◦
(dichloromethane–hexane) [lit.51 89 C]; dH(400 MHz; CDCl3)
yl-phenyl trimethylsilylamine 12 (153 mg, 0.6 mmol, 1.2 eq) gave
the title compound 23c (84 mg, 53%) as a colourless oil. Rf 0.22
(1 : 1 dichloromethane–hexane); found: C, 81.6; H, 5.5; N, 4.0%.
C24H19NO2 requires C, 81.6; H, 5.4; N, 4.0%; vmax(neat)/cm−1
1710 m, 1590 m, 1492 w, 1434 w, 1392 w, 1275 s, 1176 m, 1109
w, 1024 s, 1001 s, 823 m, 762 s and 696 w; dH(400 MHz; distilled
CDCl3) 7.98 (1H, d, J 8.0, ArH), 7.91 (1H, d, J 8.0, ArH), 7.81
(1H, d, J 8.5, ArH), 7.71 (2H, d, J 8.5, ArH), 7.53 (1H, dd, J
8.5 and 8.5, ArH), 7.48 (1H, dd, J 8.0 and 8.5, ArH), 7.41–7.38
(2H, m, ArH), 7.27 (2H, dd, J 8.0 and 8.5, ArH), 7.15 (2H, d,
J 8.5, ArH), 7.06 (1H, t, J 8.0, ArH), 6.73 (2H, d, J 8.5, ArH)
and 3.73 (3H, s, OCH3); dC(100 MHz; distilled CDCl3) 165.9
(s), 152.1 (s), 146.0 (s), 141.6 (s), 135.0 (s), 130.8 (d), 130.5 (s),
129.7 (d), 128.7 (d), 127.7 (d), 127.6 (d), 127.0 (d), 126.7 (d),
126.5 (d), 124.4 (d), 124.3 (d), 123.2 (d), 120.5 (s), 117.2 (d) and
51.6 (q); m/z (ES) 354.1487 [(M + H)+. C24H20O2N requires M,
354.1489]; m/z (EI) 353 (M+, 54%).
7.86 (2H, d, J 9.0, ArH), 7.31 (4H, dd, J 8.5 and 6.5 ArH), 7.15–
7.12 (6H, m, ArH), 6.98 (2H, d, J 9.0, ArH) and 3.88 (3H, s,
OCH3). Spectroscopic data identical to literature values.
4-(Diphenylamino) benzoic acid methyl ester50,51 (14, Table 2,
entry 2). General procedure D using potassium fluoride
(58.1 mg, 1 mmol, 2 eq) gave the title compound 14 (76 mg,
50%).
4-(Diphenylamino) benzoic acid methyl ester,50,51 14 (Table 2,
entry 3). General procedure D using caesium fluoride (152 mg,
1 mmol, 2 eq) gave the title compound 14 (135 mg, 89%).
The catalytic amination of aryl bromides with diarylsilylamines
9–12 in scCO2 (general procedure E). A 10 cm3 stainless steel
high pressure cell equipped with a PTFE stirrer bar was charged
with caesium carbonate (228 mg, 0.7 mmol, 1.4 eq), caesium
fluoride (152 mg, 1 mmol, 2 eq), Pd2dba3 (11 mg, 0.013 mmol,
2.5 mol%), P(t-Bu)3 (75 lL; 10 wt% in hexane, 0.025 mmol,
5 mol%) and aryl bromide (0.5 mmol, 1.0 eq) and then sealed.
The cell was evacuated and refilled with nitrogen (3 cycles). The
diarylsilylamine (0.6 mmol, 1.2 eq) was injected through the inlet
port into the cell and the cell was connected to the CO2 manifold.
It was then filled with liquid CO2 to approximately ◦800 psi
(volume of CO2 ca. 1 cm3) and the cell heated to 100 C. The
pressure was adjusted to ca. 1800 psi by the addition of further
CO2. The reaction mixture was then stirred at this temperature
and pressure for 48 h. After the reaction mixture was cooled to
room temperature, the contents of the cell were vented into ethyl
acetate (20 cm3). The cell was opened and rinsed with further
portions of ethyl acetate (3 × 10 cm3) and the washing solutions
combined with the vented solution. The organic solution was
filtered and concentrated in vacuo to give the crude material
which was purified by flash column chromatography.
4-(Diphenylamino) benzoic acid methyl ester50,51 (14, Table 4,
entry 1). General procedure E using methyl 4-bromobenzoate
(108 mg, 0.5 mmol, 1.0 eq) and diphenylsilylamine 9 (145 mg,
0.6 mmol, 1.2 eq) gave the title compound 14 (126 mg, 83%) as
a white crystalline solid.
(4-Nitrophenyl)diphenylamine53,54 (25a, Table 4, entry 2).
General procedure E using 1-bromo-4-nitrobenzene (101 mg,
0.5 mmol, 1.0 eq) and diphenylsilylamine 9 (145 mg, 0.6 mmol,
1.2 eq) gave the title compound 25a (84 mg, 58%) as a yellow
crystalline solid. Rf 0.24 (1 : 1 dichloromethane–hexane); mp
◦
143 C (from dichloromethane–hexane) [lit.54 142–143 ◦C];
dH(400 MHz; CDCl3) 8.04 (2H, d, J 9.0, ArH), 7.37 (4H, dd, J
7.0 and 8.5, ArH), 7.21 (2H, t, J 7.0, ArH), 7.18 (4H, d, J 8.5,
ArH) and 6.92 (2H, d, J 9.0, ArH). Spectroscopic data identical
to literature values.
(4-Fluorophenyl)diphenylamine55 (25b, Table 4, entry 3).
General procedure D using 1-bromo-4-fluorobenzene (88 mg,
0.5 mmol, 1.0 eq) and diphenylsilylamine 9 (145 mg, 0.6 mmol,
1.2 eq) gave the title compound 25b (61 mg, 46%) as a pale
yellow crystalline solid. Rf 0.35 (1 : 4 dichloromethane–hexane);
mp 96 ◦C (lit.55 98–98.5 ◦C from ethanol); dH(500 MHz; CDCl3)
7.24 (4H, dd, J 8.0 and 7.5, ArH), 7.09–7.04 (2H, m, ArH), 7.05
(4H, d, J 7.5, ArH) and 7.01–6.95 (4H, m, ArH). Spectroscopic
data identical to literature values.
4-(Diphenylamino) benzoic acid methyl ester50,51 (14, Table 3,
entry 1). General procedure E using methyl 4-bromobenzoate
(108 mg, 0.5 mmol, 1.0 eq) and diphenylsilylamine 9 (145 mg,
0.6 mmol, 1.2 eq) gave the title compound 14 (126 mg, 83%) as
a white crystalline solid.
4-(Phenyl-meta-tolylamino) benzoic acid methyl ester (23a,
Table 3, entry 2). General procedure E using methyl 4-
bromobenzoate (108 mg, 0.5 mmol, 1.0 eq) and phenyl-meta-
tolyltrimethylsilylamine 10 (153 mg, 0.6 mmol, 1.2 eq) gave the
title compound 23a (84 mg, 53%) as a colourless oil. Rf 0.24 (1 : 1
dichloromethane–hexane); found: C, 79.5; H, 6.1; N, 4.4%.
C21H19NO2 requires C, 79.5; H, 6.0; N, 4.4%; vmax(neat)/cm−1
1714 s, 1589 s, 1488 m, 1434 m, 1315 m, 1273 s, 1175 m, 1107
m, 768 m and 697 m; dH(400 MHz; CDCl3) 7.86 (2H, d, J 8.5,
ArH), 7.31 (2H, dd, J 7.5 and 8.5, ArH), 7.20 (1H, dd, J 7.5
and 7.5, ArH), 7.15 (2H, d, J 8.5, ArH), 7.12 (1H, t, J 7.5,
ArH), 7.00–6.95 (5H, m, ArH), 3.88 (3H, s, OCH3) and 2.30
(3H, s, ArCH3); dC(100 MHz; distilled CDCl3) 166.9 (s), 152.1
(s), 146.6 (s), 139.5 (s), 130.8 (s), 129.5 (d), 129.3 (d), 126.6 (d),
125.7 (CH), 125.3 (d), 124.2 (d), 123.0 (d), 121.9 (s), 119.9 (d),
51.7 (q) and 21.3 (q); m/z (ES) 318.1493 [(M + H)+. C21H20O2N
requires M, 318.1489]; m/z (EI) 317 (M+, 97%).
The catalytic amination of 4, 4ꢀ-dibromobiphenyl with diarylsi-
lylamines 9–12 in scCO2 (general procedure F). A 10 cm3
stainless steel high pressure cell equipped with a PTFE stirrer
bar was charged with caesium carbonate (456 mg, 1.4 mmol, 2.8
eq), caesium fluoride (304 mg, 2 mmol, 4 eq), Pd2dba3 (22 mg,
0.025 mmol, 5 mol%), P(t-Bu)3 (150 lL; 10 wt% in hexane,
0.05 mmol, 10 mol%) and 4, 4ꢀ-dibromobiphenyl (156 mg,
0.5 mmol, 1.0 eq) and then sealed. The cell was evacuated and
refilled with nitrogen (3 cycles). The diarylsilylamine (1.2 mmol,
2.4 eq) was injected through the inlet port into the cell and the
cell connected to the CO2 manifold. It was then filled with liquid
CO2 to approximately 800 psi (volume of CO2 ca. 1 cm3) and the
cell heated to 100 ◦C. The pressure was adjusted to ca. 1800 psi
by the addition of further CO2. The reaction mixture was then
stirred at this temperature and pressure for 48 h. After the
reaction mixture was cooled to room temperature, the contents
of the cell were vented into ethyl acetate (20 cm3). The cell was
opened and rinsed with further portions of ethyl acetate (3 ×
10 cm3) and the washing solutions combined with the vented
solution. The organic solution was filtered, concentrated in vacuo
to give the crude material which was purified by flash column
chromatography.
4-Carbazol-9-yl benzoic acid methyl ester52 (23b, Table 3,
entry 3). General procedure E using methyl 4-bromobenzoate
(108 mg, 0.5 mmol, 1.0 eq) and 9-trimethylsilyl-9H-carbazole 11
(144 mg, 0.6 mmol, 1.2 eq) gave the title compound 23b (80 mg,
54%) as a white solid. Rf 0.22 (2 : 3 dichloromethane–hexane);
dH(400 MHz; CDCl3) 8.29 (2H, d, J 8.5, ArH), 8.15 (2H, d, J
7.5, ArH), 7.69 (2H, d, J 8.5, ArH), 7.45 (4H, m, ArH, ArH),
7.32 (2H, dd, J 7.5 and 1.0, ArH) and 4.00 (3H, s, OCH3).
Spectroscopic data identical to literature values.
Nꢀ,Nꢀ,Nꢀ,Nꢀ-Tetraphenylbenzidine56 (27a, Table 5, entry 1).
General procedure F using N-trimethylsilyldiphenylamine 9
(290 mg, 1.2 mmol, 2.4 eq) gave the title compound 27a (128 mg,
58%) as a white solid. Rf 0.27 (1 : 20 diethyl ether–hexane v/v);
4-(Naphthalen-1-yl-phenylamino) benzoic acid methyl ester
(23c, Table 3, entry 4). General procedure E using methyl 4-
bromobenzoate (108 mg, 0.5 mmol, 1.0 eq) and naphthalen-1-
3 7 7 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 3 7 6 7 – 3 7 8 1