Synthesis and characterization of 1-phenyl-3-alkylbenzimidazol-2-ylidene salts and their catalytic activities in the Heck and Suzuki cross-coupling reactions

Article abstract of DOI:10.1080/00958972.2013.786053

The synthesis and characterization of 1-phenyl-3-alkyl-substituted carbene precursors that were prepared from 1-phenyl substituted benzimidazole and various alkyl halides are reported. The new benzimidazolium salts (1a-e) were characterized by 1H NMR, 13C

Full text of DOI:10.1080/00958972.2013.786053

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Synthesis and characterization of 1-
phenyl-3-alkylbenzimidazol-2-ylidene
salts and their catalytic activities in
the Heck and Suzuki cross-coupling
reactions
Senem Akkoc a & Yetkin Gok b
a Faculty of Science, Department of Chemistry , Erciyes
University , Kayseri , Turkey
b Faculty of Science and Arts, Department of Chemistry , Inönü
University , Malatya , Turkey
Accepted author version posted online: 18 Mar 2013.Published
online: 10 Apr 2013.
To cite this article: Senem Akkoc & Yetkin Gok (2013) Synthesis and characterization of 1-
phenyl-3-alkylbenzimidazol-2-ylidene salts and their catalytic activities in the Heck and
Suzuki cross-coupling reactions, Journal of Coordination Chemistry, 66:8, 1396-1404, DOI:
10.1080/00958972.2013.786053
To link to this article: http://dx.doi.org/10.1080/00958972.2013.786053
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Journal of Coordination Chemistry, 2013
Vol. 66, No. 8, 1396–1404, http://dx.doi.org/10.1080/00958972.2013.786053
Synthesis and characterization of 1-phenyl-3-
alkylbenzimidazol-2-ylidene salts and their catalytic activities
in the Heck and Suzuki cross-coupling reactions
SENEM AKKOC*† and YETKIN GOK‡
†Faculty of Science, Department of Chemistry, Erciyes University, Kayseri, Turkey;
‡Faculty of Science and Arts, Department of Chemistry, Inönü University, Malatya,
Turkey
(Received 23 October 2012; in final form 15 January 2013)
The synthesis and characterization of 1-phenyl-3-alkyl-substituted carbene precursors that were
prepared from 1-phenyl substituted benzimidazole and various alkyl halides are reported. The new
benzimidazolium salts (1a–e) were characterized by 1H NMR, 13C NMR, FT-IR spectroscopic
methods and elemental analyses. New in situ generated palladium-benzimidazolium complexes
were tested for catalytic activity in the Mizoroki-Heck and Suzuki-Miyaura cross-coupling
reactions.
Keywords: N-Heterocyclic carbene; Benzimidazolium salts; Alkyl substituent; Mizoroki-Heck
reaction; Suzuki-Miyaura reaction
1. Introduction
Heterocyclic salts containing a benzimidazolium group are significant as a carbene ancil-
lary both in catalytic reactions and in the synthesis of carbene complexes. N-Heterocyclic
carbene (NHC) complexes have high catalytic activities for many organic transformations
such as C–C and C–N cross-coupling reactions, C–H bond activation and metathesis [1–
7]. Carbon-carbon cross-coupling reactions have played a very important role in organic
synthesis [8]. The Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions are two of
the modern catalytic carbon-carbon bond-forming reactions. These reactions play an
important role in the synthesis of natural products, drug design, and industrially important
starting materials [9–12].
Active catalysts in the production of new products with minimal waste are needed.
Numerous transition metal complexes containing phosphine ligands have been synthesized
and used as catalysts. However, catalytic reactions are carried out in the presence of an
excess of these ligands; palladium complexes of NHC ligands offer distinct advantages as
alternatives to palladium-phosphine systems in C–C coupling reactions [13–15] and NHCs
have attracted the attention of a large number of research groups [7, 16–18]. Some highly
*Corresponding author. Email: senemakkoc@erciyes.edu.tr
Ó 2013 Taylor & Francis

Heck and Suzuki reactions
1397
active palladium systems with carbene ligands for activation of aryl halides have been
developed [19, 20]; in situ formation of the NHC complex by deprotonation of the azo-
lium salt led to significantly better results than the use of the preformed complex [21].
Our research group has focused on NHC derivatives and their metal complexes with
synthesis, characterization, crystal structure, and catalytic activities such as Mizoroki-Heck,
Suzuki-Miyaura, arylation, transfer hydrogenation and amination [6, 8, 22–25]. In order to
find more efficient palladium catalysts, we have prepared a series of new benzimidazolium
salts and reported here the use of in situ generated benzimidazolidin-2-ylidene palladium
(II) complexes that are composed of commercially available Pd(OAc)2 and the 1-phenyl-3-
alkylbenzimidazolium salts (1a–e) for Heck and Suzuki cross-coupling reactions in
aqueous media. The use of water as a solvent for the Heck and Suzuki cross-coupling
reactions clearly has both economical and environmental advantages because it is inexpen-
sive, abundant, nontoxic, nonflammable, and readily separable from organic compounds
1
[26]. The structures of these five new benzimidazolium salts were confirmed by H NMR,
13C NMR, FT-IR spectroscopic methods, and elemental analysis.
2. Experimental
2.1. Materials and methods
Reactions for the preparation of 1a–e were carried out under argon in flame–dried glass-
ware using standard Schlenk-type flasks and high vacuum-line techniques. Solvents were
of analytical grade and distilled under nitrogen from sodium benzophenone (Et2O,
dioxane). Flash chromatography: Merck silica gel 60 (230–400 mesh), eluent ethylacetate/
hexane (1 : 5). The 1-phenyl-3-alkylbenzimidazolium salts (1a–e) were prepared according
1
to known methods [27–29]. All reagents were purchased from Aldrich and Merck. H and
13C NMR spectra were obtained in CDCl3 and DMSO with a Bruker AC300P FT spec-
trometer operating at 300.13 MHz (1H) and 75.47 MHz (13C). Chemical shifts (δ) are given
in ppm relative to TMS and coupling constants (J) are given in Hz. FT-IR spectra were
recorded on a Mattson 1000 spectrophotometer and wavenumbers were recorded in cmÀ1
.
Melting points were measured in open capillary tubes with an Electrothermal-9200 melting
point apparatus. Elemental analyses were performed by the Technological and Scientific
Research Council of Turkey (TÜBİTAK) Microlab.
2.2. General procedure for the preparation of the benzimidazolium salts (1a–e)
Alkyl halide (1.0 mM) was added slowly to a solution of 1-phenylbenzimidazole (1.0 mM)
in DMF (4 mL) at 25 °C and the resulting mixture was heated to 80 °C for 12 h. Diethyl-
ether (15 mL) was added to obtain a white crystalline solid which was filtered off. The
solid was washed with diethylether (2 Â 15 mL) and dried under vacuum. The crude prod-
uct was recrystallized from CH2Cl2–Et2O at room temperature.
2.2.1. 1-Phenyl-3-(2-hydroxyethyl)benzimidazolium bromide (1a). This compound
was prepared from a solution of N-phenyl benzimidazole (1.96 g, 10.10 mM) in DMF
(4 mL) and 2-bromoethanol (1.27 g, 10.13 mM) was added. The resulting solution was

1398
S. Akkoc and Y. Gok
stirred for 48 h at room temperature. Then Et2O (15 mL) was added to the reaction mix-
ture. A solid precipitate occurred in this period. The precipitate was then crystallized from
CH2Cl2/Et2O (1 : 2). Yield: 83%, m.p.: 189–190 °C, IR v(CN): 1554.14 cmÀ1 1H NMR
.
(300.13 MHz, DMSO),
NCH2CH2OH); 4.69 (t, 2H, J: 5.1 Hz, NCH2CH2OH); 7.70–8.27 (m, 9H, Ar–H); 10.26
(s, 1H, 2–CH). 13C NMR (75.47 MHz, DMSO),
50.4 (NCH2CH2OH); 59.2
δ 3.47 (s, 1H, NCH2CH2OH); 3.94 (t, 2H, J: 4.9 Hz,
δ
(NCH2CH2OH); 113.9, 114.9, 125.7, 127.3, 127.8, 130.9, 131.9, 132.0, 133.6 (Ar–C);
143.3 (2–CH). Anal. Calcd for C15H15N2OBr (%): C, 56.44; H, 4.74; N, 8.78; Br, 25.03;
O, 5.01. Found: C, 56.48; H, 4.75; N, 8.79; Br, 25.03; O, 5.02.
2.2.2. 1-Phenyl-3-[2-(diethylamino)ethyl]benzimidazolium
chloride
(1b). This
compound was prepared from N-phenyl benzimidazole (1.07 g, 5.57 mM) and N-(2-chloro-
ethyl)diethylamine (0.74 g, 5.46 mM) in DMF (4 mL). Yield: 81%, m.p.: 339–340 °C, IR
1
v
(CN): 1594.82 cmÀ1. H NMR (300.13 MHz, DMSO), δ 1.78 (t, 6H, J: 6.9 Hz, NCH2CH2N
(CH2CH3)2; 3.67 (q, 4H, J: 6.9 Hz, NCH2CH2N(CH2CH3)2; 2.51 (m, 2H, NCH2CH2N
(CH2CH3)2; 4.66 (m, 2H, NCH2CH2N(CH2CH3)2; 7.53–8.58 (m, 9H, Ar–H); 10.22 (s, 1H,
2–CH). 13C NMR (75.47 MHz, DMSO), δ 12.1, 46.7, 47.6, 51.1 (NCH2CH2N(CH2CH3)2;
111.1, 120.4, 122.9, 124.2, 125.6, 128.2, 130.6, 131.0, 133.5 (Ar–C); 143.8 (2–CH). Anal.
Calcd for C19H24N3Cl (%): C, 69.18; H, 7.33; N, 12.74; Cl, 10.75. Found: C, 69.29; H,
7.22; N, 12.69; Cl, 10.75.
2.2.3. 1-Phenyl-3-(N-prophyl phthalimido)benzimidazolium bromide (1c). This
compound was prepared from N-phenyl benzimidazole (1.0 g, 5.15 mM) and N-(3-bromo-
propyl)-phthalimide (1.31 g, 5.15 mM) in DMF (4 mL). Yield: 86%, m.p.: 206–207 °C, IR
v
(CN): 1556.43 cmÀ1 1H NMR (300.13 MHz, CDCl3), δ 2.64 (p, 2H, J: 6.7 Hz,
.
NCH2CH2CH2N); 3.89 (t, 2H, J: 6.5 Hz, NCH2CH2CH2N); 5.05 (t, 2H, J: 6.9 Hz,
NCH2CH2CH2N); 7.58–8.13 (m, 13H, Ar–H); 11.21 (s, 1H, 2–CH). 13C NMR
(75.47 MHz, CDCl3), δ 28.1, 34.8, and 45.9 (NCH2CH2CH2N); 113.5, 113.7, 123.4,
125.0, 127.7, 127.8, 130.8, 130.9, 131.4, 131.8, 131.9, 134.2 (Ar–C); 142.6 (2–CH).
168.2 (C=O). Anal Calcd. for C24H20N3O2Br (%): C, 62.35; H, 4.36; N, 9.09; Br, 17.28;
O, 6.92. Found: C, 62.31; H, 4.32; N, 9.05; Br, 17.27; O, 6.92.
2.2.4. 1-Phenyl-3-(2-methyl-1,4-benzodioxano)benzimidazolium bromide (1d). This
compound was prepared from N-phenyl benzimidazole (1.08 g, 5.57 mM) and 2-bromo-
methyl-1,4-benzodioxane (1.27 g, 5.55 mM) in DMF (4 mL). Yield: 89%, m.p.: 185–186 °C,
IR v(CN): 1590.08 cmÀ1 1H NMR (300.13 MHz, CDCl3), δ 4.54 (d, 2H, J: 2.5 Hz,
.
NCH2CHCH2O2C6H4); 5.04 (m, 1H, NCH2CHCH2O2C6H4); 5.69 (d, 2H, J: 2.1 Hz,
NCH2C2H3O2C6H4); 6.66–7.98 (m, 13H, Ar–H); 11.41 (s, 1H, 2–CH). 13C NMR
(75.47 MHz, CDCl3), δ 47.9 (NCH2CHCH2O2C6H4); 64.8 (NCH2CHCH2O2C6H4); 72.5
(NCH2C2H3O2C6H4); 113.3, 114.3, 117.4, 117.8, 122.2, 124.9, 127.6, 127.8, 130.9, 132.5,
132.9, 141.4, 142.4 (Ar–C); 142.9 (2–CH). Anal. Calcd for C22H18N2O2Br (%): C, 62.57;
H, 4.30; N, 6.63; Br, 18.92; O, 7.58. Found: C, 62.56; H, 4.21; N, 6.64; Br, 18.91; O, 7.59.
2.2.5. 1-Phenyl-3-(4-vinylbenzyl)benzimidazolium chloride (1e). This compound was
prepared from N-phenyl benzimidazole (1.35 g, 6.96 mM) and 4-vinylbenzyl chloride
(1.06 g, 6.95 mM) in DMF (4 mL). Yield: 87%, m.p.: 165–166 °C, IR v(CN): 1593.50 cmÀ1
.

Heck and Suzuki reactions
1399
1H NMR (300.13 MHz, CDCl3), δ: 5.31 (d, 2H, J: 7.0 Hz, NCH2C6H4CH = CH2); 6.19
(s, 2H, NCH2C6H4CH = CH2); 6.67 (t, 1H, J: 6.7 Hz, NCH2C6H4CH = CH2); 7.28–7.77
(m, 13H, Ar–H); 12.08 (s, 1H, 2–CH). 13C NMR (75.47 MHz, CDCl3), δ: 51.4
(NCH2C6H4CH = CH2); 113.7 (NCH2C8H7); 114.0 (C6H4CH = CH2); 115.2, 124.8, 127.1,
127.5, 129.1, 130.8, 131.4, 132.3, 132.9, 135.9, 138.5 (Ar–C); 143.2 (2–CH). Anal. Calcd
for C22H19N2Cl (%): C, 76.18; H, 5.52; N, 8.08; Cl, 10.22. Found: C, 76.16; H, 5.48; N,
8.09; Cl, 10.21.
2.3. General procedure for Heck and Suzuki cross-coupling reactions
Test reactions for the catalytic activity of the palladium catalysts in the Heck and Suzuki
cross-coupling reactions were carried out in the presence of air.
For the Heck reaction, Pd(OAc)2 (1.0 mM), 1-phenyl-3-alkylbenzimidazolium salts (1a–e)
(2.0 mM), aryl bromide (1.0 mM), styrene (1.5 mM), K2CO3 (2.0 mM), water (3 mL) and
DMF (3 mL) were added to a small Schlenk tube and the mixture was heated to 80 °C for 2 h.
For the Suzuki reaction, Pd(OAc)2 (1.0 mM), 1-phenyl-3-alkylbenzimidazolium salts
(1a–e) (2.0 mM), aryl chloride (1.0 mM), phenylboronic acid (1.5 mM), K2CO3 (2.0 mM),
water (3 mL) and DMF (3 mL) were added to a small Schlenk tube and the mixture was
heated to 80 °C for 2 h. At the end of the Heck and Suzuki cross-coupling reactions, the
mixture was cooled, extracted with ethylacetate/hexane (1 : 5), filtered through a pad of silica
gel with copious washings, concentrated and purified by flash chromatography on silica gel.
The purity of the compounds was checked by NMR and GC. Yields are based on arylbro-
mide for the Heck and arylchloride for the Suzuki. All reactions were monitored by GC-FID
with an HP-5 column of 30 m length, 0.32 mm diameter and 0.25 μm film thickness.
3. Results and discussion
3.1. Synthesis and characterization of phenyl substituted benzimidazolium salts (1a–e)
During our work in the field of NHC precursors, 1-phenyl-3-alkylbenzimidazol-2-ylidene
salts, were isolated. 1-Phenyl-3-alkyl substituted benzimidazolium salts (1a–e) are conven-
tional NHC precursors. The functionalized benzimidazolium salts were synthesized by
alkylation of 1-phenylbenzimidazole, obtained in almost quantitative yield by quaterniza-
tion of 1-phenylbenzimidazole in DMF with alkyl halides [30, 31] (scheme 1). The salts
are air and moisture stable both in the solid state and in solution. The structures of 1a–e
were determined by their characteristic spectroscopic data and elemental analyses. 1H
NMR spectra of the heterocyclic salts containing benzimidazolium further support the
assigned structures; the resonances for C(2)–H were sharp singlets at 10.26, 10.22, 11.21,
11.41 and 12.08 ppm for 1a–e, respectively. 13C NMR chemical shifts were consistent with
the proposed structure; the imino carbons appeared as singlets at 143.3, 143.8, 142.6,
142.9 and 143.2 ppm for the heterocyclic salts (1a–e), respectively. FT-IR data for 1a–e
clearly indicate the presence of the –C=N– group with v(C=N) at 1554, 1594, 1556, 1590
and 1593 cmÀ1, respectively. The palladium catalysts were prepared in situ from Pd(OAc)2
and the appropriate 1-phenyl-3-alkylbenzimidazol-2-ylidene salts in DMF–water mixture.
After having established the optimized coupling reaction conditions, the scope of the
reaction and efficiencies of the salts were evaluated by investigating the coupling of

1400
S. Akkoc and Y. Gok
N
N
Br-
N
N
CI-
O
1b
1c
N
N
O
Br
Cl
O
N
O
O
O
Br
Br
N
N
N
N
OH
-
Br-
Br
N
N
O
O
OH
1a
1d
H2C=HC
CI
N
CI-
N
1e
CH=CH2
Scheme 1. The synthesis of 1a–e.
arylboronic acid and styrene with various p-substituted aryl halides. The results are
summarized in tables 1 and 2.
3.2. Palladium-catalyzed Heck and Suzuki reactions
3.2.1. Mizoroki-Heck cross-coupling reaction. Mizoroki-Heck cross-coupling reactions
[32–35] have attracted a great deal of attention since its discovery in the early 1970s [36,
37]. The coupling of aryl halides with alkenes has been used in the synthesis of industrially
applicable compounds [12] along with a number of natural products [38]. Rates of the Heck
and Suzuki cross-coupling reactions are dependent on parameters such as temperature,

Heck and Suzuki reactions
1401
solvent, base and catalyst loading. Generally, Heck reactions are conducted with tertiary
phosphine [39] or NHC [40] complexes requiring temperatures above 120 °C and polar
solvents such as DMAc, DMF or DMA in the presence of base. Both K2CO3 and t-BuOK
were tested as bases for the reactions. For each base, approximately the same results are
obtained. So, in the Heck and Suzuki cross-coupling reactions, we prefer K2CO3 because it
is cheaper than t-BuOK. The results are summarized in table 1. We have not conducted
control experiments because Özdemir, Yaşar, et al. have made these experiments and the
results indicate that the Heck and Suzuki cross-coupling reactions do not occur in the
absence of ligand precursors [41, 42].
Under the reaction conditions, a wide range of aryl bromides bearing electron-donating
or electron-withdrawing groups such as p-bromoacetophenone, p-bromobenzaldehyde,
p-bromobenzene, p-bromoanisole, and p-bromotoluene gave excellent yields. These results
indicate that the catalytic systems generated in situ from these benzimidazolium salts and
Pd(OAc)2 have good activities. The yield of Heck coupling reaction is between 80 and
100%. The activities of the catalysts are close to each other. NHC precursor that contains
Table 1. The Heck coupling reaction of styrene by aryl bromides.a–d
Pd(OAc)2 (1 mmol % )
1a-e (2 mmol %)
K2CO3, DMF/H2O
R
R
Br
+
Entry
R
LHX
Product
Yield (%)
1
2
3
4
5
COCH3
COCH3
COCH3
COCH3
COCH3
1a
1b
1c
1d
1e
98
98
96
98
95
COCH3
CHO
OCH3
CH3
6
7
8
9
CHO
CHO
CHO
CHO
CHO
1a
1b
1c
1d
1e
98
99
91
94
92
10
11
12
13
14
15
OCH3
OCH3
OCH3
OCH3
OCH3
1a
1b
1c
1d
1e
90
88
98
96
90
16
17
18
19
20
CH3
CH3
CH3
CH3
CH3
1a
1b
1c
1d
1e
97
100
100
99
97
21
22
23
24
25
H
H
H
H
H
1a
1b
1c
1d
1e
92
80
94
95
95
H
aReaction conditions: p-R-C6H4Br (1.0 mM), styrene (1.5 mM), K2CO3 (2.0 mM), Pd(OAc)2 (1.0 mM%), 1
c
(2.0 mM%), water (3 mL)-DMF (3 mL), 80 °C, 2 h. bPurity of compounds is checked by NMR. All reactions were
monitered by GC spectroscopy and yields are based on arylbromide. dIsolated yields.

1402
S. Akkoc and Y. Gok
dioxane substituents (1d) is the most effective of the examined salts. Chloroarenes do not
react under standard conditions, and the yields are typically less than 5%.
3.2.2. Suzuki-Miyaura cross-coupling reaction. The palladium-catalyzed Suzuki-
Miyaura cross-coupling reaction of aryl halides and pseudohalides represents a powerful
method for C–C bond formation [43]. Suzuki reaction of aryl chlorides catalyzed by
palladium/tertiary phosphine [39] and palladium/NHC [44–46] systems have been studied
owing to the economically attractive nature of the starting materials and production of less
toxic by-products (e.g. NaCI instead of NaBr). The coupling of aryl halides with phenyl
boronic acid has been used in the synthesis of industrially important compounds along
with natural products. Here, various benzimidazolium salts (1a–e) were compared as
ligand precursors under the same reaction conditions. To survey the parameters for the
Suzuki reaction, we have found that the reactions performed in DMF/H2O (1 : 1) with
K2CO3 or t-BuOK at 80 °C appear to be the best within 2 h. The results are summarized
in table 2.
Table 2. The Suzuki-Miyaura coupling reaction of phenylboronic acid using aryl chlorides.a–-d
Pd(OAc)2 (1 mmol % )
1a-e (2 mmol %)
R
+
B(OH)2
R
CI
K2CO3, DMF/H2O
Entry
R
LHX
Product
Yield (%)
1
2
3
4
5
COCH3
COCH3
COCH3
COCH3
COCH3
1a
1b
1c
1d
1e
93
86
100
91
H3COC
88
6
7
8
9
CHO
CHO
CHO
CHO
CHO
1a
1b
1c
1d
1e
78
88
87
76
76
OHC
10
11
12
13
14
15
OCH3
OCH3
OCH3
OCH3
OCH3
1a
1b
1c
1d
1e
88
78
81
70
79
H3CO
16
17
18
19
20
CH3
CH3
CH3
CH3
CH3
1a
1b
1c
1d
1e
75
71
75
85
78
H3C
21
22
23
24
25
H
H
H
H
H
1a
1b
1c
1d
1e
96
83
93
80
81
H
aReaction conditions: p-R-C6H4Cl (1.0 mM), phenylboronic acid (1.5 mM), Pd(OAc)2 (1.0 mM%), K2CO3
(2.0 mM), 1 (2.0 mM%), water (3 mL)-DMF (3 mL), 80 °C, 2 h. bPurity of compounds is checked by NMR. cAll
reactions were monitered by GC spectroscopy and yields are based on arylchloride. dIsolated yields.

Heck and Suzuki reactions
1403
In 1a–e/Pd(OAc)2 catalysts, the Suzuki-Miyaura coupling yields of 4-chloroacetophenone,
4-chlorobenzaldehyde, 4-chloroanisole, 4-chlorotoluene and 4-chlorobenzene with phenylbo-
ronic acid were obtained. The 1-phenyl-3-alkylbenzimidazol-2-ylidene salts that contain a
wide range of aryl chlorides bearing electron-donating or electron-withdrawing groups react
with phenyl boronic acid affording the coupled products in yields of 70–100%. The activities
of ligand precursor are close to each other. As a result, synthesized benzimidazolium salts are
effective ligands in the Mizoroki-Heck and the Suzuki-Miyaura cross-coupling reactions.
These results are in agreement with other reports on palladium-carbene-catalyzed
Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions [8, 21, 23, 27, 29, 41, 42].
4. Conclusions
Air and water stable benzimidazolium salts (1a–e) were synthesized and characterized by 1H
NMR, 13C NMR, FT-IR and elemental analyses. These salts were active for the Heck and
Suzuki reactions in a DMF–water mixture. Only aryl chlorides are reluctant to give the Heck
reaction in the presence of Pd(OAc)2/1-phenyl-3-alkylbenzimidazolium salts (1a–e). The
LHX efficiency used in the Mizoroki-Heck and Suzuki-Miyaura coupling reactions were
similar with best yields achieved for activated p-bromotoluene and p-chloroacetophenone,
respectively.
Acknowledgments
This work was financially supported by Inönü University Research Fund (I.U. B.A.P.
2011/130).
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