42
S. Ameen et al. / Dyes and Pigments 124 (2016) 35e44
300 mmol) was added drop-wise under stirring. The mixture was
stirred at room temperature for 5 h followed by hydrolysis with
500 mL of water. The product was extracted with CH2Cl2
(3 ꢂ 200 mL). The organic layer was washed with H2O (2 ꢂ 300 mL),
dried over MgSO4, and evaporated under vacuum to yield 25.4 g
(91%) of a light green solid which was recrystallized from absolute
ethanol to get an off-white solid.
3.3.5. Synthesis of 1,8-dibromo-3,6-di-tert-butyl-9-ethyl-9H-
carbazole (5)
Compound (5) was prepared following the method used for the
preparation of (2) using (3) (3.07 g, 10 mmol), DMF (30 mL), and
NBS (3.56 g, 20 mmol). Pure product (4.1 g, 88.4%) was obtained as
white crystals upon recrystallization from absolute ethanol.
1H NMR (300 MHz, CDCl3, ppm):
d
¼ 7.96 (d, J ¼ 1.5 Hz, 1H), 7.65
1H NMR (300 MHz, CDCl3, ppm):
d
¼ 8.07 (s, 2H), 7.85 (s, 1H),
(d, J ¼ 1.8 Hz, 1H), 5.22 (q, J ¼ 7.2 Hz, 2H), 1.43 (s, 18H), 1.39 (t,
7.47 (m, 2H), 7.33 (d, J ¼ 8.4 Hz, 2H), 1.45 (s, 18H).
J ¼ 6.9 Hz, 3H).
13C NMR (100 MHz, CDCl3, ppm):
123.29, 116.15, 109.98, 34.68, 32.03.
d
¼ 142.20, 138.00, 123.49,
13C NMR (100 MHz, CDCl3, ppm):
d
¼ 144.16, 136.09, 130.27,
126.20, 115.30, 103.04, 39.30, 34.57, 31.77, 17.12.
3.3.6. General procedure for BuchwaldeHartwig coupling
A mixture of the bromocompound (1 mol. eq. w.r.t. Br), diaryl-
amine (1 mol. eq. w.r.t. NH), Pd2(dba)3 (5 mol.% eq.), tBu3P
(20 mol.%), and tBuONa (3 mol. eq.) in toluene was heated under N2
atmosphere at reflux temperature for 10e20 h. The reaction
mixture was then filtered. The filtrate was evaporated under vac-
uum and the residue was subjected to column chromatography on
silica gel.
3.3.2. Synthesis of 1-bromo-3,6-di-tert-butyl-9H-carbazole (2)
To a solution of (1) (10.5 g, 37.5 mmol) in DMF (100 mL), a so-
lution of N-bromosuccinimide (6.66 g, 37.5 mmol) in DMF (10 mL)
was added drop-wise, under light protection, over 10 min, and the
mixture was stirred at room temperature for 3 h. Water (300 mL)
was added and the resulting mixture was extracted with CH2Cl2
(50 mL ꢂ 3). The combined organic phase was washed with water
(150 mL ꢂ 2), dried over anhydrous MgSO4, and evaporated in
vacuo where upon an off white sticky liquid was obtained which
was subjected to silica gel column chromatography (hexane/
dichloromethane, 4/1) to get a colourless oil. This oil was dissolved
in methanol followed by evaporation of the solvent to get a white
glassy solid (11.5 g, 85.4%).
3.3.7. Synthesis of 3,6-di-tert-butyl-9-ethyl-N,N-diphenyl-9H-
carbazol-1-amine (DPACz1)
Compound (5) was prepared by employing the general Pd-
catalyzed coupling procedure using (3) (0.966 g, 2.5 mmol),
diphenylenediamine (0.457 g, 2.7 mmol), Pd2(dba)3 (0.116 g,
0.127 mmol), tBu3P (0.104 g, 0.507 mmol), and tBuONa (0.72 g,
7.5 mmol) in toluene (10 mL). (5) was obtained as a white solid
(0.99 g, 83.9%) by column chromatography (n-Hexane/DCM, 2:1).
1H NMR (300 MHz, CDCl3, ppm): 8.05 (m, 3H), 7.59 (d, J ¼ 1.5 Hz,
1H), 7.52 (m, 1H), 7.39 (m, 1H), 1.45 (s, 9H), 1.44 (s, 9H).
13C NMR (100 MHz, CDCl3, ppm):
136.69, 125.72, 124.61, 124.34, 123.62, 116.62, 115.45, 110.51, 103.66,
34.86, 34.73, 31.97, 30.90.
d
¼ 144.00, 142.89, 137.73,
1H NMR (400 MHz, CDCl3, ppm):
d
¼ 8.10 (d, J ¼ 1.2Hz,1H), 8.03(d,
J ¼ 2.0 Hz, 1H), 7.50 (dd, J ¼ 8.8, 2.0 Hz, 1H), 7.24 (d, J ¼ 8.8 Hz, 1H),
7.20e7.16 (m, 5H), 7.08 (d, 8.0 Hz, 4H), 6.90 (t, J ¼ 7.2 Hz, 2H), 4.36 (q,
J ¼ 6.8 Hz, 2H), 1.45 (s, 9H), 1.36 (s, 9H), 0.87 (t, J ¼ 6.8 Hz, 3H).
3.3.3. Synthesis of 3,6-di-tert-butyl-9-ethyl-9H-carbazole (3)
To a stirred solution of 3,6-di-tert-butyl-9H-carbazole (5.59 g,
20 mmol) and tetrabutylammonium bromide (TBAB) (0.32 g,
1 mmol) in acetone (30 mL) was added, drop-wise, bromoethane
(3.0 g, 27.5 mmol). After stirring for 5 min, powdered NaOH (1.1 g,
27.5 mmol) was added in three portions and the reaction mixture
was heated under reflux until the reaction was complete (1 h).
Water (100 mL) was added and the product was extracted with
ethyl acetate (50 mL). The organic layer was separated, washed
with water, dried over MgSO4 and concentrated. Pure product
(5.7 g, 92.7%) was obtained as white solid was obtained upon
recrystallization from ethanol.
13C NMR (75 MHz, CDCl3, ppm):
d
¼ 147.72, 143.20, 142.03,
139.10, 135.02, 129.33, 129.01, 126.86, 125.69, 123.64, 122.94, 121.28,
120.97, 115.90, 114.72, 108.67, 39.04, 34.66, 34.54, 32.04, 31.88,
14.39.
HRMS (EIþ): calculated for
C34H38N2, 474.3035; found,
474.3026.
3.3.8. Synthesis of 3,6-di-tert-butyl-9-ethyl-N1,N1,N8,N8-
tetraphenyl-9H-carbazole-1,8-diamine (DPACz2)
Compound (6) was prepared by employing the general Pd-
catalyzed coupling procedure using (4) (0.233 g, 0.5 mmol),
diphenylenediamine (0.22 g, 1.3 mmol), Pd2(dba)3 (0.046 g,
0.05 mmol), tBu3P (0.041 g, 0.20 mmol), and tBuONa (0.144 g,
1.5 mmol) in toluene (5 mL). Compound (6) was obtained as a white
solid (0.20 g, 62.3%) upon column chromatography (n-Hexane/
DCM, 2:1).
1H NMR (300 MHz, CDCl3, ppm):
d
¼ 8.10 (d, J ¼ 1.5 Hz, 2H), 7.51
(dd, J ¼ 6.9, 1.8 Hz, 2H), 7.32 (d, J ¼ 8.7 Hz, 2H), 4.35 (q, J ¼ 6.9 Hz,
2H), 1.46 (s, 18H), 1.44 (t, J ¼ 7.2 Hz, 3H).
13C NMR (100 MHz, CDCl3, ppm):
d
¼ 141.47, 138.49, 123.24,
122.79, 116.37, 107.81, 37.55, 34.69, 32.11, 13.99.
1H NMR (400 MHz, CDCl3, ppm):
d
¼ 7.99 (d, J ¼ 1.6 Hz, 2H), 7.19
(d, J ¼ 2.0 Hz, 2H), 7.12 (d, J ¼ 8.4 Hz, 4H), 7.10 (d, J ¼ 7.2 Hz, 4H), 6.97
(d, 8.0 Hz, 8H), 6.87 (t, J ¼ 7.2 Hz, 4H), 4.26 (q, J ¼ 6.8 Hz, 2H), 1.35 (s,
18H), 0.65 (t, J ¼ 6.8 Hz, 3H).
3.3.4. Synthesis of 1-bromo-3,6-di-tert-butyl-9-ethyl-9H-carbazole
(4)
Compound (4) was prepared using the same procedure as for (3)
using (2) (7.17 g, 20 mmol), the other reagents being in the same
amounts as in case of (3). Pure product 7.1 g (92.2%) as a white
crystalline solid was obtained by recrystallization from absolute
13C NMR (75 MHz, CDCl3, ppm):
d
¼ 147.50, 143.99, 135.83,
130.82, 128.87, 126.91, 126.84, 121.49, 121.22, 113.94, 39.89, 34.56,
31.81, 15.24.
HRMS (EIþ): calculated for C34H38N2, 641.3770; found, 641.3766.
ethanol. 1H NMR (300 MHz, CDCl3, ppm):
d
¼ 8.05 (d, J ¼ 1.5 Hz,1H),
3.3.9. Synthesis of N4,N40-bis(3,6-di-tert-butyl-9-ethyl-9H-
carbazol-1-yl)-N4,N40-diphenyl-[1,10-biphenyl]-4,40-diamine
(DPACz3)
8.02 (d, J ¼ 1.5 Hz, 1H), 7.60 (d, J ¼ 1.8 Hz, 1H), 7.55 (dd, J ¼ 1.8,
8.7 Hz, 1H), 7.34 (d, J ¼ 8.7 Hz, 1H), 4.75 (q, J ¼ 7.2 Hz, 2H), 1.45 (s,
9H), 1.43 (s, 9H), 1.42 (t, J ¼ 7.2 Hz, 3H).
Compound (7) was prepared by employing the general Pd-
4
4
13C NMR (100 MHz, CDCl3, ppm):
d
¼ 143.19, 142.47, 139.60,
catalyzed coupling procedure using (3) (0.772 g, 2 mmol), N ,N -
diphenylbenzidine (0.336 g, mmol), Pd2(dba)3 (0.092 g,
0.1 mmol), tBu3P (0.081 g, 0.4 mmol), and tBuONa (0.577 g,
0
135.00, 128.66, 126.25, 124.22, 122.31, 116.07, 115.52, 108.46, 102.33,
38.78, 34.70, 34.56, 32.00, 31.87, 15.61.
1