Synthesis and preliminary biological study of bisindolylmethanes accessed by an acid-catalyzed hydroarylation of vinyl indoles

Article abstract of DOI:10.1016/j.tet.2012.03.075

An acid-catalyzed hydroarylation reaction of vinyl indoles is reported, which tolerates a wide range of heterocycles as the exogenous nucleophile, such as indoles, pyrroles, and indolizines. The method rapidly accesses the biologically relevant bisindolylmethane scaffold in good to excellent yields. Evaluation of the biological activity of several synthesized analogues reveals cytotoxic activity against and selectivity for the MCF-7 breast cancer cell line.

Full text of DOI:10.1016/j.tet.2012.03.075

Tetrahedron 68 (2012) 5203e5208
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and preliminary biological study of bisindolylmethanes accessed by an
acid-catalyzed hydroarylation of vinyl indoles
,
Tejas P. Pathak a, Jaroslaw G. Osiak a, Rachel M. Vaden a, Bryan E. Welm b, Matthew S. Sigman a
*
a Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112, USA
b Department of Surgery, Huntsman Cancer Institute, 2000 Circle of Hope, Salt Lake City, UT 84112, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
An acid-catalyzed hydroarylation reaction of vinyl indoles is reported, which tolerates a wide range of
heterocycles as the exogenous nucleophile, such as indoles, pyrroles, and indolizines. The method rapidly
accesses the biologically relevant bisindolylmethane scaffold in good to excellent yields. Evaluation of the
biological activity of several synthesized analogues reveals cytotoxic activity against and selectivity for
the MCF-7 breast cancer cell line.
Received 18 January 2012
Received in revised form 11 March 2012
Accepted 20 March 2012
Available online 28 March 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Acid catalysis
Bisindolylmethanes
Hydroarylation
Heterocycles
Breast cancer
1. Introduction
Recently, various groups have reported the synthesis of un-
symmetrical bisindolylmethanes using a leaving group strategy
Bisindolylmethane scaffolds are present in many natural prod-
ucts isolated from both terrestrial and marine natural sources.1
These natural products exhibit a broad range of biological activity
including anticancer activity against several common cancer cell
lines.2 Naturally occurring bisindolylmethanes, such as vibrindole
A (1) are useful in the treatment of fibromyalgia, chronic fatigue, and
irritable bowel syndrome.3 Additionally, diindolylmethane (2) in-
hibits the proliferation of both estrogen dependent and independent
breast cancer cell lines (Fig. 1).4 Synthetic bisindolylmethanes are
not only useful in biological applications,2,5 but also have found use
in materials chemistry.6 Due to their extensive utility, a number of
methods have been reported for the synthesis of symmetrical
bisindolylmethanes, whereas the efficient synthesis of un-
symmetrical bisindolylmethanes remains a challenge.
(Scheme 1a).7 Although this strategy is useful, it has some limita-
tions in terms of substrates that can be employed. For example,
substrates with an aryl group at the benzylic position of the indole
are preferred presumably due to the additional stabilization they
impart to the cationic alkylideneindoleninium intermediate A.1,8,9
Moreover, intermediate A is a proposed key intermediate in vari-
ous synthetic transformations to access functionalized indole core
structures including unsymmetrical bisindolylmethanes.8,9 Hence,
an efficient and simple method to access the alkylideneindoleni-
nium intermediate would be attractive. Considering this, we be-
came interested in developing new methods to access
bisindolylmethanes, which would provide an alternative to existing
methods. Herein, we report the use of readily accessible vinyl in-
dole derivatives as precursors to alkylideneindoleninium in-
termediates of type A. It is proposed that the protonation of a vinyl
indole with a Brønsted acid will afford intermediate A, which will
subsequently react with an exogenous nucleophilic indole de-
rivative to yield unsymmetrical bisindolylmethanes (Scheme 1b).10
2. Results and discussion
Fig. 1. Structure of biologically relevant natural products.
The parent substrate 3-vinyl-1H-indole (3) was selected for
initial optimization. In contrast to previous reports, substrate 3
does not have any additional stabilization of the putative cationic
intermediate A, which makes it a more challenging substrate to
* Corresponding author. Tel.: þ1 801 585 0774; e-mail address: sigman@chem.-
utah.edu (M.S. Sigman).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.03.075

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T.P. Pathak et al. / Tetrahedron 68 (2012) 5203e5208
Table 2
Scope of hydroarylation of 3-vinyl-1H-indole
Scheme 1. Different strategies for synthesis of BIMs.
functionalize. When 3 was treated with 20 mol % of p-TsOH in ei-
ther dichloromethane (DCM), dichloroethane (DCE) or toluene,
complete conversion of 3 was observed within a few hours with
<10% yield of the desired product and poor mass balance (Table 1,
entries 1e3). This observation alludes to the tendency of substrate 3
to polymerize under acidic conditions. Further evaluation of the
reaction conditions revealed that the addition of the Lewis basic
solvent dimethylacetamide (DMA) as a co-solvent improved the
yield of the desired product (Table 1, compare entries 4 and 5). The
reaction in DMA as the sole solvent gave the desired product in 89%
GC yield (Table 1, entry 6).
Table 1
Optimization of reaction conditions
aYields are average of at least two runs at 0.3 mmol scale.
bReactions were performed at 70 ꢀC.
Entry
X
Y
Solvent
t (h)
% Conv.a
% 1a
1
2
3
4
20
20
20
20
20
20
10
10
15
15
15
15
15
15
7
DCM
DCE
Toluene
9:1 Toluene/DMA
1:1 Toluene/DMA
DMA
2
2
2
16
16
16
16
16
>99
>99
>99
>99
>99
>99
>99
>99
<5
<5
9
36
71
89
73c
81c
remaining nucleophile was recovered. N-Methyl indole also gave
the corresponding 3,30-bisindolylmethane in good yield (entry 2b).
Furthermore, various substituted indoles are well-tolerated under
thereaction conditionsincluding sterically demanding2-substituted
indoles (entries 2ceg). The 3,20-bisindolylmethanes are obtained
using this method as demonstrated by successful use of 3-methyl
indole to give product 2h although a higher reaction temperature
was required. A pyrrole and an indolizine can be used as alternative
nucleophiles to give the corresponding bisheteroarylmethanes in
good yields (entries 2i and 2j). Finally, a disubstituted vinyl indole is
also a competent reaction partner giving the desired product in ex-
cellent yield (entries 2k).
5
6
7b
8b
DMA
DMA
10
This entry is bold to highlight optimized conditions.
a
The conversion and yield were measured by GC with an internal standard.
Concentration of the reaction mixture (with respect to 3): 0.2 M.
Isolated yield.
b
c
Further optimization of acid and nucleophile loadings gave the
optimal conditions, in which 81% isolated yield of the desired
product was obtained (Table 1, compare entries 7 and 8).
The scope of the exogenous nucleophile was evaluated using 3-
vinyl-1H-indole (3) as the standard substrate. Unprotected 1H-in-
dole as a nucleophile gave the natural product vibrindole A (1) in 80%
isolated yield, without precautions to exclude air or moisture from
the system (Table 2, entry 2a). It should be noted that >90% of the
Encouraged by these results, substituted vinyl indole 4 was
prepared in high yield by condensation of indole with the corre-
sponding cyclic ketone.11 As expected, substrate 4 underwent
smooth hydrofunctionalization with N-Meeindole as the exoge-
nous nucleophile, to give the desired product in excellent yield
(Table 3, entry 3a). The bisindolylmethane obtained (3a) not only
has one quaternary carbon but a similar bisindolylmethane,
reported by Wang and co-workers 5, also exhibits in vivo activity

T.P. Pathak et al. / Tetrahedron 68 (2012) 5203e5208
5205
Table 3
Scope of hydroarylation of 4
Fig. 2. (a) Evaluation of biological activity of newly synthesized bisindolylmethanes in
MCF-7 cells at 10 mM concentration. (b) Dose response curves for compound 3a (left)
and 2j (right).
aYields are average of at least two runs at 0.2 mmol scale.
4. Experimental section
4.1. General method
bReaction time¼30 h.
against lung cancer cell lines.12 Additionally, both electron-rich and
electron-deficient indoles are well-tolerated (entries 3bec) as well
as the use of a pyrrole and an indolizine as nucleophiles (entry
3dee).
In light of the previously established biological activity of diin-
dolylmethane 2 against a breast cancer cell line13 and our recent
discovery of cytotoxic indole containing compounds,14 the bi-
ological activity of the newly synthesized bisindolylmethanes was
probed in MCF-7 breast cancer cell line. Upon evaluating various
derivatives in this whole cell assay, several compounds including
compounds 2c and 3a were found to reduce cell count in com-
parison to the DMSO control (Fig. 2a). Excitingly, compound 3a
displays excellent differential activity between MCF-7 and MCF-
10A (normal breast) cells. Even at the highest concentration eval-
Toluene, dichloromethane, and THF were dried before use by
passing through a column of activated alumina. All other reagents
(including indoles) were purchased from commercial sources and
used without further purification. Yields were calculated for ma-
terial judged homogeneous by thin-layer chromatography and
NMR. Thin-layer chromatography was performed with EMD silica-
gel 60 F254 plates eluting with the solvents indicated, visualized by
a 254 nm UV lamp, and stained either with potassium permanga-
nate, p-anisaldehyde, phosphomolybdic acid or vanillin. Flash col-
umn chromatography was performed with EcoChrom MP Silitech
ꢀ
32-63D 60 A silica gel, slurry packed with solvents indicated in
glass columns. Nuclear magnetic resonance spectra were acquired
at 400 MHz for 1H, and 100 MHz for 13C. Chemical shifts for proton
nuclear magnetic resonance (1H NMR) spectra are reported in parts
per million downfield relative to the line of CHCl3 singlet at
7.26 ppm. Chemical shifts for carbon nuclear magnetic resonance
uated (100
mM), 3a does not generally affect the growth of MCF-10A
cells whereas it leads to an EC50 of 4.3
mM in MCF-7 cells (Fig. 2b). Of
additional interest, an EC50 of w50 nM is observed for compound 2j
although no selectivity for either cell line is observed (Fig. 2b).
(
13C NMR) spectra are reported in parts per million downfield rel-
ative to the center-line of the CDCl3 triplet at 77.2 ppm. The ab-
breviations s, d, t, q, td, dd, and m stand for the resonance
multiplicities singlet, doublet, triplet, quartet, triplet of doublet,
doublet of doublet and multiplet, respectively. IR spectra were
recorded using a Nicolate FT-IR instrument. Reported melting
points are uncorrected. Glassware for all reactions was oven-dried
at 110 ꢀC and cooled while purging with nitrogen prior to use.
3. Conclusions
In conclusion, we have successfully developed a simple and ef-
ficient reaction to access biologically relevant bisindolylmethanes
from vinyl indoles. This method offers a distinct alternative to ac-
cess alkylideneindoleninium intermediates in situ, which can in
turn be subjected to the reaction with various nucleophiles to
provide functionalized indoles. Broad scope and ease of the re-
action highlight this method. Future work is focused on the further
evaluation of analogues of compound 3a and the identification of
its biological target.
4.2. General procedure for substrate scope (Table 2)
To a 2.5 dr vial equipped with a stir bar was added 5.13 mg of p-
TsOH (0.030 mmol, 0.100 equiv), 351.3 mg of N-Heindole

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T.P. Pathak et al. / Tetrahedron 68 (2012) 5203e5208
(3.00 mmol, 10.0 equiv), and 42.9 mg of 1 (0.300 mmol, 1.00 equiv).
To this 1.5 mL of DMA was added via syringe. The vial was capped
and was stirred for given time at room temperature. The crude
mixture was purified with flash silica-gel column chromatography.
(Note: In case of liquid nucleophiles, p-TsOH was added last.)
10.0 equiv) was used. Yield¼76% (average of two run), Rf¼0.25 w/
20% EtOAC/Hex, colorless solid, mp¼57e59 ꢀC. 1H NMR (400 MHz,
CDCl3)
d
¼7.86 (s, 1H), 7.75 (s, 1H), 7.63 (d, J¼7.9 Hz, 1H), 7.32 (d,
J¼8.1 Hz, 1H), 7.23e7.18 (m, 2H), 7.11e7.06 (m, 2H), 6.89e6.85 (m,
3H), 4.66 (q, J¼7.1 Hz, 1H), 3.80 (s, 3H), 1.83 (d, J¼7.1 Hz, 3H). 13C
NMR {1H} (100 MHz, CDCl3)
122.2, 121.9, 121.6, 121.5, 121.4, 119.9, 119.1, 111.9, 102.0, 56.0, 28.3,
21.8. IR 3403, 1452, 1206, 1091, 739 cmꢁ1. HRMS C19H18N2O (MþH)þ
calcd 291.1492, obsd 291.1489.
d
¼153.7, 136.8, 132.0, 127.4, 127.0,
4.2.1. Characterization data for 3,30-(ethane-1,1-diyl)bis(1H-indole)
(entry 2a). Followed same procedure as general procedure.
Yield¼80% (average of two run).
The 1H NMR spectrum of product was matched with literature.
4.2.7. Characterization data for 3-(1-(1H-indol-3-yl)ethyl)-7-ethyl-
1H-indole (entry 2g). Followed same procedure as general pro-
cedure except 435.6 mg of 7-ethyl-1H-indole (3.00 mmol,
10.0 equiv) was used. Yield¼62% (average of two run), Rf¼0.35 w/
20% EtOAC/Hex, pale green solid, mp¼50e52 ꢀC. 1H NMR
4.2.2. Characterization data for 3-(1-(1H-indol-3-yl)ethyl)-1-
methyl-1H-indole (entry 2b). Followed same procedure as general
procedure. Yield¼81% (average of two run), Rf¼0.30 w/20% EtOAC/
Hex, pale green solid, mp¼51e53 ꢀC. 1H NMR (400 MHz, CDCl3)
d¼7.37 (s, 1H), 7.66 (d, J¼7.9 Hz, 2H), 7.35 (dt, J¼7.2, 0.9 Hz, 2H),
(400 MHz, CDCl3)
d¼7.78e7.76 (m, 2H), 7.61 (d, J¼7.9 Hz, 1H),
7.30e7.22 (m, 2H), 7.13 (ddd, J¼7.9, 7.0, 0.8 Hz, 2H), 6.91 (d,
J¼2.3 Hz, 1H), 6.82 (s, 1H), 4.75 (q, J¼7.1 Hz, 1H), 3.72 (s, 3H), 1.88 (d,
7.49e7.47 (m, 1H), 7.34 (d, J¼8.1 Hz, 1H), 7.19 (td, J¼7.6, 0.9 Hz, 1H),
7.10e7.04 (m, 3H), 6.90e6.86 (m, 2H), 4.69 (q, J¼7.1 Hz, 1H), 2.85 (q,
J¼7.6 Hz, 2H), 1.83 (d, J¼7.1 Hz, 3H), 1.38 (t, J¼7.6 Hz, 3H). 13C NMR
J¼7.1 Hz, 3H). 13C NMR {1H} (100 MHz, CDCl3)
¼137.5, 136.8, 127.5,
d
127.1, 126.2, 121.9, 121.5, 121.4, 120.3, 120.0, 119.9, 119.2, 118.6, 111.2,
109.3, 32.7, 28.3, 22.2. IR 3411, 2967, 1455, 1335, 760 cmꢁ1. HRMS
C19H19N2 (MþH)þ calcd 275.1543, obsd 275.1554.
{1H} (100 MHz, CDCl3)
d
¼136.8, 135.6, 127.1, 126.8, 126.5, 122.3,
121.9, 121.8, 121.4, 121.0, 120.4, 119.9, 119.4, 119.1, 117.6, 111.2, 28.4,
24.1, 21.9, 13.9. IR 3403, 1455, 1293, 1091, 739 cmꢁ1. HRMS C20H21N2
(MþH)þ calcd 289.1699, obsd 289.1681.
4.2.3. Characterization data for 3-(1-(1H-indol-3-yl)ethyl)-1,2-
dimethyl-1H-indole (entry 2c). Followed same procedure as entry
2b except 432.0 mg of indole (3.00 mmol, 10.0 equiv) was added.
Yield¼85% (average of two run), Rf¼0.35 w/20% EtOAC/Hex, colorless
4.2.8. Characterization data for 2-(1-(1H-indol-3-yl)ethyl)-3-
methyl-1H-indole (entry 2h). Followed same procedure as general
procedure except 393.6 mg of 3-methyl-1H-indole (3.00 mmol,
10.0 equiv) was used. Yield¼54% (average of two run), Rf¼0.41 w/
20% EtOAC/Hex, colorless solid, mp¼64e66 ꢀC. 1H NMR (400 MHz,
solid, mp¼52e54 ꢀC, 1H NMR (400 MHz, CDCl3)
¼7.81 (s, 1H), 7.64
d
(d, J¼7.9 Hz, 1H), 7.45 (d, J¼7.9 Hz, 1H), 7.31 (dd, J¼12.4, 8.1 Hz, 2H),
7.19e7.15 (m, 2H), 7.06e7.00 (m, 3H), 4.72 (qd, J¼7.2,1.1 Hz,1H), 3.67
(s, 3H), 2.40 (s, 3H), 1.89 (d, 3H). 13C NMR {1H} (100 MHz, CDCl3)
CDCl3)
d
¼7.99 (m, 1H), 7.59e7.56 (m, 2H), 7.35 (t, J¼8.2 Hz, 2H),
7.21e7.08 (m, 3H), 6.99 (t, J¼7.5 Hz,1H), 4.72 (q, J¼7.1 Hz,1H), 2.45 (s,
d
¼136.9,136.8,131.2,127.4,127.1,121.9,121.8,121.1,120.3,119.8,119.5,
3H), 1.76 (d, J¼7.1 Hz, 3H). 13C NMR {1H} (100 MHz, CDCl3)
¼138.7,
d
119.1,118.5,115.2,111.1,108.7, 29.6, 29.3, 21.2,10.7. IR 3419,1457,1233,
136.7, 135.0,129.8, 126.9, 122.5, 121.4, 120.9, 119.8,119.7,119.5, 119.0,
765 cmꢁ1. HRMS C20H21N2 (MþH)þ calcd 289.1699, obsd 289.1701.
118.2,111.2,110.6,105.9, 28.6, 20.6, 8.7. IR 3412,1455,1335, 740 cmꢁ1
.
HRMS C19H19N2 (MþH)þ calcd 275.1543, obsd 275.1554.
4.2.4. Characterization data for 3-(1-(1H-indol-3-yl)ethyl)-1-
methyl-2-phenyl-1H-indole (entry 2d). Followed same procedure
as general procedure except 616.8 mg of 1-methyl-2-phenyl-1H-
indole (3.00 mmol, 10.0 equiv) and additional 1 mL of DMA were
used. Yield¼55% (average of two run), Rf¼0.32 w/20% EtOAC/Hex,
4.2.9. Characterization data for 3-(1-(1H-pyrrol-2-yl)ethyl)-1H-in-
dole (entry 2i). Followed same procedure as general procedure
except 201.2 mg of 1H-pyrrole (3.00 mmol, 10.0 equiv) was added.
Yield¼55% (average of two run), Rf¼0.43 w/20% EtOAC/Hex, color-
colorless solid, mp¼178e180 ꢀC. 1H NMR (400 MHz, CDCl3)
d
¼7.80
less liquid, 1H NMR (400 MHz, CDCl3)
d
¼7.94e7.78 (m, 2H), 7.48 (d,
(s, 1H), 7.67 (d, J¼7.9 Hz, 1H), 7.49e7.43 (m, 3H), 7.39 (dd, J¼7.7,
1.6 Hz, 2H), 7.34 (t, J¼8.6 Hz, 1H), 7.28 (t, J¼7.6 Hz, 1H), 7.21 (td,
J¼7.6, 1.1 Hz, 1H), 7.13e7.09 (m, 1H), 7.05e6.94 (m 3H), 4.55 (dq,
J¼7.2, 0.8 Hz, 1H), 3.60 (s, 3H), 1.86 (d, J¼7.2 Hz, 3H). 13C NMR {1H}
J¼7.9 Hz, 1H), 7.37 (d, J¼8.2 Hz, 1H), 7.22 (td, J¼7.6, 0.9 Hz, 1H),
7.11e7.07 (m, 1H), 6.97 (d, J¼2.4 Hz, 1H), 6.59 (q, J¼2.1 Hz, 1H), 6.21
(q, J¼2.9 Hz, 1H), 6.17e6.16 (m, 1H), 4.45 (q, J¼7.1 Hz, 1H), 1.74 (d,
J¼7.1 Hz, 3H). 13C NMR {1H} (100 MHz, CDCl3)
¼136.7, 129.2, 126.7,
d
(100 MHz, CDCl3)
d¼137.7, 137.2, 136.7, 132.4, 130.9, 130.8, 128.4,
122.3, 121.4, 120.2, 119.7, 119.6, 116.3, 111.3, 108.1, 104.3, 30.0, 21.3. IR
3401, 1291, 1091, 743 cmꢁ1. HRMS C14H14N2 (MþH)þ calcd 211.123,
obsd 211.1224.
128.1, 126.8, 121.8, 121.7, 121.4, 121.3, 120.9, 119.9, 118.9, 118.8, 117.4,
110.9, 109.5, 30.9, 28.6, 21.7. IR 3414, 2969, 1466, 740 cmꢁ1. HRMS
C25H23N2 (MþH)þ calcd 351.1856, obsd 351.1843.
4.2.10. Characterization data for methyl 3-(1-(1H-indol-3-yl)ethyl)
indolizine-1-carboxylate (entry 2j). Followed same procedure as
general procedure except 525.5 mg of methyl indolizine-1-
carboxylate (3.00 mmol, 10.0 equiv) was used. Yield¼68% (aver-
age of two run), Rf¼0.28 w/20% EtOAC/Hex, colorless solid,
4.2.5. Characterization data for 3-(1-(1H-indol-3-yl)ethyl)-5-bromo-
1H-indole (entry 2e). Followed same procedure as general pro-
cedure except 588.1 mg of 5-bromo-1H-indole (3.00 mmol,
10.0 equiv) was used. Yield¼46% (average of two run), Rf¼0.30 w/
20% EtOAC/Hex, colorless solid, mp¼47e50 ꢀC. 1H NMR (400 MHz,
mp¼77e79 ꢀC. 1H NMR (400 MHz, CDCl3)
¼8.22 (d, J¼9.0 Hz, 1H),
d
CDCl3)
d
¼7.88 (s, 2H), 7.71e7.70 (m, 1H), 7.54 (dd, J¼7.9, 0.7 Hz, 1H),
8.11 (s, 1H), 7.68 (d, J¼7.1 Hz, 1H), 7.61 (d, J¼7.9 Hz, 1H), 7.35 (d,
J¼8.1 Hz, 1H), 7.31 (s, 1H), 7.23e7.19 (m, 1H), 7.12 (t, J¼7.5 Hz, 1H),
6.98 (dd, J¼9.0, 6.6 Hz, 1H), 6.59 (d, J¼2.4 Hz, 1H), 6.52 (td, J¼6.8,
0.7 Hz, 1H), 4.57 (q, J¼7.0 Hz, 1H), 3.93 (s, 3H), 1.85 (d, J¼7.0 Hz, 3H).
7.36 (dt, J¼8.1, 0.8 Hz, 1H), 7.26e7.16 (m, 3H), 7.06 (ddd, J¼7.9, 7.0,
0.9 Hz,1H), 6.91 (td, J¼2.2, 0.8 Hz, 2H), 4.61 (q, J¼7.1 Hz,1H),1.79 (d,
J¼7.1 Hz, 3H). 13C NMR {1H} (100 MHz, CDCl3)
¼136.8, 135.3, 128.8,
d
126.9, 124.7, 122.6, 122.3, 122.0, 121.5, 119.8, 119.2, 112.6, 112.5, 111.3,
28.2, 21.7. IR 3405, 1453, 1092, 739 cmꢁ1. HRMS C18H15BrN2 (M)þ
calcd 338.0429, obsd 338.0419.
13C NMR {1H} (100 MHz, CDCl3)
d
¼165.7, 136.8, 136.3, 129.1, 126.4,
124.0, 122.3, 121.8, 121.5, 119.8, 119.6, 118.8, 117.9, 113.6, 112.1, 111.6,
102.4, 51.0, 28.6, 20.8. IR 3314, 2966, 1662, 1214, 735 cmꢁ1. HRMS
C20H19N2O2 (MþH)þ calcd 319.1441, obsd 319.1453.
4.2.6. Characterization data for 3-(1-(1H-indol-3-yl)ethyl)-5-
methoxy-1H-indole (entry 2f). Followed same procedure as gen-
eral procedure except 588.1 mg of 5-bromo-1H-indole (3.00 mmol,
4.2.11. Characterization data for 3-(1-(1H-indol-3-yl)propyl)-1-
methyl-1H-indole (entry 2k). Followed same procedure as general

T.P. Pathak et al. / Tetrahedron 68 (2012) 5203e5208
5207
procedure except reaction was ran at 70 ꢀC. Yield¼84% (average of
(400 MHz, CDCl3)
d
¼8.14 (s, 1H), 7.70 (d, J¼0.6 Hz, 1H), 7.35 (dt,
two run), Rf¼0.40 w/20% EtOAC/Hex, colorless solid, mp¼88e90 ꢀC.
J¼7.3, 0.9 Hz, 1H), 7.15 (td, J¼7.6, 1.1 Hz, 1H), 7.01e6.96 (m, 2H), 6.55
(td, J¼2.6, 1.5 Hz, 1H), 6.23e6.16 (m, 2H), 3.60 (ddd, J¼13.3, 7.5,
3.9 Hz, 2H), 3.49e3.44 (m, 2H), 2.47e2.41 (m, 2H), 2.26 (ddd,
J¼13.3 Hz, 8.5, 4.3 Hz, 2H), 1.47 (s, 9H). 13C NMR {1H} (100 MHz,
1H NMR (400 MHz, CDCl3)
d
¼7.82 (s,1H), 7.64 (dt, J¼7.9, 0.9 Hz, 2H),
7.33e7.29 (m, 2H), 7.26e7.32 (m, 2H), 7.07 (ddd, J¼8.0, 7.0, 1.1 Hz,
2H), 6.99 (d, J¼1.6 Hz, 1H), 6.86 (s, 1H), 4.41 (t, J¼7.4 Hz, 1H), 3.72 (s,
3H), 2.27 (quintet, J¼7.4 Hz, 2H) 1.05 (t, J¼7.4 Hz, 3H). 13C NMR {1H}
CDCl3)
d
¼155.2, 137.7, 137.1, 125.8, 122.3, 122.1, 120.9, 120.8, 119.7,
(100 MHz, CDCl3)
d
¼137.4, 136.7, 128.2, 127.8, 127.4, 126.5, 121.8,
116.6, 111.4, 108.0, 104.9, 79.5, 38.3, 36.6, 28.6. IR 3369, 2969, 2928,
1594, 1484, 1381, 789 cmꢁ1. HRMS C22H28N3O2 (MþH)þ calcd
366.2176, obsd 366.2182.
121.6, 121.4, 120.6, 120.0, 119.1, 119.0, 118.6, 111.2, 109.3, 36.0, 32.7,
29.1, 13.3. IR 3406, 2963, 1584, 1451, 1335, 1095, 738 cmꢁ1. HRMS
C20H21N2 (MþH)þ calcd 289.1699, obsd 289.1705.
4.3.5. Characterization data for methyl-3-(1-(tert-butoxycarbonyl)-
4-(1H-indol-3-yl)piperidin-4-yl)indolizine-1-carboxylate (entry 3e).
Followed same procedure as the general procedure. Yield¼90%
(average of two run), Rf¼0.30 w/66% EtOAC/Hex, colorless solid,
4.3. General procedure for substrate scope (Table 3)
To a 2.5 dr vial equipped with a stir bar was added 3.44 mg of p-
TsOH (0.020 mmol, 0.100 equiv), 262.4 mg of N-Me-indole
(2.00 mmol, 10.0 equiv), and 59.7 mg of 1 (0.200 mmol, 1.00 equiv).
To this 1.0 mL of DMA was added via syringe. The vial was capped
and was stirred for given time at 70 ꢀC in oil bath. The crude
mixture was purified with flash silica-gel column chromatography.
(Note: In case of liquid nucleophiles, p-TsOH was added last.)
mp¼197e199 ꢀC.1H NMR (400 MHz, CDCl3)
¼8.62 (d, J¼1.7 Hz,1H),
d
8.17 (dt, J¼9.0, 1.1 Hz, 1H), 7.84 (d, J¼7.2 Hz, 1H), 7.54 (s, 1H), 7.30 (d,
J¼8.2 Hz, 1H), 7.21 (d, J¼2.5 Hz, 1H), 7.05 (ddd, J¼8.1, 7.1, 1.0 Hz, 1H),
6.98 (d, J¼8.1 Hz,1H), 6.85 (ddd, J¼9.0 Hz, 6.6, 0.9 Hz,1H), 6.78 (ddd,
J¼8.1 Hz, 7.1, 0.9 Hz,1H), 6.31 (td, J¼6.9,1.3 Hz,1H), 3.95 (s, 3H), 3.73
(br s, 2H), 3.48 (br s, 2H), 2.5 (m, 4H), 1.48 (s, 9H). 13C NMR {1H}
(100 MHz, CDCl3)
d
¼165.8, 155.1, 137.1, 136.9, 129.2, 128.8, 125.4,
4.3.1. Characterization data for tert-butyl-4-(1H-indol-3-yl)-4-(1-
125.1, 122.3, 121.7, 121.6, 120.0, 119.9, 119.6, 119.3, 115.7, 111.7, 111.4,
102.5, 79.8, 51.1, 37.9, 28.6. IR 3303, 1667, 1509, 734 cmꢁ1. HRMS
C28H32N3O4 (MþH)þ calcd 474.2387, obsd 474.2397.
methyl-1H-indol-3-yl)piperidine-1-carboxylate
(entry
3a).
Followed same procedure as the general procedure. Yield¼91%
(average of two run), Rf¼0.35 w/66% EtOAC/Hex, colorless solid,
mp¼133e135 ꢀC. 1H NMR (400 MHz, CDCl3)
d¼8.14 (s, 1H), 7.52 (dd,
4.4. Biological evaluation
J¼12.1, 9.1 Hz, 2H), 7.31 (d, J¼8.1 Hz, 1H), 7.26 (d, J¼8.2 Hz, 1H),
7.16e7.08 (m, 2H), 7.03 (d, J¼2.5 Hz, 1H), 6.96e6.90 (m, 3H), 3.73 (s,
3H), 3.65e3.55 (m, 4H), 2.62 (t, J¼5.4 Hz, 4H), 1.52 (s, 9H). 13C NMR
4.4.1. General culture procedure. MCF-10A and MCF-7 cells were
cultured in monolayer in Dulbecco’s Modified Eagle’s Medium/
Nutrient Mixture F-12 Ham (DME/F-12) containing HEPES buffer
{1H} (100 MHz, CDCl3)
d
¼155.4, 137.9, 137.3, 126.9, 126.5, 126.1,
122.3, 121.8, 121.6, 121.4, 121.2, 120.4, 118.9, 118.4, 111.4, 109.4, 79.4,
38.1, 35.9, 32.9, 28.7. IR 3303, 2947, 1667, 734 cmꢁ1. HRMS
C27H31N3O2 (MþNa)þ calcd 452.2308, obsd 452.2314.
and L-glutamine (HyClone) supplemented with 10% (v/v) fetal bo-
vine serum (FBS, HyClone), 1% (v/v) penicillin/streptomycin (P/S),
1% (v/v) insulin-transferrin-selenium-X (ITS, Gibco), and 2.5 nM
human epidermal growth factor, recombinant (EFG, BD Bio-
sciences). Cells were maintained in a humidified incubator at 37 ꢀC
and 5% CO2.
4.3.2. Characterization data for tert-butyl-4-(1H-indol-3-yl)-4-(5-
methoxy-1-methyl-1H-indol-3-yl)piperidine-1-carboxylate
(entry
3b). Followed same procedure as the general procedure.
Yield¼90% (average of two run), Rf¼0.35 w/66% EtOAC/Hex, color-
4.4.2. Initial 3-point screening of compounds 2bek, 3aee. In a 96-
well flat bottom plate, MCF-7 cells were seeded at 1500 cells/well
and MCF-10A cells were seeded at 9000 cells/well using the 10%
FBS medium described in the general culture procedure. The cells
were then incubated in a humidified incubator at 37 ꢀC and 5% CO2
for 18 h. From a 100 mM stock of each compound in molecular
less solid, mp¼186e188 ꢀC. 1H NMR (400 MHz, CDCl3)
¼8.10 (d,
d
J¼1.1 Hz, 1H), 8.01 (d, J¼1.2 Hz, 1H), 7.49 (d, J¼8.0 Hz, 1H), 7.29 (d,
J¼8.1 Hz, 1H), 7.18 (d, J¼8.8 Hz, 1H), 7.10e7.02 (m, 3H), 6.90 (dd,
J¼3.8, 1.7 Hz, 1H), 6.75 (dd, J¼8.8, 2.4 Hz,1H), 3.66 (s, 3H), 3.58 (br s,
4H), 2.63e2.52 (m, 4H), 1.49 (s, 9H). 13C NMR {1H} (100 MHz, CDCl3)
d
¼155.4, 153.1, 137.3, 132.5, 129.2, 126.6, 126.1, 123.0, 122.2, 121.7,
biology grade DMSO (Sigma) was made a 50
of each compound in DME/F-12 supplemented with 2% (v/v) FBS,1%
(v/v) P/S, 1% (v/v) ITS, and 2.5 nM EFG. From this 50 M standard
solution, serial dilutions of 10 M and 1 M were made. The media
was aspirated from the cells in the 96-well plates after the initial
incubation period and 100 L of the appropriately diluted com-
pound in media was added (day 0). The cells were incubated and on
days 2 and 4, the media was aspirated and 100 L of fresh
compound-containing media was added. On day 5, an MTS assay
was performed using CellTiter 96 AQueous Non-Radioactive Cell
Proliferation Assay (Promega). The absorbance measurements were
normalized to the DMSO control and these values were plotted
against the ꢂstandard deviation of 2 wells per condition.
mM standard solution
121.6, 121.4, 121.2, 118.9, 111.8, 111.4, 11.2, 104.0, 79.5, 55.9, 37.9, 35.7,
20.7. IR 3305, 1524, 1425, 793 cmꢁ1. HRMS C27H31N3O3 (MþNa)þ
calcd 468.2258, obsd 468.2267.
m
m
m
4.3.3. Characterization data for methyl-3-(1-(tert-butoxycarbonyl)-
4-(1H-indol-3-yl)piperidin-4-yl)-1-methyl-1H-indole-5-carboxylate
(entry 3c). Followed same procedure as the general procedure.
Yield¼71% (average of two run), Rf¼0.30 w/66% EtOAC/Hex, color-
m
m
less solid, mp¼266e268 ꢀC, 1H NMR (400 MHz, CDCl3)
¼8.35 (d,
d
J¼0.4 Hz, 1H), 8.12 (d, J¼0.6 Hz, 1H), 8.05 (d, J¼0.9 Hz, 1H), 7.56 (dd,
J¼8.6, 1.5 Hz, 1H), 7.45 (d, J¼8.6 Hz, 1H), 7.40 (d, J¼8.1 Hz, 1H), 7.31
(d, J¼8.1 Hz,1H), 7.25 (d, J¼2.5 Hz,1H), 7.11e7.05 (m, 2H), 6.90e6.86
(m, 1H), 3.87 (s, 3H), 3.57 (br s, 4H), 2.64e2.51 (m, 4H), 1.48 (s, 9H).
13C NMR {1H} (100 MHz, CDCl3)
d
¼155.3, 137.2, 136.5, 129.7, 125.9,
4.4.3. 12-Point doseeresponse curve of compounds 2c, 2j, and 3a. In
a 96-well flat bottom plate, MCF-7 cells were seeded at 1500 cells/
well and MCF-10A cells were seeded at 9000 cells/well using the
10% FBS medium described in the general culture procedure. The
cells were then incubated in a humidified incubator at 37 ꢀC and 5%
CO2 for 18 h. From a 100 mM stock of each compound in molecular
125.2, 123.4, 122.7, 122.0, 121.9, 121.4, 121.0, 120.6, 119.9, 119.0, 113.7,
111.4, 79.6, 52.0, 37.9, 35.8, 28.6. IR 3303, 1667, 1509, 734 cmꢁ1
.
HRMS C28H32N3O4 (MþH)þ calcd 474.2401, obsd 474.2401.
4.3.4. Characterization data for tert-butyl-4-(1H-indol-3-yl)-4-(1H-
pyrrol-2-yl)piperidine-1-carboxylate (entry 3d). Followed same
procedure as the general procedure. Yield¼85% (average of two
run), Rf¼0.32 w/66% EtOAC/Hex, colorless thick liquid, 1H NMR
biology grade DMSO (Sigma) was made a 100
of each compound in DME/F-12 supplemented with 2% (v/v) FBS,1%
(v/v) P/S, 1% (v/v) ITS, and 2.5 nM EFG. From this 100 M standard
mM standard solution
m

5208
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m
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Acknowledgements
This work was supported by the National Institutes of Health
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Supplementary data
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