New cyclopalladated benzothiophenes: A catalyst precursor for the Suzuki coupling of deactivated aryl chlorides

Article abstract of DOI:10.1039/b927367k

Dimeric benzothiophene-based palladacycles were synthesized from thioanisole-substituted perfluoroalkyl propargyl imines and palladium(ii) salts via an intramolecular thiopalladation pathway. The treatment of benzothiophene-based palladacycles with an exc

Full text of DOI:10.1039/b927367k

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
New cyclopalladated benzothiophenes: a catalyst precursor for the Suzuki
coupling of deactivated aryl chlorides†
Madavu Salian Subhas,a Shailesh S. Racharlawar,a B. Sridhar,b P. Kavin Kennady,c Pravin R. Likhar,*a
Mannepalli Lakshmi Kantama and Suresh K. Bhargavad
Received 7th January 2010, Accepted 8th April 2010
First published as an Advance Article on the web 17th May 2010
DOI: 10.1039/b927367k
Dimeric benzothiophene-based palladacycles were synthesized from thioanisole-substituted
perfluoroalkyl propargyl imines and palladium(II) salts via an intramolecular thiopalladation pathway.
The treatment of benzothiophene-based palladacycles with an excess of phosphine ligands in benzene
at room temperature selectively afforded trans-bis(phosphine) palladium complexes in good yields. The
trans-bis(tricyclohexylphosphine) palladium complex was found to be an active catalyst in the Suzuki
coupling of electron rich aryl chlorides. The complex was also employed in the catalytic synthesis of
sterically hindered biaryls. The anticancer activity of palladacycles is also discussed.
and 2) whereas thioether-based palladacycle, 3 afforded mixtures
Introduction
of tricyclohexylphosphine (PCy3) adducts, predominantly trans-
bis(phosphine) species (4).7a,b,8 The bis(phosphine) PCP palladium
Palladacycles are a class of organometallic compounds of consid-
erable interest due to their air and moisture tolerant character
and also due to the variety of applications in catalysis, mate-
rial science, organic synthesis, and in biological and medicinal
chemistry as a potential anticancer agent.1 In recent times, several
complex is acyclic and does not contain a Pd–S bond. Notably,
the in situ-prepared mixtures of products (4 and a mixture of PCy3
adduct complexes) from 3 and tricyclohexylphosphine have been
found to be active in the Suzuki coupling of aryl chlorides.
novel palladacycles with PC, SC and NC donor ligands, and
PCN, NCN, SCS and PCP pincer-type palladacycles have been
successfully used in C–C coupling reactions with the advantages
of their structural versatility, easy synthetic accessibility, high
stability and high yield of products.2 Similarly, in situ-generated
palladium nanoparticles from palladacycles were also reported
as excellent catalysts for coupling of activated aryl halides with
arylboronic acids.3 However, very few palladacycles are effective
at activating less reactive aryl bromides substituted with electron
donating groups or readily available aryl chlorides under relatively
mild reaction conditions.4 In this regard, the phosphine and
N-heterocyclic carbene adduct palladacycles have emerged as
active catalysts for C–C coupling, especially for the Suzuki
coupling of aryl chlorides, and they are far more active than
their parent dimeric palladacycles.5,6 Among the phosphines,
Surprisingly, the closely related phosphino PCP pal-
secondary and tertiary phosphine, HP(tBu)2, HPCy2, or PCy3,
ladium pincer complexes [Pd{OC(O)CF3}{C6H3(CH2PPri2)2-
etc., have been found to exhibit high activity in Suzuki coupling
2,6}], [Pd{OC(O)CF3}{C6CH2-1-(CH2PR2)2-2,6-(CH2)2-3,5-H-
reactions of aryl chlorides.7 Of particular note, in the synthesis of
4}] (R = Pri, But) were found to be inactive in the Heck coupling
tricyclohexylphosphine (PCy3) containing palladacycles, Bedford
and coworkers selectively isolated mono phosphine adducts when
phosphite-, imine-, and amine-based palladacycles were used (1
of aryl chlorides and pincer-type POCOP, bis (dicyclohexylphos-
phinito) palladium complexes afforded only low yields of biaryl
product in coupling of 4-chloronitrobenzene with phenyl boronic
acid.9,10 In contrast, Shen observed that PdCl2(PCy3)2 was an
effective palladium catalyst for the Suzuki coupling of deactivated
aryl chlorides.11
aInorganic and Physical Chemistry Division, Indian Institute Chemical
Technology, Uppal Road, Tarnaka, Hyderabad, 500670, India. E-mail:
plikhar@iict.res.in; Fax: +91-40-27160921; Tel: 91 4027191667
Recently, we have reported the synthesis of dimeric
benzothiophene-based palladacycles via intramolecular thiopal-
ladation of perfluoroalkyl propargyl imines.12 In this paper,
we report the selective synthesis of new acyclic bis(phosphine)
palladium complexes from benzothiophene based palladacycles
as precursors and their application to Suzuki coupling reactions.
The air and moisture stable new acyclic bis(phosphine) palladium
complexes have also found to be active for the synthesis of sterically
bX-Ray Crystallography Division, Indian Institute Chemical Technology,
Uppal Road, Tarnaka, Hyderabad, India
cFlow-Cytometry Facility, Centre for Cellular and Molecular Biology,
Hyderabad, India
dSchool of Applied Sciences, RMIT University, Melbourne, Australia
† Electronic supplementary information (ESI) available: NMR spectra of
all compounds and anticancer study data of compounds 6 and 8. CCDC
reference number 756102. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/b927367k
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 3001–3006 | 3001
©

View Article Online
hindered biaryls. We also herein report the anticancer activity of
benzothiophene-based palladacycles in human leukemia cell lines.
[Pd(PCy3)2dba].14 The 19F NMR also showed a single peak which
confirmed the presence of a single compound.
A single crystal of 9a was obtained upon slow evaporation of
chloroform and carbon tetrachloride (9 : 1) at room temperature.
The molecular structure of complex 9a was determined by X-ray
diffraction analysis, confirming disruption of chloride bridges and
Pd–N bonds by coordinated PPh3 (Fig. 1).15 Complex 9a adopts a
distorted square planar geometry at the metal centre with the two
triphenylphosphine ligands disposed trans relative to each other.
The stability of the Pd–N bond in cyclopalladated derivatives is,
in general, highly dependent on the basicity of the nitrogen atom.
The basicity of the nitrogen atom in cyclopalladated compound
5 is reduced due to the presence of the electron withdrawing
trifluoromethyl group, thus, facilitating ring opening by the more
basic phosphines.
Results and discussion
The chloride-bridged benzothiophene-based palladacycles and
SCN pincer palladacycles were isolated from thioanisole substi-
tuted perfluoroalkyl propargyl imines and Li2PdCl4 in MeOH
at 0 ◦C (Scheme 1). Later the preparation of chloride bridged
benzothiophene based palladacycle was selectively achieved using
bis-benzonitrile palladium chloride.12 All the palladacycles 5, 6,
7 and 8 were fully characterized by multi-nuclear NMR, IR, and
mass spectroscopy.
Scheme 1
In an attempt to form monomers of the benzothiophene-
based palladacycle 5, various phosphorous based ligands were
used with the expectation that they could serve as an active
catalyst in the C–C coupling reactions. We found that trivalent
phosphine ligands are most suitable ligands for the formation of
adduct complex. Initially, 5 was treated with two equivalents of
triphenylphosphine in benzene at room temperature to give 9a as
an air and moisture stable yellow bis(phosphine) adduct complex
in 44% yield. In the reaction mixture, no trace of a monophosphine
adduct was observed. By increasing the stoichiometry of PPh3 to
four equivalents, the yield of 9a was increased to 91% (Scheme 2).
The 1H NMR spectrum and CHN analysis showed 9a contains two
molecules of phosphine per molecule of benzothiophene ligand.
The presence of a single peak in the 31P NMR at 22.1 ppm
indicating the phosphine ligands are magnetically equivalent and
coordinated in a trans arrangement about the palladium atom.13
Fig. 1 The molecular structure of 9a, with the atom-numbering scheme.
Displacement ellipsoids are drawn at the 30% probability level. The minor
components of the disordered F11/F21/F31 and H atoms have been
omitted for clarity.
Next, we screened the catalytic activity of palladium complexes
9a and 9b for the Suzuki coupling of aryl halides. Complex 9a was
initially applied to the Suzuki coupling of 4-chloroanisole with
phenylboronic acid using 1 mol% of the catalyst in 1,4-dioxane
and in the presence of Cs2CO3 at 100 ◦C without any external
additive such as [NBu4Br], [PPh4]Cl etc. The corresponding biaryl
was only formed in low yields. Though the complex 9a was not
active enough for chloroanisole, excellent yields of biaryl were
achieved using bromoanisole (Table 1, entry 2). With the reduction
of catalyst loading to 0.2 mol%, there was no significant change
in yield. Complex 9b was also subjected to Suzuki coupling of
chloroanisole with phenylboronic acid using 1 mol% of the catalyst
under same conditions, and the corresponding biaryl was isolated
in 94% yield; <2% biphenyl was observed as a homo-coupled
product from phenylboronic acid after 8 h. On decreasing the
catalyst loading to 0.5 mol%, no significant change in yield was
observed, although the reaction time was extended up to 10 h
for completion. The maximum yield was optimized in presence of
Cs2CO3 as a base and 1,4-dioxane as a solvent at 100 ◦C.
Scheme 2
Similarly, the reaction of tricyclohexylphosphine with 5 yielded
only the air and moisture stable bis(tricyclohexylphosphino)
complex 9b in 77% yield; there was no evidence for a mono-
phosphine adduct. The phosphorous chemical shift [d 22.49 (s)]
is similar to that of trans-[Pd(PCy3)2(C6H5)Cl] compound [d
22.9 (s)] obtained by the oxidative addition of chlorobenzene to
The coupling of sterically hindered aryl chlorides is one of
the more important and challenging area in organic synthe-
sis. To explore the application of complex 9b in the Suzuki
coupling of sterically hindered substrates, the methodology was
3002 | Org. Biomol. Chem., 2010, 8, 3001–3006
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
Table 1 Catalytic activity of complexes 9a and 9b in the Suzuki coupling
Table 2 IC50 of compounds represented in mg ml-1 in 3 million cells by
MTT assay
of chloro and bromoanisoles with phenyl boronic acida
Compounds
HL60
K562
CCRF
Compound 5
Compound 6
Compound 7
Compound 8
14.8
4.8
19.9
25.2
10.7
5.1
9.9
5.2
14.7
4.9
19.9
15.0
Entries
X
Catalyst (mol%)
Time/h
Isolated yield (%)
anticancer activity. Therefore, cyclopalladated compounds are
receiving much attention in the field of medicinal chemistry.
We have tested the palladacycles (5–8) for anticancer activ-
ity using three human leukemia cell lines. The cytotoxicity of
the compounds was evaluated by MTT assay.16 The modified
cytotoxicity assay was performed on different panels of human
leukemic cell lines HL60 (Human promyelocytic leukemia cells),
K562 (Chronic myelogenous leukemia) and CCRF-CEM (Human
acute lymphocytic leukemia). The cells were grown in RPMI
1640 medium supplemented with 10% fetal calf serum under
standard contentions (37 ◦C temperature with 5% CO2). For
cytotoxicity assay two million cells were plated in a 96 well plates
containing 100 mL of medium and pre-incubated for 24 h at 37 ◦C
with 5% CO2. After 24 h the cyclopalladated compounds were
introduced with respective concentration including DMSO and
cyclohexamide in a separate well as a vehicle control and positive
control respectively. Each treatment was performed in triplicate
in three different experiments. To evaluate the number of viable
cells at the end of compound incubation, MTT solution (sigma
10m/well) was added to the cells. The plates were incubated for
3 h at 37 ◦C with 5% CO2. After 3 h, DMSO (200 ml) was
added and then the absorbance was measured at 550 nm using
Spectra Max. 1909 plate reader. The results are expressed SD
of the percentage of viable cells at each compound concentration
compared to untreated control cells and the concentrations that
inhibited cell growth by 50% (IC50) were calculated on the means of
three experiments. The concentrations of all compounds required
achieving the 50% inhibition of cell growth (IC50) with the exposure
of the compounds for 24 h were determined. The IC50 values of
the compounds are summarized in the bar diagram (Table 2 and
Fig. 2). Compound 6 displayed the greatest inhibition to three
human leukemia cell lines, HL60 (Human promyelocytic leukemia
cells), K562 (Chronic myelogenous leukemia) and CCRF-CEM
(Human acute lymphocytic leukemia) with an IC50 value of 9.5 mM.
as well as compound 8 showed greatest inhibition to K562 (Chronic
myelogenous leukemia) with an IC50 value of 8.5 mM.
1
2
3
4
5
Cl
Br
Br
Cl
Cl
9a (1)
24
5
12
6
12
96
94
94
92
9a (1)
9a (0.2)
9b (1)
9b (0.5)
10
a Reaction Condition: aryl halide (2 mmol), phenyl boronic acid
(3.0 mmol), Cs2CO3 (6 mmol), 1, 4-dioxane (5 mL), 100 ◦C.
extended to hindered o-tolylboronic acid, electron withdrawing o-
formylphenyl boronic acid and 2-chlorotoluene. Excellent yield
of respective Suzuki coupled product, 10a and 10b (Chart 1),
were obtained. The sterically hindered 2-chloro-m-xylene was
also tested with electron donating, electron withdrawing and
hindered boronic acids and excellent yields of the respective
coupled product, 10c, 10d, 10e and 10f was observed (Chart 1).
The coupling of electron rich 2, 3 and 4-chloroanisoles gave the
corresponding biaryls, 10g, 10h, 10i and 10j in 91–95% yields
(Chart 1). The heterocyclic based palladium complexes derived
from the annulated benzothiophene-based palladacycles shows
excellent catalytic activity in the C–C coupling of deactivated aryl
chlorides and boronic acids.
Chart 1 Reaction conditions: aryl chloride (1 mmol), phenyl boronic acid
(1.5 mmol), catalyst 9b, Cs2CO3 (3 mmol), 1,4-dioxane (3 mL), 100 ◦C,
10–12 h.
Anticancer activity of cyclopalladated compounds
Research interest towards palladium complexes has increased
considerably in order to obtain metal-based drugs that possess
reduced toxicity compared to cisplatin and analogous compounds.
However, palladium complexes have a tendency to undergo fast
hydrolysis, to the similar platinum based complexes. This problem
has been over come by the introduction of cyclopalladated
complexes that are more stable, less toxic and show specific
Fig. 2 IC50 (mg mL-1) of palladacycles (5–8) evaluated in three human
leukemic cell lines.
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 3001–3006 | 3003
©

View Article Online
Table 3 Annexin V positive in human promyelocytic leukemia cells
br = broad; coupling constants are reported in Hz. Elemental
(CHN) analyse were performed in Vario MICRO cube. The
benzothiophene-based palladacycles were prepared according to
a published procedure.12
S. No.
Treatment
% of Annexin V + Cells
1
2
3
4
Control
DMSO
Compound 8
Compound 6
1.29
0.72
9.25
24
General method for the synthesis of palladium complexes
In a Schlenk tube under an atmosphere of nitrogen were placed the
palladacycle 5 (0.25 mmol) and benzene (1 mL). The appropriate
phosphine (1 mmol, 4 equiv) was added and the resultant mixture
was then stirred at room temperature for 2 h. The solvent was
removed from the reaction mixture under reduced pressure. The
crude product was then crystallized from a mixture of hexane–
EtOAc (50 : 50) to give analytically pure palladium phosphine
adduct.
Membrane permeability study and apoptosis study
To evaluate the necrotic cell death, the chosen cell lines were
cultured till it attains 50 to 60 percent confluence, then the cells
HL60, K562 and CCRF were harvested and suspended in plain
RPMI 1640 medium. The samples were maintained at room
temperature before the treatment with compounds. The cells were
incubated with compound 6 and 8 for 24 h then stained with
propidium iodide and analyzed in the Fluorescence Activated Cell
Sorter (FACS). In the FACS propidium iodide was excited with
488 nm laser light and the emission (fluorescence) signals were
collected and recorded using the appropriate optical filters (585/45
Spectral data for 9a complex
Yield: 454 mg (91%). Yellow solid, 1H NMR (300 MHz, CDCl3):
7.96-7.91 (m, 1H), 7.47-7.34 (m, 13H), 7.30–7.23 (m, 6H), 7.18–
7.10 (m, 12H), 7.07–7.00 (m, 1H), 6.86-6.76 (m, 3H), 6.52 (d,
J = 9.0 Hz, 2H), 3.88 (s, 3H). 19F NMR (376 MHz, CDCl3):
-58.47 (s, 3F). 31P NMR (162 MHz CDCl3): 22.29 Anal. Calcd.
for C53H41ClF3NOP2PdS·CHCl3·CCl4: C 51.85, H 3.32, N 1.10.
Found: C 51.80, H 3.33, N 1.15.
R
band pass filter) and computer aided software Cell Questꢀ
software. The result suggested that the cells positive to propidium
iodide were membrane permeabilized cells and the necrotic cell
death occurred over a period of 24 h (for Figure see the ESI†).
In the first 6 h, the cells undergo early an apoptotic event like
expression of phosphatidylserine monitored by Annexin V. The
cells positive to Annexin V are represented in Table 3.
Spectral data for 9b complex
1
Yield: 400 mg (77%). Yellow solid, H NMR (400 MHz, C6D6):
8.90-8.85 (m, 1H), 7.57-7.54 (m, 1H), 7.33 (d, J = 8.8 Hz, 2H),
7.28-7.23 (m, 1H), 7.14-7.09 (m, 1H), 6.92 (d, J = 8.8 Hz, 2H),
3.29 (s, 3H), 2.30-2.21 (m, 6H), 2.13–2.02 (m, 12H), 1.78–1.48
(m, 30H), 1.18–0.93 (m, 18H). 19F NMR (376 MHz, CDCl3):
-57.50 (s, 3F). 31P NMR (162 MHz CDCl3): 22.49 Anal. Calcd. for
C53H77F3NOP2SPdCl: C 61.38, H 7.48, N 1.35. Found: C 61.40,
H 7.55, N 1.29.
Conclusions
In summary, we have developed a new class of dimeric
benzothiophene-based palladacycles, which act as precursor for
the preparation of monomeric bis(phosphine) palladium com-
plexes, in good yields under mild reaction conditions. These
complexes are efficient catalysts for the synthesis of hindered
biaryls from aryl chlorides and boronic acids. Palladacycles 6 and
8 show excellent anticancer activity (highest inhibitory against
HL60, K562 and CCRF leukaemia cells with an IC50 values
9.5 mM and 8.5 mM, respectively). The membrane permeability and
apoptotic studies suggested that the mechanism of the anticancer
activity is mediated through apoptosis followed by membrane
permeability.
General method for the Suzuki coupling of aryl halides and aryl
boronic acids
In an oven dried reaction vessel, aryl halide (1 mmol), aryl boronic
acid (1.5 mmol), Cs2CO3 (3 mmol), catalyst 9a or 9b, were charged
with 1,4-dioxane (3 mL). The mixture was stirred at 100 ◦C
under a N2 atmosphere and the progress of the reaction was
monitored by GC. After completion of the reaction, water was
added and the reaction mixture was extracted with EtOAc (3 ¥
20 mL). The combined organic layers were dried over anhydrous
MgSO4 and the solvent was evaporated under reduced pressure.
The crude product was purified by column chromatography (silica
gel, hexane) to obtain pure biaryl.
Experimental
All reactions were carried out in oven dried glassware under
an atmosphere of dry nitrogen. Chemicals were purchased from
Aldrich and used as received unless mentioned otherwise. All
solvents used were dried before use. Product purification by
column chromatography was accomplished using silica gel 60–
120 mesh. Technical grade solvents were used for chromatography
and distilled prior to use. NMR spectra were recorded in Fourier
transform mode. The 1H NMR, 31P NMR and 19F NMR spectra
were recorded on a Bruker-Avance (300 MHz) and Varian-
Inova (400 MHz) spectrometer using CDCl3 and C6D6 solvents,
and TMS as the internal standard. 31P and 19F are referenced
to an external standard 85% H3PO4 and CFCl3 respectively.
Multiplicities in the 1H NMR spectra are described as: s =
singlet, d = doublet, t = triplet, q = quartet, m = multiplet,
Spectral data
2,2¢-Dimethyl-biphenyl 10a. Colorless liquid; 1H NMR
(300 MHz, CDCl3): d 7.23-7.13 (m, 6H), 7.08-7.03 (m, 2H), 2.05 (s,
3H). 13C NMR (75 MHz, CDCl3): d 19.81, 125.50, 127.11, 129.24,
129.77, 135.78, 141.56. EI-MS (m/z): 182 (M+). Anal. Calcd. for
C14H14: C 92.26, H 7.74. Found: C 92.21, H 7.77.
1
2¢-Methylbiphenyl-2-carbaldehyde 10b. Yellow oil; H NMR
(300 MHz, CDCl3): d 9.72 (s, 1H), 8.03-7.98 (m, 1H), 7.64-7.57
3004 | Org. Biomol. Chem., 2010, 8, 3001–3006
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
(m, 1H), 7.51-7.45 (m, 1H), 7.32-7.14 (m, 5H), 2.10 (s, 3H). 13C
NMR (75 MHz, CDCl3): d 20.23, 125.59, 126.97, 127.73, 128.20,
129.99, 130.09, 130.66, 133.63, 133.72, 136.06, 137.38, 145.56,
192.13. EI-MS (m/z): 196 (M+). Anal. Calcd. for C14H12O: C 85.68,
H 6.16. Found: C 85.61, H 6.21.
2-Methoxy-2¢-methyl-biphenyl 10j. Colorless oil; 1H NMR
(300 MHz, CDCl3): d 7.33-7.04 (m, 6H), 6.99-6.87 (m, 2H), 3.74
(s, 3H), 2.12 (s, 3H). 13C NMR (75 MHz, CDCl3): d 19.90, 55.36,
110.61, 120.40, 125.40, 127.27, 128.52, 129.54, 129.96, 130.81,
130.97, 136.78, 138.60, 156.56. EI-MS (m/z): 198 (M+). Anal.
Calcd. for C14H14O: C 84.81, H 7.12. Found: C 84.85, H 7.16.
4-(2¢,6¢-Dimethyl-biphenyl-4-yl)-morpholine 10c. White solid:
◦
1
mp 82-84 C; H NMR (500 MHz, CDCl3): d 7.07-6.97(m, 5H),
6.93-6.87 (m, 2H), 3.88-3.82 (m, 4H), 3.20-3.14 (m, 4H), 2.02 (s,
6H). 13C NMR (125 MHz, CDCl3): d 20.91, 49.36, 66.91, 115.47,
126.78, 127.18, 129.82, 132.73, 136.53, 141.53, 160.04. ESI-MS
(m/z): 268 (M+H+) HRMS: m/z calcd for C18H21NO (M+H+)
268.1701, found 268.1703. Anal. Calcd. for C18H21NO: C 80.86, H
7.92, N 5.24. Found: C 80.82, H 7.95, N 5.27.
Biological Methods
Tissue culture. All the experiments pertaining anticancer
activity were done with the HL60, K562 and CCRF cell lines.
The cell lines were stored in the liquid nitrogen for long-
term preservation. These cells were maintained in RPMI 1640
(Gibco Life Technologies, USA) containing 10% fetal calf serum
(Sigma Chemicals Company, St. Louis, USA) with 1% NaHCO3,
penicillin streptomycin and Gentamycin. The cultures were grown
in 5% CO2 in air at 37 ◦C and the cells were used within the first
5–7 passages after being revived from liquid nitrogen.
1
4¢-Fluoro-2,6-dimethyl-biphenyl 10d. Colorless oil; H NMR
(300 MHz, CDCl3): d 7.13-6.99 (m, 7H), 2.0 (s, 6H). 13C NMR
(75 MHz, CDCl3): d 20.80, 115.35 (d, Jc = 21.41 Hz), 127.21,
127.33, 128.54 (d, Jc = 8.23 Hz), 130.55 (d, Jc = 7.68 Hz), 136.20,
136.84 (d, Jc = 3.84 Hz), 140.78, 161.72 (d, Jc = 245.35 Hz). EI-
MS (m/z): 200 (M+). Anal. Calcd. for C18H21NO: C 80.86, H 7.92,
N 5.24. Found: C 80.82, H 7.95, N 5.27.
Flow cytometry. The flow cytometric studies were done in
the FACS Calibur flow cytometer. The membrane permeability
and apoptosis studies were analyzed in FACS. The cells were
grown up to sub confluence in a 75 Sq cm cell culture flask. The
cell membrane permeability was evaluated upon cyclopalladated
compound treatment. The cells were harvested, washed and
counted. One million cells were taken in a sample tube then treated
with cyclopalladated compound 6 and 8 for 6 h then the cells were
stained with propidium iodide for 30 min the stained samples
were applied in the flow cytometer and analyzed. The propidium
iodide was excited with an argon-ion laser 488 nm. The emission
light was collected at 585/45-band pass filter. The scatter and the
fluorescence data were collected from the FACS machine. The data
2,6,2¢-Trimethyl-biphenyl 10e. Colorless liquid; 1H NMR
(300 MHz, CDCl3): d 7.27-7.17 (m, 3H), 7.15-6.95 (m, 4H), 1.97
(s, 3H), 1.94 (s, 6H). 13C NMR (75 MHz, CDCl3): d 19.55,
20.50, 126.17, 127.02, 127.10, 127.35, 128.90, 130.05, 135.47,
135.63, 140.66, 141.04. EI-MS (m/z): 196 (M+). Anal. Calcd. for
C18H21NO: C 80.86, H 7.92, N 5.24. Found: C 80.82, H 7.95, N
5.27.
1-(2,6-Dimethyl-phenyl)-naphthalene 10f. White solid: mp: 74-
◦
1
75 C; H NMR (300 MHz, CDCl3): d 7.89-7.78 (m, 2H), 7.55-
7.39 (m, 2H). 7.34-7.29 (m, 2H), 7.25-7.09 (m,4H), 1.90 (s, 6H).
13C NMR (75 MHz, CDCl3): d 20.38, 125.34, 125.68, 125.74,
126.03, 126.41, 127.17, 127.24, 127.29, 128.26, 131.71, 133.72,
136.97, 138.72, 139.61. EI-MS (m/z): 232 (M+). Anal. Calcd. for
C18H16: C 93.06, H 6.94. Found: C 93.10, H 6.99.
R
was analyzed using Becton Dickinson Cell Questꢀ software.
Apoptosis study. In order to investigate the apoptotic property
for cyclopalladated compounds, HL60 (Human Promyelocytic
leukemia cells) cells were treated with the compound 6 and 8 for
6 h and stained the cells with Annexin V FITC. The resultant cells
were analyzed in the FACS (fluorescence activated cell sorter).
1-(2-Methoxyphenyl)naphthalene 10g. White solid: mp: 98-
◦
1
99 C; H NMR (300 MHz, CDCl3): d 7.85-7.76 (m, 2H), 7.56-
7.18 (m, 7H), 7.05-6.94 (m, 2H), 3.66 (s, 3H). 13C NMR (75 MHz,
CDCl3): d 55.53, 110.97, 120.55, 125.37, 125.56, 125.63, 126.42,
127.29, 127.64, 128.12, 128.99, 129.50, 131.93, 132.15, 133.45,
136.93, 157.26. EI-MS (m/z): 232 (M+). Anal. Calcd. for C17H14O:
C 87.15, H 6.02. Found: C 87.12, H 5.99.
Acknowledgements
M. S. S. and S. R. thank CSIR for providing research fellowships.
We are thankful to the NMR, MS, and Analytical Division, IICT,
for providing spectral data.
3¢-Methoxy-2-methyl-biphenyl 10h. Colorless oil; 1H NMR
(300 MHz, CDCl3): d 7.31-7.13 (m, 5H), 6.88-6.78 (m, 3H), 3.81
(s, 3H), 2,26 (s, 3H). 13C NMR (75 MHz, CDCl3): d 20.44, 55.21,
112.24, 114.80, 121.65, 125.68, 127.27, 129.00, 129.61, 130.26,
135.30, 141.77, 143.34, 159.24. EI-MS (m/z): 198 (M+). Anal.
Calcd. for C14H14O: C 84.81, H 7.12. Found: C 84.79, H 7.15.
Notes and references
1 Reviews: (a) W. A. Herrmann, V. P. W. Bohm and C. P. Reisinger,
J. Organomet. Chem., 1999, 576, 23; (b) J. Dupont, M. Pfeffer and J.
Spencer, Eur. J. Inorg. Chem., 2001, 1917; (c) I. P. Beletskaya and A. V.
Cheprakov, J. Organomet. Chem., 2004, 689, 4055; (d) J. Dupont, C. S.
Consorti and J. Spencer, Chem. Rev., 2005, 105, 2527; (e) V. V. Dunina
and O. N. Gorunova, Russ. Chem. Rev., 2005, 74, 871; (f) M. Ghedini,
I. Aiello, A. Crispini, A. Golemme, M. La. Deda and D. Pucci, Coord.
Chem. Rev., 2006, 250, 1373; (g) A. C. F. Caires, Anticancer Agents
Med. Chem, 2007, 7, 484; (h) A. Garoufis, S. K. Hadjikakou and N.
Hadjiliadis, Coord. Chem. Rev., 2009, 253, 1384.
2 (a) W. A. Herrmann, C. Brossmer, K. Ofele, C. P. Reisinger, T.
Priermeier, M. Beller and H. Fischer, Angew. Chem., Int. Ed. Engl.,
1995, 34, 1844; (b) M. Beller, H. Fischer, W. A. Herrmann, K. Ofele
and C. Brossmer, Angew. Chem., Int. Ed. Engl., 1995, 34, 1848; (c) E.
Alacid, D. A. Alonso, L. Botella, C. Najera and M. C. Pacheco, Chem.
Rec., 2006, 6, 117; (d) C. S. Consorti, M. L. Zanini, S. Leal, G. Ebeling
2,4,4¢-Trimethoxy-biphenyl 10i. Yellow viscous liquid; 1H
NMR (500 MHz, CDCl3): d 7.40-7.34 (m, 2H), 7.19-7.14 (m, 1H),
6.92-6.86 (m, 2H), 6.52-6.48 (m, 2H), 3.83 (s, 3H), 3.79 (s, 3H).
13C NMR (75 MHz, CDCl3): d 55.10, 55.25, 55.36, 98.83, 104.41,
113.34, 123.09, 130.33, 130.65, 130.86, 157.24, 158.20, 159.86. ESI-
MS (m/z): 245 (M+H)+. HRMS: m/z calcd for C15H16O3 (M+H)+
245.1177, found 245.1186. Anal. Calcd. for C15H16O3: C 73.75, H
6.60. Found: C 73.71, H 6.66.
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 3001–3006 | 3005
©

View Article Online
and J. Dupont, Org. Lett., 2003, 5, 983; (e) A. S. Gruber, D. Zim, G.
Ebeling, A. L. Monteriro and J. Dupont, Org. Lett., 2000, 2, 1287;
(f) G. R. Rosa, G. Ebeling, F. R. Flores, F. Rominger and J. Dupont,
Synthesis, 2003, 2894.
3 (a) C. -L. Chen, Y. -H. Liu, S. -M. Peng and S. -T. Liu, Organometallics,
2005, 24, 1075; (b) J. Louie and J. F. Hartwig, Angew. Chem., Int. Ed.
Engl., 1996, 35, 2359; (c) R. -Y. Lai, C. -L. Chen and S. -T. Liu, J. Chin.
Chem. Soc., 2006, 53, 979.
Int. Ed., 2002, 41, 4120; (c) R. B. Bedford, S. L. Hazelwood and
M. E. Limmert, Chem. Commun., 2002, 2610; (d) R. B. Bedford, S. L.
Hazelwood, M. E. Limmert, D. A. Albisson, S. M. Draper, P. N. Scully,
S. J. Coles and M. B. Hursthouse, Chem.–Eur. J., 2003, 9, 3216; (e) R. B.
Bedford, C. S. J. Cazin, S. J. Coles, T. Gelbrich, P. N. Horton, M. B.
Hursthouse and M. E. Light, Organometallics, 2003, 22, 987; (f) R. B.
Bedford, S. L. Hazelwood, P. N. Horton and M. B. Hursthouse, Dalton
Trans., 2003, 4164.
4 D. A. Alonso, C. N’ajera and M. C. Pacheco, J. Org. Chem., 2002, 67,
5588.
8 R. B. Bedford, C. S. J. Cazin, M. B. Hursthouse, M. E. Light and V. J. M.
Scordia, Dalton Trans., 2004, 3864.
5 (a) R. B. Bedford, C. S. J. Cazin and D. Holder, Coord. Chem. Rev.,
2004, 248, 2283 and references citied therein; (b) N. Marion and S. P.
Nolan, Acc. Chem. Res., 2008, 41, 1440.
9 D. Morales-Morales, R. Redon, C. Yung and C. M. Jensen, Chem.
Commun., 2000, 1619.
10 J. -F. Gong, Y. -H. Zhang, M. -P. Song and C. Xu, Organometallics,
2007, 26, 6487.
11 W. Shen, Tetrahedron Lett., 1997, 38, 5575.
12 P. R. Likhar, M. S. Subhas, S. Roy, M. L. Kantam, B. Sridhar, K. V.
Mohan and B. Jagadeesh, Organometallics, 2009, 28, 3966.
13 J. Albert, J. Granell, R. Moragas, J. Sales, M. F. Bardia and X. Solans,
J. Organomet. Chem., 1995, 494, 95.
14 M. Huser, M. -T. Youinou and J. A. Osborn, Angew. Chem., Int. Ed.
Engl., 1989, 28, 1386.
15 CCDC reference number 756102 (9a) contains the supple-
mentary crystallographic data for this paper. These data are available
as ESI†.
6 Reviews on Suzuki–Miyaura coupling: (a) N. Miyaura and A. Suzuki,
Chem. Rev., 1995, 95, 2457; (b) S. P. Stanforth, Tetrahedron, 1998, 54,
263; (c) A. Suzuki, J. Organomet. Chem., 1999, 576, 147; (d) S. Kotha, K.
Lahiri and D. Kashinath, Tetrahedron, 2002, 58, 9633; (e) N. Miyaura,
Top. Curr. Chem., 2002, 219, 11; (f) F. Bellina, A. Carpita and R. Rossi,
Synthesis, 2004, 15, 2419; (g) R. Martin and S. L. Buchwald, Acc. Chem.
Res., 2008, 41, 1461; (h) N. Marion and S. P. Nolan, Acc. Chem. Res.,
2008, 41, 1440; (i) F. Alonso, I. P. Beletskaya and M. Yus, Tetrahedron,
2008, 64, 9633; (j) H. Doucet and J. C. Hierso, Curr. Opin. Drug Discov.
Dev., 2007, 10, 672; (k) S. Kotha and K. Mandal, Chem.–Asian J., 2009,
4(3), 354–363.
7 (a) R. B. Bedford and C. S. J. Cazin, Chem. Commun., 2001, 1540;
(b) R. B. Bedford, C. S. J. Cazin and S. L. Hazelwood, Angew. Chem.,
16 A. H. Cory, T. C. Owen, J. A. Barltrup and J. G. Cory, Cancer Commun.,
1991, 3, 207.
3006 | Org. Biomol. Chem., 2010, 8, 3001–3006
This journal is
The Royal Society of Chemistry 2010
©