Lewis acid catalyzed C-3 alkylidenecyclopentenylation of indoles: An easy access to functionalized indoles and bisindoles

Article abstract of DOI:10.1039/c5ra01107h

A Lewis acid catalyzed C-3 alkylidenecylopentenylation of indoles through the ring opening of pentafulvene derived diazabicyclic olefins has been developed. The present protocol offers an efficient route toward the synthesis of indole and bisindole derivatives. The role of the hydrazine group, as a reaction carrier in the strategy has also been demonstrated by the stepwise synthesis of functionalized bisindole.

Full text of DOI:10.1039/c5ra01107h

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Lewis acid catalyzed C-3
alkylidenecyclopentenylation of indoles: an easy
Cite this: RSC Adv., 2015, 5, 38075
access to functionalized indoles and bisindoles†
ab
ab
b
b
b
S. Sarath Chand, B. S. Sasidhar, Praveen Prakash, P. Sasikumar, P. Preethanuj,
c
c
c
ab
Florian Jaroschik, Dominique Harakat, Jean-Luc Vasse and K. V. Radhakrishnan*
Received 19th January 2015
Accepted 16th March 2015
A Lewis acid catalyzed C-3 alkylidenecylopentenylation of indoles through the ring opening of pentafulvene
derived diazabicyclic olefins has been developed. The present protocol offers an efficient route toward the
synthesis of indole and bisindole derivatives. The role of the hydrazine group, as a reaction carrier in the
strategy has also been demonstrated by the stepwise synthesis of functionalized bisindole.
DOI: 10.1039/c5ra01107h
www.rsc.org/advances
Indole, an important nitrogen containing heterocyclic scaf- as well as free (NH) indoles toward the efficient synthesis of
fold, is one of the primary building blocks of many natural mono and bisindolyl functionalized alkylidenecyclopentenes.
products, biologically active molecules and functional mate-
rials. Moreover, indole is the key component in many phar- cross conjugated system, have been well explored as a 2p, 4p or
maceutical agents such as triptan and its derivatives, a class of 6p component for the construction of numerous biologically
In various cycloaddition reactions, pentafulvenes, a cyclic
1
9
psychoactive drugs used in the treatment of 5HT receptor relevant molecules. Additionally, desymmetrization of dia-
2
related disorders (Fig. 1). Owing to the great prevalence of the zabicyclic olens under transition metal catalysis or acid
indole nucleus, enormous research effort has been devoted catalysis has been developed as an efficient protocol by several
10
towards the synthesis and functionalization, especially at the research groups, including our laboratory for the synthesis of
3
11
C-3 position, of this privileged core. Various synthetic meth- highly functionalized cyclopentene derivatives.
odologies, involving Lewis and Brønsted acids, organo- As part of our continuous interest in the chemistry of
catalysts or transition metal catalysts, have been developed by strained norbornene derivatives, we have utilized diazabicyclic
different research groups for the selective C-3 functionaliza- olens derived from different pentafulvenes as a simple
4
tion of indoles. In 2001, Kobayashi et al. achieved the C-3 precursor for the synthesis of substituted alkylidenecyclo-
cyclopentenylation of indoles through
a
Lewis acid/ pentenes and complex heterocyclic scaffolds in the presence of
surfactant catalyzed Friedel–Cras type conjugate addition a palladium catalyst or Lewis acid. In our previous report we
5
in aqueous medium. Later, King and coworkers explored the have demonstrated a Lewis acid catalyzed ring-opening of
Lewis acid catalyzed Michael addition of indoles to cyclopent- pentafulvene derived diazabicyclic olens using various ortho-
2
-enone for the preparation of 3-cis-(3-aminocyclopentenyl) functionalized aryl iodides such as 2-iodoanilines, 2-iodophe-
6
indoles as potent inhibitors of hSERT. Among indole deriva- nols and 2-iodobenzene thiols and aliphatic alcohols to access a
tives, bisindole moieties are present in several natural alka- variety of trans-3,4-disubstituted alkylidenecyclopentenes. In
loids and many of these compounds show promising
medicinal properties (Fig. 1). So the design and development
12
7
8
of new atom economic methods for construction of bisindole
derivatives remains as a highly demanding strategy in organic
synthesis. Herein, we disclose a Lewis acid catalyzed ring-
opening of pentafulvene derived bicyclic olens with N-alkyl
a
Academy of Scientic and Innovative Research (AcSIR), New Delhi 110001, India.
E-mail: radhu2005@gmail.com
b
Organic Chemistry Section, National Institute for Interdisciplinary Science and
Technology (CSIR), Trivandrum 695019, India
c
Universit ´e de Reims, 51687 Reims Cedex 2, France
1
13
†
Electronic supplementary information (ESI) available: H and C NMR spectra
of all new compounds. CCDC 1034718 and 989506. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c5ra01107h
Fig. 1 Bioactive compounds with indole or bisindole scaffolds.
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the same report, a palladium/Lewis acid mediated trans-
formation of pentafulvene derived diazabicyclic olens has also
been described for the synthesis of novel spiropentacyclic
motifs with indoline/dihydrobenzothiophene and pyrazolidine
fused to the cyclopentene core. As a perpetuation of our ongoing
investigations in the area of strained bicyclic olens, we have
decided to undertake the Lewis acid catalyzed desymmetriza-
tion of pentafulvene derived diazabicyclic olens by employing
biologically signicant indoles as nucleophiles. The developed
method successfully leads to the C-3 functionalization of
indoles with alkylidenecyclopentenes, along with the formation
of bisindole derivatives.
Scheme 2 Sc(OTf)
indole 2b with diazabicyclic olefin 1a in acetonitrile.
3
catalyzed C-3 functionalization of N-methyl-
1a–d easily underwent ring opening with 1H-indole 2a and gave
the corresponding indole derivatives 3aa–da and bisindole 4aa
in good to moderate yields (entries 1–4). To demonstrate the
generality of the reaction, several C-1, C-2 and C-5 substituted
indoles 2b–f were subjected to C-3 alkylidenecyclopentenyla-
tion. Reaction was found to be compatible to a variety of indoles
We initiated our investigation by the treatment of penta-
fulvene derived diazabicyclic olen 1a (1.2 equiv.) with N-
methylindole 2b (1 equiv.) in the presence of Sc(OTf) (2 mol%)
3
in toluene at room temperature (Scheme 1). Aer 4 h, the
reaction afforded the desired trans-3,4-disubstituted alkylidene
cyclopentene derivative 3ab in 44% yield. The structure of 3ab
was established by the usual spectroscopic techniques and also
2
having substituents such as –F, –OH, –NO etc. and yielded the
C-3 functionalized indoles and bisindoles (entries 5–9).
12
Next, we turned our attention to explore the scope of C-3
functionalization of indoles with diazabicyclic olens derived
from different pentafulvenes (Table 3). Alkylidenecyclopente-
nylation of indoles proceeds efficiently through the ring
opening of diazabicyclic alkenes 1e–h to provide the desired
indole and bisindole derivatives. In the case of diphenylfulvene
derived bicyclic olen 1h with indoles 2a and 2b, corresponding
bisindole derivatives were formed in 84% and 81% yield
respectively (entries 7 and 8). Furthermore, the stereochemistry
of the bisindole product 4 was unambiguously conrmed by the
single crystal X-ray analysis of compound 4ha (Fig. 2, ESI†).
Based on these results we propose a plausible mechanism
based on comparison with our previous report. Furthermore,
the structure and stereochemistry of the product was conrmed
by single crystal X-ray analysis of a similar derivative 3eb (see
ESI†).
Further screening of solvents such as DMF, THF, 1,2-
dichloroethane, DCM and CH CN revealed that CH CN was the
3 3
most favorable medium for the transformation. Astonishingly,
when CH CN was employed as the solvent, the bisindolyl
3
functionalized alkylidene cyclopentene 4ab was observed along
with the expected 3,4-disubstituted alkylidene cyclopentene 3ab
(
Scheme 2). Various Lewis acids were also tested for the ring-
opening of 1a with 2b in acetonitrile. Among them, Sn(OTf)
and Fe(OTf) provided the product 3ab in comparable yields.
2
1
2
as shown in Scheme 3. As similar to our previous reports, the
3
During optimization studies, we perceived that the change in
equivalents of starting materials 1a or 2b played a crucial role in
the outcome of the reaction. Use of 2 equiv. of N-methylindole
Table 1 Screening of the reactivity of various Lewis acids in different
2
b resulted in the formation of bisindole product 4ab (58% solventsa
yield) in excess over 3ab (31% yield) (entry 16). Under optimal
conditions (2 mol% Sc(OTf) in CH CN), the reaction could be
nely tuned towards the formation of alkylidenecyclopentenyl
Yield (%)
3
3

Entry
Lewis acid
Solvent
3ab
4ab
derivative of indole 3ab or bisindole 4ab by simply altering the
equivalents of starting materials 1a or 2b.
Under the optimized catalytic conditions for the preparation
of alkylidenecyclopentenyl derivative of indole (Table 1, entry 6)
and bisindole (Table 1, entry 16), we examined the scope
of different olens and indoles (Table 2). Diazabicyclic alkenes
1
2
3
4
5
6
7
8
9
Sc(OTf)
Sc(OTf)
Sc(OTf)
Sc(OTf)
Sc(OTf)
3
3
3
3
3
Toluene
DMF
THF
DCE
DCM
44
38
30
65
58
75
37
Trace
35
46
70
62
Trace
53
—
—
—
5
Trace
14
—
—
—
—
8
6
—
Trace
—
58
Sc(OTf)3
CH CN
3
Yb(OTf)
Zn(OTf)
3
CH
CH
CH
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
3
3
3
CN
CN
CN
CN
CN
CN
CN
CN
CN
CN
2
La(OTf)
Cu(OTf)
Sn(OTf)
3
1
1
1
1
1
1
1
0
1
2
3
4
5
6
2
2
Fe(OTf)
AgOTf
3
AlCl
BF OEt
Sc(OTf)
3
3
2
36
31
b
3
CH
3
a
Reaction conditions: alkene (1.2 equiv.), N-methylindole (1 equiv.),
b
catalyst (2 mol%), solvent (2 mL), at rt. for 4 h. Reaction in the
Scheme 1 Lewis acid catalyzed C-3 functionalization of N-methyl- presence of 1.0 equiv. of alkene and 2 equiv. of N-methylindole.
indole 2b with diazabicyclic olefin 1a.
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a
Table 2 Substrate scope of indoles with various 6,6-pentamethylene fulvene derived diazabicyclic olefins
Yield (%)
Entry
1
Bicyclic olen
Indole
Product 3
Product 4
3
4
7
2
3
7
16
64
b
b
1a
2a
7
1
2
4
16
72
b
b
b
b
b
b
b
b
2
3
4
1b
1c
1d
2a
2a
2a
4aa
4aa
4aa
4
2
2
7
14
28
3
1
9
7
12
33
7
3
5
1
14
58
5
1a
2b
7
3
8
2
11
54
b
b
6
7
8
1a
1a
1a
2c
2d
2e
6
2
1
4
14
52
b
b
5
2
9
6
12
48
b
b
5
2
6
8
8
39
b
b
9
1a
2f
a
b
Reaction conditons: alkene (1.2 equiv.), indole (1 equiv.), catalyst (2 mol%), solvent (2 mL), at rt. for 4 h. Reaction in presence of 1 equiv. of alkene
and 2 equiv. of indole.
catalytic cycle is initiated by coordination of the Lewis acid provided strong supporting evidence for the formation of
with the carbonyl oxygen of one of the carbamate groups of intermediates C and D (see ESI†).
diazabicyclic olen 1 and subsequent cleavage of the C–N
To conrm the Lewis acid catalyzed generation of an inter-
bond leads to the generation of a transient allylic cation mediate from 3 by the elimination of hydrazine moiety, we have
species A. Regioselective nucleophilic attack of indole from carried out a reaction with 1 equiv. of 3,4-disubstituted alkyli-
the opposite side with respect to the hydrazine moiety of dene cyclopentene 3ha and 1.2 equiv. of indole 2a (Scheme 4).
intermediate A delivers trans-3,4-disubstituted alkylidene As expected, bisindole product 4ha was obtained in 62% yield,
cyclopentene 3. In the next step, the Lewis acid coordinates supporting the role of 3,4-disubstituted alkylidene cyclopentene
with the carbonyl group of the hydrazine moiety, followed by as an intermediate in the course of reaction. It is to be noted
the elimination of the hydrazine group through C–N bond that the hydrazine group acts as a key functional moiety in the
cleavage, resulting in the formation of intermediate D. Attack present atom economic strategy toward the synthesis of func-
of the second molecule of indole to intermediate D furnishes tionalized bisindoles. In addition, oxidation of the generated
the bisindole product 4. Furthermore, ESI-MS studies hydrazine could provide the corresponding dialkyl diazene-1,2-
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a
Table 3 Substrate scope of various pentafulvene derived diazabicyclic olefins for the C-3 functionalization of indole
Yield (%)
Entry
1
Bicyclic olen
Indole
Product 3
Product 4
3
4
6
2
9
4
18
64
b
b
1e
2a
6
2
5
7
15
56
b
b
2
3
1e
1f
2b
2a
7
2
0
5
9
b
b
53
6
3
6
0
24
58
b
b
4
5
1g
1g
2a
2b
7
3
0
2
16
55
b
b
6
1
6
3
14
74
b
b
6
7
1g
1h
1h
2c
2a
2b
6
8
2
28
84
b
b
6
1
8
0
24
81
b
b
8
a
b
Reaction conditons: alkene (1.2 equiv.), indole (1 equiv.), catalyst (2 mol%), solvent (2 mL), at rt. for 4 h. Reaction in presence of 1 equiv. of alkene
and 2 equiv. of indole.
dicarboxylates, which can be reused in the cycloaddition
reactions.
In summary, we have developed a Lewis acid catalyzed C-3
alkylideneclopentenylation of indoles through the ring
opening of pentafulvene derived diazabicyclic olens. The
developed method provides an efficient synthetic route to
furnish pharmaceutically valuable indole and bisindole
derivatives of alkylidenecyclopentenes from easily accessible
starting materials. While multiple steps are involved in
conventional synthetic strategies, this protocol offers a one-
pot access to cyclopentene–bisindole hybrids. Moreover, the
present strategy is compatible with both N-alkyl and free (NH)
indoles. Further investigations to elaborate the scope of the
Fig. 2 Single crystal X-ray structure of compound 4ha.
reaction on other N-heterocycles and also to explore the
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(ppm) downeld from SiMe
4
(d 0.0) and relative to the signal of
chloroform-d (d 7.25, singlet). Multiplicities were given as: s
singlet); d (doublet); t (triplet); q (quadret); dd (double
doublet); m (multiplet). Coupling constants are reported as J
(
1
3
value in Hz. Carbon nuclear magnetic resonance spectra ( C
NMR) are reported as d in units of parts per million (ppm)
downeld from SiMe (d 0.0) and relative to the signal of
4
chloroform-d (d 77.03, triplet). Mass spectra were recorded
under EI/HRMS at 60 000 resolution using Thermo Scientic
Exactive mass spectrometer. IR spectra were recorded on Bruker
FT-IR spectrometer.
General procedure for the Lewis acid catalyzed reaction of
pentafulvene derived bicyclic hydrazines towards the synthesis
of 3. A mixture of pentafulvene derived bicyclic hydrazine (1.2
eqiuv.), indole (1.0 equiv.) and Sc(OTf)
in a Schlenk tube and degassed for 10 minutes. Dry CH
3
(2 mol%) were weighed
CN (2
3
mL) was added and the reaction mixture was purged with argon
and allowed to stir at room temperature for 4 hours. The solvent
was evaporated in vacuo and the residue on silica gel (100–200
mesh) column chromatography yielded trans-3,4-disubstituted
alkylidene cyclopentene (3) along with minor amount of trans-
3,4-disubstituted bisindolyl product (4).
General procedure for the Lewis acid catalyzed reaction of
pentafulvene derived bicyclic hydrazines towards the synthesis
Scheme 3 Plausible mechanism.
of 4. A mixture of pentafulvene derived bicyclic hydrazine (1.0
eqiuv.), indole (2.0 equiv.) and Sc(OTf) (2 mol%) were weighed
3
in a Schlenk tube and degassed for 10 minutes. Dry CH CN (2
3
mL) was added and the reaction mixture was purged with argon
and allowed to stir at room temperature for 4 hours. The solvent
was evaporated in vacuo and the residue on silica gel (100–200
mesh) column chromatography yielded trans-3,4-disubstituted
bisindolyl product (4) along with minor amount of trans-3,4-
disubstituted alkylidene cyclopentene (3).
Diethyl
1-(2-cyclohexylidene-5-(1H-indol-3-yl)cyclopent-3-
Scheme 4 Lewis acid catalyzed synthesis of bisindole derivative
catalyzed synthesis of bisindole derivative.
enyl)hydrazine-1,2-dicarboxylate (3aa). Yield: 73%; pale yellow
ꢀ
solid; M. p. 122–124 C; R : 0.31 (hexane/ethyl acetate ¼ 3 : 1). IR
f
(
Neat) nmax: 3334, 3054, 2976, 2920, 2853, 1709, 1586, 1458,
ꢁ1 1
biological applications of synthesized molecules are currently 1410, 1330, 1220, 1120, 1052, 920, 745 cm . H NMR (500 MHz,
underway.
3
CDCl , TMS): d 8.10 (brs, 1H), 7.68 (brs, .03) (m, 1H), 6.84 (s,
1
5
H), 6.53 (d, J ¼ 6 Hz, 1H), 6.26 (brs, 1H), 6.04 (brs, 1H), 5.34–
.12 (m, 1H), 4.50–4.40 (m, 1H), 4.24–4.17 (m, 4H), 2.39–2.33
Experimental section
General methods
(
5
m, 2H), 2.08–2.07 (m, 2H), 1.66–1.53 (m, 6H), 1.30–1.29 (m,
13
H), 1.02 (brs, 1H). C NMR (125 MHz, CDCl , TMS): d 156.6,
3
All chemicals were of the best grade commercially available and 155.1, 136.7, 136.2, 134.0, 129.7, 126.6, 121.9, 120.0, 119.2,
are used without further purication. All solvents were puried 118.1, 110.0, 65.4, 64.1, 62.4, 61.9, 47.4, 32.0, 31.0, 28.4, 28.1,
according to standard procedure; dry solvents were obtained 26.6, 14.5, 14.2. HRMS (ESI): calcd for
according to the literature methods and stored over molecular 460.22123; found: 460.22171.
25 31 3 4
C H N O Na:
sieves. Analytical thin layer chromatography was performed on
Diethyl
1-(2-cyclohexylidene-5-(1-methyl-1H-indol-3-yl)-
glass plates coated with silica gel containing calcium sulfate cyclopent-3-enyl)hydrazine-1,2-dicarboxylate (3ab). Yield: 75%;
ꢀ
binder. Gravity column chromatography was performed using pale yellow solid; M. p. 120–122 C, R
: 0.33 (hexane/ethyl
f
6
0–120 or 100–200 mesh silica gel and mixtures of hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3323, 3055, 2981, 2932, 2855,
acetate were used for elution.
1710, 1619, 1583, 1513, 1458, 1415, 1339, 1302, 1227, 1096,
ꢁ1 1
3
Melting points were determined on a Buchi melting point 1061, 920, 743 cm . H NMR (500 MHz, CDCl , TMS): d 7.68
apparatus and are uncorrected. Proton nuclear magnetic reso- (brs, 1H), 7.25–7.23 (m, 2H), 7.05 (t, J ¼ 7 Hz, 1H), 6.73 (s, 1H),
1
nance spectra ( H NMR) were recorded on a Bruker AMX 500 6.53 (d, J ¼ 5.5, 1H), 6.23 (brs, 1H), 6.04 (s, 1H), 5.31–5.09 (m,
1
spectrophotometer (CDCl
3
as solvent). Chemical shis for H 1H), 4.49–4.39 (m, 1H), 4.24–4.18 (m, 4H), 3.72 (s, 3H), 2.38–2.34
NMR spectra are reported as d in units of parts per million (m, 2H), 2.07–2.03 (m, 2H), 1.61–1.53 (m, 6H), 1.31–1.26 (m,
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1
3
5
H), 1.05–1.04 (brs, 1H). C NMR (125 MHz, CDCl
3
, TMS): d 62.2, 41.9, 32.0, 28.2, 26.5, 19.4, 19.2, 14.5. HRMS (ESI): calcd for
156.4, 155.1, 137.4, 133.7, 129.6, 127.0, 125.7, 121.5, 120.1, C H N O Na: 476.21614; found: 476.21658.
25 31 3 5
118.7, 109.1, 108.8, 65.5, 62.3, 61.8, 47.5, 32.5, 31.9, 28.3, 28.0,
Diisopropyl 1-(2-cyclohexylidene-5-(1H-indol-3-yl)cyclopent-
2
6.5, 14.5. HRMS (ESI): calcd for C H N O Na: 474.23688; 3-enyl)hydrazine-1,2-dicarboxylate (3ba). Yield: 72%; pale
2
6
33 3 4
found: 474.23764.
yellow viscous liquid; R
f
: 0.33 (hexane/ethyl acetate ¼ 3 : 1). IR
Diethyl
cyclopent-3-enyl)hydrazine-1,2-dicarboxylate (3ac). Yield: 78%; 1514, 1462, 1380, 1304, 1238, 1108, 1042, 957, 931, 743 cm . H
yellow viscous liquid; R , TMS): d 8.16 (brs, 1H), 7.75–7.71 (m,
Neat) nmax: 3324, 2980, 2930, 2854, 1701, 1519, 1472, 1420, 1H), 7.31–7.23 (m, 1H), 7.18–7.05 (m, 2H), 6.88 (brs, 1H), 6.56–
1-(2-cyclohexylidene-5-(2-phenyl-1H-indol-3-yl)- (Neat) nmax: 3331, 3068, 2981, 2932, 2857, 1688, 1621, 1583,
ꢁ
1 1
f
: 0.36 (hexane/ethyl acetate ¼ 3 : 1). IR NMR (500 MHz, CDCl
3
(
ꢁ
1 1
1382, 1332, 1261, 1233, 1097, 1060 cm . H NMR (500 MHz, 6.27 (m, 2H), 6.07 (brs, 1H), 5.34–5.14 (m, 1H), 5.00–4.95 (m,
CDCl , TMS): d 8.16 (brs, 1H), 7.60–7.25 (m, 6H), 7.19–7.03 (m, 2H), 4.53–4.43 (m, 1H), 2.36 (brs, 2H), 2.09–1.81 (m, 2H), 1.61–
3
1
3
2
(
H), 7.03 (d, J ¼ 7 Hz, 1H), 6.55 (brs, 1H), 6.20–6.03 (m, 1H), 5.91 1.51 (m, 6H), 1.44–1.22 (m, 12H). C NMR (125 MHz, CDCl3,
brs, 1H), 5.59–5.45 (m, 1H), 4.68–4.53 (m, 1H), 4.16–4.12 (m, TMS): d 156.5, 154.7, 136.8, 133.8, 129.8, 129.0, 128.2, 126.7,
4
0
1
1
2
5
H), 2.58 (brs, 1H), 2.39–2.12 (m, 3H), 1.75–1.59 (m, 6H), 1.29– 125.3, 121.7, 119.1, 110.9, 69.9, 69.5, 63.9, 47.2, 31.6, 30.8, 29.7,
1
3
.88 (m, 6H). C NMR (125 MHz, CDCl
37.7, 136.3, 134.7, 132.8, 129.0, 128.6, 128.2, 127.6, 125.3, 488.25253; found: 488.25286.
21.9, 120.3, 119.4, 110.9, 62.4, 61.7, 60.3, 48.3, 34.6, 32.1, 26.9, Di-tert-butyl 1-(2-cyclohexylidene-5-(1H-indol-3-yl)cyclopent-
6.7, 21.5, 14.5, 14.2. HRMS (ESI): calcd for C H N O Na: 3-enyl)hydrazine-1,2-dicarboxylate (3ca). Yield: 42%; pale
3 35 3 5
, TMS): d 156.2, 155.4, 28.3, 26.9, 22.7, 22.4, 22.1. HRMS (ESI): calcd for C27H N O Na:
3
1
35 3 4
36.25253; found: 536.25289.
Diethyl 1-(2-cyclohexylidene-5-(5-uoro-1H-indol-3-yl)- (Neat) n : 3375, 3078, 2992, 2943, 2836, 1690, 1610, 1583,
cyclopent-3-enyl)hydrazine-1,2-dicarboxylate (3ad). Yield: 61%; 1565, 1468, 1462, 1400, 1316, 1238, 1152, 1123, 969, 938, 746
yellow viscous liquid; R : 0.40 (hexane/ethyl acetate ¼ 3 : 1). IR
f
max
ꢁ
1 1
colourless viscous liquid; R
f
: 0.26 (hexane/ethyl acetate ¼ 3 : 1). cm . H NMR (500 MHz, CDCl
3
, TMS): d 8.00 (d, J ¼ 11 Hz, 1H),
IR (Neat) nmax: 3363, 3277, 3054, 2984, 2931, 2854, 1711, 1582, 7.99–7.79 (m, 1H), 7.32–7.28 (m, 1H), 7.20–7.06 (m, 2H), 6.87 (s,
ꢁ
1 1
1
500, 1149, 1411, 1330, 1120, 1050, 1010, 919, 744 cm . H 1H), 6.55 (d, J ¼ 5.5 Hz, 1H), 6.15–6.00 (m, 2H), 5.30–5.08 (m,
NMR (500 MHz, CDCl , TMS): d 8.26 (s, 1H), 7.34 (brs, 1H), 7.27– 1H), 4.54–4.44 (m, 1H), 2.37 (brs, 2H), 2.12 (brs, 2H), 1.63–1.53
.22 (m, 1H), 6.96–6.92 (brs, 1H), 6.65–6.56 (m, 2H), 6.40–6.31 (m, 24H). C NMR (125 MHz, CDCl , TMS): d 155.7, 154.0,
3
1
3
7
3
(
m, 1H), 6.02 (d, J ¼ 3.5 Hz, 1H), 5.32–5.11 (m, 1H), 4.46–4.18 136.7, 136.5, 126.7, 122.1, 121.8, 119.2, 118.2, 111.1, 110.9,
(m, 5H), 2.41–2.33 (m, 2H), 2.07–2.05 (m, 2H), 1.62–1.45 (m, 110.7, 81.3, 80.7, 65.5, 44.3, 32.0, 31.1, 28.3, 28.2, 28.0, 26.6.
1
3
6
1
1
2
H), 1.35–1.07 (m, 6H). C NMR (125 MHz, CDCl
58.5, 156.8, 155.3, 136.9, 133.3, 130.0, 126.9, 123.1, 118.1, 516.28414.
11.5, 110.3, 104.9, 65.4, 62.6, 62.3, 47.5, 32.0, 31.1, 28.3, 28.0, Dibenzyl 1-(2-cyclohexylidene-5-(1H-indol-3-yl)cyclopent-3-
6.5, 14.4. HRMS (ESI): calcd for C25 Na: 478.21180; enyl)hydrazine-1,2-dicarboxylate (3da). Yield: 39%; yellow
viscous liquid; R
: 0.31 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat)
: 3358, 3059, 3027, 2920, 2858, 1702, 1580, 1489, 1449, 1400,
3 39 3 4
, TMS): d HRMS (ESI): calcd for C29H N O Na: 516.28383; found:
H
3 4
30FN O
found: 478.21223.
f
Diethyl
1-(-2-cyclohexylidene-5-(5-nitro-1H-indol-3-yl)-
n
max
ꢁ1 1
cyclopent-3-enyl)hydrazine-1,2-dicarboxylate (3ae). Yield: 59%; 1311, 1281, 1050, 1000, 743 cm . H NMR (500 MHz, CDCl ,
pale yellow solid; M. p. 132–134 C; R : 0.22 (hexane/ethyl TMS): d 8.28 (brs, 1H), 7.66 (brs, 1H), 7.39–6.90 (m, 13H), 6.75
3
ꢀ
f
acetate ¼ 3 : 1). IR (Neat) nmax: 3365, 3071, 2960, 2852, 1712, (brs, 2H), 6.46 (s, 1H), 5.98–5.86 (m, 1H), 5.36–5.05 (m, 5H),
1
623, 1582, 1469, 1410, 1380, 1318, 1245, 1173, 1115, 1058, 743 4.52–4.29 (m, 1H), 2.36–2.32 (m, 2H), 2.02–1.94 (m, 2H), 1.56–
ꢁ
1
1
13
3 3
cm . H NMR (500 MHz, CDCl , TMS): d 9.22 (brs, 1H), 8.56 (s, 1.26 (m, 6H). C NMR (125 MHz, CDCl , TMS): d 156.4, 154.8,
1
1
4
H), 7.92 (brs, 1H), 7.17–7.13 (m, 1H), 6.92–6.82 (m, 1H), 6.61 (d, 136.7, 135.8, 133.4, 128.6, 128.5, 128.3, 128.2, 127.9, 126.6,
H, J ¼ 4.5 Hz), 6.34 (brs, 1H), 5.98 (brs, 1H), 5.39–5.17 (m, 1H), 122.0, 121.2, 119.9, 119.4, 117.5, 110.9, 68.1, 67.6, 47.5, 32.0,
1
3
.49–4.23 (m, 5H), 2.56–2.06 (m, 4H), 1.76–1.22 (m, 12H).
C
31.0, 28.3, 28.0, 26.5. HRMS (ESI): calcd for C H N O Na:
35 35 3 4
NMR (125 MHz, CDCl , TMS): d 156.3, 155.6, 141.3, 139.8, 137.7, 584.25253; found: 584.25288.
3
1
6
30.1, 129.0, 128.2, 125.5, 125.3, 124.2, 117.6, 117.2, 111.0, 64.3,
2.9, 62.2, 47.5, 32.1, 31.3, 28.2, 26.6, 21.5, 14.5, 14.2. HRMS enyl)hydrazine-1,2-dicarboxylate (3ea). Yield: 69%; colourless
Na: 505.20630; found: 505.20668. viscous liquid; R
: 0.29 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat)
1-(2-cyclohexylidene-5-(5-hydroxy-1H-indol-3-yl)- max: 3317, 3056, 2982, 2931, 1719, 1620, 1582, 1512, 1415, 1382,
cyclopent-3-enyl)hydrazine-1,2-dicarboxylate (3af). Yield: 56%; 1229, 1096, 1062, 744 cm . H NMR (500 MHz, CDCl
pale yellow viscous liquid; R
: 0.17 (hexane/ethyl acetate ¼ 3 : 1). 8.30 (s, 1H), 7.71 (brs, 1H), 7.34–7.27 (m, 1H), 7.19–7.08 (m, 2H),
IR (Neat) nmax: 3380, 3280, 3054, 2976, 2928, 2853, 1709, 1586, 6.86–6.78 (m, 2H), 6.52 (d, 1H, J ¼ 5 Hz), 6.05 (s, 1H), 5.35–5.14
Diethyl 1-(2-(1H-indol-3-yl)-5-(propan-2-ylidene)cyclopent-3-
(ESI): calcd for C25
H
30
N
4
O
6
f
Diethyl
n
ꢁ1 1
3
, TMS): d
f
ꢁ1
1
499, 1149, 1410, 1330, 1220, 1120, 1052, 1011, 920, 745 cm
.
(m, 1H), 4.53–4.18 (m, 5H), 1.89 (s, 3H), 1.67 (brs, 3H), 1.29–1.26
1
13
H NMR (500 MHz, CDCl , TMS): d 7.89 (brs, 1H), 7.23–7.15 (m, (m, 6H). C NMR (125 MHz, CDCl , TMS): d 156.9, 155.8, 136.8,
3
3
2
5
H), 6.79–6.77 (m, 1H), 6.56–6.28 (m, 2H), 6.05 (brs, 1H), 5.32– 136.6, 135.5, 129.0, 126.7, 125.3, 121.7, 119.9, 119.1, 119.0,
.09 (m, 1H), 4.45–4.11 (m, 5H), 2.37–2.33 (m, 2H), 2.07–2.06 117.9, 111.3, 66.0, 62.6, 62.2, 47.6, 21.5, 14.4. HRMS (ESI): calcd
1
3
(m, 2H), 1.60–1.38 (m, 6H), 1.29–1.13 (m, 5H), 0.99 (brs, 1H).
C
27 3 4
for C22H N O Na: 420.18993; found: 420.18866.
NMR (125 MHz, CDCl
3
, TMS): d 155.2, 154.5, 147.5, 135.8, 135.0,
Diethyl 1-(2-(1-methyl-1H-indol-3-yl)-5-(propan-2-ylidene)-
134.3, 127.2, 126.8, 125.3, 111.9, 111.8, 108.5, 104.5, 64.9, 62.8, cyclopent-3-enyl)hydrazine-1,2-dicarboxylate (3eb). Yield: 65%;
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13
colourless solid; M. p. 124–126 C, R
f
: 0.33 (hexane/ethyl acetate 1.01–0.87 (m, 6H). C NMR (125 MHz, CDCl
3
, TMS): d 156.4,
¼
3 : 1). IR (Neat) nmax: 3385, 3055, 2981, 2924, 1707, 1611, 1474, 155.3, 137.4, 131.3, 130.6, 128.1, 128.0, 121.5, 120.2, 119.0,
1
413, 1379, 1321, 1265, 1219, 1163, 1122, 1061, 1021, 933, 739 113.5, 109.3, 65.9, 62.3, 61.7, 47.8, 39.5, 39.4, 37.0, 35.1, 34.6,
ꢁ
1 1
cm . H NMR (500 MHz, CDCl , TMS): d 7.73 (s, 1H), 7.29–7.23 30.8, 28.2, 28.1, 14.7. HRMS (ESI): calcd for C H N O Na:
3
36 41 3 4
(
1
5
m, 2H), 7.10 (t, J ¼ 7 Hz, 1H), 6.77 (brs, 1H), 6.53 (d, J ¼ 5 Hz, 602.29948; found: 602.29977.
H), 6.39 (brs, 1H), 6.07 (s, 1H), 5.36–5.14 (m, 1H), 4.53–4.20 (m,
Diethyl 1-(2-(diphenylmethylene)-5-(1-methyl-1H-indol-3-yl)
1
3
H), 3.73 (s, 3H), 1.90 (s, 3H), 1.69 (s, 3H), 1.31–1.05 (m, 6H).
C
cyclopent-3-enyl)hydrazine-1,2-dicarboxylate (3ha). Yield: 62%;
ꢀ
NMR (125 MHz, CDCl
3
, TMS): d 156.7, 155.6, 137.5, 136.7, 135.6, pale yellow solid, M. p. 182–184 C; R
f
: 0.24 (hexane/ethyl
1
30.5, 128.3, 127.1, 125.9, 121.6, 120.1, 118.8, 116.7, 109.0, 66.2, acetate ¼ 3 : 1). IR (Neat) nmax: 3362, 3051, 2968, 2911, 2852,
62.5, 61.9, 47.5, 32.6, 21.5, 13.8. HRMS (ESI): calcd for 1736, 1710, 1552, 1514, 1467, 1454, 1411, 1384, 1364, 1308,
ꢁ
1 1
C H N O Na: 434.20588; found: 434.20615.
1287, 1243, 1231, 1168, 1157, 1069, 1063, 1022, 742 cm . H
2
3
29 3 4
Diethyl 1-(2-cycloheptylidene-5-(1H-indol-3-yl)cyclopent-3- NMR (500 MHz, CDCl , TMS): d 7.85–7.79 (m, 1H), 7.42–7.03 (m,
3
enyl)hydrazine-1,2-dicarboxylate (3fa). Yield: 70%; colourless 12H), 6.90–6.59 (m, 3H), 6.32–6.22 (brs, 1H), 6.04–5.91 (m, 2H),
viscous liquid; R
f
: 0.31 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) 5.08 (brs, 1H), 4.23–4.13 (m, 4H), 3.92–3.73 (m, 1H), 1.35–1.01
13
n
max: 3348, 3056, 2924, 2853, 1708, 1617, 1458, 1414, 1380, 1226, (m, 6H). C NMR (125 MHz, CDCl
3
, TMS): d 156.0, 154.7, 142.5,
ꢁ1 1
1
8
6
(
2
177, 1121, 1061, 741 cm . H NMR (500 MHz, CDCl , TMS): d 142.4, 141.3, 140.8, 137.4, 130.0, 129.9, 128.6, 128.2, 127.7,
3
.09 (brs, 1H), 7.66 (brs, 1H), 7.28 (brs, 1H), 7.16–7.04 (m 2H), 127.4, 126.8, 121.6, 120.2, 119.1, 116.9, 115.5, 110.2, 65.6, 62.0,
.84 (brs, 1H), 6.51 (d, J ¼ 5.5 Hz, 1H), 6.25–6.21 (m, 1H), 6.04 61.8, 47.9, 14.8. HRMS (ESI): calcd for C H N O Na:
3
2
31 3 4
brs, 1H), 5.33–5.11 (m, 1H), 4.50–4.18 (m, 5H), 2.50–2.41 (m, 544.22123; found: 544.22151.
1
3
H), 2.20–2.16 (brs, 2H), 1.71–1.03 (m, 14H). C NMR (125
, TMS): d 156.3, 155.5, 136.8, 129.0, 128.2, 126.6, cyclopent-3-enyl)hydrazine-1,2-dicarboxylate (3hb). Yield: 68%;
25.3, 121.7, 119.0, 119.0, 111.1, 62.4, 61.9, 47.6, 32.7, 32.3, 29.1, yellow viscous liquid; R
Diethyl 1-(2-(diphenylmethylene)-5-(1-methyl-1H-indol-3-yl)-
MHz, CDCl
3
1
2
4
f
: 0.29 (hexane/ethyl acetate ¼ 3 : 1). IR
Na: (Neat) nmax: 3340, 3068, 2981, 2932, 2857, 1688, 1621, 1602,
1583, 1555, 1514, 1462, 1380, 1315, 1238, 1108, 1042, 931, 743
8.2, 27.6, 14.5, 14.2. HRMS (ESI): calcd for C26
74.23688; found: 474.23714.
Compound 3ga. Yield: 66%; colourless viscous liquid; R
33 3 4
H N O
ꢁ
1 1
f
:
3
cm . H NMR (500 MHz, CDCl , TMS): d 7.79 (brs, 1H), 7.34–
0
.33 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3323, 3057, 7.19 (m, 14H), 7.09–6.97 (m, 2H), 6.61–6.55 (m, 1H), 6.32 (brs,
2920, 2848, 1713, 1620, 1475, 1413, 1381, 1305, 1294, 1216, 1H), 5.82–5.56 (m, 2H), 4.70–4.65 (m, 1H), 4.25–4.15 (m, 4H),
ꢁ1 1
1116, 1085, 1065, 1025, 742 cm . H NMR (500 MHz, CDCl , 3.76 (brs, 3H), 1.32–1.29 (m, 4H), 1.03 (brs, 1H), 0.69 (brs, 1H).
3
1
3
TMS): d 8.21 (brs, 1H), 7.70 (brs, 1H), 7.32–7.25 (m, 2H), 7.20–
3
C NMR (125 MHz, CDCl , TMS): d 156.9, 154.9, 142.6, 142.3,
7
1
4
1
1
1
3
C
.05 (m, 3H), 6.86 (brs, 1H), 6.56 (d, J ¼ 5.5 Hz, 1H), 6.29 (brs, 141.3, 140.7, 137.4, 130.0, 129.9, 128.5, 128.1, 127.4, 127.3,
H), 6.05 (brs, 1H), 5.39–5.16 (m, 1H), 4.53–4.41 (m, 1H), 4.30– 127.1, 126.6, 121.4, 120.2, 118.8, 116.0, 115.3, 108.9, 65.5, 62.0,
.13 (m, 4H), 3.06 (brs, 1H), 2.59 (brs, 1H), 2.08–1.64 (m, 12H), 61.8, 47.6, 32.6, 14.5, 13.8. HRMS (ESI): calcd for C33 Na:
33 3 4
H N O
1
3
.35–1.08 (m, 6H). C NMR (125 MHz, CDCl
55.2, 144.4, 136.5, 130.2, 129.0, 128.3, 126.6, 125.3, 121.4,
21.1, 119.9, 119.0, 117.1, 111.1, 63.8, 62.5, 62.0, 47.6, 39.9, 39.5, (4aa). Yield: 64%; pale yellow coloured solid, M. p. 152–156 C; R :
3
, TMS): d 156.7, 558.23688; found: 558.23721.
0
3,3 -(5-Cyclohexylidenecyclopent-3-ene-1,2-diyl)bis(1H-indole)
ꢀ
f
9.1, 37.0, 35.1, 34.4, 28.1, 28.0, 21.5, 14.6. HRMS (ESI): calcd for 0.43 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) n : 3405, 2922,
max
ꢁ1 1
29
H
35
N
3
O
4
: 512.25253; found: 515.25290.
2851, 2362, 2349, 1590, 1459, 1421, 1364, 1120, 1033 cm . H
Compound 3gb. Yield: 70%; pale yellow viscous liquid; R
.36 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3315, 3054, 7.57 (m, 2H), 7.38–7.34 (m, 2H), 7.22–7.17 (m, 2H), 7.09–6.94 (m,
910, 2852, 1711, 1612, 1472, 1413, 1379, 1305, 1221, 1124, 4H), 6.78 (d, J ¼ 5.5 Hz, 1H), 6.04 (dd, J ¼ 5.5 Hz, J ¼ 2.5 Hz,
, TMS): d 7.71 1H), 4.32 (brs, 1H), 4.19 (brs, 1H), 2.46 (t, J ¼ 6 Hz, 2H), 2.04–1.97
f
:
3
NMR (500 MHz, CDCl , TMS): d 7.93 (s, 1H), 7.85 (s, 1H), 7.61–
0
2
1
1
2
ꢁ
1 1
061, 1019, 740 cm . H NMR (500 MHz, CDCl
3
1
3
(
brs, 1H), 7.7–7.21 (m, 2H), 7.07 (t, J ¼ 7 Hz, 1H), 6.80 (brs, 1H), (m, 2H), 1.67–1.29 (m, 6H). C NMR (125 MHz, CDCl , TMS): d
3
6
1
1
.55 (d, J ¼ 5.5 Hz, 1H), 6.25 (brs, 1H), 6.05 (s, 1H), 5.35–5.12 (m, 139.1, 136.9, 135.9, 133.0, 129.9, 129.1, 128.3, 126.7, 126.6, 125.4,
H), 4.53–4.28 (m, 1H), 4.23–4.13 (m, 4H), 3.75 (s, 3H), 3.05 (s, 121.9, 121.8, 121.0, 120.9, 120.2, 120.1, 119.6, 118.9, 111.2, 111.0,
1
3
H), 2.58 (brs, 1H), 2.02–1.63 (m, 12H), 1.37–1.09 (m, 6H).
, TMS): d 156.6, 154.9, 137.4, 130.2, 127.1,
25.8, 121.5, 120.2, 118.7, 108.9, 62.3, 61.9, 47.2, 39.6, 37.0, 35.1,
C
52.3, 45.8, 32.1, 31.8, 28.6, 27.7, 26.9. HRMS (ESI): calcd for
NMR (125 MHz, CDCl
3
C
27
H
26
0
2
N Na: 401.19937; found: 401.19968.
1
3
3,3 -(5-Cyclohexylidenecyclopent-3-ene-1,2-diyl)bis(1-methyl-
4.7, 32.6, 28.1, 26.9, 25.3, 22.9, 20.8, 14.9. HRMS (ESI): calcd for 1H-indole) (4ab). Yield: 58%; pale yellow viscous liquid; R
Na: 526.26818; found: 526.26862.
(hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 2935, 2855, 2358,
Compound 3gc. Yield: 66%; pale yellow viscous liquid; Rf: 2353, 1680, 1595, 1449, 1431, 1358, 1156, 1120, 1033 cm . H
f
: 0.48
30 37 3 4
C H N O
ꢁ1 1
0
2
1
.38 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3378, 3058, NMR (500 MHz, CDCl , TMS): d 7.56–7.52 (m, 2H), 7.28–7.16 (m,
3
978, 2908, 2848, 1756, 1704, 1467, 1445, 1409, 1379, 1364, 4H), 7.14–6.99 (m, 2H), 6.83 (s, 1H), 6.75 (s, 1H), 6.71 (dd, J ¼
1
338, 1308, 1277, 1248, 1218, 1172, 1157, 1097, 1062, 1022 5.5 Hz, J
2
¼ 1 Hz, 1H), 5.97 (dd, J
1
¼ 5.5 Hz, J ¼ 2.5 Hz, 1H), 4.26
2
ꢁ
1 1
cm . H NMR (500 MHz, CDCl
3
, TMS): d 7.58–7.44 (m, 6H), (s, 1H), 4.11 (s, 1H), 3.77 (s, 3H), 3.74 (s, 3H), 2.45–2.41 (m, 2H),
7
.33–7.19 (m, 3H), 7.04 (brs, 1H), 6.50–6.42 (m, 1H), 6.12–5.81 2.02–2.00 (m, 1H), 1.94–1.92 (m, 1H), 1.63–1.45 (m, 4H), 1.34–
1
3
3
(m, 2H), 5.45 (brs, 1H), 4.25–4.15 (m, 4H), 3.58 (s, 3H), 3.06 (brs, 1.31 (m, 1H), 1.18–1.17 (m, 1H). C NMR (125 MHz, CDCl ,
1H), 2.65–2.61 (m, 1H), 2.03–1.85 (m, 10H), 1.59–1.25 (m, 2H), TMS): d 139.2, 137.5, 137.4, 136.1, 132.8, 129.6, 129.0, 128.2,
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1
1
2
27 26 2 2
27.1, 126.9, 125.6, 125.3, 121.5, 121.3, 120.4, 120.3, 120.2, 28.6, 27.6, 26.8. HRMS (ESI): calcd for C H N O Na:
18.8, 118.6, 118.3, 109.1, 108.9, 52.3, 45.7, 32.6, 32.5, 32.0, 31.9, 433.18920; found: 433.18954.
0
8.6, 27.7, 26.9. HRMS (ESI): calcd for C H N Na: 429.23067;
3,3 -(5-(Propan-2-ylidene)cyclopent-3-ene-1,2-diyl)bis(1H-indole)
2
9
30 2
found: 429.23102.
(4ea). Yield: 64%; colourless viscous liquid; R : 0.45 (hexane/
f
0
3
,3 -(5-Cyclohexylidenecyclopent-3-ene-1,2-diyl)bis(2-phenyl- ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3315, 2920, 2857, 2377,
ꢀ
ꢁ1
1
1
R
H-indole) (4ac). Yield: 54%; pale yellow solid, M. p. 160–164 C; 1648, 1590, 1520, 1468, 1367, 1160, 1119, 1037 cm . H NMR
: 0.52 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3342, 3075, (500 MHz, CDCl , TMS): d 7.99 (s, 1H), 7.92 (s, 1H), 7.60–7.56 (m,
953, 2912, 2857, 1695, 1611, 1514, 1462, 1380, 1238, 1100, 2H), 7.40–7.37 (m, 2H), 7.23–7.18 (m, 3H), 7.09–7.05 (m, 3H),
f
3
2
1
1
7
1
1
1
1
1
3
5
ꢁ
1 1
030, 931, 740 cm . H NMR (500 MHz, CDCl
3
, TMS): d 7.98 (s, 7.00 (s, 1H), 6.94 (s, 1H), 6.74 (dd, 1H, J
1
¼ 5.5 Hz, J ¼ 2 Hz),
2
H), 7.88 (s, 1H), 7.68 (d, J ¼ 8 Hz, 1H), 7.59 (d, J ¼ 8 Hz, 1H), 6.05 (dd, 1H, J ¼ 5.5 Hz, J ¼ 2.5 Hz), 4.28 (s, 1H), 4.22 (s, 1H),
1
2
1
3
.42–7.37 (m, 4H), 7.28–6.80 (m, 13H), 6.14 (m, 1H), 4.76 (brs, 1.93 (s, 3H), 1.61 (s, 3H). C NMR (125 MHz, CDCl , TMS): d
3
H), 4.71 (brs, 1H), 2.51–2.49 (m, 1H), 2.38–2.18 (m, 1H), 1.83– 141.9, 137.1, 136.9, 135.8, 130.4, 127.3, 126.8, 125.8, 125.7,
.07 (m, 8H). C NMR (125 MHz, CDCl , TMS): d 138.4, 136.5, 124.4, 121.5, 121.3, 120.5, 120.3, 120.0, 118.4, 118.2, 117.9,
3
36.4, 136.3, 135.1, 134.5, 133.4, 132.6, 132.5, 130.5, 128.4, 110.8, 110.7, 52.4, 46.4, 21.3. HRMS (ESI): calcd for C24H N Na:
22 2
28.3, 128.2, 127.9, 127.8, 127.4, 127.3, 122.3, 122.2, 121.3, 361.16807; found: 361.16848.
20.9, 119.6, 119.2, 117.3, 114.7, 110.5, 110.3, 50.6, 44.8, 32.5,
0.8, 28.6, 27.1, 26.8. HRMS (ESI): calcd for C39
53.26197; found: 553.26233.
1
3
0
3,3 -(5-(Propan-2-ylidene)cyclopent-3-ene-1,2-diyl)bis(1-methyl-
ꢀ
H
34
N
2
Na: 1H-indole) (4eb). Yield: 56%; pale yellow solid, M. p. 162–164 C;
R : 0.50 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) n : 2925, 2852,
f
max
0
ꢁ1
3,3 -(5-Cyclohexylidenecyclopent-3-ene-1,2-diyl)bis(5-uoro- 2371, 1649, 1586, 1523, 1465, 1364, 1254, 1167, 1122, 1042 cm
.
1
1H-indole) (4ad). Yield: 52%; pale yellow viscous liquid; R : 0.40
H NMR (500 MHz, CDCl , TMS): d 7.66–7.61 (m, 2H), 7.38–7.31
3
f
(
2
1
hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3356, 3052, 2978, (m, 2H), 7.29–7.27 (m, 2H), 7.14–7.09 (m, 2H), 6.90 (s, 1H), 6.83
939, 2849, 1689, 1619, 1583, 1514, 1462, 1415, 1402, 1380, (s, 1H), 6.78 (dd, 1H, J
1
¼ 5.5 Hz, J
2
¼ 2 Hz), 6.09 (dd, H, J
1
¼ 5.5
ꢁ
1 1
304, 1238, 1111, 1047, 942, 740 cm
. H NMR (500 MHz, Hz, J
2
¼ 2.5 Hz), 4.32 (s, 1H), 4.25 (s, 1H), 3.81 (s, 3H), 3.79 (s,
1
3
CDCl
3
, TMS): d 8.03 (s, 1H), 7.94 (s, 1H), 7.31–7.20 (m, 4H), 7.07 3H), 1.99 (s, 3H), 1.60 (s, 3H). C NMR (125 MHz, CDCl , TMS): d
3
(
s, 1H), 7.00–6.77 (m, 4H), 6.00 (t, 1H, J ¼ 3 Hz), 4.22 (s, 1H), 4.09 142.2, 137.6, 137.5, 135.9, 130.5, 127.1, 127.0, 125.9, 125.7, 124.4,
(s, 1H), 2.46–2.42 (m, 2H), 2.06–2.04 (m, 1H), 1.96–1.94 (m, 1H), 121.5, 121.3, 120.3, 120.2, 119.9, 118.8, 118.7, 118.4, 109.2, 109.1,
1
3
1
1
1
3
4
.67–1.44 (m, 6H). C NMR (125 MHz, CDCl , TMS): d 158.5, 52.6, 46.6, 31.7, 21.4. HRMS (ESI): calcd for C H N Na:
3
26 26 2
56.7, 138.5, 135.3, 133.8, 133.5, 130.3, 126.9, 122.9, 122.7, 389.19937; found: 389.19969.
0
21.9, 120.3, 111.7, 111.6, 110.5, 110.3, 110.2, 105.2, 105.0, 45.6,
3,3 -(5-Cycloheptylidenecyclopent-3-ene-1,2-diyl)bis(1H-indole)
24 2 2 f
2.0, 31.8, 28.5, 27.6, 26.8. HRMS (ESI): calcd for C27H F N Na: (4fa). Yield: 53%; colourless viscous liquid; R : 0.43 (hexane/ethyl
37.18052; found: 437.18088.
acetate ¼ 3 : 1). IR (Neat) nmax: 3408, 3056, 2923, 2853, 1703,
0
ꢁ1
3
,3 -(5-Cyclohexylidenecyclopent-3-ene-1,2-diyl)bis(5-nitro- 1619, 1583, 1517, 1485, 1455, 1338, 1227, 1095, 1012, 741 cm
.
1
1
H-indole) (4ae). Yield: 48%; orange red viscous liquid; R
f
: 0.40
3
H NMR (500 MHz, CDCl , TMS): d 7.97 (s, 1H), 7.89 (s, 1H),
(
2
1
hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3326, 3056, 2955, 7.59–7.57 (d, J ¼ 8 Hz, 2H), 7.37–7.34 (m, 2H), 7.21–7.16 (m, 2H),
932, 2850, 1675, 1629, 1583, 1457, 1385, 1300, 1238, 1100, 7.07–7.05 (m, 2H), 6.98–6.93 (m, 2H), 6.76 (dd, J ¼ 5.5 Hz, J ¼
1
2
ꢁ1 1
040, 931, 7445 cm . H NMR (500 MHz, CDCl , TMS): d 8.91 2.5 Hz, 1H), 6.04 (dd, J ¼ 5.5 Hz, J ¼ 3 Hz, 1H), 4.27 (s, 1H), 4.18
3
1
2
(s, 1H), 8.74 (s, 1H), 8.53–8.52 (m, 2H), 8.12–8.09 (m, 2H), 7.45– (brs, 1H), 2.57–2.51 (m, 2H), 2.25–2.19 (m, 1H), 2.07–2.06 (m,
1
3
7
5
2
1
.41 (m, 2H), 7.26 (d, J ¼ 10.5 Hz, 1H), 7.14 (s, 1H), 6.86 (d, J ¼ 1H), 1.72–1.29 (m, 8H). C NMR (125 MHz, CDCl
3
, TMS): d
.5 Hz, 1H), 5.99 (d, J ¼ 4.5 Hz, 1H), 4.33 (s, 1H), 4.22 (brs, 1H), 142.1, 136.9, 136.7, 135.9, 134.3, 130.4, 129.0, 128.2, 126.7, 126.6,
.61–2.58 (m, 1H), 2.44–2.42 (m, 1H), 2.07–2.04 (m, 1H), 1.93– 121.9, 121.5, 120.8, 120.7, 120.2, 120.1, 119.2, 119.0, 111.0, 110.9,
1
3
.90 (m, 1H), 1.89–1.37 (m, 6H). C NMR (125 MHz, CDCl
3
,
52.5, 46.1, 32.8, 32.5, 29.8, 28.8, 27.2, 26.9. HRMS (ESI): calcd for
TMS): d 141.4, 141.2, 140.1, 140.0, 137.6, 135.1, 134.6, 130.9, C H N Na: 415.21502; found: 415.21538.
2
8
28 2
1
1
25.9, 125.7, 124.1, 124.0, 123.8, 122.2, 117.7, 117.6, 117.5,
Compound 4ga. Yield: 58%; colourless viscous liquid; Rf:
12.9, 111.3, 52.3, 45.7, 32.1, 32.0, 28.2, 27.7, 26.7. HRMS (ESI): 0.43 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3289, 3066,
calcd for C27
H
24
N
2
O
4
Na: 491.16952; found: 491.16993.
2931, 2857, 1668, 1620, 1582, 1520, 1455, 1304, 1238, 933, 744
0
ꢁ1
1
3
,3 -(5-Cyclohexylidenecyclopent-3-ene-1,2-diyl)bis(1H-indol-
cm . H NMR (500 MHz, CDCl
3
, TMS): d 7.88 (s, 1H), 7.79 (s,
5
-ol) (4af). Yield: 39%; pale yellow viscous liquid; R
f
: 0.19 1H), 7.62 (d, J ¼ 8 Hz, 1H), 7.55 (d, J ¼ 8 Hz, 1H), 7.54–7.21 (m,
(
2
1
hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3339, 3061, 2990, 2H), 7.19–7.13 (m, 2H), 7.05–6.93 (m, 4H), 6.72–6.71 (m, 1H),
940, 2842, 1680, 1623, 1580, 1514, 1380, 1302, 1240, 1110, 5.94 (dd, J
1
¼ 5.5 Hz, J
2
¼ 3 Hz, 1H), 4.30 (s, 1H), 4.11 (brs, 1H),
ꢁ1 1
042, 931, 740 cm . H NMR (500 MHz, CDCl , TMS): d 7.87 3.12 (brs, 1H), 2.49 (brs, 1H), 2.04–1.68 (m, 9H), 1.53–1.43 (m,
3
1
3
(brs, 1H), 7.78 (brs, 1H), 7.27–7.22 (m, 2H), 7.03–6.98 (m, 3H), 2H), 0.88–0.84 (m, 1H). C NMR (125 MHz, CDCl , TMS): d
3
6
.92 (d J ¼ 2 Hz, 1H), 6.81–6.74 (m 3H), 6.01–6.00 (dd, J ¼ 6 Hz, 140.8, 137.8, 137.0, 136.9, 135.4, 135.2, 129.5, 129.1, 128.3,
1
J
2
¼ 3 Hz, 1H), 4.82 (d, J ¼ 6.5 Hz, 2H), 4.16 (s, 1H), 4.07 (s, 1H), 126.8, 126.5, 125.4, 122.0, 121.8, 120.9, 120.4, 119.2, 118.9,
.45–2.39 (m, 2H), 1.99–1.94 (m, 2H), 1.50–1.44 (m 3H), 1.33– 111.2, 111.1, 52.4, 45.2, 39.8, 39.4, 38.2, 37.3, 35.1, 34.8, 28.4,
2
0
1
1
1
3
3 30 2
.87 (m 5H). C NMR (125 MHz, CDCl , TMS): d 149.1, 148.9, 21.6. HRMS (ESI): calcd for C31H N Na: 453.23067; found:
38.8, 135.6, 133.1, 132.1, 130.0, 127.3, 122.2, 121.3, 119.8, 453.23101.
11.8, 111.7, 111.6, 111.6, 104.8, 104.7, 51.7, 45.8, 32.0, 31.8,
38082 | RSC Adv., 2015, 5, 38075–38084
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Paper
Compound 4gb. Yield: 55%; colourless viscous liquid; R
RSC Advances
f
:
no.: SB/S1/OC-24/2014), Indo-French Centre for Promotion of
0
2
1
.48 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3090, 2950, Advanced Research (IFCPAR/CEFIPRA (Project 4505-1)), and
932, 2857, 1688, 1621, 1583, 1514, 1462, 1380, 1304, 1238, Council of Scientic and Industrial Research (12th FYP project,
ꢁ
1 1
108, 1042, 957, 931, 743 cm
.
H NMR (500 MHz, CDCl
3
,
ORIGIN-CSC-0108), New Delhi are greatly acknowledged.
TMS): d 7.65 (d, J ¼ 8 Hz, 1H), 7.58 (d, J ¼ 8 Hz, 1H), 7.33–7.20 Thanks are due to Dr K. M. Sureshan and Mr Alex Andrews of
m, 6H), 7.08–7.02 (m, 2H), 6.89 (s, 1H), 6.83 (s, 1H), 6.73 (d, J ¼ IISER Trivandrum, for single crystal X-ray analysis. The authors
.5 Hz, 1H), 5.95 (t, J ¼ 2.5 Hz, 1H), 4.32 (s, 1H), 4.13 (s, 1H), 3.81 also thank Mrs Saumini Mathew, Mrs S. Viji and Mr Saran
s, 3H), 3.77 (s, 3H), 3.17 (s, 1H), 2.53 (s, 1H), 2.01–1.58 (m, 12H). P. Raveendran of CSIR-NIIST and Mr B. Adarsh of IISER Tri-
(
5
(
1
3
C NMR (125 MHz, CDCl
3
, TMS): d 140.6, 137.6, 135.6, 135.2, vandrum for recording NMR and mass spectra.
1
1
3
4
29.2, 127.2, 127.0, 125.6, 125.5, 121.5, 120.5, 120.3, 118.8,
18.8, 118.6, 109.1, 108.9, 52.5, 45.2, 39.8, 39.3, 38.2, 37.3, 35.0,
Notes and references
4.4, 32.6, 32.5, 28.4, 28.3. HRMS (ESI): calcd for C33
81.26197; found: 481.26141.
34 2
H N Na:
1 (a) M. Bandini and A. Eichholzer, Angew. Chem., Int. Ed.,
2009, 48, 9608–9644; (b) A. J. Kochanowska-Karamyan and
M. T. Hamann, Chem. Rev., 2010, 110, 4489–4497; (c)
R. J. Sundberg, The Chemistry of Indoles, Academic press,
New York, 1996, p. 113.
Compound 4gc. Yield: 74%; colourless viscous liquid; Rf:
.55 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 2981, 2915,
833, 1671, 1621, 1586, 1542, 1380, 1300, 1238, 1042, 957, 931,
0
2
7
7
ꢁ
1 1
43 cm . H NMR (500 MHz, CDCl
.38–6.96 (m, 12H), 6.66 (dd, J
¼ 5.5 Hz, J
¼ 5.5 Hz, J ¼ 2.5 Hz, 1H), 4.41 (brs, 1H), 4.22 (brs, 1H),
.61 (s, 3H), 3.57 (s, 3H), 2.98 (brs, 1H), 2.32 (brs, 1H), 1.83–1.50
3
, TMS): d 7.62–7.47 (m, 6H),
¼ 2.5 Hz, 1H), 6.04
2 M. Berger, J. A. Gray and B. L. Roth, Annu. Rev. Med., 2009, 60,
355–366.
1
2
(
dd, J
1
2
3
3 (a) S. Cacchi and G. Fabrizi, Chem. Rev., 2005, 105, 2873–
2920; (b) K. Kr u¨ ger (n ´e e Alex), A. Tillack and M. Beller, Adv.
Synth. Catal., 2008, 350, 2153–2167; (c) J. Zhou and
Y. Tang, J. Am. Chem. Soc., 2002, 124, 9030–9031; (d)
K. B. Jensen, J. Thorhauge, R. G. Hazell and
K. A. Jørgensen, Angew. Chem., Int. Ed., 2001, 40, 160–163.
4 (a) R. J. Phipps, N. P. Grimster and M. J. Gaunt, J. Am. Chem.
Soc., 2008, 130, 8172–8174; (b) S. M. A. H. Siddiki, K. Kon and
K.-I. Shimizu, Chem.–Eur. J., 2013, 19, 14416–14419; (c)
G. Bartoli, G. Bencivenni and R. Dalpozzo, Chem. Soc. Rev.,
2010, 39, 4449–4465; (d) G. Yan, C. Kuang, Y. Zhang and
J. Wang, Org. Lett., 2010, 12, 1052–1055; (e) A. Mahadevan,
H. Sard, M. Gonzalez and J. C. McKew, Tetrahedron Lett.,
2003, 44, 4589–4591; (f) Y. L. Hu, H. Jiang and M. Lu,
Green Chem., 2011, 13, 3079–3087; (g) D. A. Evans,
K. A. Scheidt, K. R. Fandrick, H. W. Lam and J. Wu, J. Am.
Chem. Soc., 2003, 125, 10780–10781; (h) G. Blay,
I. Fernandez, J. R. Pedro and C. Vila, Org. Lett., 2007, 9,
2601–2604; (i) K. Gao and J. Wu, Org. Lett., 2008, 10, 2251–
2254.
1
3
(m, 12H). C NMR (125 MHz, CDCl
3
, TMS): d 140.2, 137.9,
1
1
1
3
37.4, 136.2, 135.8, 134.6, 133.9, 133.4, 131.3, 130.5, 129.7,
28.7, 128.2, 127.7, 127.5, 126.6, 125.3, 122.3, 121.4, 120.3,
19.5, 119.1, 119.0, 117.5, 115.2, 108.9, 108.7, 51.0, 45.3, 39.3,
8.9, 37.8, 37.4, 34.9, 33.1, 30.9, 28.1. HRMS (ESI): calcd for
C
45
H
42
0
N
2
Na: 633.32457; found: 633.32486.
3,3 -(5-(Diphenylmethylene)cyclopent-3-ene-1,2-diyl)bis(1H-
ꢀ
indole) (4ha). Yield: 84%; pale yellow solid, M. p. 154–156 C; R
f
:
0
2
.43 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3294, 2857,
ꢁ1 1
366, 2335, 1647, 1590, 1369, 1120, 1037, 702 cm . H NMR
(500 MHz, CDCl , TMS): d 7.90 (s, 1H), 7.67–7.51 (m, 3H), 7.37–
3
7
1
1
1
1
4
4
.06 (m, 9H), 6.98–6.78 (m, 9H), 6.40 (d, J ¼ 4 Hz, 1H), 6.24 (brs,
13
3
H), 4.51–4.49 (m, 2H). C NMR (125 MHz, CDCl , TMS): d
48.1, 143.2, 142.6, 140.4, 136.8, 136.5, 135.0, 133.1, 129.8,
29.3, 127.9, 127.4, 126.7, 126.5, 126.2, 125.9, 122.0, 121.5,
20.8, 120.1, 119.8, 119.5, 119.3, 119.0, 118.9, 111.1, 110.9, 57.7,
8.5. HRMS (ESI): calcd for C34H N Na: 485.19937; found:
26 2
85.19969.
0
3
,3 -(5-(Diphenylmethylene)cyclopent-3-ene-1,2-diyl)bis(1-
methyl-1H-indole) (4hb). Yield: 81%; yellow solid, M. p. 160–162
5 (a) G. A. Olah, R. Krishnamurti and G. K. S. Prakash,
Comprehensive Organic Synthesis, ed. B. M. Trost and I.
Fleming, Pergamon Press, Oxford, 1991, vol. 3, p. 293; (b)
K. Manabe, N. Aoyama and S. Kobayashi, Adv. Synth.
Catal., 2001, 343, 174–176.
ꢀ
C; R
f
: 0.48 (hexane/ethyl acetate ¼ 3 : 1). IR (Neat) nmax: 3053,
2
1
7
927, 1709, 1688, 1613, 1513, 1469, 1427, 1372, 1328, 1242,
ꢁ1 1
156, 1130, 1013, 740 cm . H NMR (500 MHz, CDCl
3
, TMS): d
.78–7.76 (m, 2H), 7.72–7.30 (m, 9H), 7.20–6.99 (m, 6H), 6.87
(
brs, 3H), 6.52 (t, J ¼ 3 Hz, 1H), 6.09 (dd, J
1
¼ 4 Hz, J
2
¼ 2.5 Hz,
6 H. D. King, Z. Meng, J. A. Deskus, C. P. Sloan, Q. Gao,
B. R. Beno, E. S. Kozlowski, M. A. Lapaglia, G. K. Mattson,
T. F. Molski, M. T. Taber, N. J. Lodge, R. J. Mattson and
J. E. Macor, J. Med. Chem., 2010, 53, 7564–7572.
7 A. W. Schmidt, K. R. Reddy and H. Knolker, Chem. Rev., 2012,
112, 3193–3228.
8 (a) K. S. Ryan and C. L. Drennan, Chem. Biol., 2009, 16, 351–
364; (b) M. Shiri, M. A. Zolgol, H. G. Kruger and
Z. Tanbakouchian, Chem. Rev., 2010, 110, 2250–2293; (c)
J. S. Oakdale and D. L. Boger, Org. Lett., 2010, 12, 1132–
1
H), 4.66 (brs, 1H), 4.57–4.54 (m, 1H), 3.81 (s, 3H), 3.58 (s, 3H).
1
3
C NMR (125 MHz, CDCl , TMS): d 148.8, 143.3, 143.0, 140.8,
3
1
1
1
3
5
37.6, 137.3, 134.9, 132.9, 129.9, 129.3, 129.2, 128.4, 128.0,
27.4, 127.2, 127.2, 126.8, 126.5, 125.8, 125.7, 121.7, 121.1,
20.3, 120.0, 118.9, 118.4, 118.1, 117.6, 109.3, 109.1, 51.8, 48.9,
2.6, 32.2. MS (ESI): calcd for C36
13.23098.
H
30
N
2
Na: 513.23067; found:
Acknowledgements
1134; (d) T. Haahimoto, A. Yasuda, K. Akazawa, S. Takaoka,
SCS, PS and PP thank UGC for a research fellowship. Financial
assistance from Department of Science and Technology (DST
M. Tori and Y. Asakawa, Tetrahedron Lett., 1994, 35, 2559–
2560.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 38075–38084 | 38083

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