Synthesis of novel analogues of marine indole alkaloids: Mono(indolyl)-4-trifluoromethylpyridines and bis(indolyl)-4-trifluoromethylpyridines as potential anticancer agents

Article abstract of DOI:10.1016/S0968-0896(01)00070-0

Mono(indolyl)-4-trifluoromethylpyridines and bis(indolyl)-4-trifluoromethylpyridines were synthesized using Suzuki cross-coupling reaction between 2-chloro-4-trifluoromethylpyridine 9, 2,6-dichloro-4-trifluoromethylpyridine 6 or 2,6-dichloro-3-cyano-4-tri

Full text of DOI:10.1016/S0968-0896(01)00070-0

Bioorganic & Medicinal Chemistry 9 (2001) 1773–1780
Synthesis of Novel Analogues of Marine Indole Alkaloids:
Mono(indolyl)-4-trifluoromethylpyridines and
Bis(indolyl)-4-trifluoromethylpyridines as Potential
Anticancer Agents
Wen-Nan Xiong, Cai-Guang Yang and Biao Jiang*
Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
354 Fenglin Road, Shanghai 200032, PR China
Received 17 January 2001; accepted 10 March 2001
Abstract—Mono(indolyl)-4-trifluoromethylpyridines and bis(indolyl)-4-trifluoromethylpyridines were synthesized using Suzuki
cross-coupling reaction between 2-chloro-4-trifluoromethylpyridine 9, 2,6-dichloro-4-trifluoromethylpyridine 6 or 2,6-dichloro-3-
cyano-4-trifluoromethylpyridine 23 and N-tosyl-3-indolylboronic acid 10. They were evaluated for cytotoxic activity against P388
and A-549 cells with IC50 values. 4-Trifluoromethyl-2,6-bis[30-(N-tosyl-60-methoxylindolyl)]pyridine 18 was identified as the most
potent in this series. # 2001 Elsevier Science Ltd. All rights reserved.
Introduction
indole alkloids to optimize the structure–activity rela-
tionships (SAR) and to develop the more potent and
selective antitumor agents. As a part of our ongoing
structure–activity relationship study on indole alkaloids,
we incorporated fluorines into indole alkaloids to
investigate the effects of fluorine on cytotoxity. A range
of trifluoromethyl containing indole alkaloids were
designed and synthesized.
Marine natural products are very important source of
novel bioactive compounds for anticancer drug devel-
opment. Marine indole alkaloids have emerged as an
important structural class based upon their high degree
of biological activities including antimicrobial, antiviral
and antitumor properties.1 Bis(indole) alkaloids, drag-
macidin D and topsentins and their analogues exhibited
activities in vitro and in vivo against P388 murine and
human tumor cells.2 Monoindole alkaloids, meridianins
B–E showed cytotoxity toward LMM3 (murine
mamarian adenocarcinoma cell line) with IC50 values
between 9.3 and 33.9 mM.3 A common structural feature
of this kind of compound incorporates an extra five-,
six- or seven-membered heterocyclic ring with one or
two indole rings. In our previous studies, we have
reported the synthesis of bis(indolyl)thiazoles,4 mono
and bis(indolyl)pyrimidines, mono and bis(indolyl)pyr-
azines,5 bis(indolyl)pyrazinones6 (Fig. 1). They acted as
very powerful inhibitors of growth for many types of
human tumor cells in vitro. These results promoted us
to design new analogues with further modification of
In this paper, we wish to report the synthesis of mono(-
indolyl)-4-trifluoromethylpyridines and bis(indolyl)-4-
*Corresponding author. Tel;+86-21-6416-3300; fax: 86-21-6416-6128;
e-mail: jlang@pub.sioc.ac.cn
Figure 1.
0968-0896/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(01)00070-0

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W.-N. Xiong et al. / Bioorg. Med. Chem. 9 (2001) 1773–1780
trifluoromethylpyridines. Their cytotoxicity toward
P388 and human tumor cell A-549 was described.
A versatile and short-step synthetic approach to 2-
chloro-4-trifluoromethylpyridine has been achieved
(Scheme 2). Addition of chloroacetonitrile to tri-
fluoroacetylvinyl ether 7 in the presence of zinc and tri-
methylchlorosilane
afforded
4-trifluoromethyl-2-
Chemistry
pyridone 8 in one pot.10,11 Chlorization of pyridone
resulted the desired 2-chloro-4-trifluoromethylpyridine
9 in good yield.
Mono(indolyl)-4-trifluoromethylpyridines and bis(indo-
lyl)-4-trifluoromethylpyridines were conveniently prepared
by using palladium catalyzed Suzuki cross-coupling
reaction of 3-indolylboronic acids with 4-trifluoro-
methyl-halogenopyridines. The key intermediates are
4-trifluoromethyl-2-chloropyridine and 4-trifluoro-
methyl-2,6-dichloropyridine that would lead themselves
to cross-coupling with various 30-indolylboronic acids.
Mono(indolyl)-4-trifluoromethylpyridines 11–16 were
prepared by Suzuki cross-coupling reaction between 2-
chloro-4-trifluoromethylpyridine 9 with 1.1 molar equiv
of N-tosyl-3-indolylboronic acid 1012 in the presence of
a
catalytic
amount
of
tetrakis(triphenylpho-
sphine)palladium13 and aqueous sodium carbonate in a
mixture of benzene and methanol under refluxing for 6 h
in good yields (Scheme 3).
The synthetic route to the key intermediate 2,6-
dichloro-4-trifluoromethylpyridine was outlined in
Scheme 1. Condensation of trifluoroacetaldehyde 1 with
two molar cyanacetamide and subsequent hydrolysis
afforded the diacid 27 which was dehydrated to give
cyclic anhydride 3. Amination of cyclic anhydride 3 lead
to monoamide 4 of glutaric acid, subsequent dehydra-
tion gave glutarimide 5.8 Treatment of glutarimide 5
with phosphorus pentachloride and phosphorus oxy-
chloride gave 2,6-dichloro-4-trifluoromethylpyridine 6.9
When 2,6-dichloro-4-trifluoromethylpyridine
6 was
reacted with 2.2 molar equiv of N-tosyl-6-methoxyl-3-
indolylboronic acid 10e under above-mentioned condi-
tion, bis(60-methoxylindolyl)-4-trifluoromethylpyridines
18 was obtained in 51% yield along with mono(-
indolyl)pyridine 17 in 33% yield. Extending the reaction
time to 10 h, the reaction was completely to produce
compound 18 in 78% yield. Bis(indolyl)-4-tri-
fluoromethylpyridines 19–22 were gained by coupling of
6 with corresponding 3-indolylboronic acids 10 under
the same conditions (Scheme 4).
2,6-Dichloro-3-cyano-4-trifluoromethylpyridine 2314 was
refluxed with 1.1 molar equiv of N-tosyl-3-indo-
lylboronic acid 10a, 10d or 10e in a mixture of benzene
and methanol for 10 h in the presence of palladium
Scheme 1. Reagents and conditions: (a) cyanacetamide, EtOH, pyri-
.
dine, rt, then 3 N HCl, reflux; (b) Ac2O, reflux; (c) NH3 H2O, rt; (d)
220–230 ꢀC, 1.5 h; (e) POCl3, reflux, 10 h.
Scheme 2. Reagents and conditions: (a) ClCH2CN, Zn, TMSCl, THF,
3 h, concn HCl, reflux; (b) POCl3, PCl5, 3 h.
Scheme 3. Reagents and conditions: (a) Pd(PPh3)4, Na2CO3, benzene/
MeOH.
Scheme 4. Reagents and conditions: (a) Pd(PPh3)4, Na2CO3, benzene, MeOH.

W.-N. Xiong et al. / Bioorg. Med. Chem. 9 (2001) 1773–1780
1775
Scheme 5. Reagents and conditions: (a) Pd(PPh3)4, Na2CO3, benzene, MeOH or DME.
catalyst and aqueous sodium carbonate to produce 2-
indolyl-6-methoxyl-4-trifluoromethylpyridines 24–26
It can be seen, compared to our previously reported
bis(indolyl)thiazoles,4 mono and bis(indolyl)pyr-
imidines, mono and bis(indolyl)pyrazines,5 bis(indo-
regioselectively in good yields (Scheme 5). The structure
of compound 25 was confirmed by X-ray single crystal
analysis (Fig. 2). The carbon–chloride bond at the 2-
position in 23 was more reactive than that at the 6-
position. While 23 was coupled with 10b or 10c by using
dimethoxyethane (DME) as solvent instead of metha-
nol, 2-indolyl-6-chloro-4-trifluoromethylpyridines 27–28
were obtained. Treatment of dichloropyridine 23 with 2
molar equiv of 3-indolylboronic acids 10 in a mixture of
benzene and DME for 10 h afforded corresponding
bis(indolyl)-4-trifluoromethylpyridines 29–34 in moderate
yields (Scheme 5).
lyl)pyrazinones,6
the
prepared
indolylpyridine
compounds containing trifluoromethyl group showed
weaker antitumor activity. To some extent, it revealed
that the central heterocyclic moiety between the indole
rings took an important role in the antitumor activity.
On the other hand, the introduction of fluorine as a
highly electronegative center seemed to not improve the
biological properties of these molecules as expected.
In conclusion, we have synthesized a series of mono(-
indolyl)-4-trifluoromethylpyridines and bis(indolyl)-4-
trifluoromethylpyridines. The preliminary screening
shows this set of compounds exhibited weak cytotoxi-
city toward murine leukemia cells (P388), and some
compounds displayed moderate inhibitory activity
against human lung cancer cells (A-549).
Pharmacological Results and Discussion
The prepared indolyl–trifluoropyridine compounds
were submitted to the Shanghai Institute of Materia
Medica for testing their cytotoxicity. Growth inhibition
on murine leukemia cells P388 was measured by 3-(4,5-
dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide
(MTT, Sigma Chemical Co.) assay15 with minor mod-
ification,16 and human lung tumor cells A-549 was
measured by the sulforhodamine B dye-staining (SRB)
method.17 The cytotoxicity screening results are shown
in Table 1 as IC50 values.
Compounds 14, 16, 19, 20, 21, 30, 31, 33 were inactive
against P388 and A-549 tumor cells with IC50 values
exceeded 100 mM. Compounds 11, 19, 28 and 32 were
inactive against P388 cells and showed weak cytotoxi-
city toward A-549 with IC50 exceeded 10 mM. Com-
pounds 12, 17, 25, 27 were inactive against P388 cells
(IC50>100 mM) and showed cytotoxicity toward A-549,
the IC50 values of which were, respectively, 4.1, 6.4, 5.0,
7.7 mM. Compound 13 exhibited moderate inhibitory
activities against P388 cell lines with IC50 value of
11 mMand A-549 cell lines with IC
value of 48 mM.
50
Compound 18 exhibited strong inhibitory activities
against P388 cell lines with IC50 values of 4.3 mMand A-
549 cell lines with IC50 values of 1.7 mM, which was
identified as the most potent in this series.
Figure 2. ORTEP drawing of the X-ray crystal structure of compound
25.

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W.-N. Xiong et al. / Bioorg. Med. Chem. 9 (2001) 1773–1780
Table 1. In vitro cytotoxicity against the P388 and A-549 cell lines
Concn
(mM)
P388
CTXa P388 IC50 (mM)
A-549
CTXb A-549 IC50 (mM)
100
10
1
0.1
100
10
1
0.1
11
12
13
14
16
17
18
19
20
21
25
27
28
30
31
32
33
49.9
32.6
95.2
15.6
2.2
47.7
99.9
14.7
8.9
13.8
54.1
50.4
22.5
—
—
10.5
17.8
35.2
—
—
6.4
—
>100
>100
11
>100
>100
>100
4.3
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
68.4
98.0
91.6
51.8
35.9
68.1
97.1
69.3
49.2
41.7
91.7
98.8
85.7
17.7
21.2
70.6
48.1
30.5
20.6
9.0
14.1
9.9
55.7
45.7
27.6
32.0
22.2
40.6
21.1
18.0
25.2
13.3
9.6
35.0
32.8
0
19.7
23.2
25.7
28.8
36.7
30.7
7.1
20.7
26.4
34.4
24.4
26.7
17.4
18.8
29.2
38.9
0
25
4.1
48
21.9
43.3
—
—
8.2
92.8
23.5
15.1
5.0
21.6
19.2
1.9
3.5
10.1
—
9.7
8.0
—
—
13.2
—
15.7
8.1
9.3
6.1
13.2
—
1.7
5.1
—
24.5
16.9
31.0
35.5
37.5
25.8
16.7
20.6
8.5
13.7
25.0
33.0
9.8
>100
>100
6.4
1.7
23
>100
>100
5.0
7.7
14
>100
>100
78
—
20.9
10.0
7.0
11.2
9.4
0.6
3.8
8.2
1.3
9.1
3.7
1.7
5.7
3.1
27.6
23.8
>100
aCytotoxicity (CTX) against murine leukemia cells (P388) was measured by the microculture tetrazolium-formazan method.
bCTX against human lung cancer cells (A-549) was measured by the sulforhodamine B dye-staining method.
Experimental
and dissolved in water (10 mL). The solution was boiled
for 30 min with about 0.5 g of charcoal. The charcoal is
removed by filtration. The dry residue was crystallized
from 95% ethanol to give product 5 (1.1 g, 30%): mp
All melting points were measured with a WRS-1A digi-
tal melting point apparatus, without correction. IR
spectra were determined with a Shimadzu IR-440 spec-
trometer. H NMR and 13C NMR spectra were recor-
136–138 ꢀC; IR (KBr) nmax 3202, 3098, 1698, 1130 cmÀ1
;
MS (EI) m/e 181 (M+, 12), 138 (23), 69 (8), 42 (100);
19F NMR (CDCl3) d À3.4 (d, J=6.6 Hz); 1H NM R
(CDCl3) d 8.60 (br s, 1H), 2.85–3.03 (m, 4H), 2.62–2.7
(m, 1H); 13C NMR (CDCl3) d 169.2, 125.6 (q,
J=276.7 Hz), 35.1 (q, J=29.8 Hz), 30.6; HRMS (EI)
calcd for C5H5F3O: 138.02925; found: 138.02948.
1
ded on a Bruker AM-300 instrument. The chemical
photo shifts are expressed in ppm and coupling con-
stants are given in Hz. Low-resolution MS spectra were
obtained on a VG-Quattro or HP-5969A spectrometer
and high-resolution MS spectra were recorded on a
Finnigan MAT-95 spectrometer. Elemental analyses
were carried out on a Heraeus Rapid-CHNO instru-
ment. Column chromatography was performed on silica
gel H (10–40 mm). Reagents purchased commercially
were used without further purification. Solvents were
dried using standard procedures.
2,6-Dichloro-4-trifluoromethylpyridine (6). A mixture of
5
(5.43 g, 30 mmol) and phosphorus oxychloride
(30 mL) was heated to reflux for 8 h. The excess phos-
phorus oxychloride was removed by distillation under
reduced pressure. The residue was poured into ice water
and extracted with CH2Cl2 (3Â50 mL). The organic
phase was washed with sat. NaHCO3 (30 mL) and brine
(30 mL). After being dried over Na2SO4, concentration
in vacuo afforded a residue that was purified by flash
chromatography to give 6 (4.2 g, 65%): MS (EI) m/e
215 (M+, 10), 217 (6), 196 (6), 180 (100), 182 (32), 160
4-Trifluoromethyl-2,6-piperidinedione (5). A mixture of
Trifluoroacetaldehyde 1 (1.96 g, 20 mmol) and cyan-
acetamide (2.8 g, 40 mmol) was refluxed in ethanol
(15 mL) with piperidine as a catalyst for 10 h. Then the
ethanol was removed in vacuo. Hydrochloric acid (2 N,
20 mL) was added. The resulting mixture was refluxed
for another 6 h, diluted with ethyl ether, washed with
brine, dried over Na2SO4 and concentrated in vacuo to
obtain crude product 2. A mixture of 2 (4 g, 20 mmol)
and acetic anhydride (15 mL) was refluxed for 14 h. The
excess acetic anhydride was removed in vacuo. Then
ammonia water (30 mL) was added and the mixture
stirred at room temperature overnight. The aqueous
layer was extracted with ethyl acetate (3Â80 mL). The
combined organic extract was washed with 1 N HCl
(75 mL) and brine (2Â50 mL), dried (anhydrous
Na2SO4) and concentrated to give a crude reaction
mixture which was directly used in the next reaction
without purification. The crude product was heated at
220–230 ꢀC until water was no longer distilled. The
reaction mixture was cooled to ambient temperature
1
(29), 144 (8), 110 (15); 19F NMR (CDCl3) d À13 (s); H
NMR (CDCl3) d 7.40 (s, 1H).
4-Trifluoromethyl-2(1H)-pyridinone (8). Trimethyl-
chlorosilane (5.3 mL, 30 mmol) was added to the solu-
tion of zinc powder (2 g, 30 mmol) in anhydrous THF
(30 mL) under N2. After stirred for 0.5 h, a solution of
chloroacetonitrile (1.27 mL, 20 mL) and tri-
fluoroacetylvinyl ether (1.68 g, 10 mmol) in anhydrous
THF (15 mL) was added dropwise slowly to keep the
temperature at 40 ꢀC. The mixture was refluxed for 2 h.
After being cooled to room temperature, concd. HCl
(5 mL) was added. The mixture was refluxed for 1 h,
then cooled to room temperature and poured into ice
water. The product was extracted with EtOAc
(3Â50 mL), and the combined extract was washed with
brine. The organic layer was dried over anhydrous

W.-N. Xiong et al. / Bioorg. Med. Chem. 9 (2001) 1773–1780
1777
Na2SO4, filtered, and evaporated to dryness to give the
residue that could be used in the next reaction without
further purification. The residue was purified by column
chromatography to afford 8 (1.2 g, 74%): IR (KBr) nmax
filtered and the filtrate was evaporated under reduced
pressure. The residue was subjected to silica gel column
chromatography, eluting with ethyl acetate/hexane to
give the corresponding mono(indolyl)-4-trifluoro-
methylpyridines and bis(indolyl)-4-trifluoromethyl-
pyridines 26–48.
3151 (N-H), 2851, 1664 (C¼O), 1621, 1072 (CF3) cmÀ1
;
MS (EI) m/e 163 (M+, 100), 144 (M+ÀF, 12), 135 (83),
116 (99), 85 (25), 69 (CF3, 15), 57 (15), 43 (15); 19F
NMR (CDCl3) d À13 (s); 1H NMR (CDCl3) d 6.49 (dd,
J=1.6 and 6.9 Hz, 1H), 6.78 (d, J=0.85 Hz, 1H), 7.75
(d, J=7.0 Hz, 1H).
4-Trifluoromethyl-2-(N-toluenesulfonyl-30-indolyl)pyridine
(11). Yield 92%; mp 141–143 ꢀC (CHCl3); IR (KBr)
nmax 1611, 1561, 1379, 1174, 1141 cmÀ1; MS (EI) m/e
416 (M+, 63), 417 (M++1, 18), 262 (20), 261, (100),
234 (46), 155 (13); 19F NM Rd À12 (s); 1H NM R
(CDCl3) d 8.97 (s, 1H), 8.72 (s, 1H), 8.11–7.99 (m, 4H),
7.66 (s, 1H), 7.45–7.27 (m, 5H), 2.35 (s, 3H); anal. calcd
for C21H15F3N2O2S: C, 60.58; H, 3.61; N, 6.73. Found:
C, 60.19; H, 3.35; N, 6.78.
2-Chloro-4-trifluoromethylpyridine (9). A mixture of 8
(3 g, 18.4 mmol) and phosphorus oxychloride (30 mL)
was heated to reflux for 3 h. The excess phosphorus
oxychloride was removed by distillation under reduced
pressure. The residue was poured into ice water and
extracted with CH2Cl2 (3Â50 mL). The organic phase
was washed with satd NaHCO3 (20 mL) and brine
(30 mL). After drying (Na2SO4), concentration in vacuo
afforded a residue that was purified by flash chromato-
graphy to give the desired 9 (2.0 g, 60%) as a colorless
oil: IR (KBr) nmax 1450, 1334, 1146 cmÀ1; MS (EI) m/e
181 (M+, 3.58), 146 (M+ ÀCl, 100), 69 (CF3, 54), 126
4-Trifluoromethyl-2-[30-(N-toluenesulfonyl-50-bromoindolyl)]-
pyridine (12). Yield 85%; mp 195–197 ꢀC (CHCl3); IR
(KBr) nmax 1610, 1553, 1438, 1344, 1174, 1131 cmÀ1; M S
(EI) m/e 496 (M+, 100), 497 (27), 341 (47), 339 (47), 260
1
(33), 233 (17), 155 (25); 19F NM RdÀ13 (s); H NM R
(CDCl3) d 8.81 (d, J=4.77 Hz, 1H), 8.54 (d, J=1.8 Hz,
1H), 8.07 (s, 1H), 7.85–7.73 (m, 4H), 7.44–7.36 (m, 2H),
7.19 (m, 2H), 2.29 (s, 3H); 13C NMR (CDCl3) d 153.9,
150.6, 145.8, 134.3, 134.3, 130.2 129.9, 128.4, 127.0,
126.7, 125.4, 117.9, 117.3, 117.2, 116.5, 116.4, 114.9,
29.7, 21.6; HRMS (EI) calcd for C21H14BrF3N2O2S:
493.99115; found: 493.99006.
1
(25); 19F NM RÀ13 (s, CF3); H NMR (CDCl3) d 8.61
(d, J=5.13 Hz, 1H), 7.58 (s, 1H), 7.47 (d, J=5.08 Hz,
1H).
General procedure for N-tosyl-3-indolylboronic acids
(10a–f). A mixture of mercuric acetate (20 mmol) and
150 mL of glacial HOAc was stirred at room tempera-
ture for 30 min. The insoluble material was removed by
filtration. To the filtrate was added substituted N-tosy-
lindole (20 mmol). The clear solution was stirred at
room temperature overnight and became white slurry.
Filtration gave a white heavy solid, which was used
directly in the next reaction without purification.
4-Trifluoromethyl-2-[30-(N-toluenesulfonyl-60-bromoindolyl)]-
pyridine (13). Yield 87%; mp 215–217 ꢀC (CHCl3); IR
(KBr) nmax 1611, 1551, 1428, 1318, 1180, 1147 cmÀ1; M S
(EI) m/e 496 (M+, 100), 494 (M+, 93.9), 477 (3.8), 475
(3.7), 341 (70.4), 339 (71.9), 314 (17.7), 312 (18.6), 260
1
(42.4), 233 (23.2), 155 (11.9); 19F NM RdÀ13 (s); H
NMR (CDCl3) d 8.9 (s, 1H), 8.59 (s, 1H), 8.26 (d,
J=1.47 Hz, 1H), 8.04–7.96 (m, 4H), 7.64 (s, 1H), 7.50
(dd, J=1.4 and 8.5 Hz, 1H), 7.32 (m, 2H); 2.37 (s, 3H);
HRMS (EI) calcd for C21H14BrF3N2O2S: 493.99115;
found: 493.98842.
To
a solution of 3-acetoxymercurio-N-tosylindole
(10 mmol) in 120 mL of dried THF purged with Ar2 was
added borane solution (10 Min eM 2S, 10 mL,
100 mmol) at room temperature and the mixture was
stirred for 1 h, followed by the addition of 8 mL of water
carefully. A clear solution and elemental mercury were
obtained. The mercury was removed by filtration, and
the solvent was evaporated at 40 ꢀC under reduced
pressure. To the white residue was then added 300 mL
of THF/EtOAc (1:9) and the insoluble material was
removed by filtration. The filtrate was washed with
water and brine, and concentrated to give a white solid
10a–f, which was pure enough for the cross-coupling
reaction without further purification.
4-Trifluoromethyl-2-[30 -(N-toluenesulfonyl-50 -methoxy-
lindolyl)]pyridine (14). Yield 90%; mp 146–148 ꢀC
(CHCl3); IR (KBr) nmax 2833, 1612, 1592, 1480, 1320,
1172, 1141 cmÀ1; MS (EI) e/e 446 (M+, 92), 291 (100),
276 (42), 264 (11), 247 (17), 155 (3); 19F NM RdÀ13 (s);
1H NMR (CDCl3) d 8.91 (s, 1H), 8.31 (s, 1H), 7.95–7.66
(m, 5H), 7.50 (s, 1H), 7.26–7.24 (m, 2H), 7.02 (dd,
J=1.8 and 9.0 Hz, 1H), 3.87 (s, 3H), 2.34 (s, 3H); 13C
NMR (CDCl3) d 157.2, 153.7, 149.5, 145.6, 134.8,130.3,
130.1, 128.8, 128.0, 127.2, 119.4, 117.4, 117.3, 114.6,
114.5, 104.4, 55.9, 21.6; HRMS (EI) calcd for
C22H17F3N2O3S: 446.09120; found 446.09605.
General procedure for the synthesis of mono(indolyl)-4-
and
trifluoromethylpyridines
bis(indolyl)-4-tri-
fluoromethylpyridines. N-Tosyl-3-indolylboronic acid 10
(1.1 or 2.2 mmol) was added to the solution of 2-chlor-
opyridine 9, 2,6-dichloropyridine 6 or 2,6-dichloro-3-
cyanopyridine 23 (0.1 mmol), aqueous sodium carbon-
4-Trifluoromethyl-2-[30 -(N-toluenesulfonyl-60 -methoxy-
lindolyl)]pyridine (15). Yield 90%; mp 159–161 ꢀC
(CHCl3); IR (KBr) nmax 2839, 1612, 1561, 1492, 1320,
1170, 1128 cmÀ1; MS (EI) e/e 446 (M+, 40.5), 291 (100),
ate
(2 mL,
2 M)
and
tetrakis(triphenylphos-
1
phine)palladium (0.2 mmol) in benzene (10 mL),
methanol or DME (2 mL). The mixture was refluxed
under an argon atmosphere. After stirring for 6 or 10 h,
anhydrous sodium sulfate was added. The mixture was
276 (5.4), 264 (9.6), 247 (8.1); 19F NM RdÀ13 (s); H
NMR (CDCl3) d 8.90 (s, 1H), 8.22–8.15 (m, 2H), 7.89–
7.83 (m, 3H), 7.56 (d, J=1.9 Hz, 1H), 7.43 (d,
J=3.2 Hz, 1H), 7.23 (m, 1H), 6.98 (dd, J=1.9 and

1778
W.-N. Xiong et al. / Bioorg. Med. Chem. 9 (2001) 1773–1780
8.8 Hz, 1H), 3.90 (s, 3H), 2.34 (s, 3H); HRMS (EI) calcd
for C22H17F3N2O3S: 446.09120; found: 446.09410.
(CHCl3); IR (KBr) nmax 1475, 1439, 1354, 1268, 1179,
1150 cmÀ1; MS (EI) e/e 745 (M+, 100), 746 (45), 590
1
(14) 591 (12), 420 (7), 69 (4); 19F NM RdÀ13 (s); H
4-Trifluoromethyl-2-[30-(N-toluenesulfonyl-50-benzoxylin-
dolyl)]pyridine (16). Yield 87%; mp 169–171 ꢀC
(CHCl3); IR (KBr) nmax 2928, 1556, 1444, 1378,
1173 cmÀ1; MS (EI) m/e 522 (M+, 7.7), 431 (5.5), 367,
(23), 368 (6.4), 276 (15), 155 (14), 91 (100); 19F NM Rd
NMR (CDCl3) d 8.18 (s, 2H), 7.95–7.92 (m, 4H), 7.84–
7.81 (m, 4H), 7.75 (s, 2H), 7.26–7.24 (m, 4H), 7.01 (dd,
J=2.6 and 9.0 Hz, 2H), 3.72 (s, 6H), 1.17 (s, 6H);
HRMS (EI) calcd for C38H30F3N3O6S2: 745.1528;
found: 745.1523.
1
À13 (s); H NMR (CDCl3) d 8.85 (d, J=5.1 Hz, 1H),
8.10 (s, 1H), 7.99 (d, J=2.6 Hz, 1H), 7.94 (s, 1H), 7.91
(s, 1H), 7.81 (m, 3H), 7.45–7.21 (m, 7H), 7.09 (dd,
J=2.6 and 9.08 Hz, 1H), 5.12 (s, 2H), 2.34 (s, 3H); anal.
calcd for C28H21F3N2O3S: C, 64.36; H, 4.05; N, 5.36.
Found: C, 64.18; H, 3.98; N, 5.68.
4-Trifluoromethyl-2,6-bis[30-(N-toluenesulfonyl-50-benzoxy-
lindolyl)]pyridine (22). Yield 79%; mp 235–237 ꢀC
(CHCl3); IR (KBr) nmax 1477, 1449, 1376, 1271, 1175,
1151 cmÀ1; MS (EI) e/e 897 (M+, 26.76), 898 (15), 807
(18), 806 (33), 743 (55), 742 (100), 652 (23), 588 (33), 497
1
(28), 496 (53), 468 (9), 155 (5); 19F NM RdÀ13 (s); H
6-Chloro-4-trifluoromethyl-2-[30 -(N-toluenesulfonyl-60 -
methoxylindolyl)]pyridine (17). Yield 33%; mp 130–
132 ꢀC (CHCl3); IR (KBr) nmax 1624, 1579, 1482, 1363,
1173, 1112 cmÀ1; MS (EI) e/e 480 (M+, 38), 481 (13),
482 (16), 361 (24), 359 (36), 326 (26), 327 (36), 325 (100);
NMR (CDCl3) d 8.17 (s, 1H), 8.04 (d, J=2.45 Hz, 1H),
7.95 (d, J=9.07 Hz, 1H), 7.82 (d, J=8.35 Hz, 1H), 7.72
(s, 1H), 7.23–7.19 (m, 8H), 7.08 (dd, J=2.55 and
9.07 Hz, 1H), 4.85 (2H, s), 2.30 (s, 3H); anal. calcd for
C50H38F3N3O6S2: C, 66.88; H, 4.27; N, 4.68. Found: C,
66.45; H, 4.59; N, 4.36.
1
19F NM RdÀ13 (s); H NMR (CDCl3) d 7.75 (s, 1H),
7.73 (s, 1H), 7.53 (s, 1H), 7.44 (d, J=3.63 Hz, 1H), 7.37
(d, J=8.62 Hz, 1H), 7.26–7.19 (m, 3H), 6.85 (dd,
J=2.32 and 8.62 Hz, 1H), 6.56 (d, J=3.65 Hz, 1H), 3.87
(s, 3H), 2.33 (s, 3H); HRMS (EI) calcd for
C22H16ClF3N2O3S: 480.05223; found: 480.05016.
2-Methoxy-3-cyano-4-trifluoromethyl-6-[30 -(N-toluene-
sulfonylindolyl)]pyridine (24). Yield 69%; mp 178–
180 ꢀC (MeOH); IR (KBr) nmax 3177, 2217, 1597, 1534,
1473, 1380, 1171, 1140 cmÀ1; MS (EI) e/e 471 (M+,
100), 472 (31), 316 (43), 317 (12), 301 (26), 155 (21); 19F
4-Trifluoromethyl-2,6-bis[30-(N-toluenesulfonyl-60-meth-
oxylindolyl)]pyridine (18). Yield 78%; mp 221–223 ꢀC
(CHCl3); IR (KBr) nmax 1614, 1534, 1436, 1307, 1173,
1120 cmÀ1; MS (EI) e/e 745 (M+, 36), 590 (50), 445
(100), 435 (37), 290 (63), 262 (23); 19F NM RdÀ13 (s);
1H NMR (CDCl3) d 7.93 (s, 1H), 7.90 (d, J=8.4 Hz,
1H), 7.60 (d, J=3.53 Hz, 1H), 7.55 (d, J=8.62 Hz, 1H),
7.43–7.24 (m, 3H), 6.85 (d, J=3.50 Hz, 1H), 6.71 (s,
1H), 3.93 (s, 3H), 2.35 (s, 3H); HRMS (EI) calcd for
C38H30F3N3O6S2: 745.1528; found: 745.1505.
NMR d À13 (s); H NMR (CDCl3) d 8.59 (s, 1H), 8.15
1
(dd, J=0.62 and 8.5 Hz, 1H), 8.08 (d, J=8.2 Hz, 1H),
7.43–7.25 (m, 4H), 7.05 (s, 1H), 4.14 (s, 3H), 2.34 (s,
3H); HRMS (EI) calcd for C23H16F3N3O3S: 471.08645;
found: 471.08571.
2-Methoxy-3-cyano-4-trifluoromethyl-6-[30 -(N-toluene-
sulfonyl-50-methoxylindolyl)]pyridine (25). Yield 67%;
mp 199–201 ꢀC; IR (KBr) nmax 3167, 2219, 1612, 1537,
1477, 1382, 1174, 1145 cmÀ1; MS (EI) e/e 501 (M+, 86),
502 (26), 346 (100), 347 (24), 316 (20), 288 (5), 155 (5);
4-Trifluoromethyl-2,6-bis[30 -(N-toluenesulfonylindolyl)]-
pyridine (19). Yield 83%; mp 229–231 ꢀC (CHCl3); IR
(KBr) nmax 1598, 1568, 1446, 1370, 1172, 1135 cmÀ1; M S
(EI) e/e 685 (M+, 100), 686 (46), 530 (60), 531 (24), 375
19F NM RdÀ14 (s); H NMR (CDCl3) d 8.57 (s, 1H),
1
7.98–7.88 (m, 3H), 7.66 (d, J=2.39 Hz, 1H), 7.28–7.26
(m, 3H), 7.04–7.00 (m, 2H), 4.15 (s, 3H), 3.81 (s, 3H),
2.35 (s, 3H); 13C NMR (CDCl3) d 165.2, 157.3, 157.0,
145.5, 134.6, 130.2, 130.1, 129.9, 129.6, 129.5, 127.3,
117.8, 115.3, 114.7, 114.4, 107.2, 107.1, 104.6, 55.6, 55.1,
21.6; HRMS (EI) calcd for C24H18F3N3O4S: 501.09701;
found: 501.09413.
1
(44), 374 (28), 348 (14), 155 (3); 19F NM RdÀ13 (s); H
NMR (CDCl3) d 8.40 (s, 1H), 8.37 (s, 1H), 8.23 (m, 2H),
8.07 (d, J=8.3 Hz, 2H), 7.89–7.79 (m, 6H), 7.44–7.26
(m, 8H), 2.35 (s, 6H); HRMS (EI) calcd for
C36H26F3N3O4S2: 685.1296; found: 685.1299.
2-Methoxy-3-cyano-4-trifluoromethyl-6-[30 -(N-toluene-
sulfonyl-60-methoxylindolyl)]pyridine (26). Yield 66%;
mp 208–210 ꢀC (MeOH); IR (KBr) nmax 3136, 2928,
2229, 1615, 1596, 1464, 1372, 1174 cmÀ1; MS (EI) e/e
501 (M+, 40.9), 380 (3.4), 346 (100), 347 (23.6), 155
4-Trifluoromethyl-2,6-bis[30-(N-toluenesulfonyl-60-bromo-
indolyl)]pyridine (20). Yield 60%; mp 260–262 ꢀC
(CHCl3); IR (KBr) nmax 1598, 1549, 1415, 1382, 1174,
1141 cmÀ1; MS (EI) e/e 843 (M+, 100), 844 (65), 845
(61), 841 (51), 688 (79), 689 (48), 690 (46), 533 (42), 373
1
(0.7); 19F NM RdÀ14 (s); H NMR (CDCl3) d 8.25 (d,
1
(29), 155 (15); 19F NM RdÀ13 (s); H NMR (CDCl3) d
J=8.9 Hz, 1H), 8.16 (s, 1H), 7.85 (s, 1H), 7.82 (s, 1H),
7.58–7.52 (m, 2H), 7.30–7.26 (m, 2H), 7.0 (dd, J=2.2
and 8.9 Hz, 1H), 4.23 (s, 3H), 3.91 (s, H), 2.37 (s, 3H);
HRMS (EI) calcd for C24H18F3N3O4S: 501.09701;
found: 501.09669.
8.23–8.13 (m, 6H), 7.87–7.74 (m, 6H), 7.43–7.30 (m,
6H), 2.38 (s, 6H); 13C NMR (CDCl3) d 153.8, 145.9,
140.1, 139.6, 136.3, 134.8, 130.3, 127.6, 127.5, 127.1,
126.1, 123.7, 121.4, 119.3, 116.7, 114.5, 21.7; HRMS
(EI) calcd for C36H24Br2F3N3O4S2: 840.9537; found:
840.9532.
2-Chloro-3-cyano-4-trifluoromethyl-6-[30-(N-toluenesulfonyl-
50-bromoindolyl)]pyridine (27). Yield 75%; mp 261–
263 ꢀC (MeOH); IR (KBr) nmax 2236, 1597, 1533, 1440,
1372, 1165, 1122 cmÀ1; MS (EI) e/e 555 (M+, 100), 553
4-Trifluoromethyl-2,6-bis[30-(N-toluenesulfonyl-50-meth-
oxylindolyl)]pyridine (21). Yield 76%; mp 195–198 ꢀC

W.-N. Xiong et al. / Bioorg. Med. Chem. 9 (2001) 1773–1780
1779
(71) 556 (34), 557 (33), 400 (18), 398 (13), 319 (19), 155
1
3-Cyano-4-trifluoromethyl-2,6-bis[30-(N-toluenesulfonyl-
50-bromoindolyl)]pyridine (32). Yield 50%; mp 275–
277 ꢀC (MeOH); IR (KBr) nmax 2230, 1596, 1542, 1439,
1174, 1130 cmÀ1; MS (EI) e/e 868 (M+, 100), 869 (73),
867 (71) 870 (64) 866 (46) 714 (52), 713 (45), 91 (45); 19F
(97), 91 (97); 19F NM RdÀ14 (s); H NMR (CDCl3) d
8.59 (s, 1H), 8.32 (s, 1H), 7.9–7.8 (m, 4H), 7.55 (d,
J=8.66 Hz, 1H), 7.31 (m, 2H), 2.39 (s, 3H); HRMS (EI)
calcd for C22H12BrClF3N3O2S: 552.94743; found:
552.94587.
1
NMR dÀ15 (s); H NMR (DMSO-d6) d 9.34 (s, 1H),
8.78 (s, 1H), 8.72 (s, 1H), 8.61 (s, 1H), 8.15 (s, 1H),
8.04–7.95 (m, 6H), 7.64–7.58 (m, 2H), 7.46 (m, 4H), 2.28
(s, 6H); 13C NMR (DMSO-d6) d 20.9, 114.9, 115.0,
116.1, 117.4, 118.2, 124.0, 125.4,126.9, 128.2, 128.3,
128.8, 129.7, 130.1, 130.3, 130.4, 132.1, 132.8, 133.2,
133.3, 133.5, 139.9, 146.3; HRMS (EI) calcd for
C37H23Br2F3N4O4S2: 865.94795; found: 865.94539.
2-Chloro-3-cyano-4-trifluoromethyl-6-[30-(N-toluenesulfonyl-
60-bromoindolyl)]pyridine (28). Yield 72%; mp 248–
251 ꢀC (MeOH); IR (KBr) nmax 2234, 1599, 1523, 1409,
1309, 1152 cmÀ1; MS (EI) e/e 555 (M+, 100), 553 (72)
556 (34), 557 (33), 400 (36), 398 (26), 319 (22), 155 (80),
91 (80), 69 (1); 19F NM RdÀ14 (s); 1H NM R
(CDCl3) d 8.31 (d, J=8.16 Hz, 1H), 8.30 (s, 1H), 8.19
(s, 1H), 7.91–7.85 (m, 3H), 7.54 (s, 1H), 7.33 (d,
J=8.25 Hz, 1H), 7.27 (s, 1H), 2.40 (s, 3H); HRMS
(EI) calcd for C22H12BrClF3N3O2S: 552.94743; found:
552.94909.
3-Cyano-4-trifluoromethyl-2,6-bis[30-(N-toluenesulfonyl-
60-bromoindolyl)]pyridine (33). Yield 52%; mp 276–
278 ꢀC (MeOH); IR (KBr) nmax 2225, 1594, 1532, 1405,
1382, 1149 cmÀ1; MS (EI) e/e 868 (M+, 100), 869 (73),
870 (68), 866 (48), 713 (54), 712 (40), 559 (27), 155 (21),
3-Cyano-4-trifluoromethyl-2,6-bis[30-(N-toluenesulfonylin-
dolyl)]pyridine (29). Yield 69%; mp 228–230 ꢀC
(MeOH); IR (KBr) nmax 2927, 2226, 1595, 1447, 1378,
1176, 1141 cmÀ1; MS (EI) e/e 710 (M+, 100), 711 (45),
555 (48), 556 (27), 400 (37), 373 (12), 155 (9); 19F NM R
91 (38); 19F NM RdÀ15 (s); H NMR (DMSO-d6) d
1
9.29 (s 1H), 8.76 (s, 1H), 8.72 (s, 1H), 8.28 (d, J=9 Hz,
1H), 8.18–8.00 (m, 6H), 7.53–7.41 (m, 6H), 7.87 (d,
J=8.4 Hz, 1H), 2.35 (s, 6H); HRMS (EI) calcd for
C37H23Br2F3N4O4S2: 865.94795; found: 865.95243.
1
dÀ13 (s); H NMR (CDCl3) d 8.56 (s, 1H), 8.41 (d,
J=8.0 Hz, 1H), 8.37 (s, 1H), 8.13–8.09 (m, 2H), 8.03 (d,
J=8.35 Hz, 1H), 7.96–7.93 (m, 3H), 7.89–7.86 (m, 2H),
7.45–7.38 (m, 2H), 7.30–7.24 (m, 7H), 2.36 (s, 3H), 2.35
(s, 3H); HRMS (EI) calcd for C37H25F3N4O4S2:
710.12693; found: 710.12727.
3-Cyano-4-trifluoromethyl-2,6-bis[30-(N-toluenesulfonyl-
50-benzoxylindolyl)]pyridine (34). Yield 54%; mp 288–
290 ꢀC (MeOH); IR (KBr) nmax 2224, 1610, 1595, 1539,
1449, 1376, 1191, 1127 cmÀ1; MS (EI) e/e 923 (M++1,
6), 400 (27), 402 (16), 319 (29), 239 (100), 209 (27), 165
1
(28); 19F NM RdÀ14 (s); H NMR (CDCl3) d 8.53 (s,
3-Cyano-4-trifluoromethyl-2,6-bis[30-(N-toluenesulfonyl-
50-methoxylindolyl)]pyridine (30). Yield 65%; mp 230–
232 ꢀC (MeOH); IR (KBr) nmax 2230, 1594, 1537, 1479,
1380, 1172, 1141 cmÀ1; MS (EI) e/e 770 (M+, 100), 771
(49), 615 (31), 616 (20), 461 (11), 460 (21), 445 (39), 446
(12), 155 (2); 19F NM Rd À13.5 (s); 1H NMR (CDCl3) d
8.51 (s, 1H), 8.32 (s, 1H), 7.99–7.84 (m, 9H), 7.60 (d,
J=2.37 Hz, 1H), 7.29–7.26 (m, 3H), 7.03–6.97 (m, 2H),
3.57 (s, 3H), 3.44 (s, 3H), 2.37 (s, 3H), 2.34 (s, 3H); 13C
NMR (CDCl3) d 157.3, 157.2, 157.0, 145.9, 145.5, 134.6,
130.3, 130.2, 129.7, 129.5, 128.6, 128.5, 127.3, 127.1,
119.8, 118.4, 115.7, 115.1, 114.9, 114.5, 114.3, 113.8,
113.7, 105.1, 104.4, 55.4, 55.2, 21.7, 21.6; HRMS (EI)
calcd for C39H29F3N4O6S2: 770.14807; found:
770.14824.
1H), 8.32 (s, 1H), 8.08 (s, 1H), 8.00 (d, J=9.0 Hz, 1H),
7.97–7.74 (m, 7H), 7.24–7.01 (m, 16H); anal. calcd for
C51H37F3N4O6S2: C, 66.37; H, 4.04; N, 6.07. Found: C,
66.05; H, 4.41; N, 6.38.
X-ray crystallgraphic analysis. Colorless prismatic crys-
tals of 25 were obtained from ethyl acetate. They were
stable without the mother liquor in air and were selected
at room atmosphere for X-ray crystallography. Formula
C24H18O4N3F3S, space group P1 (No. 2), a=11.372(2),
ꢀ
˚
b=11.765(3), c=8.564(2) A, a=93.75(2) , b=99.34(1),
3
˚
g=87.07(1), V=1127.2 (4) A , Z=2, No. of observa-
tions 3024; No. of variables 317; Residuals: R; Rw
0.041; 0.051; Goodness of fit indicator 1.87. All measure-
ments were made on a Rigaku AFC7R diffractometer
with graphite monochromated Mo-Ka radiation.
3-Cyano-4-trifluoromethyl-2,6-bis[30-(N-toluenesulfonyl-
60-methoxylindolyl)]pyridine (31). Yield 61%; mp 249–
251 ꢀC (MeOH); IR (KBr) nmax 3141, 2229, 1616, 1596,
1492, 1376, 1179 cmÀ1; MS (EI) e/e 770 (M+, 100), 771
(47), 616 (51), 615 (89), 461 (45), 460 (58), 445 (36), 446
Acknowledgements
The authors express deep thanks to Dr. Jian Ding, Dr.
Dong Xiao and their colleagues of the Shanghai Insti-
tute of Materia Medica for conducting the in vitro dis-
ease-orient primary antitumor screen. This work was
financially supported by grant from Shanghai Munici-
pal Committee of Science and Technology.
1
(15); 19F NM RdÀ14 (s); H NMR (CDCl3) d 8.45 (s,
1H), 8.27 (d, J=8.9 Hz, 1H), 8.22 (s, 1H), 8.00–7.84 (m,
6H), 7.61 (d, J=2.3 Hz, 1H), 7.53 (d, J=2.2 Hz, 1 H),
7.31–7.26 (m, 4H), 6.91–6.86 (m, 2H), 3.92 (s, 3H), 3.88
(s, 3H), 2.37 (s, 3H), 2.36 (s, 3H); 13C NMR (CDCl3) d
158.7, 158.6, 157.1, 156.9, 145.9, 145.6, 136.8, 136.1,
134.7, 134.6, 130.3, 130.2, 127.6, 127.3, 127.1, 126.9,
123.8, 122.9, 122.3, 121.2, 120.3, 118.6, 115.1, 114.1,
114.0, 113.9, 113.5, 113.4, 97.8, 97.5, 55.9, 55.8, 21.7;
HRMS (EI) calcd for C39H29F3N4O6S2: 770.14807;
found: 770.14605.
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