Challenges associated with the synthesis of unusual o-carboxamido stilbenes by the Heck protocol: Intriguing substituent effects, their toxicological and chemopreventive implications

Article abstract of DOI:10.1039/c0ob00296h

The syntheses of fourteen unusual o-carboxamido stilbenes by the Heck protocol revealed surprising complexity related to intriguing substituent effects with mechanistic implications. The unexpected cytotoxic and chemopreventive properties also seem to be substituent dependent. For example, although stilbene 15d (with a 4-methoxy substituent) showed cytotoxicity on HT29 colon cancer cells with an IC₅₀ of 4.9 μM, the 3,4-dimethoxy derivative (15c) is inactive. It is interesting to observe that the 3,5-dimethoxy derivative (15e) showed remarkable chemopreventive activity in WRL-68 fetal hepatocytes, surpassing the gold standard, resveratrol. The resveratrol concentration needed to be 5 times higher than that of 15e to produce comparable elevation of NQO1.

Full text of DOI:10.1039/c0ob00296h

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Challenges associated with the synthesis of unusual o-carboxamido stilbenes
by the Heck protocol: Intriguing substituent effects, their toxicological and
chemopreventive implications†
Chin Hui Kee,a Azhar Ariffin,a Khalijah Awang,a Koichi Takeya,b Hiroshi Morita,c Salmaan Inayat Hussain,d
Kok Meng Chan,d Pauline J. Wood,e Michael D. Threadgill,e Chuan Gee Lim, f SeikWeng Ng,a
Jean Fre´de´ric F. Weberg and Noel F. Thomas*a
Received 21st June 2010, Accepted 6th September 2010
DOI: 10.1039/c0ob00296h
The syntheses of fourteen unusual o-carboxamido stilbenes by the Heck protocol revealed surprising
complexity related to intriguing substituent effects with mechanistic implications. The unexpected
cytotoxic and chemopreventive properties also seem to be substituent dependent. For example,
although stilbene 15d (with a 4-methoxy substituent) showed cytotoxicity on HT29 colon cancer cells
with an IC50 of 4.9 mM, the 3,4-dimethoxy derivative (15c) is inactive. It is interesting to observe that the
3,5-dimethoxy derivative (15e) showed remarkable chemopreventive activity in WRL-68 fetal
hepatocytes, surpassing the gold standard, resveratrol. The resveratrol concentration needed to be
5 times higher than that of 15e to produce comparable elevation of NQO1.
Introduction
In the fields of creative organic synthesis and medicinal chem-
istry, the aminostilbenes in general, and the o-amidostilbenes in
particular, are beginning to attract the attention of the synthetic
community.
Stilbene 1 (Fig. 1) prepared by the Stille protocol has been skil-
fully exploited by the Mun˜iz group in a novel Pd(OAc)2/PhI(OAc)2
promoted syntheses bisindolines (incorporating the diazabicyclo
[3.3.0] octane skeleton.1 By contrast, O’Shea2 has, by means of
some imaginative carbolithiation chemistry, transformed the stil-
bene 2 (prepared by the Suzuki–Miyaura coupling) to quinolines.
We, by contrast, have discovered that treatment of the protected
acetamido stilbene catecholic ether 3 with FeCl3 gave rise via a
radical cationic cascade to the indoline and the corresponding
C(3)–C(3¢) bisindoline.3,4 By contrast treatment of the resorcinolic
ether analogue 4 under the same conditions produced the un-
precedented chloroindolostilbenes (incorporating two stereogenic
axes).5
Fig. 1 Examples of trans stilbenes.
The intriguing properties of resveratrol 5 (Fig. 2) and questions
relating to its mechanism of action in vivo have been the focus
aDepartment of Chemistry, Faculty of Science, University of Malaya, 50603,
Kuala Lumpur, Malaysia. E-mail: noelfthomas@um.edu.my; Fax: +603-
79674193; Tel: +603-79674065
bDepartment of Pharmacognosy, Tokyo University of Pharmaceutical and
Life Science, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan
cFaculty of Pharmaceutical Sciences, Hoshi University, Shinagawa-ku,
Tokyo, 142-8501, Japan
Fig. 2 Examples of biologically active trans stilbenes.
dFaculty of Allied Health Sciences, Universiti Kebangsaan Malaysia, 50300,
Kuala Lumpur, Malaysia
of intense research activity over the past ten years. Resveratrol,
a phytoalexin, has a range of biological characteristics which,
as previously stated, include antibacterial, antileukemic and
antitumor properties.6 It also shows chemopreventive behaviour
which seems to be associated with its strong antioxidant and
anti-inflammatory activities.7 Resveratrol’s low water solubility
explains, at least in part, increasing interest in the synthesis and
pharmacological evaluation of analogues.
eDepartment of Pharmacy and Pharmacology, University of Bath, Claverton
Down, Bath, BA2 7AY, UK
f
Environmental and Bioprocess Technology Centre, SIRIM Berhad, 40000,
Shah Alam, Malaysia
gIKUS, Faculty of Pharmacy, Universiti Teknologi MARA, 40450, Shah
Alam, Malaysia
† Electronic supplementary information (ESI) available: Proposed mecha-
nisms and NMR spectra. See DOI: 10.1039/c0ob00296h
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Table 1 Pd(OAc)2 catalyzed synthesis of stilbene derivativesa
Thus we find that in a recent study,8 the resveratrol aliphatic
acid 6 inhibited cell apoptosis through TLR2 by the involvement
of the AKt/GSK3b pathway. Moran et al.9 have synthesized
and evaluated fluorinated resveratrol derivatives incorporating
nitro groups by the decarbonylative Heck and Wittig procedures.
Reduction of the nitro group to the amino function and stan-
dard EDC coupling procedures provided aminostilbenes and the
corresponding amino acid derivatives respectively. By such proce-
dures, the fluoroacetoxystilbene 7 and the trifluoroacetylamino
analogues 8 were prepared. Resveratrol 5 and the fluorinated
acetate 7 were the most potent antiproliferative agents with IC50
values of 15 3 mM and 10 2 mM. This activity was obtained
when these compounds were tested against the non-small lung cell
carcinoma cell line DLKP. The (E)-3,5-di(trifluroacetylamino)-
4¢-fluorostilbene 8, when tested in combination with epirubicin,
showed the greatest antiproliferative effect. It was suggested that
this synergy may indicate interaction with the multidrug resistant
protein, P-glycoprotein (P-gp).9
It seemed to us that the synthetic and pharmacological exami-
nation of the fourteen trans-aminostilbene carboxamides we have
described in this report (having the carboxamide moiety at the
ortho position) could very well fill a gap in the current literature.
We were aware, as the reader would glean from our introductory
comments, that other published methods for the syntheses of
stilbenes including aminostilbenes could have been chosen as
alternatives to the mechanistically complex Heck.10 Nevertheless,
imposing new steric and electronic demands on the proposed
building blocks for our stilbene synthesis would have an impact
on the efficacy of the reaction leading to the stilbenes described
in this report and therefore compel us to examine the Heck’s
highly original mechanistic proposal from a different perspective.
This, quite apart from the toxicological questions related to the
stilbenes, is of some significance as it would provide an opportunity
for us to re-evaluate our own preconceptions regarding the Heck
mechanism, not least because this generally accepted mechanism
has not been experimentally proven in all the steps.11
Entry
SM1
SM2
Product
Yield [%]
1
2
3
4
5
6
9a
9b
9c
9c
9d
9e
10a
10a
10a
10b
10a
10a
11a
11b
11c
11d
11e
11f
21
15
31
30
18
27
In our syntheses described herein, structural modifications in
the amide moiety (R = methyl, isopropyl, benzyl, furyl, naphthyl),
and in the B ring (Scheme 1; R1 could even be aryl) should
be illuminating. This is because variations in the yields of
stilbenes resulting from the Heck procedure should enable us to
reexamine the traditional Heck mechanism with a view to gaining
new insights into this fascinating and important reaction. We
believe these stilbene o-carboxamides are new chemical entities.
In our experience, the structure of the stilbene profoundly affects
radical-cationic properties. For this reason and other issues
to be addressed later, careful comparative examination of the
high resolution NMR spectra of our unusual stilbenes should
provide much needed information that will hopefully guide future
synthetic/mechanistic and toxicological studies.
a All reactions were carried out using Pd(OAc)2, Et3N in DMF at 120 ◦C
for 36 h.
The questions to be addressed among others are:
1. Would the Heck construction (Scheme 2) tolerate structural
modifications in the carboxamide moiety? The orthoamidostil-
benes synthesized and presented in Tables 1, 2 and 3 show
variations in steric bulk and electron-withdrawing tendencies
as reflected in the NMR spectra (see electronic supplementary
information†). The implications for palladacycle formation are
discussed in the mechanistic section.
Scheme 1 Retrosynthetic analysis of our stilbene carboxamides.
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Scheme 2 Application of the traditional Heck mechanism to our stilbene (*Note that for the ionic mechanism, the active form of the catalyst would be
[Pd0(OAc)(Et3N)2]-).
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Table 2 Pd(OAc)2 catalyzed synthesis of biphenyl stilbene derivativesa
Table 3 Pd(OAc)2 catalyzed synthesis of furancarboxamido stilbene
derivativesa
Entry
SM1
SM2
Product
Yield[%]
1
2
3
9d
9f
9g
12
12
12
13a
13b
13c
31
9
7
Entry Styrene Major product Yield [%] Minor productb Yield [%]
1
2
3
4
5
10c
10d
10a
10b
10e
15a
15b
15c
15d
15e
49
33
16
36
17
16a
16b
16c
16d
—
8
6
4
9
—
a All reactions were carried out using Pd(OAc)2, Et3N in DMF at 120 ◦C
for 36h. Products 14a and 14b were isolated in minute quantities.
2. How would the carboxamide moiety influence the carbopal-
ladation step IV to VIII (Scheme 2) involving electron rich styrenes
(as opposed to electron deficient styrenes which are known to be
superior coupling partners)?12
3. Would electronic and steric differences observed in the various
stilbenes, and as indicated by variations in the chemical shift of the
NH and olefinic moieties, profoundly affect both structure activity
relationships and the oxidative radical cation chemistry?
In examining the traditional Heck reaction (Scheme 2) below as
applied to our stilbenes, certain mechanistic questions naturally
arise:
1. What is the real structure of intermediate II and if it is cyclic,
how does this affect the syn insertion step IV to VIII?
2. Fourteen different stilbene carboxamides of generalized
structure I (Scheme 2) have been prepared. Is oxidative addition
leading to I the rate determining step in all these cases?
3. Following from (1), should E-2 elimination of HPdIL be
considered (given the proximity of the electron withdrawing amide
moiety) as competing with the more common syn-b-hydride
elimination (IX, Scheme 2) possibly within a cyclic palladium
complex ?
a All reactions were carried out using Pd(OAc)2, Et3N in DMF at 120 ◦C
for 36 h. b Minor product 1714 was also isolated (average yield was 7%).
syntheses and spectroscopic examination described in the next
section. Although some X-ray crystallographic details have been
published, this is the first full description of the synthetic and
In this report we suggest tentative but thought-provoking
answers to some of these questions. We duly embarked on the
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spectroscopic aspects of our study. Biological activities of our
stilbenes in several cell lines originating from colon (HT29), liver
(HepG2 and WRL-68) and blood (Jurkat and P388) are also
described.
It is perhaps significant that the Heck reaction of 9d with 3,4-
dimethoxystyrene 10a (Table 1) produced the desired stilbene 11e
in 18% yield. With regard to the latter observation, the same Heck
procedure is able to generate stilbenes 11c and 11d (Table 1) that
incorporate bulky cyclohexylamides in ~30% yield irrespective of
the presence of 3,4-dimethoxy or 4-methoxy substitution; a pattern
that contrasts with furancarboxamido stilbene generation under
the same Heck conditions as we previously discussed (see Table 3,
entries 3 and 4). One might tentatively suggest that in the latter
cases (the furancarboxamido stilbenes) produced by the coupling
of 3,4 and 3,5-dimethoxy substituted styrenes respectively, the syn
insertion into the carboxamide palladium chelate complex (see 27,
Scheme 7 below) is now the rate determining step and this step is
sensitive to the styrene substitution pattern. Note the syn insertion
step, IV to VIII, in Scheme 2.
Clearly there are a number of subtle steric and electronic effects
to be evaluated in these reactions from a mechanistic standpoint
and our careful consideration of these factors has influenced the
particular attention that has been paid to the NMR spectra of the
stilbene products. Two other points are worthy of attention.
Firstly, purification/chromatographic complexities should not
be overlooked and are a factor, among others, to be taken
into consideration where overall yields are concerned. This is
particularly true of stilbenes that bear the biphenyl moiety as
indicated in Table 2. We have therefore tried to resist the temptation
to be dogmatic where mechanistic proposals are concerned.
Secondly, the N,N-biphenyl-2-carboxamide dimer 17 and the
geminally substituted ene carboxamide 16a–d are formed in
amounts large enough for characterization only in the case of
iodophenylamide 9f incorporating the furan moiety. 16a–d and
17 are of course generated in low yields 4–9% and 7% (average)
respectively. A possible mechanism for the formation of 17 can be
found in the supporting information.†
Results and discussion
The difficulties encountered in this study are both synthetic
and chromatographic. The key C–C bond forming event is the
Heck coupling exemplified by Scheme 1. All reaction products in
Tables 1, 2, and 3 were subjected to chromatographic purification
and all side products (as revealed by TLC) were isolated and char-
acterized. The iodophenylamides (including ortho-halobenzamide
9d)13 were prepared by exposure of iodoaniline to the correspond-
ing acyl chlorides in Et3N prior to Heck coupling leading to the
first series of stilbenes shown in Table 1.
Our second series of stilbenes were synthesized by coupling of
the corresponding N-(2-iodophenyl)benzamide 9d, furan carbox-
amide 9f and acetamide 9g to 4-vinyl biphenyl 12 (Table 2). Our
third series (Table 3) are the furancarboxamido stilbenes prepared
by Heck coupling of the N-(2-Iodophenyl)furancarboxamide 9f
with various substituted styrenes 10a–e. The geminally function-
alized olefins are minor products 16a–d. Close examination of
Tables 1 to 3 reveals certain entries that should be compared
as these observations raise interesting mechanistic questions. In
Table 1 (entries 3 and 4), notice that the substitution pattern
in the styrene has little effect on the yield of the stilbene in
contrast to Table 3 (entries 3 and 4), where a doubling in yield
is observed as single methoxy substitution in the styrene 10b
replaces dimethoxy substitution in styrene 10a. In the case of
Table 2 (entries 1 and 3), a 22% drop in yield is observed when
the benzene ring in 9d is replaced by a furan ring in 9f. A full
spectroscopic discussion relating to these stilbenes can be found
in the supporting information.†
The Heck coupling is known to proceed with much greater effi-
ciency with alkenes possessing electron-withdrawing groups.15 The
Heck coupling of electron rich styrenes such as ours was therefore
always likely to be difficult. The presence of increasingly sterically
demanding carboxamides would be expected to exacerbate these
difficulties.
In the following sections, we will attempt (with all due caution)
to comment on the mechanistic aspects with one eye on the
traditional Heck mechanism (Scheme 2). We will revisit the
question of the nature of structure II (Scheme 2), i.e. open or
cyclic? We will consider alternative modes for the syn insertion,
i.e. exo or endo; dehydropalladation (E-2 elimination) within a
cyclic palladium complex and dehydropalladation (internal base).
Mechanistic considerations
Although a full mechanistic investigation is outside the scope
of this work, we do hope that some of our tentative mecha-
nistic hypotheses could form the basis for future studies. Some
general observations relating to variations in yields in the Heck
reaction and the effect of the styrene substitution pattern seem
appropriate as these may have mechanistic implications. Some
kind of “match/mismatch” principle with respect to styrene
and iodophenylcarboxamide components must pertain (a phe-
nomenon that has not previously been reported to the best of our
knowledge in connection with the Heck reaction).
Within the furancarboxamido stilbene class (Table 3), molecules
incorporating a single methoxy group in ring B were generated in
yields higher than other compounds of this class with 15a (having
an ortho methoxy group in ring B), generated in the highest yield
(49%).
It is interesting to note that the furancarboxamido stilbene
incorporating the biphenyl 13b (Table 2) was generated by our
Heck procedure in the lowest yields (9%). Furthermore and in
complete contrast, replacement of the furan in 9f with the benzene
ring in the iodophenyl amide 9d (Table 2) which was then “Heck”
coupled to the vinylbiphenyl 12 gave the corresponding stilbene
13a in 31% yield.
Pd(II) to Pd(0)
The electron rich styrenes (e.g. 3,4-dimethoxystyrene 10a) are
capable of reducing Pd(II) to Pd(0) (see Scheme 3). Triethylamine
is also an effective reductant for Pd(II).16 syn Dehydropalladation
converts 20 to 21 followed by regeneration of Pd(0).
Oxidative addition by Pd(0)
In the course of the synthesis of, for example 15a (Table 3, entry
1), it is reasonable to suppose that Pd(0) is in the form of 23.
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boxamides (which are more electron withdrawing) – a property
reflected in the NMR spectrum of the products 15a, 15b and 15d.
This is provided the styrene carries a single methoxy group. It
is possible that the iodophenylcyclohexylamide follow a different
course and formation of a complex analogous to 27 is prohibited
(note the more shielded NH in the spectrum of 11c and 11d).
On the other hand, the intramolecular complexation described
above (see 27) may well accelerate the oxidative addition step but
at the expense of a decelerated alkene coupling (carbopalladation
step – which is now the rate determining step). The observation
that substituents (with heteroatoms) at the ortho position in an
aromatic ring are capable of chelating to a Pd species (intramolec-
ularly) is significant here.15 Intramolecular chelation of an amide
to a Pd species at the ortho position of a benzene ring has been
proposed by Horino and Inoue18 with relatively little mechanistic
comment (Scheme 5). By contrast, we have studied a more diverse
range of such carboxamides as Table 3 amply demonstrates.
Numerous palladacycles, including 28,18 shown below are known
to be catalytically active19 in the Heck reaction.
Scheme 3 Reduction of Pd(II) to Pd(0).
The intermediacy of the cationic complex 22 cannot be ruled out
entirely.16
The following proposal (Scheme 4) for the oxidative addition
step is reasonable in the light of the electron-withdrawing tendency
of furancarboxamide group (compared to other groups).
Scheme 4 Proposed oxidative addition step (9f → 24).17
If oxidative addition is accelerated by virtue of the presence of
the furancarboxamide, it may help to explain the greater efficiency
relatively speaking of stilbene formation from iodophenylcar-
Scheme 5 Pd(OAc)2 mediated construction of styrenes and stilbenes via
an intramolecular amide/Pd complex leading to ortho-vinylation.18
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Alkene syn insertion and the problem of dehydropalladation
What are the options for a syn insertion mechanism? Two modes
of addition can be envisaged. The aryl palladium carboxamide
complex (or palladacycle) 27 can be attacked by the styrene in
either the endo mode (Scheme 6) or the exo mode (Scheme 7).
The E-2 elimination of Pd(0) and HOAc (see 30, Scheme 6) is
analogous to the loss of Pd(0) and HCl described by Tsuji20 (see
Scheme 6).
Scheme 7 exo Mode insertion of the styrene into the palladacycle 27
followed by E-2 elimination of Pd0.
(for example) remains, at least, a reasonable hypothesis (and may
be in competition with the more conventional pathway). Another
possibility is a non-palladacyclic E-2 elimination of PdH as illus-
trated (see Scheme 8). The “internal” base E-2 elimination does
not involve the “internal” palladacycle. The amide moiety (aza-
enolate) removes the C-8 proton thus promoting the elimination
of HPdOAc. This mechanism might be the preferred path for
those iodophenylcarboxamides with less electron withdrawing
amides (where the furan ring has been replaced by, for example,
cyclohexyl). The steric bulk of the cyclohexyl rings may render
complexes analogous to 30 (Scheme 6) and 31 (Scheme 7) less
stable than the furan analogues.
Scheme 6 endo Mode insertion of the styrene into the palladacycle 27
followed by E-2 elimination (30 to 16d).
The tantalizing possibility of a based-induced E-2 elimination
of PdH (30, Scheme 6 or 31, Scheme 7) (in contrast to the more
conventional b-hydride elimination) has been considered in careful
review by Beletskaya19 although in the special and restricted
context of the arylation of disubstituted olefins with Hermann’s
palladacycle catalyst. Beletskaya felt this mechanistic option had
a low probability. Whether this pathway, as depicted in the very
different setting shown in our chemistry Scheme 7 (for example),
is operating requires careful examination beyond the scope of our
present studies.
Scheme 8 The “internal base” E-2 elimination.
Biological evaluation of the stilbenes
The synthesized stilbenes were evaluated for biological activity in
several cell lines originating from colon (HT29), liver (HepG2 and
WRL-68) and blood (Jurkat and P388). However the pattern of
cytotoxicity varied in these cell lines. The most potent from our
At the present level of knowledge and with respect to the type of
stilbenes we are examining, the based promoted anti-elimination
of PdH (as depicted above) leading to the desired stilbene 15d
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Table 4 Biological evaluation of selected stilbenes
IC50/mMa
library of compounds was 15d where the IC50s were 2.2 mM and
4.9 mM in P388 and HT29 cells respectively (Table 4). This is a
significant result as the cytotoxicity of o-amidostilbenes bearing
a furan carboximido moiety had not previously been reported.
This result also demonstrates the importance of a methoxy group
specifically in the para position. However, no cytotoxicity was
observed in HepG2 and Jurkat cells up to 100 mM for 15d. In
contrast, 15b and 15c showed cytotoxicity of 13.9 mM (HT29) and
48.7 mM (P388) respectively. In addition, 13a showed a modest
cytotoxicity in P388 cell with an IC50 of 79.9 mM.
Stilbene
HT29
HepG2
ND
Jurkat
P388
>100
ND
>100
Since some of our stilbenes were not cytotoxic in HepG2 and
Jurkat cells, it is possible that these compounds may demonstrate
chemopreventive activities including upregulation of detoxifying
enzymes such as NAD(P)H: quinone oxidoreductase 1 (NQO1).
In this respect, we assessed 15e on WRL-68 fetal hepatocytes
which can be induced to elevate the NQO1 expression. In order
to determine the concentrations of 15e for the NQO1 study,
cytotoxicity tests were carried out at three concentrations, namely
IC10, IC25 and IC50 (Fig. 3 and 4).
Our study demonstrated a 2.4 fold increase of NQO1 activity
in 15e (IC10) -treated WRL-68 cells. In contrast, resveratrol,
a known chemopreventive stilbene showed similar elevation of
NQO1 activity of around 2.6 fold when cells were treated with
100 mM concentration which was five times higher than 15e. This
was in agreement with Hwang et al.21 whereby the synthesized
furan containing compound namely furan-2-yl-3-pyridin-2-yl-
propenone has been demonstrated to elevate NQO1.
>100
>100
>100
ND
ND
ND
>100
>100
>100
79.9
>100
>100
>100
>100
>100
>100
Experimental
Unless otherwise noted, materials were purchased from commer-
cial suppliers and used without purification. THF was freshly dis-
tilled from calcium hydride. DMF was dried over molecular sieves
˚
4 A(Sigma–Aldrich) prior to use. Column chromatography was
13.9
>100
>100
>100
>100
ND
48.7
performed using Merck silica gel (0.040–0.063 mm). For thin layer
chromatography, Merck TLC aluminium sheets (silica gel 60 F254
)
were used; centrifugal chromatography, Merck silica gel 60 PF254
containing gypsum was used. Infrared spectra were recorded on a
Perkin Elmer FTIR Spectrum RX-1 spectrometer at wavenumbers
from 4000–400 cm-1. Nuclear magnetic resonance (NMR) spectra
were obtained on a JEOL JNM-LA 400 and JEOL ECA-400.
Spectra are reported in units of ppm on the scale, relative to
chloroform and the coupling constants are given in Hz. Ultra
violet (UV) spectra were recorded from wavelength 190–400 nm,
in methanol, on a Shimadzu UV-Visible Spectrophotometer 1650.
Mass spectra were measured using Agilent 6530 Accurate-Mass
Q-TOF LC/MS system. Melting points were determined with
Mel-Temp II melting point apparatus. The HT29 experiments
were run in Prof. Michael D. Threadgill’s laboratory, HepG2,
Jurkat and NQO1 experiments were run in Prof. Salmaan Inayat
Hussain’s laboratory and P388 experiments were run in Prof.
Hiroshi Morita’s laboratory.
>100
4.9
>100
>100
>100
>100
2.2
ND
>100
General procedure22a for the preparation of compounds 9a–f
To a stirred, cooled (0–5 ◦C) solution of 2-iodoaniline (1 equiv) and
Et3N (1 equiv) in dry THF (20 ml) a solution of an appropriate
acyl chloride (1 equiv) in dry THF (5 ml) was added dropwise.
The ice bath was removed and the mixture was stirred vigorously
a ND = Not determined.
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Fig. 3 Cytotoxicity of 15e in WRL-68 fetal hepatocytes.
138.8 (C-6), 138.3 (C-1), 129.4 (C-3), 126.0 (C-4), 122.1 (C-5), 90.0
(C-2), 40.0 (C-8, CH2), 19.2 (C-9, CH2), 13.7 (C-10, CH3).
N-(2-Iodophenyl) cyclohexanecarboxamide (9c)
Off-white solid (6.13 g, 74%); mp 134–136 ◦C (lit.,22a 139–140 ◦C);
dH(400 MHz; CDCl3) 8.24 (d, J = 8.2 Hz, H-6, 1H), 7.75 (dd, J =
8.2 Hz, 1.4 Hz, H-3, 1H), 7.51 (br s, NH, 1H), 7.32 (td, J = 7.4 Hz,
1.4 Hz, H-5, 1H), 6.82 (td, J = 7.8 Hz, 1.8 Hz, H-4, 1H), 2.30
(tt, J = 11.7 Hz, 3.4 Hz, H8, CH, 1H), 1.23–2.06 (m, H-9, H-10,
H-11, H-12, H-13, CH2, 10H); dC(100 MHz; CDCl3) 174.4 (C-7),
138.8 (C-3), 138.3 (C-1), 129.3 (C-5), 125.9 (C-4), 122.1 (C-6), 90.2
(C-2), 46.7 (C-8, CH), 29.8 (C-9, C-13, CH2), 25.8 (C-10, C-11,
C-12, CH2).
Fig. 4 NQO1 protein expression and activity in 15e treated WRL-68
fetal hepatocytes. Legend: CON – Vehicle control; IC10 – Inhibition
concentration 10% (21 mM); IC25 – Inhibition concentration 25% (36 mM);
IC50 – Inhibition concentration 50% (81 mM); RSV – Resveratrol.
overnight at room temperature. The solid Et3N·HCl was filtered off
and washed with THF (3 ¥ 5 ml). The resulting organic fractions
were combined and THF was removed under reduced pressure to
yield crude amides. Recrystallization from hexanes/chloroform
and drying under vacuum afforded the desired product.
N-(2-Iodophenyl) benzamide (9d)
Yellowish solid (6.55 g, 81%); mp 135–137 ◦C (lit.,13a 133–134 ◦C);
dH(400 MHz; CDCl3) 8.46 (d, J = 8.3 Hz, H-6, 1H), 8.30 (br s,
NH, 1H), 7.96–7.98 (m, H-9, H-13, 2H), 7.82 (dd, J = 7.9 Hz,
1.5 Hz, H-3, 1H), 7.51–7.61 (m, H-10, H-11, H-12, 3H), 7.41 (td,
J = 7.8 Hz, 1.5 Hz, H-5, 1H), 6.89 (td, J = 7.7 Hz, 1.5 Hz, H-4,
1H); dC(100 MHz; CDCl3) 165.4 (C-7), 138.9 (C-3), 138.4 (C-1),
134.6 (C-8), 132.3 (C-11), 129.5 (C-5), 129.0 (C-10, C-12), 127.3
(C-9, C-13), 126.2 (C-4), 121.9 (C-6), 90.3 (C-2).
N-(2-Iodophenyl)isobutyramide (9a)
Off-white solid (5.46 g, 75%); mp 110–111 ◦C (lit.,22a 117–118 ◦C);
dH(400 MHz; CDCl3) 8.23 (d, J = 8.0 Hz, H-6, 1H), 7.75 (d, J =
8.1 Hz, H-3, 1H), 7.51 (br s, NH, 1H), 7.32 (t, J = 7.6 Hz, H-4, 1H),
6.82 (t, J = 7.3 Hz, H-5, 1H), 2.59 (septet, J = 7.0 Hz, H-8, CH,
1H), 1.30 (d, J = 6.8 Hz, H-9, H-10, 2 ¥ CH3, 6H); dC(100 MHz;
CDCl3) 175.3 (C-7), 138.8 (C-3), 138.2 (C-1), 129.4 (C-4), 125.9
(C-5), 122.0 (C-6), 90.2 (C-2), 37.1 (C-8, CH), 19.7 (C-9, C-10,
CH3).
N-(2-Iodophenyl)-1-naphthamide (9e)
To a stirred, cooled (0–5 ◦C) solution of 2-iodoaniline (1.06 g,
4.82 mmol) and Et3N (3.20 ml, 22.96 mmol) in ethyl acetate (50 ml)
was slowly added 1-naphthoyl chloride (0.70 ml, 4.66 mmol). The
ice bath was removed and the mixture was stirred vigorously
overnight at room temperature. The resulting suspension was
filtered and the solid was washed with ether (3 ¥ 15 ml) and
NaHCO3 aqueous saturated solution (3 ¥ 15 ml) to yield the
N-(2-Iodophenyl)butyramide (9b)
◦
Off-white solid (2.00 g, 69%); mp 81–83 C (lit.,22a 83–84 ◦C);
dH(400 MHz; CDCl3) 8.22 (d, J = 7.8 Hz, H-6, 1H), 7.76 (dd, J =
8.0 Hz, 1.4 Hz, H-3, 1H), 7.43 (br s, NH, 1H), 7.33 (td, J = 8.0 Hz,
1.4 Hz, H-4, 1H), 6.82 (t, J = 7.8 Hz, H-5, 1H), 2.40 (d, J = 7.6 Hz,
H-8, CH2, 2H), 1.79 (sextet, J = 7.8 Hz, H-9, CH2, 2H), 1.03 (t,
J = 7.3 Hz, H-10, CH3, 3H); dC(100 MHz; CDCl3) 171.3 (C-7),
◦
title compound as a yellow solid (757 mg, 42%); mp 158–160 C
(lit.,22c 160–161 ◦C); dH(400 MHz; CDCl3) 8.48–8.52 (m, H-6, H-
7¢, 2H), 8.08 (br s, NH, 1H), 8.00 (d, J = 8.3 Hz, H-4¢, 1H), 7.91
(d, J = 7.3 Hz, H-9¢, 1H), 7.86 (d, J = 7.1 Hz, H-6¢, 1H), 7.83 (dd,
5654 | Org. Biomol. Chem., 2010, 8, 5646–5660
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J = 8.1 Hz, 1.5 Hz, H-3, 1H), 7.52–7.62 (m, H-5¢, H-8¢, H-10¢, 3H),
7.44 (t, J = 7.7 Hz, H-5, 1H), 6.92 (td, J = 7.7 Hz, 1.4 Hz, H-4,
1H); dC(100 MHz; CDCl3) 167.4 (C-7), 138.9 (C-3), 138.5 (C-1),
133.9 (C-2¢/C-3¢), 133.8 (C-2¢/C-3¢), 131.5 (C-4¢), 130.2 (C-1¢),
129.3 (C-5), 128.4 (C-9¢), 127.4 (C¢5¢), 126.7 (C-10¢), 126.3 (C-4),
125.4 (C-7¢), 125.3 (C-6¢), 124.8(C¢8¢), 122.2 (C-6), 90.4 (C-2).
J = 17.8 Hz, 11.4 Hz, H-7, 1H), 6.93 (t, J = 7.3 Hz, H-4, 1H),
6.87 (d, J = 8.2 Hz, H-6, 1H), 5.73 (dd, J = 17.8 Hz, 1.4 Hz, H-
8b, 1H), 5.25 (dd, J = 9.1 Hz, 1.4 Hz, H-8a, 1H), 3.84 (s, OCH3,
3H); dC(100 MHz; CDCl3) 156.9 (C-1), 131.9 (C-7), 129.0 (C-5),
126.9 (C-2), 126.7 (C-3), 120.8 (C-4), 114.6 (C-8), 111.0 (C-6), 55.6
(OCH3).
N-(2-Iodophenyl) furan-2-carboxamide (9f)
1-Methoxy-3-vinylbenzene (10d)
Yellowish solid (5.49 g, 69%); mp 80–81 ◦C; nmax(NaCl)/cm-1
3364, 1683, 1582, 1526, 1430, 1304, 1162, 1010 and 750; lmax
(MeOH)/nm: 257, 231; dH(400 MHz; CDCl3) 8.52 (br s, NH,
1H), 8.39 (dd, J = 8.7 Hz, 1.4 Hz, H-6, 1H), 7.80 (dd, J = 7.8 Hz,
1.4 Hz, H-3, 1H), 7.56 (d, J = 1.4 Hz, H-5¢, 1H), 7.36 (td, J =
8.7 Hz, 1.4 Hz, H-5, 1H), 7.26 (d, J = 3.7 Hz, H-3¢, 1H), 6.85
(td, J = 7.8 Hz, 1.4 Hz, H-4, 1H), 6.57 (dd, J = 3.6 Hz, 1.8 Hz,
H-4¢, 1H); dC(100 MHz; CDCl3) 156.1(C-7), 147.7 (C-2¢), 144.8
(C-5¢), 139.0 (C-3), 138.0 (C-1), 129.4 (C-5), 126.1 (C-4), 121.7 (C-
6), 115.8 (C-3¢), 112.8 (C-4¢), 89.9 (C-2); HRMS (+ESI) [M+H]+:
313.9671, C11H9INO2 requires 313.9672.
Colourless oil (2.95 g, 60%); dH(400 MHz; CDCl3) 7.26 (t, J =
8.0 Hz, H-5, 1H), 7.03 (t, J = 7.8 Hz, H-4, 1H), 6.98 (s, H-2, 1H),
6.83 (dd, J = 8.2 Hz, 2.8 Hz, H-6, 1H), 6.71 (dd, J = 17.8 Hz,
11.0 Hz, H-7, 1H), 5.77 (d, J = 17.8 Hz, H-8b, 1H), 5.27 (d, J =
11.0 Hz, H-8a, 1H), 3.83 (s, OCH3, 3H); dC(100 MHz; CDCl3)
159.9 (C-1), 139.1 (C-3), 136.9 (C-7), 129.6 (C-5), 119.1 (C-4),
114.2 (C-8, CH2), 113.5 (C-6), 111.6 (C-2), 55.3 (OCH3).
1,3-Dimethoxy-5-vinylbenzene (10e)
Colourless oil (2.68 g, 54%); dH(400 MHz; CDCl3) 6.66 (dd, J =
17.5 Hz, 10.7 Hz, H-2, 1H), 6.59 (d, J = 2.2 Hz, H-4, H-6, 2H),
6.41 (t, J = 2.3 Hz, H-7, 1H), 5.75 (dd, J = 17.6 Hz, 0.76 Hz,
H-8b 1H), 5.26 (dd, J = 10.9 Hz, 0.72 Hz, H-8a, 1H), 3.80 (s, 2 ¥
OCH3, 6H); dC(100 MHz; CDCl3) 160.8 (C-1, C-3), 139.5 (C-5),
136.8 (C-7), 114.2 (C-8, CH2), 104.2 (C-4, C-6), 99.9 (C-2), 55.1
(2 ¥ OCH3).
N-(2-Iodophenyl)acetamide (9g)
To a stirred, cooled (0–5 ◦C) solution of 2-iodoaniline (2.53 g,
11.57 mmol) in dry DMF (20 ml), sodium hydride (0.93 g,
23.14 mmol) and acetic anhydride (5.40 ml, 61.75 mmol) were
added into the reaction flask. Then the ice bath was removed and
the mixture was allowed to stir overnight at room temperature.
Saturated ammonium chloride was added to the reaction mixture
followed by extraction with ethyl acetate. The combined ethyl
acetate extracts were then washed with distilled water to remove
DMF. The solution was then filtered and dried over anhydrous
sodium sulfate. The crude product, obtained after evaporation
under reduced pressure, was purified by column chromatography
to give the purified product as yellowish solid (1.82 g, 60%); mp
103–105 ◦C (lit.,22a 111–112 ◦C); dH(400 MHz; CDCl3) 8.17 (d, J =
7.6 Hz, H-6, 1H), 7.75 (d, J = 7.8 Hz, H-3, 1H), 7.40 (br s, NH,
1H), 7.32 (t, J = 7.3 Hz, H-4, 1H), 6.82 (t, J = 7.4 Hz, H-5, 1H), 2.22
(s, CH3, 3H); dC(100 MHz; CDCl3) 168.1 (C-7), 138.8 (C-3), 138.2
(C-1), 129.2 (C-4), 126.0 (C-5), 122.1 (C-6), 90.0 (C-2), 24.8 (CH3).
4-Vinylbiphenyl (12)
◦
White solid (0.54 g, 55%); mp 115–117 C (lit.,22b 118–120 ◦C);
dH(400 MHz; CDCl3) 7.60 (d, J = 6.8 Hz, H-2, H-6, 2H), 7.57 (d,
J = 8.2 Hz, H-2¢, H-6¢, 2H), 7.49 (d, J = 8.7 Hz, H-3¢, H-5¢, 2H),
7.44 (t, J = 7.5 Hz, H-3, H-5, 2H), 7.34 (t, J = 7.3 Hz, H-4¢, 1H),
6.76 (dd, J = 17.8 Hz, 11.0 Hz, H-7, 1H), 5.80 (d, J = 17.8 Hz,
H-8b, 1H), 5.28 (d, J = 11.0 Hz, H-8a, 1H); dC(100 MHz; CDCl3)
140.9 (C-1¢), 140.7 (C-1), 136.7 (C-4), 136.5 (C-7), 128.9 (C-3¢,
C-5¢), 127.5 (C-4¢), 127.4 (C-2¢, C-6¢), 127.1 (C-2, C-6), 126.8 (C-3,
C-5), 114.0 (C-8, CH2).
General procedure for the preparation of stilbenes 11a–f, 13a–c,
and 15a–e
General procedure for the preparation of styrenes 10c–e and 12
In a dry, two necked flask, the desired N-(2-iodophenyl)acylamide
9a–g (1 equiv) was dissolved in dry DMF (20–25 ml) and stirred
under nitrogen. The solution was heated at 120 C and refluxed
To a suspension of methyltriphenylphosphonium iodide (1 equiv)
in dry THF (25 ml), potassium tert-butoxide (1 equiv) was added
in one portion. The mixture was stirred for 1 h under nitrogen at
-70 to -80 ◦C. The appropriate aldehyde (1 equiv) was added to the
solution. The ice bath was removed and the mixture was allowed
to warm to room temperature. After consumption of starting
material and product formation, the reaction was quenched with
saturated ammonium chloride solution. The mixture was extracted
with ethyl acetate (3 ¥ 30 ml) and washed with distilled water (3 ¥
30 ml). The resulting organic extracts were combined and solvent
was removed under reduced pressure to yield crude product. Purifi-
cation by column chromatography afforded the desired product.
◦
for a few minutes. Palladium(II) acetate (0.01 equiv) was added,
followed by triethylamine (4–5 equiv). The desired styrene 10a–e
or 12 (1.1–1.6 equiv) was added to the reaction flask. The mixture
was refluxed under nitrogen until consumption of 9a–g (monitored
by TLC) was complete. The reaction mixture was quenched with
saturated ammonium chloride and extracted with ethyl acetate
and washed with distilled water (3 ¥ 30 ml). The resulting organic
fractions were combined, dried over anhydrous sodium sulfate
and solvent was removed under reduced pressure to yield crude
product. Purification by column chromatography (hexane–ethyl
acetate, 8 : 2 for 11a–f, 9 : 1 for 13a–c, 6 : 4 for 15a–e) afforded the
desired products. (Note: 10a (CAS No.: 6380-23-0) and 10b (CAS
No.: 637-69-4) were purchased from Sigma–Aldrich and Merck
respectively, and were used without further purification.)
1-Methoxy-2-vinylbenzene (10c)
Colourless oil (2.83 g, 57%); dH(400 MHz; CDCl3) 7.46 (dd, J =
7.8 Hz, 1.8 Hz, H-3, 1H), 7.23 (t, J = 7.8 Hz, H-5, 1H), 7.04 (dd,
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(E)-N-(2-(3,4-Dimethoxystyryl)phenyl)isobutyramide (11a)
(MeOH)/nm: 283; dH(400 MHz; CDCl3) 7.86 (d, J = 8.2 Hz, H-6¢,
1H), 7.49 (d, J = 7.8 Hz, H-3, 1H), 7.43 (d, J = 9.2 Hz, H-2, H-6,
2H), 7.26 (td, J = 7.8 Hz, 1.4 Hz, H-5¢, 1H), 7.17 (br s, NH, 1H),
7.15 (t, J = 7.3 Hz, H-4¢, 1H), 6.99 (d, J = 16.4 Hz, H-8, 1H), 6.94
(d, J = 16.1 Hz, H-7, 1H), 6.92 (d, J = 8.7 Hz, H-3, H-5, 2H), 3.84 (s,
OCH3, 3H), 2.29 (tt, J = 11.9 Hz, 3.6 Hz, H-8¢, CH, 1H), 1.23–2.02
(m, H-9¢(x2), H-10¢(x2), H- 11¢, CH2, 10H); dC(100 MHz; CDCl3)
174.4 (C-7¢), 159.8 (C-4), 134.7 (C-11¢), 132.3 (C-7), 130.5 (C-2¢),
129.9 (C-1), 128.1 (C-5¢), 128.0 (C-2, C-6), 126.9 (C-3¢), 125.3 (C-
4¢), 123.9 (C-6¢), 121.3 (C-8), 114.3 (C-3, C-5), 55.5 (OCH3), 46.4
(CH, C-8¢), 29.9 (CH2, C-9¢(x2)), 25.8 (CH2, C-10¢(x2), C-11¢);
HRMS (+ESI) [M+H]+: 336.1955, C22H26NO2 requires 336.1958.
Off-white solid (0.45 g, 27%); mp 166–168 ◦C; nmax/cm-1
(NaCl): 3274, 1652, 1516, 1269, 1141, 1025, 961, 801, 752; lmax
1
(MeOH)/nm: 210, 236, 325; H NMR (CDCl3, 400 MHz): 7.74
(d, J = 7.8 Hz, H-6¢, 1H), 7.49 (d, J = 7.3 Hz, H-3¢, 1H), 7.31
(br s, NH, 1H), 7.24 (t, J = 7.8 Hz, H-5¢, 1H), 7.15 (t, J = 7.6 Hz,
H-4¢, 1H), 7.01 (d, J = 7.8 Hz, H-6, 1H), 7.00 (s, H-2, 1H), 6.97
(d, J = 16.4 Hz, H-8, 1H), 6.90 (d, J = 16.5 Hz, H-7, 1H), 6.85
(d, J = 8.7 Hz, H-5, 1H), 3.89 (s, 2 ¥ OCH3, 6H), 2.54–2.61 (m,
H-8¢, 1H), 1.27 (d, J = 6.9 Hz, H-9¢, 6H); dC(100 MHz; CDCl3)
175.6 (C-7¢), 149.3 (C-4), 149.2 (C-3), 134.6 (C-1¢), 132.1 (C-7),
130.9 (C-2¢), 130.2 (C-1), 128.1 (C-5¢), 126.8 (C-3¢), 125.7 (C-4¢),
124.5 (C-6¢), 121.7 (C-8), 120.1 (C-6), 111.3 (C-5), 108.9 (C-2),
56.1 (OCH3), 55.9 (OCH3), 36.5 (CH, C-8¢), 19.9 (2 ¥ CH3, C-9¢).;
HRMS (+ESI) [M+H]+: 326.1759, C20H24NO3 requires 326.1756.
(E)-N-(2-(3,4-Dimethoxystyryl)phenyl)benzamide (11e)
White solid (0.10 g, 18%); mp 169–171 ◦C; nmax/cm-1 (NaCl):
3273, 3012, 1646, 1572, 1509, 1265, 749; lmax (MeOH)/nm: 231,
324; dH(400 MHz; CDCl3) 8.03 (br s, NH, 1H), 7.87 (d, J = 7.8 Hz,
H-6¢, H-9¢, H-13¢, 3H), 7.51– 7.55 (m, H-3¢, H-11¢, 2H), 7.44 (t,
J = 7.3 Hz, H-10¢, H-12¢, 2H), 7.28 (t, J = 7.8 Hz, H-5¢, 1H), 7.20
(t, J = 7.5 Hz, H-4¢, 1H), 7.04 (d, J = 16.0 Hz, H-8, 1H), 6.98 (d,
J = 9.2 Hz, H-6, 1H), 6.97 (s, H-2, 1H), 6.93 (d, J = 16.0 Hz, H-7,
1H), 6.82 (d, J = 8.2 Hz, H-5, 1H), 3.86 (s, OCH3, 3H), 3.83 (s,
OCH3, 3H); dC(100 MHz; CDCl3) 166.0 (C-7¢), 149.4 (C-4), 149.2
(C-3), 134.8 (C-8¢), 134.7 (C-1¢), 132.5 (C-7), 132.0 (C-11¢), 131.1
(C-2¢), 130.2 (C-1), 128.9 (C-10¢, C-12¢), 128.2 (C-5¢), 127.3 (C-9¢,
C-13¢), 127.0 (C-3¢), 125.9 (C-4¢), 124.5 (C-6¢), 121.7 (C-8), 120.1
(C-6), 111.3 (C-5), 109.1 (C-2), 56.0 (OCH3), 55.9 (OCH3); HRMS
(+ESI) [M+H]+: 360.1602, C23H22NO3 requires 360.1594.
(E)-N-(2-(3,4-Dimethoxystyryl)phenyl)butyramide (11b)
Off-white solid (0.05 g, 15%); mp 139–140 ◦C; nmax/cm-1 (NaCl):
3280, 2963, 1510, 1267, 1025, 759; lmax (MeOH)/nm: 206, 323;
dH(400 MHz; CDCl3) 7.63 (d, J = 7.8 Hz, H-6¢, 1H), 7.56 (br s,
NH, 1H), 7.46 (d, J = 7.8 Hz, H-3¢, 1H), 7.18 (t, J = 7.0 Hz, H-
5¢, 1H), 7.11 (t, J = 7.3 Hz, H-4¢, 1H), 6.98 (d, J = 7.8 Hz, H-6,
1H), 6.97 (s, H-2, 1H), 6.95 (d, J = 15.6 Hz, H-8, 1H), 6.85 (d,
J = 16.2 Hz, H-7, 1H), 6.81 (d, J = 8.2 Hz, H-5, 1H), 3.86 (s,
OCH3, 3H), 3.85 (s, OCH3, 3H), 2.31 (t, J = 7.3 Hz, H-8¢, CH2,
2H), 1.69–1.75 (m, H-9¢, CH2, 2H), 0.97 (t, J = 7.3 Hz, H-10¢,
CH3, 3H); dC(100 MHz; CDCl3) 172.0 (C7¢), 149.2 (C-4), 149.1
(C-3), 134.6 (C-1¢), 131.6 (C-7), 131.1 (C-2¢), 130.3 (C-1), 127.9
(C-5¢), 126.5 (C-3¢), 125.7 (C-4¢), 124.9 (C-6¢), 121.8 (C-8), 120.1
(C-6), 111.3 (C-5), 109.1 (C-2), 56.0 (OCH3), 55.9 (OCH3), 39.3
(CH2, C-8¢), 19.4 (CH2, C-9¢), 13.9 (CH3, C-10¢).; HRMS (+ESI)
[M+H]+: 326.1756, C20H24NO3 requires 326.1751.
(E)-N-(2-(3,4-Dimethoxystyryl)phenyl)-1-naphthamide (11f)
White solid (0.15 g, 27%); mp 175–177 ◦C; nmax/cm-1 (NaCl):
3201, 1640, 1515, 1262, 1140, 1026, 730; lmax (MeOH)/nm: 287,
320; dH(400 MHz; CDCl3) 8.42 (dd, J = 5.9, 3.2 Hz, H-5¢¢, 1H),
8.03 (d, J = 7.8 Hz, H-6¢, 1H), 7.95 (d, J = 8.2 Hz, H-7¢¢, 1H), 7.89
(dd, J = 5.4, 3.2 Hz, H-9¢¢, 1H), 7.76 (d, J = 8.4 Hz, H-6¢¢, 1H),
7.78 (br s, NH, 1H), 7.58 (d, J = 8.2 Hz, H-3¢), 7.52–7.56 (m, H-4¢¢,
H-10¢¢, 2H), 7.47 (t, J = 7.6 Hz, H-8¢, 1H), 7.36 (t, J = 7.1 Hz, H-5¢,
1H), 7.25 (t, J = 7.3 Hz, H-4¢, 1H), 7.06 (d, J = 16.5 Hz, H-8, 1H),
6.93–6.99 (m, H-2, H-6, H-7, 3H), 6.79 (d, J = 8.7 Hz, H-5, 1H),
3.86 (s, OCH3, 3H), 3.77 (s, OCH3, 3H); dC(100 MHz; CDCl3)
168.0 (C-7¢), 149.3 (C-4), 149.1 (C-3), 134.6 (C-1¢), 134.4 (C-1¢¢),
133.9 (C-2¢¢), 132.6 (C-7), 131.23 (C-7¢¢), 131.17 (C-2¢), 130.3 (C-
3¢¢), 130.0 (C-1), 128.6 (C-9¢¢), 128.2 (C-5¢), 127.4 (C-4¢¢), 127.0
(C-3¢), 126.7 (C-10¢¢), 126.2 (C-4¢), 125.4 (C-5¢¢), 125.2 (C-6¢¢),
124.9 (C-8¢¢), 124.4 (C-6¢), 121.4 (C-8), 120.2 (C-6), 111.2 (C-5),
109.0 (C-2), 56.0(OCH3), 55.9 (OCH3); HRMS (+ESI) [M+H]+:
410.1750, C27H24NO3 requires 410.1756.
(E)-N-(2-(3,4-Dimethoxystyryl)phenyl)cyclohexane carboxamide
(11c)
White solid (0.07 g, 31%); mp 204–206 ◦C; nmax/cm-1 (NaCl): 2930,
2853, 1682, 1515, 1449, 1269, 1137, 1026, 757; lmax (MeOH)/nm:
217, 300; dH(400 MHz; CDCl3) 7.77 (d, J = 8.2 Hz, H-6¢, 1H), 7.50
(d, J = 7.3 Hz, H-3¢, 1H), 7.25 (td, J = 8.0 Hz, 1.4 Hz, H-5¢, 1H),
7.21 (br s, NH, 1H), 7.16 (d, J = 7.6 Hz, H-4, 1H), 7.03 (d, J =
7.3 Hz, H-6, 1H), 7.02 (s, H-2, 1H), 6.97 (d, J = 16.5 Hz, H-8, 1H),
6.91 (d, J = 16.5 Hz, H-7, 1H), 6.87 (d, J = 9.2 Hz, H-5, 1H), 3.91
(s, OCH3, 3H), 3.90 (s, OCH3, 3H), 2.31 (tt, J = 11.7 Hz, 3.4 Hz,
H-8¢, CH, 1H), 1.22–2.01 (m, H-9¢(x2), H-10¢(x2), H-11¢,CH2,
10H); dC(100 MHz; CDCl3) 174.5 (C-7¢), 149.3 (C-4), 149.2 (C-3),
134.6 (C-1¢), 132.2 (C-7), 130.8 (C2¢), 130.2 (C-1), 128.1 (C-5¢),
126.8 (C-3¢), 125.6 (C-4¢), 124.4 (C-6¢), 121.7 (C-8), 120.1 (C-6),
111.3 (C-5), 108.9 (C-2), 56.1 (OCH3), 55.9 (OCH3), 46.3 (CH, C-
8¢), 29.9 (CH2, C-9¢(x2)), 25.8 (C-10¢(x2), C-11¢); HRMS (+ESI)
[M+H]+: 366.2069, C23H28NO3 requires 366.2069.
(E)-N-(2-(2-(Biphenyl-4-yl)vinyl) phenyl)benzamide (13a)
White solid (0.06 g, 31%); mp 167–169 ◦C; nmax/cm-1 (NaCl): 3271,
1648, 1517, 1487, 1302, 764; lmax (MeOH)/nm: 319; dH(400 MHz;
CDCl3) 8.05 (br s, NH, 1H), 7.91 (d, J = 7.3 Hz, H-6¢, H-9¢,
H-13¢, 3H), 7.43–7.62 (m, H-2, H-2¢¢, H-3, H-3¢¢, H-6, H-6¢¢, H-
5, H-5¢¢, H-4¢¢, H-10¢, H-11¢, H-12¢, 12H), 7.31–7.36 (m, H-3¢,
H-5¢, 2H), 7.22–7.26 (m, H-8, H-4¢, 2H), 7.06 (d, J = 16.5 Hz,
H-7, 1H); dC(100 MHz; CDCl3) 166.0 (C-7¢), 140.9 (C-4), 140.6
(C-1¢¢), 136.1 (C-4), 134.8 (C-1¢), 134.7 (C-8¢), 132.2 (C-7), 132.1
(E)-N-(2-(4-Methoxystyryl)phenyl)cyclohexanecarboxamide (11d)
11d crystallized easily during work up. The white solid was filtered
off via a Kirsch funnel and washed with a small amount of hexane,
followed by diethyl ether. Yield 0.47 g (30%). mp 204–205 ◦C;
n
max/cm-1 (NaCl): 3271, 2930, 2848, 1648, 1513, 1250, 666; lmax
5656 | Org. Biomol. Chem., 2010, 8, 5646–5660
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(C-11¢), 131.0 (C-2¢), 129.0 (C-3¢¢, C-5¢¢, C-10¢, C-12¢), 128.5 (C-3¢),
127.6 (C-4¢¢), 127.5 (C-2¢¢, C-6¢¢), 127.3 (C-9¢, C-13¢), 127.2 (C-2,
C-6), 127.1 (C-12), 127.0 (C-3, C-5), 126.0 (C-4¢), 124.7 (C-6¢),
123.5 (C-8); HRMS (+ESI) [M+H]+: 376.1691, C27H22NO requires
376.1701.
(E)-N-(2-(2-Methoxystyryl)phenyl)furan-2-carboxamide (15a)
White solid (0.75 g, 49%); mp 128–129 ◦C; nmax/cm-1 (NaCl):
3285, 1671, 1585, 1304, 1247, 751; lmax (MeOH)/nm: 262, 321;
dH(400 MHz; CDCl3) 8.25 (br s, NH, 1H), 8.04 (d, J = 8.2 Hz,
H-6¢, 1H), 7.60 (dd, J = 7.8 Hz, 0.92 Hz, H-3¢, 1H), 7.56 (dd, J =
7.6 Hz, 1.4 Hz, H-6, 1H), 7.49 (d, J = 0.92 Hz, H-5¢¢, 1H), 7.40 (d,
J = 16.5 Hz, H-7, 1H), 7.29 (d, J = 16.8 Hz, H-8, 1H), 7.28–7.33
(m, H-4, H-5¢, H-3¢¢, 3H), 7.20 (t, J = 7.1 Hz, H-4¢¢, 1H), 6.98 (t,
J = 7.6 Hz, H-5, 1H), 6.91 (d, J = 8.2 Hz, H-3, 1H), 6.55 (dd,
J = 3.7 Hz, 1.8 Hz, H-4¢, 1H), 3.85 (s, OCH3, 3H); dC(100 MHz;
CDCl3) 157.3 (C-2), 156.4 (C-7¢), 148.0 (C-2¢¢), 144.5 (C-5¢¢), 134.1
(C-1¢), 130.7 (C-2¢), 129.3 (C-4), 128.3 (C-8), 128.2 (C-7), 127.3
(C-6), 127.2 (C-3¢), 126.2 (C-1), 125.6 (C-4¢), 123.7 (C-5¢), 123.5
(C- 6¢), 120.9 (C-5), 115.4 (C-3¢¢), 112.7 (C-4¢¢), 111.1 (C-3), 55.5
(OCH3); HRMS (+ESI) [M+H]+: 320.1285, C20H18NO3 requires
320.1281.
(E)-N-(2-(2-(Biphenyl-4-yl)vinyl)phenyl)furan-2-carboxamide
(13b)
◦
Yellowish solid (0.04 g, 9%); mp 142–143 C; nmax/cm-1 (NaCl):
3283, 1671, 1585, 1521, 1487, 1452, 1304, 762; lmax (MeOH)/nm:
204, 267, 323; dH(400 MHz; CDCl3) 8.19 (br s, NH, 1H), 8.04 (d,
J = 7.8 Hz, H-6¢, 1H), 7.58–7.64 (m, H-2, H-2¢¢, H-3, H-4¢¢, H-5,
H-6, H-6¢¢, 7H), 7.52 (t, J = 0.92 Hz, H-3¢¢¢, 1H), 7.44–7.48 (m,
H-3¢¢, H-5¢¢, 2H), 7.32–7.38 (m, H-3¢, H-5¢, 2H), 7.21–7.30 (m, H-
8, H-4¢, H-5¢¢¢, 3H), 7.10 (d, J = 16.5 Hz, H-7, 1H); dC(100 MHz;
CDCl3) 156.4 (C-7¢), 148.0 (C-2¢¢¢), 144.5 (C- 5¢¢¢), 141.0 (C-1),
140.6 (C-1¢¢), 136.1 (C-4), 134.2 (C-1¢), 132.5 (C-7), 130.2 (C-2¢),
129.0 (C-3¢¢, C-5¢¢), 128.6 (C-3¢), 127.6 (C-4¢¢), 127.5 (C-2¢¢, C-6¢¢),
127.3 (C-2, C-6, C-5¢), 127.0 (C-3, C-5), 125.7 (C-4¢), 123.7 (C-6¢),
123.3 (C-8), 115.6 (C-3¢¢¢), 112.7 (C-4¢¢¢); HRMS (+ESI) [M+Na]+:
388.1324, C25H19NNaO2 requires 388.1308. X-ray crystallographic
details for 13b have been reported.23
(E)-N-(2-(3-Methoxystyryl)phenyl)furan-2-carboxamide (15b)
White solid (0.15 g, 33%); mp 96–97 ◦C; nmax/cm-1 (NaCl): 3285,
1669, 1585, 1521, 1304, 1163, 755; lmax (MeOH)/nm: 210, 264, 300;
dH(400 MHz; CDCl3) 8.17 (br s, NH, 1H), 8.02 (d, J = 8.2 Hz,
H-6¢, 1H), 7.55 (d, J = 7.8 Hz, H-3¢, 1H), 7.50 (d, J = 0.92 Hz,
H-5¢¢, 1H), 7.33 (t, J = 7.2 Hz, H-5¢, 1H), 7.29 (t, J = 8.0 Hz,
H-5, 1H), 7.26 (d, J = 3.2 Hz, H-3¢, 1H), 7.22 (d, J = 16.0 Hz,
H-8, 1H), 7.21 (t, J = 7.6 Hz, H-4¢¢, 1H), 7.12 (d, J = 7.8 Hz, H-6,
1H), 7.04 (s, H-2, 1H), 7.02 (d, J = 16.5 Hz, H-7, 1H), 6.85 (dd,
J = 8.5 Hz, 2.3 Hz, H-4, 1H), 6.56 (dd, J = 3.7 Hz, 1.8 Hz, H-4¢,
1H), 3.83 (s, OCH3, 3H); dC(100 MHz; CDCl3) 160.0 (C-3), 156.4
(C-7¢), 147.9 (C-2¢¢), 144.5 (C-5¢¢), 138.5 (C-1), 134.2 (C-1¢), 132.9
(C-7), 130.1 (C-2¢), 129.9 (C-5), 128.6 (C-5¢), 127.3 (C-3¢), 125.6
(C-4¢), 123.6 (C- 6¢, C-8), 119.4 (C-6), 115.6 (C-3¢¢), 113.7 (C-4),
112.7 (C-4¢¢), 112.3 (C-2), 55.4 (OCH3); HRMS (+ESI) [M+H]+:
320.1281, C20H18NO3 requires 320.1281.
(E)-N-(2-(2-(Biphenyl-4-yl)vinyl)phenyl)acetamide (13c)
White solid (0.04 g, 7%); mp 197–199 ◦C; nmax/cm-1 (NaCl): 3271,
3030, 1668, 1522, 1488, 1450, 1298, 754, 697; lmax (MeOH)/nm:
245, 296; dH(400 MHz; CDCl3) 7.75 (d, J = 7.8 Hz, H-6¢, 1H),
7.54–7.63 (m, H-2¢¢, H-2, H-4¢¢, H-6, H-6¢¢, NH, 6H), 7.44–7.47
(m, H-3¢¢, H-5¢¢, 2H), 7.25–7.38 (m, H-3, H-5, H-3¢, H-5¢, 4H),
7.15–7.20 (m, H-8, H-4¢, 2H), 7.01 (d, J = 16.5 Hz, H-7, 1H),
2.21 (s, CH3, 3H); dC(100 MHz; CDCl3) 168.8 (C-7¢), 140.9 (C-1),
140.6 (C-1¢¢), 136.1 (C-4), 134.7 (C-1¢), 132.0 (C-7), 130.6 (C-2¢),
129.0 (C-3¢¢, C-5¢¢), 128.5 (C-3¢), 127.6 (C-4¢¢), 127.5 (C-2¢¢, C-6¢¢),
127.2 (C-2,C-6), 127.0 (C-3, C-5), 126.9 (C-5¢), 125.8 (C-4¢), 124.6
(C-6¢), 123.6 (C-8), 24.6 (CH3); HRMS (+ESI) [M+H]+: 314.1540,
C22H20NO requires 314.1539. For full crystallographic data refer
to CCDC no. 757184.
(E)-N-(2-(3,4-Dimethoxystyryl)phenyl)furan-2-carboxamide (15c)
White solid (0.10 g, 16%); mp 142–144 ◦C; nmax/cm-1 (NaCl):
3239, 1651, 1575, 1514, 1456, 1265, 1157, 1137, 1027, 751; lmax
(MeOH)/nm: 210, 252, 326; dH(400 MHz; CDCl3) 8.19 (br s, NH,
1H), 8.00 (d, J = 8.2 Hz, H-6¢, 1H), 7.52 (d, J = 7.8 Hz, H-3¢, 1H),
7.47 (dd, J = 1.8 Hz, 0.92 Hz, H-5¢¢, 1H), 7.29 (t, J = 7.8 Hz, H-5¢,
1H), 7.23 (d, J = 2.8 Hz, H-3¢¢, 1H), 7.18 (t, J = 7.8 Hz, H-4¢, 1H),
7.07 (d, J = 16.5 Hz, H-8, 1H), 7.05 (d, J = 8.9 Hz, H-6, 1H), 7.03
(s, H-2, 1H), 6.96 (d, J = 16.5 Hz, H-7, 1H), 6.85 (d, J = 8.2 Hz,
2.3 Hz, H-5, 1H), 6.54 (dd, J = 3.4 Hz, 1.8 Hz, H-4¢¢, 1H), 3.89
(s, OCH3, 3H), 3.88 (s, OCH3, 3H); dC(100 MHz; CDCl3) 156.4
(C-7¢), 149.4 (C-4), 149.2 (C-3), 148.0 (C-2¢¢), 144.5 (C-5¢¢), 134.0
(C-1¢), 132.7 (C-7), 130.4 (C-2¢), 130.2 (C-1), 128.2 (C-5¢), 127.1
(C-3¢), 125.6 (C-4¢), 123.7 (C-6¢), 121.4 (C-8), 120.1 (C-6), 115.4
(C-3¢¢), 112.7 (C-4¢¢), 111.4 (C-5), 109.3 (C-2), 56.1 (OCH3), 56.0
(OCH3); HRMS (+ESI) [M+H]+: 350.1411, C21H20NO4 requires
350.1392.
N-Phenylbenzamide (14a)
Trace amount was isolated. Mp 163–164 ◦C; dH(400 MHz; CDCl3)
7.89 (br s, NH, 1H), 7.86 (d, J = 7.3 Hz, H-9, H-13, 2H), 7.64 (d,
J = 8.2 Hz, H-2, H-6, 2H), 7.54 (t, J = 7.3 Hz, H-11, 1H), 7.47
(t, J = 7.5 Hz, H-10, H-12, 2H), 7.36 (t, J = 7.8 Hz, H-3, H-5,
2H), 7.15 (t, J = 7.6 Hz, H-4, 1H); dC(100 MHz; CDCl3) 165.9 (C-
7), 138.0 (C-1), 135.1 (C-8), 131.9 (C-11), 129.2 (C-3, C-5), 128.9
(C-10, C-12), 127.1 (C-9, C-13), 124.7 (C-4), 120.3 (C-2, C-6).
N-Phenylfuran-2-carboxamide (14b)
Trace amount was isolated. dH(400 MHz; CDCl3) 8.14 (br s, NH,
1H), 7.65 (d, J = 7.8 Hz, H-2, H-6, 2H), 7.49 (d, J = 1.8 Hz, H-5¢,
1H), 7.35 (t, J = 8.0 Hz, H-3, H-5, 2H), 7.22 (dd, J = 3.6 Hz,
0.92 Hz, H-3¢, 1H), 7.13 (t, J = 7.6 Hz, H-4, 1H), 6.54 (dd, J =
3.6 Hz, 1.8 Hz, H-4¢, 1H); dC(100 MHz; CDCl3) 156.2 (C-7), 147.9
(C-8), 144.3 (C-5¢), 137.5 (C-1), 129.2 (C-3, C-5), 124.6 (C-4), 120.0
(C-2, C-6), 115.4 (C-3¢), 112.7 (C-4¢).
(E)-N-(2-(4-Methoxystyryl)phenyl)furan-2-carboxamide (15d)
White solid (0.19 g, 36%); mp 120–121 ◦C; nmax/cm-1 (NaCl):
3276, 1669, 1584, 1509, 1251, 755; lmax (MeOH)/nm: 271, 323;
dH(400 MHz; CDCl3) 8.17 (br s, NH, 1H), 8.04 (d, J = 8.2 Hz,
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H-6¢, 1H), 7.54 (d, J = 7.8 Hz, H-3¢, 1H), 7.50 (d, J = 0.92 Hz,
H-5¢, 1H), 7.47 (t, J = 7.6 Hz, H-2, H-6, 2H), 7.31 (td, J = 7.3 Hz,
1.3 Hz, H-5¢, 1H), 7.26 (d, J = 3.7 Hz, H-3¢, 1H), 7.19 (t, J =
7.6 Hz, H-4¢, 1H), 7.09 (d, J = 16.5 Hz, H-8, 1H), 7.00 (d, J =
16.5 Hz, H-7, 1H), 6.92 (t, J = 7.6 Hz, H-3, H-5, 2H), 6.56 (dd,
J = 3.2 Hz, 1.8 Hz, H-4¢¢, 1H), 3.83 (s, OCH3, 3H); dC(100 MHz;
CDCl3) 159.8 (C-4), 156.3 (C-7¢), 148.0 (C-2¢¢), 144.5 (C-5¢¢), 134.0
(C-1¢), 132.7 (C-7), 130.4 (C-2¢), 129.9 (C-1), 128.2 (C- 5¢), 128.1
(C-2, C-6), 127.1 (C-3¢), 125.6 (C-4¢), 123.5 (C-6¢), 121.0 (C-8),
115.5 (C-3¢¢), 114.3 (C-3, C-5), 112.7 (C-4¢¢), 55.5 (OCH3); HRMS
(+ESI) [M+H]+: 320.1302, C20H18NO3 requires 320.1287.
dC(100 MHz; CDCl3) 160.0 (C-3), 155.9 (C-7¢), 147.9 (C-2¢), 146.3
(C-7), 144.2 (C-5¢¢), 141.0 (C-1), 134.9 (C-1¢), 131.9 (C-2¢), 130.4
(C-3¢), 129.9 (C-5), 129.0 (C-5¢), 124.4 (C-4¢), 121.2 (C-6¢), 119.5
(C-6), 117.9 (C-8, CH2), 114.9 (C-3¢¢), 113.9 (C-4), 112.7 (C-2),
112.4 (C-4¢¢), 55.3 (OCH3); HRMS (+ESI) [M+H]+: 320.1284,
C20H18NO3 requires 320.1281.
(E)-N-(2-(1-(3,4-Dimethoxyphenyl)vinyl)phenyl)furan-2-
carboxamide (16c)
Yield 0.02 g (4%); nmax/cm-1 (NaCl): 3388, 1681, 1584, 1513,
1450, 1311, 1257, 1138, 1025, 756; lmax (MeOH)/nm: 209, 263;
dH(400 MHz; CDCl3) 8.37 (d, J = 8.2 Hz, H-6¢, 1H), 8.15 (br s,
NH, 1H), 7.39 (t, J = 7.9 Hz, H-5¢, 1H), 7.27–7.30 (m, H-3¢, H-5¢¢,
2H), 7.16 (td, J = 7.6 Hz, 0.92 Hz, H-4¢, 1H), 7.03 (d, J = 3.6 Hz,
H-3¢¢, 1H), 6.94 (d, J = 1.8 Hz, H-2, 1H), 6.83 (dd, J = 8.5 Hz,
2.3 Hz, H-6, 1H), 6.76 (d, J = 8.2 Hz, H-5, 1H), 6.42 (dd, J =
3.2 Hz, 1.8 Hz, H-4¢¢, 1H), 5.81 (d, J = 0.92 Hz, H-8b, CH2, 1H),
5.31 (d, J = 0.92 Hz, H-8a, CH2, 1H), 3.83 (s, OCH3, 3H), 3.82 (s,
OCH3, 3H); dC(100 MHz; CDCl3) 155.9 (C-7¢), 149.6 (C-4), 149.2
(C-3), 147.9 (C-2¢), 146.0 (C-7), 144.1 (C-5¢¢), 135.0 (C-1¢), 132.2
(C-1), 132.1 (C-2¢), 130.4 (C-3¢), 128.9 (C-5¢), 124.4 (C-4¢), 121.2
(C-6¢), 120.0 (C-6), 116.0 (C-8, CH2), 114.9 (C-3¢), 112.4 (C-4¢),
111.1 (C-5), 109.8 (C-2), 56.0 (2 ¥ OCH3); HRMS (+ESI) [M+H]+:
350.1395, C21H20NO4 requires 350.1387.
(E)-N-(2-(3,5-Dimethoxystyryl)phenyl)furan-2-carboxamide (15e)
White solid (0.10 g, 17%); mp 109–110 ◦C; nmax/cm-1 (NaCl):
3282, 1670, 1590, 1520, 1455, 1303, 1204, 1152, 1065, 755; lmax
(MeOH)/nm: 239, 269, 308; dH(400 MHz; CDCl3) 8.16 (br s, NH,
1H), 8.04 (d, J = 7.8 Hz, H-6¢, 1H), 7.54 (dd, J = 7.8 Hz, 1.4 Hz,
H-3¢, 1H), 7.50 (d, J = 0.92 Hz, H-5¢¢, 1H), 7.33 (td, J = 7.8 Hz,
1.4 Hz, H-5¢, 1H), 7.26 (d, J = 3.2 Hz, H-3¢¢, 1H), 7.21 (d, J =
16.0 Hz, H-8, 1H), 7.20 (t, J = 7.5 Hz, H-4¢, 1H), 6.99 (d, J =
16.0 Hz, H-7, 1H), 6.66 (s, H-2, H-6, 2H), 6.56 (dd, J = 3.6 Hz,
1.8 Hz, H-4¢¢, 1H), 6.43 (t, J = 1.8 Hz, H-4, 1H), 3.81 (s, 2 ¥
OCH3, 6H); dC(100 MHz; CDCl3) 161.1 (C-3, C-5), 156.3 (C-7¢),
147.9 (C-2¢¢), 144.5 (C-5¢¢), 139.1 (C-1), 134.2 (C-1¢), 133.0 (C-7),
129.9 (C-2¢), 128.6 (C-5¢), 127.3 (C-3¢), 125.6 (C-4¢), 123.9 (C-8),
123.6 (C-6¢), 115.6 (C-3¢¢), 112.7 (C-4¢¢), 105.0 (C-2), 100.3 (C-4),
55.9 (2 ¥ OCH3); HRMS (+ESI) [M+H]+: 350.1412, C21H20NO4
requires 350.1392.
(E)-N-(2-(1-(4-Methoxyphenyl)vinyl)phenyl)furan-2-carboxamide
(16d)
Yield 0.05 g (9%); nmax/cm-1 (NaCl): 3389, 1682, 1607, 1584, 1526,
1509, 1449, 1309, 1252, 1180, 838, 755; lmax (MeOH)/nm: 205,
261; dH(400 MHz; CDCl3) 8.44 (d, J = 8.2 Hz, H-6¢, 1H), 8.22
(br s, NH, 1H), 7.39 (t, J = 8.0 Hz, H-5¢, 1H), 7.26–7.31 (m, H-2,
H-6, H-3¢, H-5¢¢, 4H), 7.16 (td, J = 7.6 Hz, 1.4 Hz, H-4¢, 1H), 7.04
(d, J = 4.1 Hz, H-3¢¢, 1H), 6.84 (d, J = 8.7 Hz, H-3, H-5, 2H), 6.42
(dd, J = 3.4 Hz, 1.8 Hz, H-4¢¢, 1H), 5.84 (d, J = 0.92 Hz, H-8b, CH2,
1H), 5.29 (d, J = 1.36 Hz, H-8a, CH2, 1H), 3.76 (s, OCH3, 3H);
dC(100 MHz; CDCl3) 160.0 (C-4), 155.9 (C-7¢), 147.9 (C-2¢¢), 145.6
(C-7), 144.2 (C-5¢¢), 135.0 (C-1¢), 132.1 (C-2¢), 131.8 (C-1), 130.4
(C-3¢), 128.8 (C-5¢), 128.2 (C-2, C-6), 124.3 (C-4¢), 120.9 (C-6¢),
115.7 (C-8, CH2), 114.8 (C-3¢), 114.1 (C-3, C-5), 112.4 (C-4¢), 55.4
(OCH3); HRMS (+ESI) [M+H]+: 320.1295, C20H18NO3 requires
320.1287.
(E)-N-(2-(1-(2-Methoxyphenyl)vinyl)phenyl)furan-2-carboxamide
(16a)
Yield 0.13 g (8%); nmax/cm-1 (NaCl): 3390, 1678, 1584, 1526, 1448,
1310, 1245, 754; lmax (MeOH)/nm: 236, 279; dH(400 MHz; CDCl3)
8.72 (br s, NH, 1H), 8.37 (d, J = 8.2 Hz, H-6¢, 1H), 7.42 (d, J =
0.92 Hz, H-5¢¢, 1H), 7.26–7.32 (m, H-4, H-6, H-5¢, 3H), 7.14–7.16
(m, H-3¢, H-3¢¢), 7.06 (t, J = 7.3 Hz, H-4¢¢, 1H), 6.96 (t, J = 7.6 Hz,
H-5, 1H), 6.84 (d, J = 8.2 Hz, H-3, 1H), 6.50 (dd, J = 3.4 Hz,
1.4 Hz, H-4¢, 1H), 5.76 (d, J = 1.8 Hz, H-8b, CH2, 1H), 5.47 (d,
J = 1.8 Hz, H-8a, CH2, 1H), 3.61 (s, OCH3, 3H); dC(100 MHz;
CDCl3) 156.9 (C-2), 156.1 (C-7¢), 148.4 (C-2¢¢), 144.2 (C-5¢¢), 144.0
(C-1¢), 134.5 (C-7), 133.5 (C-2¢), 130.9 (C-1), 130.1 (C-6), 129.5 (C-
4), 129.0 (C-3¢), 128.0 (C-5¢), 123.9 (C-4¢), 121.2 (C-6¢), 121.1 (C-8,
CH2), 120.9 (C-5), 114.8 (C-3¢¢), 112.5 (C-4¢¢), 111.3 (C-3), 55.5
(OCH3); HRMS (+ESI) [M+H]+: 320.1284, C20H18NO3 requires
320.1281.
N,N¢-(Biphenyl-2,2¢-diyl)difuran-2-carboxamide (17)
Yield 0.03 g (7%); mp 173–175 ◦C; nmax/cm-1 (NaCl): 3395,
1671, 1585, 1518, 1458, 1310, 754; lmax (MeOH)/nm: 211, 253;
dH(400 MHz; CDCl3) 8.49 (d, J = 8.2 Hz, H-6, H-6¢, 2H), 8.03
(br s, NH, NH¢, 2H), 7.47 (t, J = 7.8 Hz, H-5, H-5¢, 2H), 7.22–7.29
(m, H-4, H-4¢, H-3, H-3¢, H-5¢¢, H-5¢¢¢, 6H), 7.01 (d, J = 3.2 Hz,
H-3¢¢, H-3¢¢¢, 2H), 6.38 (dd, J = 3.2 Hz, 1.8 Hz, H-4¢¢, H-4¢¢¢,
2H); dC(100 MHz; CDCl3) 156.2 (C-7, C-7¢), 147.4 (C-2¢¢, C-2¢¢¢),
144.8 (C-5¢¢, C-5¢¢¢), 135.5 (C-1, C-1¢), 130.6 (C-3, C-3¢), 129.9 (C-
5, C-5¢), 127.3 (C-2, C-2¢), 124.9 (C-4, C-4¢), 121.7 (C-6, C-6¢),
115.3 (C-3¢¢, C-3¢¢¢), 112.4 (C-4¢¢, C4¢¢¢); HRMS (+ESI) [M+H]+:
373.1192, C22H17N2O4 requires 373.1188. X-Ray crystallographic
details for 17 have been reported.14
(E)-N-(2-(1-(3-Methoxyphenyl)vinyl)phenyl)furan-2-carboxamide
(16b)
Yield 0.03 g (6%); nmax/cm-1 (NaCl): 3389, 1681, 1584, 1527, 1450,
1310, 755; lmax (MeOH)/nm: 210, 250; dH(400 MHz; CDCl3) 8.39
(d, J = 8.2 Hz, H-6¢, 1H), 8.13 (br s, NH, 1H), 7.39 (t, J = 8.0 Hz,
H-5¢, 1H), 7.30 (d, J = 1.8 Hz, H-5¢¢, 1H), 7.29 (d, J = 7.8 Hz,
H-3¢, 1H), 7.22 (d, J = 7.8 Hz, H-5, 1H), 7.16 (td, J = 7.5 Hz,
1.4 Hz, H-4¢, 1H), 7.03 (d, J = 3.2 Hz, H-3¢, 1H), 6.94–6.90 (m,
H-2, H-6, 2H), 6.83 (dd, J = 8.0 Hz, 2.3 Hz, H-4, 1H), 6.43 (dd,
J = 3.7 Hz, 1.8 Hz, H-4¢¢, 1H), 5.90 (d, J = 1.4 Hz, H-8b, CH2,
1H), 5.41 (d, J = 0.92 Hz, H-8a, CH2, 1H), 3.75 (s, OCH3, 3H);
5658 | Org. Biomol. Chem., 2010, 8, 5646–5660
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MTS Cell proliferation assay
reduced/min mg-1 protein using the DCPIP molar extinction
coefficient of 21000 and the protein concentration of sample.
HT29 human colon carcinoma cells were supplied by Cancer Re-
search UK, and maintained in DMEM with high glucose (4.5g L-1)
and L-glutamine, supplemented with penicillin 100 U ml-1, strep-
tomycin 100 mg ml-1 and 10% foetal bovine serum. Cells were
maintained in 75 cm3 tissue culture flasks (Nunc) with a weekly
1 : 10 split. HT29 cells were seeded into a 96 well tissue culture
grade plate (Nunc) at 500 cells in 50 ml per well. Plates were
incubated at 37 ◦C, in humidified 5% CO2 in air for 2–4 h.
Test agents were prepared at 100¥ final concentration in DMSO
(Sigma), diluted 1 in 50 in culture medium and 50 ml added to
the appropriate wells, to give a final volume of 100 ml. Plates were
Western blotting of NQO1
WRL-68 fetal hepatocytes (5.5 ¥ 105 cells) were prepared for SDS-
PAGE as described by Zafar et al.24 Cellular proteins were resolved
on 12% SDS-PAGE at 150 V followed by electroblotting to
polyvinylidene fluoride membranes for 2 h at 100V. The standard
immunoblotting procedure was carried out using an anti NQO1
monoclonal antibody (Sigma). b-Actin was used as a loading
control.
◦
incubated at 37 C, in humidified 5% CO2 in air for 3 days and
Conclusions
the MTS reagent was added, 20 ml per well. Plates were incubated
at 37 ◦C, in humidified 5% CO2 in air, for colour development.
Optical density readings at 490 nm were taken at 1–4 h. IC50 values
were calculated using the pharmacology function in SigmaPlot 11.
This work demonstrates for the first time the remarkable cyto-
toxic and chemopreventive properties of some unusual stilbene
carboxamides e.g. 15d and 15e. Altogether fourteen stilbenes
were constructed by the Heck reaction and intriguing substituent
effects have been observed. The Pd catalyzed union of iodophenyl
carboxamides (e.g 9f) with styrenes possessing a single methoxy
substituent (e.g 10c) proceeds in higher yield (49%) than that
shown in the coupling of 9f to 3,4-dimethoxystyrene 10a (16%)
or 3,5-dimethoxystyrene 10e (17%). These “matching” preferences
have led us to consider in some details the role of 6-membered ring
palladacycles (e.g 30) which incorporate the -N C(Ar)-O-PdL
moiety. It is important to observe that intramolecular direct arene
arylation is not observed in the chemistry presented in Tables 2 and
3 contrary to what one might have expected. Surprisingly biaryl
formation seems to be more facile than intramolecular direct arene
arylation (see electronic supplementary information†).
MTT Cytotoxicity assay
HepG2 cells were seeded in 96-well plate at a density of 1 ¥ 104
cells per well in a volume of 200 ml and kept under 5% CO2 at
37 ◦C. The cells were treated with our stilbenes (11d, 11e, 11f, 13a,
15b, 15c and 15e) at concentrations of 0–100 mM. Jurkat cells (1 ¥
106 cells ml-1) were directly treated with similar concentrations of
the compounds. After 24 h incubation, 20 ml of 5 mg ml-1 MTT
was added to each treated cells and further incubated for 4 h at
37 ◦C. Subsequently, the total medium was discarded from HepG2
cells whereas 150 ml medium was discarded from Jurkat cells
before adding 200 ml and 150 ml DMSO. For complete dissolution,
the plate was incubated for 15 min followed with gentle shaking
for 5 min. The cytotoxic effect of the stilbenes on HepG2 and
Jurkat was assessed by measuring the absorbance of each well at
570 nm. Mean absorbance for each concentration was expressed
as a percentage of vehicle control absorbance and plotted versus
compound concentration.
P388 cells, supplied by the Japan Foundation for Cancer
Research, were maintained in RPMI-1640 medium (Nissui Pharm.
Co., Ltd) supplemented with 5% fetal calf serum (Mitsubishi
Chemical Industry Co., Ltd) and kanamycin (100 mg ml-1). The
cells (3 ¥ 103 cells/well) were cultured in Corning disposable 96-
well plates containing 100 ml of growth medium per well and were
incubated at 37 ◦C in a humidified atmosphere of 5% CO2. Various
sample concentrations (10 ml) were added to the cultures at day 1
after the transplantation. At day 3, 20 ml MTT solution (5 mg ml-1)
per well was added to each cultured medium. After a further 4 h of
incubation, 100 ml of 10% SDS – 0.01 N HCl solution was added
to each well and the formazan crystals in each well were dissolved
by stirring with a pipette. The optical density measurements were
made by using a microplate reader (Tohso MPR-A4i) witha a two
wavelength system (550 and 700 nm). In all these experiments, 3
replicate wells were used to determine each point.
Acknowledgements
The authors (NFT, AA, KA) thank MOSTI (eScienceFund: 14-
02-03-4013) and University of Malaya (UMRG: RG023/09AFR).
CHK thanks University of Malaya (Vote: P0263/2007A and
PS195/2008A), Malaysia Toray Science Foundation (08/G21)
and MOSTI for a NSF scholarship. SIH and KMC thank
Universiti Kebangsaan Malaysia (UKM NN015-2007).
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5660 | Org. Biomol. Chem., 2010, 8, 5646–5660
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