Ph
1e Ph
95
44
(A, o-xylene, reflux, 3)
2-thienyl, Br
(A, o-xylene, reflux, 3)
1f Ph
37
42
52
53
48
69
Scheme 1 illustrates the synthesis of unsymmetrically
substituted 5,10-diaryl-5,10-dihydrophenazines. The reaction
of aryllithium (Ar1Li; 1.3-1.4 equiv in ether or ether-
cyclohexane) with phenazine (1.0 equiv) in toluene or
o-xylene proceeds smoothly at room temperature. Quenching
of the reaction with deaerated water gave air-sensitive 5-aryl-
5,10-dihydrophenazine (2). The organic layer containing 2
was transferred with a syringe into another flask containing
dried Na2SO4 under inert atmosphere and kept in a refrigera-
tor as a stock solution of 2. The cross-coupling reaction of
2 with aryl halide (Ar2X; 0.75 equiv, mainly bromide) was
achieved using a catalyst combination of NaOtBu (1.50
equiv)-Pd(OAc)2 (0.020 equiv)-P(tBu)3 (0.015 equiv) in
toluene or o-xylene under heated conditions (method A),6
or using NaOtBu (1.50 equiv)-Pd(dba)2 (0.020 equiv)-
P(tBu)3 (0.015 equiv) at room temperature (method B),7
giving the desired unsymmetrically substituted diaryldihy-
drophenazines 1 (Table 1).8
1g p-n-butylphenyl Ph, Br
(A, toluene, reflux, 3)
1h p-n-butylphenyl p-tolyl, Br
(A, toluene, reflux, 3)
1i p-n-butylphenyl p-anisyl, Br
(A, toluene, reflux, 3)
1j Ph
1j Ph
1k Ph
p-(N,N-diphenylamino)phenyl, Br
(A, o-xylene, reflux, 3)
p-(N,N-diphenylamino)phenyl, Br
(B, o-xylene, rt, 3)
p-[N-(1-naphthyl)-N-phenylamino]- 66
phenyl, Br
(B, o-xylene, rt, 3)
1l Ph
p-(N,N-diphenylamino)biphenyl, I
(B, toluene, reflux, 4)
70
The reaction similarly proceeded when Ar1 was an
n-butylphenyl group (1g-i). These experiments (for 1g-i)
are useful when one applies them to compounds with
multiple coupling sites, where the products may have poor
solubility in organic solvents. For instance, we could easily
prepare 5,5′-(m-phenylene)bis(10-p-n-butylphenyl-5,10-di-
hydrophenazine) using m-diiodobenzene as a double-coupler
in a good yield (∼65%). The n-butyl derivative was soluble
in various organic solvents in contrast to the hardly soluble
5,5′-(m-phenylene)bis(10-phenyldihydrophenazine).9
Furthermore, this method can be extended to prepare
electronically interesting diarylamine-incorporating dihydro-
phenazines 1j-l, which are potentially useful compounds
as electroluminescent materials.
5-p-Formylphenyl-10-phenyl-5,10-dihydrophenazine 1d
was synthesized through the protection of the aldehyde group.
4-Cyanophenyl and heteroaromatic thienyl groups could also
be introduced, although the yields were moderate.
(8) Selected Compound Data. 1f: colorless needles; mp 251 °C; 1H
NMR (600 MHz, C6D6) δ 5.80 (dd, 2H, J ) 7.8, 1.3 Hz), 6.21 (dd, 2H, J
) 7.8, 1.3 Hz), 6.31 (td, 2H, J ) 7.7, 1.4 Hz), 6.36 (td, 2H, J ) 7.6, 1.3
Hz), 6.64-6.68 (m, 2H), 6.82 (dd, 1H, J ) 5.3, 1.6 Hz), 7.03 (t, 1H, J )
7.4 Hz), 7.07 (d, 2H, J ) 7.3 Hz), 7.14 (d, 2H, J ) 7.7 Hz); 13C NMR
(150 MHz, C6D6) δ 113.21, 114.03, 121.45, 122.24, 126.25, 126.79, 128.28,
128.46, 131.33, 131.53, 136.48, 137.03, 140.60, 142.90; MS (FAB) m/z
340 [M]+. Anal. Calcd for C22H16N2S: C, 77.62; H, 4.74; N, 8.23. Found:
1
C, 77.50; H, 4.57; N, 8.12. 1j: yellow powder; mp 270 °C dec; H NMR
(400 MHz, C6D6) δ 5.81 (dd, 2H, J ) 7.8, 1.5 Hz), 6.03 (dd, 2H, J ) 7.8,
1.4 Hz), 6.28 (td, 2H, J ) 7.6, 1.2 Hz), 6.35 (td, 2H, J ) 7.6, 1.2 Hz), 6.85
(tt, 2H, J ) 7.1, 1.2 Hz), 7.00-7.10 (m, 17 H); 13C NMR (100 MHz, C6D6)
δ 113.05, 121.34, 121.43, 123.67, 125.29, 129.75, 131.37, 131.60, 132.21,
134.11, 137.26, 137.34, 140.82, 147.84, 147.95; HRMS (FAB) m/z calcd
for C36H27N3 501.2205, found 501.2225. 1k: yellow powder; mp 254 °C;
1H NMR (300 MHz, C6D6) δ 5.78-5.81 (m, 2H), 6.01-6.04 (m, 2H), 6.25-
6.37 (m, 4H), 6.79 (t, 1H, J ) 7.1 Hz), 6.95-7.24 (m, 17H), 7.53 (d, 1H,
J ) 7.7 Hz), 7.63 (d, 1H, J ) 7.1 Hz), 8.11 (d, 1H, J ) 8.1 Hz); 13C NMR
(75 MHz, C6D6) δ 113.01, 121.29, 121.41, 122.73, 122.90, 123.65, 124.53,
126.57, 126.68, 126.84, 126.96, 128.80, 129.62, 131.36, 131.60, 131.71,
132.19, 135.88, 137.25, 137.38, 143.76, 148.27, 148.51; MS (FAB) m/z
551 [M]+. Anal. Calcd for C40H29N3: C, 87.08; H, 5.30; N, 7.62. Found:
C, 86.91; H, 5.25; N, 7.55. 1l: yellow powder; mp >300 °C; 1H NMR
(300 MHz, C6D6) δ 5.82-5.85 (m, 2H), 5.92-5.95 (m, 2H), 6.26-6.34
(m, 4H), 6.87 (t, 2H, J ) 7.0 Hz), 7.04-7.23 (m, 17 H), 7.34 (d, 2H, J )
8.6 Hz), 7.49 (d, 2H, J ) 8.4 Hz); 13C NHR (75 MHz, C6H6) δ 113.11,
113.19, 121.45, 123.38, 124.18, 124.93, 129.62, 129.67, 131.41, 131.60,
131.93, 134.42, 137.13, 137.18, 139.39, 140.67, 140.79, 147.99, 148.14;
MS (FAB) m/z 577 [M]+. Anal. Calcd for C42H31N3: C, 87.32; H, 5.41; N,
7.27. Found: C, 87.03; H, 5.34; N, 6.97.
Synthesis of symmetrically substituted diaryldihydro-
phenazine is much simpler than that of the unsymmetrically
substituted ones, as illustrated in Scheme 2.
The double-coupling reaction of dihydrophenazine (1.0
equiv) with bromobenzene (2.0 equiv) in the presence of
NaOtBu (3.0 equiv)-Pd(OAc)2 (0.040 equiv)-P(tBu)3 (0.030
equiv) in toluene at 80 °C (method A) produced 5,10-
diphenyl-5,10-dihydrophenazine (3a) in 85% yield, in con-
trast to the poor 16% yield by the Ullmann-type procedure.1
A similar procedure using NaOtBu (3.0 equiv)-Pd(dba)2
(0.040 equiv)-P(tBu)3 (0.030 equiv) (method B) effectively
(9) Terada, E.; Okamoto, T.; Kozaki, M.; Sato, K.; Shiomi, D.; Takui,
T.; Okada, K. To be published.
374
Org. Lett., Vol. 5, No. 3, 2003