Synthesis of C,N′-linked bis-heterocycles using a deprotometalation-iodination-N-arylation sequence and evaluation of their antiproliferative activity in melanoma cells

Article abstract of DOI:10.1016/j.bmc.2014.04.028

Benzothiophene, benzofuran, benzothiazole and benzoxazole were deprotometalated using the lithium-zinc combination prepared from ZnCl ₂·TMEDA (TMEDA = N,N,N′,N′- tetramethylethylenediamine, 1 equiv) and lithium 2,2,6,6-tetramethylpiperidide (LiTMP, 3 equiv). Subsequent interception of the 2-metalated derivatives using iodine as electrophile led to the iodides in 81%, 82%, 67% and 42% yields, respectively. These yields are higher (10% more) than those obtained using ZnCl₂·TMEDA (0.5 equiv) and LiTMP (1.5 equiv), except in the case of benzoxazole (10% less). The crude iodides were involved in the N-arylation of pyrrole, indole, carbazole, pyrazole, indazole, imidazole and benzimidazole in the presence of Cu (0.2 equiv) and Cs₂CO₃ (2 equiv), and using acetonitrile as solvent (no other ligand) to provide after 24 h reflux the expected N-arylated azoles in yields ranging from 33% to 81%. Using benzotriazole also led to N-arylation products, but in lower 34%, 39%, 36% and 6% yields, respectively. A further study with this azole evidenced the impact of 2,2,6,6-tetramethylpiperidine on the N-arylation yields. Most of the C,N′-linked bis-heterocycles thus synthesized (in particular those containing benzimidazole) induced a high growth inhibition of A2058 melanoma cells after a 72 h treatment at 10^-5 M.

Full text of DOI:10.1016/j.bmc.2014.04.028

Accepted Manuscript
Synthesis of C,N’-linked bis-heterocycles using a deprotometalation-iodina-
tion-N-arylation sequence and evaluation of their antiproliferative activity in
melanoma cells
Madani Hedidi, Ghenia Bentabed-Ababsa, Aïcha Derdour, Thierry Roisnel,
Vincent Dorcet, Floris Chevallier, Laurent Picot, Valérie Thiéry, Florence
Mongin
PII:
S0968-0896(14)00282-X
http://dx.doi.org/10.1016/j.bmc.2014.04.028
BMC 11523
DOI:
Reference:
Bioorganic & Medicinal Chemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
7 February 2014
15 April 2014
15 April 2014
Please cite this article as: Hedidi, M., Bentabed-Ababsa, G., Derdour, A., Roisnel, T., Dorcet, V., Chevallier, F.,
Picot, L., Thiéry, V., Mongin, F., Synthesis of C,N’-linked bis-heterocycles using a deprotometalation-iodination-
N-arylation sequence and evaluation of their antiproliferative activity in melanoma cells, Bioorganic & Medicinal
Chemistry (2014), doi: http://dx.doi.org/10.1016/j.bmc.2014.04.028
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Graphical Abstract
1) base prepared from
ZnCl2·TMEDA (0.5 equiv)
and LiTMP (1.5 equiv)
THF, rt
N
O
N
O
N
H
N
2) I2
3) hydrolysis and work-up
4) imidazole, Cs2CO3
cat. Cu
66% yield
84% growth inhibition
after 72 h at 10-5 M in
A2058 melanoma cells
CH3CN, reflux
_____________________________________________
Synthesis of C,N’-linked bis-heterocycles using a
deprotometalation-iodination-N-arylation sequence
and evaluation of their antiproliferative activity in
melanoma cells
Madani Hedidia,b,c, Ghenia Bentabed-Ababsab,*, Aïcha Derdourb, Thierry Roisneld,
Vincent Dorcetd, Floris Chevalliera, Laurent Picote, Valérie Thiérye,*, Florence Mongina,*
a Chimie et Photonique Moléculaires, Institut des Sciences Chimiques de Rennes, UMR 6226,
CNRS-Université de Rennes 1, Bâtiment 10A, Case 1003, Campus de Beaulieu, 35042
Rennes, France
b Laboratoire de Synthèse Organique Appliquée, Faculté des Sciences, Université d’Oran,
BP 1524 El M'Naouer, 31000 Oran, Algeria
c Present address: Département de Chimie, Faculté des Sciences, Université Hassiba
Benbouali de Chlef, Hay Es-Salem, RN 19, 02000 Chlef, Algeria
d Centre de Diffractométrie X, Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS-
Université de Rennes 1, Bâtiment 10B, Campus de Beaulieu, 35042 Rennes Cedex, France
e Laboratoire Littoral Environnement et Sociétés, UMRi CNRS 7266, Université de La
Rochelle, 17042 La Rochelle, France
* Corresponding authors. Fax: +33 2 2323 6955;
e-mail addresses: badri_sofi@yahoo.fr (G. Bentabed-Ababsa),
valerie.thiery@univ-lr.fr (V. Thiéry), florence.mongin@univ-rennes1.fr (F. Mongin).
1

Abstract:
Benzothiophene, benzofuran, benzothiazole and benzoxazole were deprotometalated using the
lithium-zinc combination prepared from ZnCl2·TMEDA (TMEDA
=
N,N,N',N'-
tetramethylethylenediamine, 1 equiv) and lithium 2,2,6,6-tetramethylpiperidide (LiTMP, 3
equiv). Subsequent interception of the 2-metalated derivatives using iodine as electrophile led
to the iodides in 81, 82, 67 and 42% yields, respectively. These yields are higher (10% more)
than those obtained using ZnCl2·TMEDA (0.5 equiv) and LiTMP (1.5 equiv), except in the
case of benzoxazole (10% less). The crude iodides were involved in the N-arylation of
pyrrole, indole, carbazole, pyrazole, indazole, imidazole and benzimidazole in the presence of
Cu (0.2 equiv) and Cs2CO3 (2 equiv), and using acetonitrile as solvent (no other ligand) to
provide after 24 h reflux the expected N-arylated azoles in yields ranging from 33 to 81%.
Using benzotriazole also led to N-arylation products, but in lower 34, 39, 36 and 6% yields,
respectively. A further study with this azole evidenced the impact of 2,2,6,6-
tetramethylpiperidine on the N-arylation yields. Most of the C,N’-linked bis-heterocycles thus
synthesized (in particular those containing benzimidazole) induced a high growth inhibition
of A2058 melanoma cells after a 72 h treatment at 10-5 M.
Keywords: five-membered aromatic heterocycles, deprotonative metalation, N-arylation,
antiproliferative activity, melanoma
2

1. Introduction
The development of methods for the functionalization of aromatic heterocycles is of
interest due to their presence in numerous molecules of chemical or biological importance, as
well as in organic materials for different applications.
Deprotometalation is among the first approaches studied, notably owing to its high
regioselectivity.1 Recently, TMP-based lithium-metal combinations (TMP = 2,2,6,6-
tetramethylpiperidido), with a metal softer than an alkali metal, appeared as powerful tools for
performing both efficient and chemoselective reactions.2 In this context, our group showed
that the bimetal combination prepared from ZnCl2·TMEDA (TMEDA = N,N,N',N'-
tetramethylethylenediamine) and LiTMP (3 equiv), and which proved to be 1:1 Zn(TMP)2-
LiTMP·2LiCl(±TMEDA),3 is a powerful alternative to monometal lithium bases.1a,4
Copper-catalyzed N-arylation of azoles has recently benefited from the development of
catalyst-base systems.5 We here report our attempts to associate deprotometalation-iodination
of aromatic heterocycles with N-arylation of azoles for the synthesis of C,N’-linked bis-
heterocycles, as well as the evaluation of the latter for their antiproliferative activity in
melanoma cells.
2. Results and Discussion
2.1. Synthesis
To access bis-heterocycles, benzothiophene (1a), benzofuran (2a), benzothiazole (3a) and
benzoxazole (4a) were chosen as substrates. As previously described,3c deprotometalation
using the bimetal combination prepared from ZnCl2·TMEDA (0.5 equiv) and LiTMP (1.5
equiv) followed by interception with iodine respectively afforded the derivatives 1b, 2b, 3b
and 4b in 73, 69, 57 and 52% yields (Table 1, entries 1, 3, 5 and 7). Upon treatment with
ZnCl2·TMEDA (1 equiv) and LiTMP (3 equiv), which corresponds to doubling the amount of
3

base, it proved possible to increase the yields of the iodides 1b-3b to respectively reach 81, 82
and 67% (entries 2, 4 and 6), but not that of 4b which dropped to 42% (entry 8). For the latter,
such a result could be in relation with the formation of an arylmetal species more prone to
ring opening under these conditions.3c
Table 1. Deprotometalation-iodination of the heterocycles 1a-4a as a function of the
amount of base.
1) base prepared from
ZnCl2·TMEDA (x equiv)
and LiTMP (3x equiv)
THF, rt, 2 h
Ar
H
Ar
I
2) I2
a
b
Entry Ar-H
x
Ar-I
Product, Yield (%)a
1
0.5
1b, 733c
1b, 81
2b, 693c
2b, 82
3b, 573c
3b, 67
4b, 523c
4b, 42
1a
H
H
H
H
I
I
I
I
2
1
S
S
3
0.5
1
2a
4
O
N
O
N
5
0.5
1
3a
6
S
N
S
N
7
0.5
1
4a
8
O
O
a After purification by column chromatography.
We next turned to the N-arylation of azoles, first using the crude iodides 1b-4b generated
by using ZnCl2·TMEDA (0.5 equiv) and LiTMP (1.5 equiv). After hydrolysis and work-up,
we involved them in the reaction with 1.5 equiv of azole using metal copper (0.2 equiv) as
transition metal, cesium carbonate (2 equiv) as base, and acetonitrile as solvent at its reflux
temperature for 24 hours.6 Employing pyrrole, indole and carbazole as azole, the expected N-
arylated azoles 1c-4c (Table 2, entries 1-4), 1d-4d (Table 2, entries 5-8) and 1e-4e (Table 2,
entries 9-12) were respectively obtained in overall yields ranging from 31 to 53%. No
significant difference was noted using these three different azoles whereas benzothiazole (3a)
and, to a lesser extent, benzofuran (2a) led to slightly higher yields. The compounds 3c and 1e
were identified unambiguously by X-ray diffraction (Figure 1).
4

Table 2. Deprotometalation-iodination of the heterocycles 1a-4a followed by N-arylation
of pyrrole, indole and carbazole with the crude iodides 1b-4b.
1) base prepared from
ZnCl2·TMEDA (0.5 equiv)
and LiTMP (1.5 equiv)
THF, rt, 2 h
Ar
H
Ar
N
2) I2
a
3) hydrolysis and work-up
4) azole (1.5 equiv)
Cs2CO3 (2 equiv)
Cu (0.2 equiv)
c-e
CH3CN, reflux, 24 h
Entry Ar-H X, Y
Product, Yield (%)a
Y
N
X
1c, 43
2c, 48
3c, 48
4c, 40
1d, 33
2d, 31
3d, 53
4d, 45
1a
2a
3a
4a
1a
2a
3a
4a
1
2
3
4
5
6
7
8
S, CH
O, CH
S, N
O, N
S, CH
O, CH
S, N
Y
N
X
O, N
1e, 32
2e, 45
3e, 50
4e, 42
1a
2a
3a
4a
9
S, CH
O, CH
S, N
10
11
12
Y
N
X
O, N
a After purification by column chromatography.
Figure 1. ORTEP diagrams (30% probability) of the compounds 3c and 1e.
The same conclusions could be drawn using pyrazole and indazole as azole, with overall
yields between 40 and 54% for the compounds 1f-4f (Table 3, entries 1-4) and 1g-4g (Table
3, entries 5-8), respectively, as well as imidazole and benzimidazole, with 36-81% yields for
the compounds 1h-4h (Table 4, entries 1-4) and 1i-4i (Table 4, entries 5-8), respectively. The
structures of 1f, 1g, 2g and 4g (Figure 2), as well as those of 1h, 2h and 2i (Figure 3) were
confirmed by X-ray diffraction.
5

Table 3. Deprotometalation-iodination of the heterocycles 1a-4a followed by N-arylation
of pyrazole and indazole with the crude iodides 1b-4b.
1) base prepared from
ZnCl2·TMEDA (0.5 equiv)
and LiTMP (1.5 equiv)
N
THF, rt, 2 h
Ar
H
Ar
N
2) I2
a
3) hydrolysis and work-up
4) azole (1.5 equiv)
Cs2CO3 (2 equiv)
Cu (0.2 equiv)
f,g
CH3CN, reflux, 24 h
Entry Ar-H X, Y
Product, Yield (%)a
Y
1f, 47
2f, 54
3f, 48
4f, 41
1g, 46
2g, 40
3g, 53
4g, 44
1a
2a
3a
4a
1a
2a
3a
4a
1
2
3
4
5
6
7
8
S, CH
O, CH
S, N
N
X
N
O, N
S, CH
O, CH
S, N
Y
X
N
O, N
N
a After purification by column chromatography.
Figure 2. ORTEP diagrams (30% probability) of the compounds 1f, 1g, 2g and 4g.
Figure 3. ORTEP diagrams (30% probability) of the compounds 1h, 2h and 2i.
6

Table 4. Deprotometalation-iodination of the heterocycles 1a-4a followed by N-arylation
of imidazole and benzimidazole with the crude iodides 1b-4b.
1) base prepared from
ZnCl2·TMEDA (0.5 equiv)
and LiTMP (1.5 equiv)
THF, rt, 2 h
N
Ar
H
Ar
N
2) I2
a
3) hydrolysis and work-up
4) azole (1.5 equiv)
Cs2CO3 (2 equiv)
Cu (0.2 equiv)
h,i
CH3CN, reflux, 24 h
Entry Ar-H X, Y
Product, Overall yield (%)a
Y
1h, 36
2h, 81
3h, 69
4h, 66b
1i, 37
1a
2a
3a
4a
1a
2a
3a
4a
1
2
3
4
5
6
7
8
S, CH
O, CH
S, N
N
N
X
O, N
S, CH
O, CH
S, N
2i, 50
3i, 56
Y
N
N
4i, 39
X
O, N
a After purification by column chromatography. b Using 0.5 equiv of azole.
When benzotriazole was employed as azole, yields for the compounds 1j, 2j, 3j and 4j
dropped to 34, 39, 36 and 6%, respectively (Table 5, entries 1, 2, 4 and 6, Figure 4), a result
that could be in relation with a lower reactivity of triazoles when compared with azoles and
diazoles.7 We thus decided to attempt the overall process from 2a and 3a by using
ZnCl2·TMEDA (1 equiv) and LiTMP (3 equiv) for the deprotometalation step. Under these
conditions, bad results were obtained; indeed, 13 and 18% yields were respectively recorded
(entries 3 and 5) against 39 and 36% before. These results show that the N-arylation
efficiency is affected by compounds present in the crude iodide.
7

Table 5. Deprotometalation-iodination of the heterocycles 1a-4a followed by N-arylation
of benzotriazole with the crude iodides 1b-4b.
1) base prepared from
ZnCl2·TMEDA (x equiv)
and LiTMP (3x equiv)
N
THF, rt, 2 h
N
Ar
H
Ar
N
2) I2
a
3) hydrolysis and work-up
4) benzotriazole (1.5 equiv)
Cs2CO3 (2 equiv)
j
Cu (0.2 equiv)
CH3CN, reflux, 24 h
Entry Ar-H X, Y
x
Product, Overall yield (%)a Estimated N-arylation yield (%)b
1j, 34
2j, 39
2j, 13
3j, 36
3j, 18
4j, 6c
47
57
16
63
27
12
1a
2a
1
2
3
S, CH 0.5
O, CH
0.5
Y
X
1
N
N
N
3a
4a
4
5
6
S, N
O, N
0.5
1
0.5
a After purification by column chromatography. b Calculated from Table 1. c Using 0.5
equiv of azole.
Figure 4. ORTEP diagrams (30% probability) of the compounds 1j and 2j.
In order to attempt a rationalization of these results, we performed the N-arylation step of
benzotriazole using the purified iodides 1b-4b (Table 6). Surprisingly, these reactions
furnished the N-aryl benzotriazoles in yields in general lower than those observed using the
process without purification (Table 5). From 2-iodobenzothiazole (3a), the best N-arylation
yield was observed by carrying out the reaction in the presence of 1.5 equiv of 2,2,6,6-
tetramethylpiperidine (Table 6, entry 3), an amount equivalent to that present after the
deprotometalation-iodination sequence using ZnCl2·TMEDA (0.5 equiv) and LiTMP (1.5
equiv). NMR spectra showing the presence of 2,2,6,6-tetramethylpiperidine in the crude
iodides, it was suspected as having an effect on the course of the N-arylation.
8

Table 6. N-arylation of benzotriazole with the purified iodides 1b-4b.
Benzotriazole (1.5 equiv)
N
Cs2CO3 (2 equiv)
N
Ar
I
Ar
N
Cu (0.2 equiv)
CH3CN, reflux, 24 h
b
j
Entry Ar-I X, Y
Product, Yield (%)a
1j, 10
O, CH 2j, 28
1b
2b
3b
4b
1
2
3
S, CH
3j, 38 (47)b (35)c
4j, 3
S, N
O, N
4
a After purification by column chromatography. b In the presence of TMPH (1.5 equiv). c
In the presence of TMPH (3 equiv).
2.2. Antiproliferative activity of the bis-heterocycles in A2058 melanoma cells
Most of the C,N’-linked bis-heterocycles induced a high growth inhibition of A2058
melanoma cells after a 72 h treatment at 10-5 M (Figure 5). Compound 4h proved to be the
most cytotoxic molecule, inducing a 84.3 ± 2.7% growth inhibition. By recording growth
inhibition at different concentrations, an IC50 value of 7.1 µM was obtained for 4h. In
addition, the four bis-heterocycles containing benzimidazole (1i, 2i, 3i and 4i) were among
the seven most antiproliferative molecules, suggesting that this pharmacophore is involved in
the inhibition of specific pharmacological targets in melanoma cells. Particularly,
topoisomerase II was previously reported as a target of benzimidazoles derivatives,8 and
further studies should be considered to validate the activity of our derivatives on isolated
topoisomerase II.
3. Conclusion
Thus, a large range of C,N’-linked bis-heterocycles have been synthesized from
benzothiophene, benzofuran, benzothiazole or benzoxazole, on the one hand, and azoles or
polyazoles, on the other hand, by using a deprotometalation-iodination-N-arylation sequence.
9

Most molecules show promising activity as antiproliferative drugs in human invasive
melanoma cells, and should be further studied as potential Topoisomerase II inhibitors.
Figure 5. Growth inhibition of CRL 11147 human melanoma cells after 72 h in the
presence of 10-5 M bis-heterocycle.
4. Experimental
4.1. General
All the reactions were performed under an argon atmosphere. THF was distilled over
sodium/benzophenone. Column chromatography separations were achieved on silica gel (40-
63 μm). Melting points were measured on a Kofler apparatus. IR spectra were taken on a
1
13
Perkin-Elmer Spectrum 100 spectrometer. H and C Nuclear Magnetic Resonance (NMR)
spectra were recorded on a Bruker Avance III spectrometer at 300 MHz and 75 MHz,
respectively. 1H chemical shifts (δ) are given in ppm relative to the solvent residual peak and
10

13C chemical shifts are relative to the central peak of the solvent signal.9 The iodides 1b, 2b,
3b and 4b were previously described.3c
Crystallography. The samples were studied with graphite monochromatized Mo-K
radiation ( = 0.71073 Å). X-ray diffraction data were collected at T = 150(2) K using
APEXII Bruker-AXS diffractometer. The structure was solved by direct methods using the
SIR97 program,10 and then refined with full-matrix least-square methods based on F2
(SHELX-97)11 with the aid of the WINGX program.12 All non-hydrogen atoms were refined
with anisotropic atomic displacement parameters. H atoms were finally included in their
calculated positions. Molecular diagrams were generated by ORTEP-3 (version 2.02).13
4.2. General procedure: To a stirred, cooled (0 °C) solution of 2,2,6,6-
tetramethylpiperidine (0.25 mL, 1.5 mmol) in THF (2-3 mL) were successively added BuLi
(about 1.6 M hexanes solution, 1.5 mmol) and, 5 min later, ZnCl2·TMEDA14 (0.13 g, 0.50
mmol). The mixture was stirred for 15 min at 0 °C before introduction of the substrate (1.0
mmol) at 0-10 °C. After 2 h at room temperature, a solution of I2 (0.38 g, 1.5 mmol) in THF
(4 mL) was added. The mixture was stirred overnight before addition of an aqueous saturated
solution of Na2S2O3 (4 mL) and extraction with AcOEt (3 x 20 mL). The combined organic
layers were dried over MgSO4, filtered and concentrated under reduced pressure. To the crude
iodide were added Cs2CO3 (0.65 g, 2.0 mmol), Cu powder (13 mg, 0.20 mmol), the azole (1.5
mmol) and MeCN (5 mL) and the resulting mixture was heated under reflux for 24 h.
Filtration over celite®, washing with AcOEt, removal of the solvent and purification by
chromatography on silica gel (the eluent is given in the product description) led to the
compound described below. The structure of the new compounds was confirmed either by X-
ray diffraction (see data below) or through microanalysis.
4.2.1. 2-(1-Pyrryl)benzothiophene (1c). The general procedure using benzothiophene (1a,
0.12 mL, 1.0 mmol) and pyrrole (0.10 mL, 1.5 mmol, 1.5 equiv) gave 1c (eluent: heptane) in
11

43% yield as a beige powder: mp 168 °C; IR (ATR): 720, 773, 880, 956, 1024, 1065, 1207,
1254, 1354, 1371, 1454, 1470, 1481, 1574, 1620, 3123 cm-1; 1H NMR (CDCl3)  6.38 (t, 2H,
J = 2.2 Hz), 7.09 (d, 1H, J = 0.6 Hz), 7.13 (t, 2H, J = 2.1 Hz), 7.32 (td, 1H, J = 7.8 and 1.5
Hz), 7.39 (td, 1H, J = 7.5 and 1.2 Hz), 7.71 (dm, 1H, J = 7.5 Hz), 7.76 (dm, 1H, J = 7.8 Hz);
13C NMR (CDCl3)  119.8 (CH), 111.3 (2CH), 120.9 (2CH), 122.2 (CH), 123.2 (CH), 124.2
(CH), 125.1 (CH), 135.0 (C), 138.9 (C), 143.5 (C).
4.2.2. 2-(1-Pyrryl)benzofuran (2c). The general procedure using benzofuran (2a, 0.11 mL,
1.0 mmol) and pyrrole (0.10 mL, 1.5 mmol, 1.5 equiv) gave 2c (eluent: heptane) in 48% yield
as a whitish powder: mp 112 °C; IR (ATR): 721, 773, 880, 956, 1024, 1065, 1169, 1207,
1254, 1354, 1371, 1454, 1470, 1481, 1620, 3050, 3134 cm-1; 1H NMR (CDCl3)  6.32 (d, 1H,
J = 0.9 Hz), 6.38 (t, 2H, J = 2.2 Hz), 7.09-7.16 (m, 4H), 7.31-7.41 (m, 2H); 13C NMR
(CDCl3)  87.6 (CH), 110.9 (CH), 111.3 (2CH), 118.9 (2CH), 120.4 (CH), 123.3 (CH), 123.6
(CH), 129.0 (C), 150.3 (C), 151.4 (C).
4.2.3. 2-(1-Pyrryl)benzothiazole (3c). The general procedure using benzothiazole (3a, 0.11
mL, 1.0 mmol) and pyrrole (0.10 mL, 1.5 mmol, 1.5 equiv) gave 3c (eluent: heptane-AcOEt
90:10) in 48% yield as a white powder: mp 146 °C; IR (ATR): 695, 722, 749, 911, 996, 1051,
1
1070, 1278, 1336, 1441, 1456, 1473, 1525, 1541, 1595, 2867, 2930, 3059, 3128 cm-1; H
NMR (CDCl3)  6.39 (t, 2H, J = 2.2 Hz), 7.33 (ddd, 1H, J = 8.7, 7.5 and 1.2 Hz), 7.43-7.49
(m, 3H), 7.78 (ddd, 1H, J = 8.1, 1.2 and 0.6 Hz), 7.88 (ddd, 1H, J = 8.1, 1.2 and 0.6 Hz); 13C
NMR (CDCl3)  112.7 (2CH), 120.1 (2CH), 121.4 (CH), 122.1 (CH), 124.6 (CH), 126.7
(CH), 132.0 (C), 151.2 (C), 159.5 (C). The NMR data are analogous to those previously
described.15 Crystal data for 3c. C11H8N2S, M = 200.25, monoclinic, P21/a, a = 11.3079(9),
b = 6.4758(5), c = 12.6883(10) Å, β = 90.263(3) °, V = 929.13(13) Å3, Z = 4, d = 1.432 g cm-
3, μ = 0.303 mm-1. A final refinement on F2 with 2122 unique intensities and 128 parameters
12

converged at ωR(F2) = 0.1279 (R(F) = 0.0528) for 1924 observed reflections with I > 2σ(I).
CCDC 985374.
4.2.4. 2-(1-Pyrryl)benzoxazole (4c). The general procedure using benzoxazole (4a, 0.12 g,
1.0 mmol) and pyrrole (0.10 mL, 1.5 mmol, 1.5 equiv) gave 4c (eluent: heptane-AcOEt
90:10) in 40% yield as a whitish powder: mp 136 °C; IR (ATR): 727, 748, 761, 949, 973,
1000, 1056, 1077, 1315, 1399, 1438, 1446, 1491, 1538, 1597, 3059 cm-1; 1H NMR (CDCl3) 
6.41 (t, 2H, J = 2.2 Hz), 7.28 (td, 1H, J = 7.5 and 1.5 Hz), 7.33 (td, 1H, J = 7.5 and 1.5 Hz),
7.50 (dd, 1H, J = 7.8 and 1.5 Hz), 7.54 (t, 2H, J = 2.4 Hz), 7.63 (dd, 1H, J = 7.5 and 1.5 Hz);
13C NMR (CDCl3)  110.1 (CH), 113.1 (2CH), 119.1 (CH), 119.6 (2CH), 124.1 (CH), 125.1
(CH), 141.4 (C), 149.1 (C), 154.8 (C).
4.2.5. 2-(1-Indolyl)benzothiophene (1d). The general procedure using benzothiophene (1a,
0.12 mL, 1.0 mmol) and indole (0.12 g, 1.5 mmol, 1.5 equiv) gave 1d (eluent: heptane) in
33% yield as a green powder: mp 56-58 °C; IR (ATR): 744, 782, 798, 876, 909, 1008, 1045,
1
1145, 1158, 1246, 1301, 1438, 1471, 1523, 1738, 3064, 3131 cm-1; H NMR (CDCl3)  6.79
(dd, 1H, J = 3.3 and 0.8 Hz), 7.28-7.51 (m, 4H), 7.34 (d, 1H, J = 0.6 Hz), 7.45 (d, 1H, J = 3.3
13
Hz), 7.75-7.89 (m, 4H); C NMR (CDCl3)  105.2 (CH), 111.1 (CH), 115.1 (CH), 121.4
(CH), 121.4 (CH), 122.3 (CH), 123.3 (CH), 123.6 (CH), 124.5 (CH), 125.1 (CH), 128.9 (CH),
129.5 (C), 136.3 (C), 136.6 (C), 138.5 (C), 141.6 (C).
4.2.6. 2-(1-Indolyl)benzofuran (2d). The general procedure using benzofuran (2a, 0.11
mL, 1.0 mmol) and indole (0.12 g, 1.5 mmol, 1.5 equiv) gave 2d (eluent: heptane) in 31%
yield as a white powder: mp 64 °C; IR (ATR): 697, 723, 748, 912, 1071, 1208, 1337, 1443,
1456, 1475, 1524, 1542, 1596, 3059, 3128 cm-1; 1H NMR (CDCl3)  6.58 (d, 1H, J = 0.9 Hz),
6.75 (dd, 1H, J = 3.3 and 0.6 Hz), 7.23-7.33 (m, 3H), 7.36 (td, 1H, J = 7.6 and 1.2 Hz), 7.51-
7.55 (m, 1H), 7.57-7.61 (m, 2H), 7.70 (d, 1H, J = 7.8 Hz), 7.87 (dd, 1H, J = 8.1 and 0.9 Hz) ;
13C NMR (CDCl3)  90.8 (CH), 106.0 (CH), 111.0 (CH), 111.9 (CH), 120.5 (CH), 121.5
13

(CH), 121.8 (CH), 123.6 (CH), 123.6 (CH), 123.7 (CH), 126.0 (CH), 129.0 (C), 129.7 (C),
135.2 (C), 149.4 (C), 151.4 (C).
4.2.7. 2-(1-Indolyl)benzothiazole (3d). The general procedure using benzothiazole (3a,
0.11 mL, 1.0 mmol) and indole (0.12 g, 1.5 mmol, 1.5 equiv) gave 3d (eluent: heptane-AcOEt
90:10) in 53% yield as a pale pink powder: mp 110 °C (lit.16 107-108 °C); IR (ATR): 699,
726, 746, 907, 974, 1001, 1056, 1078, 1290, 1315, 1398, 1446, 1539, 1577, 1596, 3058 cm-1;
1H NMR (CDCl3)  6.77 (dd, 1H, J = 3.6 and 0.8 Hz), 7.30-7.37 (m, 2H), 7.43-7.53 (m, 2H),
7.66-7.70 (m, 2H), 7.80 (ddd, 1H, J = 8.0, 1.2 and 0.6 Hz), 7.98 (ddd, 1H, J = 8.1, 1.1 and 0.6
13
Hz), 8.65 (ddd, 1H, J = 8.3, 1.6 and 0.7 Hz); C NMR (CDCl3)  108.2 (CH), 114.4 (CH),
121.2 (CH), 121.4 (CH), 122.1 (CH), 122.9 (CH), 124.3 (CH), 124.5 (CH), 126.5 (CH), 126.7
(CH), 130.5 (C), 131.6 (C), 135.5 (C), 151.3 (C), 158.9 (C).
4.2.8. 2-(1-Indolyl)benzoxazole (4d). The general procedure using benzoxazole (4a, 0.12
g, 1.0 mmol) and indole (0.12 g, 1.5 mmol, 1.5 equiv) gave 4d (eluent: heptane-AcOEt 90:10)
in 45% yield as a pale pink powder: mp 134 °C; IR (ATR): 695, 723, 778, 956, 1066, 1207,
1254, 1372, 1454, 1481, 1616, 1948, 3121 cm-1; 1H NMR (CDCl3)  6.78 (dd, 1H, J = 3.6 and
0.8 Hz), 7.25-7.39 (m, 3H), 7.47 (ddd, 1H, J = 8.3, 7.3 and 1.1 Hz), 7.53 (ddd, 1H, J = 7.8,
1.3 and 0.6 Hz), 7.65-7.68 (m, 1H), 7.71 (ddd, 1H, J = 7.8, 1.4 and 0.6 Hz), 7.86 (d, 1H, J =
13
3.6 Hz), 8.58 (ddd, 1H, J = 8.3, 1.6 and 0.7 Hz); C NMR (CDCl3)  108.6 (CH), 110.0
(CH), 114.7 (CH), 118.9 (CH), 121.3 (CH), 123.1 (CH), 123.6 (CH), 124.7 (CH), 128.4 (CH),
124.9 (CH), 130.2 (C), 134.8 (C), 141.6 (C), 148.5 (C), 154.8 (C).
4.2.9. 2-(9-Carbazolyl)benzothiophene (1e). The general procedure using benzothiophene
(1a, 0.12 mL, 1.0 mmol) and carbazole (0.17 g, 1.5 mmol, 1.5 equiv) gave 1e (eluent:
heptane-AcOEt 70:30) in 32% yield as a pale yellow powder: mp 96 °C; IR (ATR): 717, 738,
790, 981, 1174, 1219, 1228, 1297, 1319, 1333, 1365, 1451, 1479, 1580, 1594, 1609, 3026 cm-
1
1; H NMR (CDCl3)  7.37 (ddd, 2H, J = 7.7, 7.2 and 1.0 Hz), 7.45-7.53 (m, 5H), 7.66 (td,
14

2H, J = 8.2 and 0.8 Hz), 7.87-7.92 (m, 2H), 8.17 (ddd, 2H, J = 7.7, 1.2 and 0.7 Hz); 13C NMR
(CDCl3)  110.5 (2CH), 120.4 (2CH), 121.0 (CH), 121.0 (2CH), 122.7 (CH), 123.9 (2C),
124.0 (CH), 124.9 (CH), 125.1 (CH), 126.5 (2CH), 138.1 (C), 138.2 (C), 139.1 (C), 141.6
(2C). Crystal data for 1e. 2(C20H13NS), M = 598.75, monoclinic, P21/c, a = 22.0832(5), b =
6.1505(2), c = 23.8915(6) Å, β = 117.3650(10) °, V = 2881.88(14) Å3, Z = 4, d = 1.38 g cm-3,
μ = 0.219 mm-1. A final refinement on F2 with 6561 unique intensities and 397 parameters
converged at ωR(F2) = 0.121 (R(F) = 0.0445) for 5254 observed reflections with I > 2σ(I).
CCDC 985365.
4.2.10. 2-(9-Carbazolyl)benzofuran (2e). The general procedure using benzofuran (2a,
0.11 mL, 1.0 mmol) and carbazole (0.17 g, 1.5 mmol, 1.5 equiv) gave 2e (eluent: heptane-
AcOEt 70:30) in 45% yield as a white powder: mp 152 °C; IR (ATR): 726, 748, 974, 1000,
1
1056, 1078, 1290, 1315, 1398, 1438, 1446, 1539, 1596, 3060 cm-1; H NMR (CDCl3)  6.84
(d, 1H, J = 0.9 Hz), 7.36-7.46 (m, 4H), 7.54 (ddd, 2H, J = 8.3, 7.3 and 1.3 Hz), 7.62-7.66 (m,
1H), 7.70-7.74 (m, 1H), 7.79 (td, 2H, J = 8.2 and 0.7 Hz), 8.17 (ddd, 2H, J = 7.8, 1.1 and 0.7
13
Hz); C NMR (CDCl3)  97.0 (CH), 111.3 (CH), 111.4 (2CH), 120.4 (2CH), 120.9 (CH),
121.6 (2CH), 123.5 (CH), 124.3 (2C), 124.3 (CH), 126.7 (2CH), 128.5 (C), 139.9 (2C), 147.7
(C), 152.1 (C).
4.2.11. 2-(9-Carbazolyl)benzothiazole (3e). The general procedure using benzothiazole
(3a, 0.11 mL, 1.0 mmol) and carbazole (0.17 g, 1.5 mmol, 1.5 equiv) gave 3e (eluent:
heptane-AcOEt 70:30) in 50% yield as a yellow powder: mp 140 °C; IR (ATR): 694, 719,
801, 956, 1016, 1067, 1208, 1253, 1331, 1373, 1440, 1454, 1476, 1516, 1571, 1622, 3125 cm-
1
1; H NMR (CDCl3)  7.38-7.45 (m, 3H), 7.53-7.61 (m, 3H), 7.89 (dd, 1H, J = 7.9 and 0.6
13
Hz), 8.10 (d, 3H, J = 7.8 Hz), 8.52 (d, 2H, J = 8.4 Hz); C NMR (CDCl3)  113.4 (2CH),
120.2 (2CH), 121.2 (CH), 122.3 (CH), 122.8 (2CH), 124.6 (CH), 125.3 (2C), 126.7 (CH),
15

127.1 (2CH), 132.1 (C), 139.3 (2C), 150.3 (C), 157.8 (C). The NMR data are in accordance
with those previously reported.17
4.2.12. 2-(9-Carbazolyl)benzoxazole (4e). The general procedure using benzoxazole (4a,
0.12 g, 1.0 mmol) and carbazole (0.17 g, 1.5 mmol, 1.5 equiv) gave 4e (eluent: heptane-
AcOEt 70:30) in 42% yield as a pale yellow powder: mp 206 °C; IR (ATR): 726, 763, 881,
987, 1129, 1176, 1211, 1345, 1375, 1456, 1476, 1523, 1542, 1576, 1604, 3056, 3143 cm-1; 1H
NMR (CDCl3)  7.26-7.45 (m, 4H), 7.55-7.63 (m, 3H), 7.75 (ddd, 1H, J = 7.8, 1.3 and 0.6
13
Hz), 8.06 (ddd, 1H, J = 7.7, 1.1 and 0.6 Hz), 8.67 (d, 1H, J = 8.4 Hz); C NMR (CDCl3) 
110.0 (CH), 115.2 (2CH), 118.9 (CH), 120.1 (2CH), 123.3 (2CH), 123.6 (CH), 125.0 (CH),
125.7 (2C), 127.4 (2CH), 138.0 (2C), 141.3 (C), 148.3 (C), 155.6 (C).
4.2.13. 2-(1-Pyrazolyl)benzothiophene (1f). The general procedure using benzothiophene
(1a, 0.12 mL, 1.0 mmol) and pyrazole (0.10 mL, 1.5 mmol, 1.5 equiv) gave 1f (eluent:
heptane) in 47% yield as a whitish powder: mp 102 °C; IR (ATR): 727, 748, 761, 973, 1000,
1
1056, 1077, 1236, 1289, 1315, 1398, 1438, 1446, 1491, 1538, 1597, 3059 cm-1; H NMR
(CDCl3)  6.46 (dd, 1H, J = 2.4 and 2.0 Hz), 7.21 (s, 1H), 7.31 (td, 1H, J = 7.2 and 1.4 Hz),
7.36 (td, 1H, J = 7.5 and 1.3 Hz), 7.67-7.70 (m, 1H), 7.72 (d, 1H, J = 1.5 Hz), 7.75-7.78 (m,
13
1H), 7.90 (d, 1H, J = 2.7 Hz); C NMR (CDCl3)  108.4 (CH), 108.6 (CH), 122.2 (CH),
123.4 (CH), 124.3 (CH), 125.0 (CH), 127.9 (CH), 135.5 (C), 138.5 (C), 141.6 (CH), 143.0
(C). Crystal data for 1f. 3(C11H8N2S), M = 600.76, monoclinic, P c, a = 7.3675(4), b =
7.8206(4), c = 25.5774(13) Å, β = 93.082(3) °, V = 1471.59(13) Å3, Z = 2, d = 1.356 g cm-3, μ
= 0.287 mm-1. A final refinement on F2 with 6115 unique intensities and 338 parameters
converged at ωR(F2) = 0.1322 (R(F) = 0.0577) for 4010 observed reflections with I > 2σ(I).
CCDC 985366.
4.2.14. 2-(1-Pyrazolyl)benzofuran (2f). The general procedure using benzofuran (2a, 0.11
mL, 1.0 mmol) and pyrazole (0.10 mL, 1.5 mmol, 1.5 equiv) gave 2f (eluent: heptane) in 54%
16

yield as a beige powder: mp 74 °C; IR (ATR): 737, 763, 881, 1017, 1129, 1172, 1212, 1344,
1
1376, 1455, 1476, 1575, 1608, 1622, 1928, 3056, 3143 cm-1; H NMR (CDCl3)  6.48 (dd,
1H, J = 2.5 and 1.8 Hz), 6.74 (d, 1H, J = 0.8 Hz), 7.24-7.31 (m, 2H), 7.46-7.51 (m, 1H), 7.54-
13
7.59 (m, 1H), 7.79 (d, 1H, J = 1.4 Hz), 8.06 (d, 1H, J = 2.5 Hz); C NMR (CDCl3)  90.0
(CH), 107.8 (CH), 111.0 (CH), 121.0 (CH), 123.8 (CH), 124.0 (CH), 127.8 (CH), 128.6 (C),
142.6 (CH), 149.4 (C), 151.6 (C).
4.2.15. 2-(1-Pyrazolyl)benzothiazole (3f). The general procedure using benzothiazole (3a,
0.11 mL, 1.0 mmol) and pyrazole (0.10 mL, 1.5 mmol, 1.5 equiv) gave 3f (eluent: heptane-
AcOEt 90:10) in 48% yield as a white powder: mp 146 °C; IR (ATR): 727, 749, 762, 973,
1000, 1056, 1077, 1288, 1315, 1398, 1438, 1446, 1491, 1538, 1597, 1793, 1832, 1975, 3058
cm-1; 1H NMR (CDCl3)  6.52 (dd, 1H, J = 2.7 and 1.8 Hz), 7.35 (td, 1H, J = 7.6 and 1.2 Hz),
7.47 (td, 1H, J = 7.6 and 1.2 Hz), 7.78 (d, 1H, J = 1.2 Hz), 7.83 (dd, 1H, J = 7.8 and 1.2 Hz),
7.89 (dd, 1H, J = 8.1 and 1.2 Hz), 8.48 (d, 1H, J = 2.7 Hz); 13C NMR (CDCl3)  109.4 (CH),
121.7 (CH), 122.4 (CH), 125.0 (CH), 126.7 (CH), 128.0 (CH), 133.2 (C), 143.4 (CH), 151.0
(C), 160.5 (C). The NMR data are analogous to those previously described.18
4.2.16. 2-(1-Pyrazolyl)benzoxazole (4f). The general procedure using benzoxazole (4a,
0.12 g, 1.0 mmol) and pyrazole (0.10 mL, 1.5 mmol, 1.5 equiv) gave 4f (eluent: heptane-
AcOEt 90:10) in 41% yield as a pale orange powder: mp 146 °C; IR (ATR): 727, 749, 761,
973, 1000, 1056, 1077, 1117, 1288, 1315, 1398, 1438, 1446, 1491, 1538, 1597, 1793, 1832,
3059 cm-1; 1H NMR (CDCl3)  6.55 (dd, 1H, J = 2.7 and 1.5 Hz), 7.31 (td, 1H, J = 7.5 and 1.8
Hz), 7.35 (td, 1H, J = 7.5 and 1.8 Hz), 7.54-7.57 (m, 1H), 7.65-7.69 (m, 1H), 7.86 (d, 1H, J =
1.2 Hz), 8.37 (d, 1H, J = 2.7 Hz); 13C NMR (CDCl3)  109.8 (CH), 110.8 (CH), 119.7 (CH),
124.8 (CH), 125.3 (CH), 129.9 (CH), 140.8 (C), 144.6 (CH), 149.5 (C), 153.8 (C).
4.2.17. 2-(1-Indazolyl)benzothiophene (1g). The general procedure using benzothiophene
(1a, 0.12 mL, 1.0 mmol) and indazole (0.11 g, 1.5 mmol, 1.5 equiv) gave 1g (eluent: heptane)
17

in 46% yield as a beige powder: mp 94 °C; IR (ATR): 700, 724, 745, 770, 902, 937, 1003,
1110, 1184, 1350, 1385, 1426, 1443, 1539, 1597, 1612, 1744, 3050 cm-1; 1H NMR (CDCl3) 
7.26-7.41 (m, 3H), 7.43 (d, 1H, J = 0.5 Hz), 7.53 (ddd, 1H, J = 8.4, 7.0 and 1.1 Hz), 7.76-7.84
(m, 3H), 7.93 (ddd, 1H, J = 8.5, 1.6 and 0.7 Hz), 8.23 (d, 1H, J = 0.9 Hz); 13C NMR (CDCl3)
 110.0 (CH), 110.9 (CH), 121.6 (CH), 122.1 (CH), 122.4 (CH), 123.4 (CH), 124.2 (CH),
124.9 (CH), 125.7 (C), 128.1 (CH), 135.6 (C), 136.7 (CH), 138.8 (C), 138.9 (C), 142.8 (C).
Crystal data for 1g. C15H10N2S, M = 250.31, orthorhombic, P 21 21 21, a = 4.9340(2), b =
11.8093(4), c = 20.1488(6) Å, V = 1174.01(7) Å3, Z = 4, d = 1.416 g cm-3, μ = 0.256 mm-1. A
final refinement on F2 with 2694 unique intensities and 170 parameters converged at ωR(F2)
= 0.0748 (R(F) = 0.0323) for 2459 observed reflections with I > 2σ(I). CCDC 985367.
4.2.18. 2-(1-Indazolyl)benzofuran (2g). The general procedure using benzofuran (2a, 0.11
mL, 1.0 mmol) and indazole (0.11 g, 1.5 mmol, 1.5 equiv) gave 2g (eluent: heptane) in 40%
yield as a pale pink powder: mp 100 °C; IR (ATR): 700, 725, 746, 770, 902, 939, 1003, 1110,
1145, 1205, 1350, 1386, 1426, 1443, 1539, 1597, 1612, 1745, 3063 cm-1; 1H NMR (CDCl3) 
6.78 (d, 1H, J = 0.9 Hz), 7.27-7.34 (m, 3H), 7.52-7.63 (m, 3H), 7.81 (dt, 1H, J = 8.0 and 1.0
13
Hz), 8.08 (dq, 1H, J = 8.5 and 0.9 Hz), 8.27 (d, 1H, J = 0.9 Hz); C NMR (CDCl3)  91.4
(CH), 111.2 (CH), 111.9 (CH), 120.8 (CH), 121.4 (CH), 122.8 (CH), 123.8 (CH), 123.8 (CH),
125.1 (C), 128.4 (CH), 128.6 (C), 137.9 (CH), 138.9 (C), 150.0 (C), 151.8 (C). Crystal data
for 2g. C15H10N2O, M = 234.25, monoclinic, C 2/c, a = 24.6806(12), b = 6.7281(3), c =
14.0318(6) Å, β = 105.777(2) °, V = 2242.25(18) Å3, Z = 8, d = 1.388 g cm-3, μ = 0.089 mm-1.
A final refinement on F2 with 2543 unique intensities and 163 parameters converged at
ωR(F2) = 0.0929 (R(F) = 0.0379) for 2096 observed reflections with I > 2σ(I). CCDC 985370.
4.2.19. 2-(1-Indazolyl)benzothiazole (3g). The general procedure using benzothiazole (3a,
0.11 mL, 1.0 mmol) and indazole (0.11 g, 1.5 mmol, 1.5 equiv) gave 3g (eluent: heptane-
AcOEt 90:10) in 53% yield as a whitish powder: mp 146 °C; IR (ATR): 724, 752, 938, 1110,
18

1
1171, 1184, 1350, 1385, 1426, 1443, 1539, 1597, 1612, 1743, 2924, 3051 cm-1; H NMR
(CDCl3)  7.30-7.38 (m, 2H), 7.47 (ddd, 1H, J = 8.5, 7.3 and 1.3 Hz), 7.62 (ddd, 1H, J = 7.6
and 1.2 Hz), 7.77 (dt, 1H, J = 8.1 and 0.8 Hz), 7.83 (dd, 1H, J = 7.9 and 0.7 Hz), 7.96 (ddd,
1H, J = 8.1, 1.0 and 0.5 Hz), 8.21 (d, 1H, J = 0.7 Hz), 8.81 (dd, 1H, J = 8.5 and 0.8 Hz); 13C
NMR (CDCl3)  114.5 (CH), 121.2 (CH), 121.3 (CH), 122.2 (CH), 123.9 (CH), 124.3 (CH),
126.2 (C), 126.3 (CH), 129.2 (CH), 132.3 (C), 138.7 (C), 138.9 (CH), 151.8 (C), 161.1 (C).
4.2.20. 2-(1-Indazolyl)benzoxazole (4g). The general procedure using benzoxazole (4a,
0.12 g, 1.0 mmol) and indazole (0.11 g, 1.5 mmol, 1.5 equiv) gave 4g (eluent: heptane-AcOEt
90:10) in 44% yield as a whitish powder: mp 148 °C; IR (ATR): 700, 724, 746, 770, 937,
1
1003, 1110, 1184, 1350, 1385, 1426, 1443, 1539, 1597, 1612, 1743, 2924, 3051 cm-1; H
NMR (CDCl3)  7.32-7.44 (m, 3H), 7.62-7.70 (m, 2H), 7.78 (dm, 1H, J = 7.3 Hz), 7.83 (dt,
1H, J = 8.0 and 0.8 Hz), 8.34 (d, 1H, J = 0.9 Hz), 8.63 (dd, 1H, J = 8.5 and 0.8 Hz); 13C NMR
(CDCl3)  110.5 (CH), 113.9 (CH), 119.3 (CH), 121.3 (CH), 124.0 (CH), 124.2 (CH), 125.0
(CH), 125.7 (C), 129.3 (CH), 138.9 (C), 140.1 (CH), 141.3 (C), 148.8 (C), 154.4 (C). Crystal
data for 4g. C14H9N3O, M = 235.24, monoclinic, P21/a, a = 8.2690(15), b = 14.389(3), c =
9.7013(17) Å, β = 110.499(8) °, V = 1081.2(4) Å3, Z = 4, d = 1.445 g cm-3, μ = 0.095 mm-1. A
final refinement on F2 with 2428 unique intensities and 163 parameters converged at ωR(F2)
= 0.1239 (R(F) = 0.0596) for 1550 observed reflections with I > 2σ(I). CCDC 985375.
4.2.21. 2-(1-Imidazolyl)benzothiophene (1h). The general procedure using
benzothiophene (1a, 0.12 mL, 1.0 mmol) and imidazole (0.10 g, 1.5 mmol, 1.5 equiv) gave 1h
(eluent: heptane-AcOEt 20:80) in 36% yield as a whitish powder: mp 128 °C; IR (ATR): 723,
1
750, 809, 822, 1038, 1066, 1103, 1231, 1438, 1457, 1481, 1575, 1660, 3112 cm-1; H NMR
(CDCl3)  7.23 (br s, 2H), 7.32 (br s, 1H), 7.34-7.44 (m, 2H), 7.74-7.80 (m, 2H), 7.94 (br s,
13
1H); C NMR (CDCl3)  113.5 (CH), 119.5 (CH), 122.2 (CH), 123.7 (CH), 125.1 (CH),
125.3 (CH), 130.6 (CH), 135.7 (C), 136.6 (CH), 138.0 (C), 138.3 (C). Crystal data for 1h.
19

C11H8N2S, M = 200.25, orthorhombic, F d 2 d, a = 9.3280(7), b = 12.0169(10), c =
16.2272(11) Å, V = 1819.0(2) Å3, Z = 8, d = 1.462 g cm-3, μ = 0.309 mm-1. A final refinement
on F2 with 772 unique intensities and 71 parameters converged at ωR(F2) = 0.0751 (R(F) =
0.0279) for 752 observed reflections with I > 2σ(I). CCDC 985368.
4.2.22. 2-(1-Imidazolyl)benzofuran (2h). The general procedure using benzofuran (2a,
0.11 mL, 1.0 mmol) and imidazole (0.10 g, 1.5 mmol, 1.5 equiv) gave 2h (eluent: heptane-
AcOEt 20:80) in 81% yield as a whitish powder: mp 60 °C; IR (ATR): 749, 783, 813, 995,
1
1058, 1102, 1205, 1253, 1330, 1453, 1472, 1485, 1512, 1623, 1644, 3114 cm-1; H NMR
13
(CDCl3)  6.56 (s, 1H), 7.26-7.35 (m, 3H), 7.48-7.58 (m, 3H), 8.18 (br s, 1H); C NMR
(CDCl3)  91.0 (CH), 111.0 (CH), 120.8 (CH), 123.8 (CH), 124.4 (CH), 127.9 (C), 130.6
(CH), 146.5 (C), 151.6 (C), 2 CH not seen. Crystal data for 2h. 6(C11H8N2O), M = 1105.16,
monoclinic, P 21/n, a = 18.6374(10), b = 13.8711(6), c = 22.2273(11) Å, β = 113.7840(10) °,
V = 5258.2(4) Å3, Z = 4, d = 1.396 g cm-3, μ = 0.093 mm-1. A final refinement on F2 with
12028 unique intensities and 758 parameters converged at ωR(F2) = 0.153 (R(F) = 0.0653) for
5680 observed reflections with I > 2σ(I). CCDC 985371.
4.2.23. 2-(1-Imidazolyl)benzothiazole (3h). The general procedure using benzothiazole
(3a, 0.11 mL, 1.0 mmol) and imidazole (0.10 g, 1.5 mmol, 1.5 equiv) gave 3h (eluent:
heptane-AcOEt 20:80) in 69% yield as a beige powder: mp 138 °C; IR (ATR): 695, 722, 761,
844, 935, 1033, 1090, 1240, 1312, 1372, 1442, 1472, 1541, 1594, 1695, 3112 cm-1; 1H NMR
(CDCl3)  7.22 (br s, 1H), 7.39 (t, 1H, J = 7.6 Hz), 7.50 (t, 1H, J = 7.6 Hz), 7.62 (s, 1H), 7.81
13
(d, 1H, J = 7.8 Hz), 7.92 (d, 1H, J = 8.1 Hz); C NMR (CDCl3)  117.7 (CH), 121.4 (CH),
122.7 (CH), 125.4 (CH), 127.0 (CH), 131.1 (CH), 132.0 (C), 135.8 (CH), 150.3 (C), 155.7
(C). The NMR data are analogous to those previously described.15
4.2.24. 2-(1-Imidazolyl)benzoxazole (4h). The general procedure using benzoxazole (4a,
0.12 g, 1.0 mmol) but imidazole (33 mg, 0.5 mmol, 0.5 equiv) gave 4h (eluent: heptane-
20

AcOEt 90:10) in 66% yield as a yellow powder: mp 112 °C; IR (ATR): 709, 739, 755, 990,
1
1006, 1051, 1094, 1239, 1318, 1408, 1456, 1486, 1583, 1634, 2924, 2955, 3115 cm-1; H
NMR (CDCl3)  7.15 (s, 1H), 7.21-7.30 (m, 2H), 7.41-7.45 (m, 1H), 7.55-7.59 (m, 1H), 7.62
13
(br s, 1H), 8.29 (br s, 1H); C NMR (CDCl3)  110.5 (CH), 117.2 (CH), 119.6 (CH), 125.0
(CH), 125.4 (CH), 131.4 (CH), 140.4 (C), 148.9 (C), 152.0 (C), one CH not seen.
4.2.25. 2-(1-Benzimidazolyl)benzothiophene (1i). The general procedure using
benzothiophene (1a, 0.12 mL, 1.0 mmol) and benzimidazole (0.12 g, 1.5 mmol, 1.5 equiv)
gave 1i (eluent: heptane) in 37% yield as a beige powder: mp 122 °C; IR (ATR): 725, 764,
987, 1017, 1071, 1129, 1210, 1241, 1338, 1375, 1457, 1475, 1523, 1542, 1596, 1621, 3057,
3143 cm-1; 1H NMR (CDCl3)  7.39-7.50 (m, 5H), 7.73-7.76 (m, 1H), 7.83-7.93 (m, 3H), 8.25
13
(br s, 1H); C NMR (CDCl3)  110.9 (CH), 117.1 (CH), 120.8 (CH), 122.5 (CH), 123.5
(CH), 124.1 (CH), 124.4 (CH), 125.4 (CH), 125.4 (CH), 136.8 (C), 137.1 (C), 137.9 (C), 1
CH and 2C not seen.
4.2.26. 2-(1-Benzimidazolyl)benzofuran (2i). The general procedure using benzofuran
(2a, 0.11 mL, 1.0 mmol) and benzimidazole (0.12 g, 1.5 mmol, 1.5 equiv) gave 2i (eluent:
heptane) in 50% yield as a whitish powder: mp 118 °C; IR (ATR): 726, 763, 987, 1018, 1129,
1
1211, 1345, 1375, 1457, 1475, 1523, 1543, 1576, 1599, 1621, 1928, 3055, 3143 cm-1; H
NMR (CDCl3)  6.69 (d, 1H, J = 0.8 Hz), 7.28-7.45 (m, 4H), 7.52-7.56 (m, 1H), 7.60-7.63
(m, 1H), 7.77 (d, 1H, J = 7.2 Hz), 7.91 (d, 1H, J = 8.1 Hz), 8.39 (br s, 1H); 13C NMR (CDCl3)
 93.0 (CH), 111.2 (CH), 111.5 (CH), 120.9 (CH), 121.0 (CH), 123.8 (CH), 124.0 (CH),
124.6 (CH), 124.7 (CH), 128.1 (C), 132.5 (C), 140.9 (CH), 143.9 (C), 145.9 (C), 151.7 (C).
Crystal data for 2i. 2(C15H10N2O), M = 468.5, monoclinic, C 2/c, a = 24.8998(14), b =
10.4891(6), c = 19.2261(11) Å, β = 118.094(2) °, V = 4429.8(4) Å3, Z = 8, d = 1.405 g cm-3, μ
= 0.090 mm-1. A final refinement on F2 with 5074 unique intensities and 325 parameters
21

converged at ωR(F2) = 0.1043 (R(F) = 0.0479) for 3471 observed reflections with I > 2σ(I).
CCDC 985372.
4.2.27. 2-(1-Benzimidazolyl)benzothiazole (3i). The general procedure using
benzothiazole (3a, 0.11 mL, 1.0 mmol) and benzimidazole (0.12 g, 1.5 mmol, 1.5 equiv) gave
3i (eluent: heptane-AcOEt 90:10) in 56% yield as a beige powder: mp 120 °C; IR (ATR):
695, 724, 735, 765, 957, 1066, 1119, 1207, 1221, 1253, 1305, 1370, 1452, 1480, 1516, 1615,
3055, 3125 cm-1; 1H NMR (CDCl3)  7.35-7.54 (m, 4H), 7.82-7.89 (m, 2H), 7.98 (ddd, 1H, J
13
= 8.1, 1.1 and 0.6 Hz), 8.30 (ddd, 1H, J = 8.1, 1.3 and 0.8 Hz), 8.59 (s, 1H); C NMR
(CDCl3)  113.4 (CH), 121.0 (CH), 121.5 (CH), 122.8 (CH), 124.6 (CH), 125.4 (CH), 125.4
(CH), 127.1 (CH), 131.8 (C), 132.0 (C), 141.3 (CH), 144.3 (C), 150.5 (C), 155.6 (C).
4.2.28. 2-(1-Benzimidazolyl)benzoxazole (4i). The general procedure using benzoxazole
(4a, 0.12 g, 1.0 mmol) and benzimidazole (0.12 g, 1.5 mmol, 1.5 equiv) gave 4i (eluent:
heptane-AcOEt 90:10) in 39% yield as a white powder: mp 160 °C; IR (ATR): 695, 723, 749,
912, 996, 1051, 1070, 1110, 1240, 1278, 1336, 1394, 1442, 1456, 1474, 1525, 1541, 1595,
1
1907, 3059, 3127 cm-1; H NMR (CDCl3)  7.29-7.43 (m, 3H), 7.48 (td, 1H, J = 8.0 and 1.2
Hz), 7.52-7.56 (m, 1H), 7.68-7.72 (m, 1H), 7.86 (d, 1H, J = 7.6 Hz), 8.36 (d, 1H, J = 8.2 Hz),
13
8.67 (s, 1H); C NMR (CDCl3)  110.4 (CH), 114.0 (CH), 119.6 (CH), 120.9 (CH), 124.8
(CH), 124.8 (CH), 125.4 (CH), 125.7 (CH), 131.0 (C), 140.1 (C), 140.8 (CH), 143.8 (C),
148.6 (C), 152.3 (C).
4.2.29. 2-(1-Benzotriazolyl)benzothiophene (1j). The general procedure using
benzothiophene (1a, 0.12 mL, 1.0 mmol) and benzotriazole (0.12 g, 1.5 mmol, 1.5 equiv)
gave 1j (eluent: heptane-AcOEt 20:80) in 34% yield as a beige powder: mp 136 °C; IR
(ATR): 699, 727, 749, 762, 948, 973, 1000, 1056, 1077, 1117, 1236, 1275, 1289, 1300, 1315,
1398, 1438, 1446, 1491, 1538, 1597, 3058 cm-1; 1H NMR (CDCl3)  7.40-7.51 (m, 3H), 7.63
(d, 1H, J = 0.3 Hz), 7.64 (ddd, 1H, J = 8.1, 7.2 and 1.2 Hz), 7.84-7.89 (m, 2H), 7.92 (dt, 1H, J
22

13
= 8.4 and 0.9 Hz), 8.17 (dt, 1H, J = 8.4 and 0.9 Hz); C NMR (CDCl3)  110.6 (CH), 114.1
(CH), 120.7 (CH), 122.4 (CH), 124.2 (CH), 125.1 (CH), 125.4 (CH), 125.5 (CH), 129.1 (CH),
132.4 (C), 136.5 (C), 137.7 (C), 138.0 (C), 146.6 (C). Crystal data for 1j. C14H9N3S, M =
251.3, orthorhombic, Pc21b, a = 5.42050(10), b = 8.1997(2), c = 25.1666(7) Å, V =
1118.57(5) Å3, Z = 4, d = 1.492 g cm-3, μ = 0.271 mm-1. A final refinement on F2 with 2454
unique intensities and 163 parameters converged at ωR(F2) = 0.0881 (R(F) = 0.0363) for 2308
observed reflections with I > 2σ(I). CCDC 985369.
4.2.30. 2-(1-Benzotriazolyl)benzofuran (2j). The general procedure using benzofuran (2a,
0.11 mL, 1.0 mmol) and benzotriazole (0.12 g, 1.5 mmol, 1.5 equiv) gave 2j (eluent: heptane-
AcOEt 20:80) in 39% yield as a pale pink powder: mp 102 °C; IR (ATR): 695, 721, 742, 957,
1054, 1068, 1118, 1208, 1249, 1331, 1372, 1455, 1476, 1516, 1615, 1947, 3056, 3127 cm-1;
1H NMR (CDCl3)  7.05 (d, 1H, J = 0.9 Hz), 7.32 (td, 1H, J = 7.3 and 1.4 Hz), 7.36 (td, 1H, J
= 7.3 and 1.7 Hz), 7.45 (ddd, 1H, J = 8.2, 7.0 and 1.0 Hz), 7.56-7.67 (m, 3H), 8.00 (dt, 1H, J
13
= 8.4 and 0.9 Hz), 8.13 (dt, 1H, J = 8.4 and 0.9 Hz); C NMR (CDCl3)  95.0 (CH), 111.4
(CH), 111.4 (CH), 120.4 (CH), 121.5 (CH), 124.1 (CH), 125.0 (CH), 125.1 (CH), 127.7 (C),
129.3 (CH), 131.7 (C), 145.8 (C), 146.4 (C), 152.3 (C). Crystal data for 2j. C14H9N3O, M =
235.24, orthorhombic, P212121, a = 4.6488(3), b = 12.9438(7), c = 18.0315(10) Å, V =
1085.01(11) Å3, Z = 4, d = 1.44 g cm-3, μ = 0.095 mm-1. A final refinement on F2 with 1471
unique intensities and 163 parameters converged at ωR(F2) = 0.0825 (R(F) = 0.0311) for 1390
observed reflections with I > 2σ(I). CCDC 985373.
4.2.31. 2-(1-Benzotriazolyl)benzothiazole (3j). The general procedure using benzothiazole
(3a, 0.11 mL, 1.0 mmol) and benzotriazole (0.12 g, 1.5 mmol, 1.5 equiv) gave 3j (eluent:
heptane-AcOEt 90:10 to 50:50) in 36% yield as a pale beige powder: mp 166 °C (lit.19 174
°C); IR (ATR): 698, 727, 749, 762, 973, 1000, 1056, 1077, 1117, 1274, 1288, 1300, 1315,
1
1398, 1438, 1446, 1538, 1597, 3059 cm-1; H NMR (CDCl3)  7.38 (td, 1H, J = 7.6 and 1.2
23

Hz), 7.45-7.52 (m, 2H), 7.67 (ddd, 1H, J = 8.2, 7.1 and 1.0 Hz), 7.85 (dd, 1H, J = 7.9 and 0.7
Hz), 7.98 (dd, 1H, J = 8.1 and 0.6 Hz), 8.12 (dt, 1H, J = 8.3 and 0.9 Hz), 8.59 (dt, 1H, J = 8.3
13
and 0.9 Hz); C NMR (CDCl3)  114.0 (CH), 120.3 (CH), 121.7 (CH), 123.1 (CH), 125.7
(CH), 126.0 (CH), 126.9 (CH), 130.1 (CH), 131.2 (C), 132.4 (C), 146.9 (C), 150.9 (C), 157.4
(C).
4.2.32. 2-(1H-1-benzotriazolyl)benzoxazole (4j).20 The general procedure using
benzoxazole (4a, 0.12 g, 1.0 mmol) but benzotriazole (40 mg, 0.5 mmol, 0.5 equiv) gave 4j
(eluent: heptane-AcOEt 90:10 to 50:50) in 6% yield as a red powder: mp 190 °C; IR (ATR):
739, 808, 938, 952, 1014, 1158, 1257, 1448, 1475, 1584, 1761, 2924 cm-1; 1H NMR (CDCl3)
 7.42-7.47 (m, 2H), 7.57 (ddd, 1H, J = 8.1, 7.2 and 0.9 Hz), 7.68-7.72 (m, 1H), 7.77 (ddd,
1H, J = 8.4, 7.2 and 0.9 Hz), 7.81-7.85 (m, 1H), 8.22 (d, 1H, J = 8.4 Hz), 8.51 (d, 1H, J = 8.4
13
Hz); C NMR (CDCl3)  111.1 (CH), 113.2 (CH), 120.3 (CH), 120.7 (CH), 125.7 (CH),
125.7 (CH), 126.2 (CH), 130.5 (CH), 131.4 (C), 139.5 (C), 140.7 (C), 146.2 (C), 149.2 (C).
4.3. Antiproliferative activity of the bis-heterocycles in human melanoma cells. The
antiproliferative activity of the synthesized bis-heterocycles was studied in the A2058
(ATCC® CRL-11147) cell line. A2058 are highly invasive human epithelial adherent
melanoma cells, derived from lymph nodes metastatic cells obtained from a 43 years male
patient. They are tumorigenic at 100% frequency in nude mice, and considered as very
resistant to anticancer drugs. All cell culture experiments were performed at 37°C. Cells were
grown to confluence in 75 cm² flasks in DMEM supplemented with 10% fetal calf serum
(FCS) and 1% Penicillin-streptomycin (Dominique Dutscher, France), in a 5% CO2
humidified atmosphere. The bis-heterocycles were solubilized in DMSO at 10-3 M and diluted
in the cell culture medium to obtain 2.10-5 M solutions. Confluent cells were trypsinized and
centrifuged in FCS at 1500 g for 5 min. The supernatant containing trypsin was discarded and
the cell pellet was suspended in cell culture medium to obtain a 4.104 cell.mL-1 suspension. At
24

t0, 50 µL of the 2.10-5 M bis-heterocycle solutions were deposited in a 96-wells flat bottom
microplate, and 50 µL of the cell suspension were added. The 2000 cells were then grown for
72 h in the cell culture medium containing 10-5 M bis-heterocycle. At t = 72 h, 20µL of a
5g.L-1 MTT solution were added in each well of the microplate, allowing living cells
containing a functional mitochondrial succinate deshydrogenase to metabolize MTT to the
corresponding blue formazan salt for 4 h. The cell culture medium was removed using an
Eppendorf epMotion 5070 pipeting robot (Eppendorf, France) and formazan crystals were
dissolved in 200 µL DMSO. Microplates were placed at 37 °C for 5 min to solubilize
formazan crystals and absorbance was read at 550 nm using a VERSAmax microplate reader
(Molecular devices, France). The percentage of growth inhibition was calculated as:
GI (%) = 100- ((A550 nm sample – A550 nm BG) / (A550 nm control– A550 nm BG)) x 100,
with:
- A550 nm sample: median absorbance of 8 wells containing cells and 10-5 M bis-heterocycle,
- A550 nm BG: median background absorbance of 8 wells containing control cell culture
medium + 1% DMSO,
- A550 nm control: median absorbance of 8 wells containing cells and control cell culture
medium + 1% DMSO.
Data are expressed as GI (%) + sem (%) from 3 independent assays.
Acknowledgements
We thank the French cancer league (Comité 17 de la Ligue Nationale contre le Cancer) for
financial support. We are also grateful to Thermofisher for the generous gift of 2,2,6,6-
tetramethylpiperidine. FM gratefully acknowledges the financial support of the Institut
Universitaire de France and Rennes Métropole.
Supplementary data
25

Supplementary data associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.
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27