K.R. Rathikrishnan et al. / Tetrahedron 67 (2011) 4025e4030
4029
C18H13N3 requires C, 79.68; H, 4.83; N, 15.49%]; m/z 271.0 (M); dH
(400 MHz, MeOD) 6.69 (1H, d, J 3.2 Hz, indole CH), 7.29 (2H, t, J
7.5 Hz, indole CH), 7.41 (2H, d, J 3.2 Hz, pyridine CH), 7.58e7.59 (2H,
m, indole CH), 8.15e8.19 (2H, m, pyridine CH), 8.58 (2H, dd, J 3.6,
8.3 Hz, pyridine CH) 8.86 (1H, d, J 7.6 Hz, pyridine CH), 8.90 (1H, s,
indole NH); dC (100 MHz, MeOD) 100.3, 119.6, 121.9, 122.0, 123.9,
124.2, 125.2, 126.5, 127.0, 129.8, 130.2, 135.6, 136.7, 136.9, 137.5,
147.0, 147.5, 148.2.
Chloride
Bromide
Fluoride
Iodide
1.0
0.8
0.6
0.4
0.2
0.0
4.2.2. 4,7-Di-thiophen-3-yl-1H-indole (B). Yield (83 mg, 81%) as
a brown solid; [found: C, 68.37; H, 3.90; N, 4.81; S, 22.72. C16H11NS2
requires C, 68.29; H, 3.94; N, 4.98; S, 22.79%]; m/z 281.3 (M); dH
(400 MHz, DMSO-d6) 6.78 (1H, s, indole CH), 7.29 (2H, q, J 7.6 Hz,
indole CH), 7.42 (1H, s, thiophene CH), 7.55 (2H, t, J 4.6 Hz, indole CH),
7.68 (1H, d, J 3.6 Hz, thiophene CH), 7.74 (1H, d, J 3.6 Hz, thiophene
CH), 7.83 (2H, dd, J 1.4, 11.6 Hz, thiophene CH), 11.10 (1H, s, indole
NH); dC (100 MHz, DMSO-d6) 101.2, 118.7, 119.3, 121.0, 121.6, 121.9,
122.1, 126.2, 126.5, 126.9, 127.0, 127.6, 127.8, 133.2, 138.9, 141.4.
DAIs
4.2.3. 4,7-Bis-(3-fluoro-phenyl)-1H-indole (C). Yield (46 mg, 41%) as
a yellow solid; [found: C, 78.59; H, 4.25; N, 4.48. C20H13F2N requires
C, 78.68; H, 4.29; N, 4.59%]; m/z 305.0 (M); dH (400 MHz, CDCl3)
6.82 (1H, d, J 2.2 Hz, indole CH), 6.83e7.09 (2H, m, Ph CH), 7.30 (4H,
q, J 7.6 Hz, Ind and Ph CH), 7.38e7.43 (5H, m, Ind and Ph CH), 8.56
(1H, s, indole NH); dC (100 MHz, CDCl3) 102.6, 113.9, 114.6, 115.7,
120.3, 122.3, 123.9, 124.0, 124.4, 125.1, 126.5, 129.9, 130.7, 130.9,
132.9, 133.9, 141.2, 143.2, 161.8, 164.6.
Fig. 10. Relative fluorimetric responses I/I0 of AeG in the presence of TBA salts in THF.
investigated. Selectivity and sensitivity for the iodide ion was well
observed for all systems. The molecular interactions between DAIs
and anions are really important because the knowledge base in the
field of chemosensors and fluorescence ‘turn on’ sensors still needs
to be improved before going for applications.
4.2.4. 4,7-Bis-(2,3-dihydro-benzofuran-4-yl)-1H-indole (D). Yield
(71 mg, 55%) as a brown solid; [found: C, 81.50; H, 5.51; N, 3.99.
C24H19NO2 requires C, 81.56; H, 5.42; N, 3.96%]; m/z 353.1 (M); dH
(400 MHz, DMSO-d6) 3.28e3.35 (4H, m, CH2), 4.59 (4H, q, J 8.4 Hz,
OCH2), 5.75 (1H, s, indole CH), 6.59 (2H, q, J 1.8 Hz, indole CH), 6.89
(2H, q, J 8.2 Hz, Ph CH), 7.05e7.07 (3H, m, Ind and Ph CH), 7.52 (2H,
d, J 3.5 Hz, Ph CH), 10.99 (1H, s, indole NH); dC (100 MHz, DMSO-d6)
29.2, 29.3, 71.0, 71.1, 100.9, 108.9, 109.2, 118.8, 121.2, 124.2, 124.9,
125.0,126.1,126.3,127.7,127.8,127.9,129.7,130.9,132.0,133.3,133.5,
158.9, 159.1.
4. Experimental section
4.1. General
All reagents were purchased from Aldrich, Fluka and/or Merck
and were used without further purification unless otherwise stated.
All reactions were carried out with dry, freshly distilled solvents
under anhydrous conditions or in an inert atmosphere. Tetrahy-
drofuran was purified by distillation from sodium in the presence of
benzophenone under nitrogen atmosphere. 1,4-Dibromo-2-nitro-
benzene and 4,7-dibromo indole were prepared using literature
methods.18 All boronic acid were purchased from Aldrich. The NMR
spectra were collected on a Bruker ACF 300 spectrometer with
MeOD, DMSO-d6, CDCl3 solvent and tetramethylsilane as internal
standard. Elemental analyses were done in VarioMicro analyzer.
UVevis spectra were recorded on a PG Instrument Ltd spectropho-
tometer. Fluorescence measurements were carried out on an RF-
5301PC Shimadzu spectrofluorophotometer.
4.2.5. (3-{7-[3-(Pyrrolidine-1-carbonyl)-phenyl]-1H-indol-4-yl}-
phenyl)-pyrrolidin-1-yl-methanone (E). Yield (68 mg, 40%) as a yel-
low solid; [found: C, 77.81; H, 6.22; N, 9.13. C30H29N3O2 requires C,
77.73; H, 6.31; N, 9.06%]; m/z 464.1 (M); dH (400 MHz, CDCl3) 1.90
(4H, m, pyrolidine CH2), 1.92 (4H, m, pyrolidine CH2), 3.53 (4H, q, J
7.1 Hz, pyrolidine CH2), 3.69 (4H, d, J 3.4 Hz, pyrolidine CH2), 6.71
(1H, s, indole CH), 6.78 (3H, t, J 1.2 Hz, indole CH), 7.27e7.31 (4H, m,
Ph CH), 7.50e7.53 (1H, m, indole CH), 7.71e7.73 (1H, m, Ph), 7.88
(2H, s, Ph CH), 9.13 (1H, s, indole NH); dC (100 MHz, CDCl3) 23.4.
25.3, 28.7, 29.9, 30.9, 45.7, 48.7, 64.8, 101.0, 119.1, 121.1, 123.3, 124.6,
124.7, 124.9,125.1, 125.7, 125.8, 126.2, 127.5, 127.8, 128.1, 128.6, 129.1,
132.1, 132.9, 136.7, 140.1, 168.6, 168.8.
4.2. General procedure for the preparation of 4,7-di-aryl-3-yl-
1H-indoles AeG
4,7-Dibromoindole (3, 100 mg, 0.364 mmol) and 3-pyridine
boronic acid (134 mg, 1.097 mmol) were dissolved in DMF and
water (3:3 mL). After the addition of Cs2CO3 (293 mg, 0.912 mmol),
the reaction mixture was degassed then bis(triphenylphosphine)
palladium(II) chloride (38 mg, 0.0547 mmol) was added and the
mixture stirred vigorously for 16 h at 120 ꢁC in sealed tube. The
mixture was then cooled to room temperature and poured into
water and extracted with ethylacetate (2ꢂ25 mL). The organic layer
was separated, washed with brine (20 mL), dried (Na2SO4), and the
solvent evaporated in vacuo. Purification of the crude product by
flash chromatography (20% ethyl acetate/hexane) gave the title
compound A.
4.2.6. 4,7-Bis-(3-N,N-diethylbenz-
amide)-1H-indole
(F). Yield
(85 mg, 50%) as a brown solid; [found: C, 77.13; H, 7.03; N, 8.91.
C30H33N3O2 requires C, 77.06; H, 7.11; N, 8.99%]; m/z 467.1 (M); dH
(400 MHz, DMSO-d6) 1.64e1.67 (12H, m, CH2Me), 3.36e3.42 (4H, m,
CH2Me), 3.61 (4H, s, NCH2), 6.65 (1H, s, indole CH), 6.67 (2H, q, J
1.7 Hz, Ph CH), 7.25 (1H, t, J 7.6 Hz, indole CH), 7.42e7.51 (4H, m, Ind
and Ph CH), 7.74 (4H, q, J 8.3 Hz, Ph CH), 11.26 (1H, s, indole NH); dC
NMR (100 MHz, DMSO-d6) 12.9,14.2, 21.0, 29.2, 39.4, 43.4, 53.4, 60.4,
120.2, 122.1, 124.3, 124.9, 125.4, 126.0, 126.6, 127.8, 128.4, 128.9, 129.2,
129.5, 132.1, 133.3, 133.9, 137.6, 137.9, 139.4, 140.7, 141.3, 171.1, 171.3.
4.2.7. (3-{7-[3-(Piperidine-1-carbonyl)-phenyl]-1H-indol-4-yl}-phe-
nyl)-piperidin-1-yl-methanone (G). Yield (82 mg, 46%) as a white
solid; [found: C, 78.24; H, 6.72; N, 8.63. C32H33N3O2 requiresC, 78.18;
4.2.1. 4,7-Di-pyridin-3-yl-1H-indole (A). Yield (45 mg, 45%) as
a pale yellow crystalline solid; [found: C, 79.51; H, 4.80; N, 15.61.