Picolyl substituted N-heterocyclic carbene/palladium catalyzed Heck reactions

Article abstract of DOI:10.3906/kim-0906-69

Novel 1,3-dialkylimidazolinium and 1,3-dialkyltetrahydropyrimidinium hexafluorophosphate salts as N-heterocyclic carbene precursors were prepared by reacting N, N'-dialkylethandiamine or N, N'-dialkylpropandiamine, triethyl orthoformate, and ammonium hexa

Full text of DOI:10.3906/kim-0906-69

Turk J Chem
34 (2010) , 327 – 334.
¨
˙
c
ꢀ TUBITAK
doi:10.3906/kim-0906-69
Picolyl substituted N -heterocyclic carbene/palladium
catalyzed Heck reactions
1
1,∗
2
˙ ˘ ˙
˙ ˘ ˙
˙
¨
˙
Beyhan YIGIT , Murat YIGIT , Ismail OZDEMIR and
3
˙
Engin C¸ ETINKAYA
1Department of Chemistry, Faculty of Science and Arts, Adıyaman University,
02040 Adıyaman- TURKEY
2
˙
Department of Chemistry, Faculty of Science and Arts, Ino¨nu¨ University,
44260 Malatya- TURKEY
3Department of Chemistry, Faculty of Science, Ege University,
˙
35100 Bornova-Izmir-TURKEY
e-mail: myigit@adiyaman.edu.tr
Received 21.06.2009
Novel 1,3-dialkylimidazolinium and 1,3-dialkyltetrahydropyrimidinium hexafluorophosphate salts as N -
heterocyclic carbene precursors were prepared by reacting N, Nꢀ -dialkylethandiamine or N, Nꢀ -dialkylpro-
pandiamine, triethyl orthoformate, and ammonium hexafluorophosphate. The salts were characterized
spectroscopically and tested in homogeneous Heck reactions.
Key Words: Heck reaction, imidazolinium salt, palladium, carbene, catalyst.
Introduction
Palladium-catalyzed C-C bond formation is one of the most fundamental and important reactions in organic
synthesis.1,2 It represents the key step in a wide range of preparative organic processes, from the synthesis of
natural products to supramolecular chemistry material science.3,4 Common methodologies used are the pal-
ladium mediated coupling of the organic halides or halide equivalents with Grignard reagents, organotin, or
organoboran reagents where monodentate phosphines are usually employed as ancillary ligands.5−8 However,
the major drawback of these is that the phosphine ligands are comparatively difficult to make or rather expen-
sive. Furthermore, most of the phosphine ligands are air- and moisture-sensitive, and P-C bond degradation
∗Corresponding author
327

˙ ˘ ˙
Picolyl substituted N -heterocyclic carbene/palladium..., B. YIGIT, et al.,
sometimes occurs at elevated temperatures, which poisons the metal, leading to decomposition of the cata-
lyst, which strongly affects conversion and selectivity.9 The Heck reaction is generally catalyzed by soluble
palladium complexes with phosphine ligands. However, the reaction suffers from severe problems related to
the separation, recovery, and instability of the homogeneous catalysts at high temperature, which have so far
precluded its widespread industrial application. On the other hand, palladium complexes of N -heterocyclic
carbene (NHC) ligands are suitable catalyst precursors that are more stable to air, moisture, and heat, and are
more tolerant toward oxidation than their phosphine counterparts.10−12 High catalyst and phosphine loading
are usually required to produce high yields for unactivated aryl halides using this methodology.
Significant improvements in catalyst performance have recently brought benefits to fine chemistry via
simple substitution of a phosphine ligand by a nucleophilic heterocyclic diaminocarbene, such as an imida-
zolylidene ligand. Illustrative examples are found in cross-coupling or Heck reactions, 13−15 ruthenium catalysts
for the formation of furans,16,17 cyclopropanation,18 methatesis,19−21 or hydrogenation,22−27 and rhodium
catalysts for arylation28−31or hydrosilylation.32,33 The ancillary ligand (NHC) coordinated to the metal center
has a number of important roles in homogeneous catalysis such as providing a stabilizing effect and controlling
activity and selectivity by alteration of steric and electronic parameters. The number, nature, and position of
the substituents on the nitrogen atom(s) and/or NHC ring have been found to play a crucial role in tuning the
catalytic activity.
We report here on the synthesis and characterization of 1,3-dialkylimidazolinium and 1,3-dialkyltetrahyd-
ropyrimidinium salts as N-heterocyclic carbene precursors and the use of the in situ generated catalytic system
composed of commercially available Pd(OAc)2 (as the palladium source) and the 1,3-dialkylimidazolinium(2a-
d) and 1,3-dialkyltetrahydropyrimidinium salts(3a-c) (as a carbene precursor) for Heck cross coupling from
aryl halides.
Experimental
All reactions for the preparation of 1,3-dialkylimidazolinium salts (2a-d) and 1,3-dialkyltetrahydropyrimidinium
salts (3a-c) were carried out under argon using standard Schlenk-type flasks. Heck coupling reactions were
carried out in air. All reagents were purchased from Aldrich Chemical Co., Turkey. All 1 H- and 13 C-NMR
spectroscopy was performed in DMSO-d6 using a Bruker AC300P FT spectrometer operating at 300.13 MHz
(1 H) or 75.47 MHz (13 C). Chemical shifts (δ) are given in ppm relative to TMS, with coupling constants
(J) in Hertz. FT-IR spectra were recorded on a Mattson 1000 spectrophotometer (wavenumbers, cm−1).
GC was performed on a Agilent 6890N gas chromatograph by GC-FID with an HP-5 column of 30 m length,
0.32 mm diameter, and 0.25 μm film thickness. Melting points were measured in open capillary tubes with
an electrothermal-9200 melting point apparatus and are uncorrected. Elemental analyses were performed at
¨
˙
TUBITAK (Ankara, Turkey) Microlab.
1,3-Di(6-methyl-2-picolyl)imidazolinium hexafluorophosphate (2a). To a solution of 1,2-bis(6-
methyl-2-picolylamino)ethane (2.25 g, 8.33 mmol) were added CH(OEt)3 (3 mL) and NH4 PF6 (1.36 g, 8.34
mmol), and the reaction mixture was heated for 12 h at 50 ◦ C. A white solid was precipitated and then
crystallized from ethanol. Yield: 3.1 g, 87%, mp: 144-145 ◦ C. IR(cm−1)ν =1658 (NCN), 1 H-NMR (DMSO-
d6)δ: 4.24 (s, 4H, NCH2 CH2 N), 4.64 (s, 4H, CH2 C5 H3 NCH3 − o), 2.41 (s, 6H, CH2 C5 H3 NCH3 − o),
328

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Picolyl substituted N -heterocyclic carbene/palladium..., B. YIGIT, et al.,
7.21, 7.24 and 7.70 (m, 6H, CH2 C5H3 NCH3 − o), 8.50 (s, 1H, 2-CH). 13 C-NMR (DMSO-d6)δ: 50.2
(NC H2C H2 N), 52.9 (C H2 C5 H3 NCH3 − o), 24.1 (CH2 C5 H3 NC H3 − o), 123.1, 124.1, 138.9, 150.4, 155.7
(CH2C5 H3 NCH3 − o), 166.5 (2-C H). Anal. Calcd for C17 H21 N4 PF6 : C, 47.89, H, 4.96, N, 13.14. Found: C,
47.65, H, 4.80, N, 13.20.
1,3-Di(2-picolyl)imidazolinium hexafluorophosphate (2b). This compound was prepared in the
same way as 2a from 1,2-bis(2-picolylamino)ethane (2.40 g, 9.91 mmol), CH(OEt)3 (3 mL), and NH4 PF6 (1.62
g, 9.93 mmol) to give white crystals of 2b. Yield: 3.4 g, 86%, mp: 132-133 ◦ C. IR(cm−1)ν =1664.3 (NCN),
1 H-NMR (DMSO-d6)δ: 3.86 (s, 4H, NCH2 CH2 N), 4.85 (s, 4H, CH2 C5 H4 N), 7.39, 7.48, 7.87 and 8.60 (m,
8H, CH2 C5H4 N), 8.89 (s, 1H, 2-CH). 13 C-NMR (DMSO-d6)δ: 49.3 (NC H2C H2 N), 52.5 (C H2 C5 H4 N),
123.5, 124.1, 138.1, 150.3, 154.1 (CH2C5 H4 N), 160.6 (2-C H). Anal. Calcd for C15 H17 N4 PF6 : C, 45.22, H,
4.27, N, 14.07. Found: C, 45.31, H, 4.35, N, 14.20.
1,3-Di(3-picolyl)imidazolinium hexafluorophosphate (2c). This compound was prepared in the
same way as 2a from 1,2-bis(3-picolylamino)ethane (2.30 g, 9.50 mmol), CH(OEt)3 (3 mL), and NH4 PF6 (1.55
g, 9.51 mmol) to give white crystals of 2c.
Yield: 3.4 g, 90%, mp: 207-208 ◦ C. IR(cm−1)ν =1664.0 (NCN), 1 H-NMR (DMSO-d6)δ: 3.76 (s, 4H,
NCH2 CH2 N), 4.72 (s, 4H, CH2 C5 H4 N), 7.46, 7.84, 8.58 and 8.63 (m, 8H, CH2 C5H4 N), 8.74 (s, 1H, 2-
CH). 13 C-NMR (DMSO-d6)δ: 48.7 (NC H2C H2 N), 49.2 (C H2 C5 H4 N), 124.5, 130.2, 137.1, 150.4, 150.5
(CH2C5 H4 N), 159.1 (2-C H). Anal. Calcd for C15 H17 N4 PF6 : C, 45.22, H, 4.27, N, 14.07. Found: C, 44.87,
H, 4.32, N, 13.24.
1,3-Di(4-picolyl)imidazolinium hexafluorophosphate (2d). This compound was prepared in the
same way as 2a from 1,2-bis(4-picolylamino)ethane (2.60 g, 10.74 mmol), CH(OEt)3 (3 mL), and NH4 PF6
(1.75 g, 10.74 mmol) to give white crystals of 2d.
Yield: 3.7 g, 86%, mp: 199-200 ◦ C. IR(cm−1)ν =1666 (NCN), 1 H-NMR (DMSO-d6)δ: 3.81 (s, 4H,
NCH2 CH2 N), 4.76 (s, 4H, CH2 C5 H4 N), 7.44 and 8.63 (d, 8H, J =4.4 Hz, CH2 C5H4 N), 8.78 (s, 1H, 2-CH).
13 C-NMR (DMSO-d6)δ: 49.1 (NC H2C H2 N), 50.5 (C H2 C5 H4 N), 123.7, 143.6, 150.8 (CH2C5 H4 N), 160.1
(2-C H). Anal. Calcd for C15 H17 N4 PF6 : C, 45.22, H, 4.27, N, 14.07. Found: C, 45.30, H, 4.16, N, 14.20.
1,3-Di(2-picolyl)tetrahydropyrimidinium hexafluorophosphate (3a). This compound was pre-
pared in the same way as 2a from 1,2-bis(2-picolylamino)propane (3.10 g, 12.10 mmol), CH(OEt)3 (3 mL),
and NH4 PF6 (1.97 g, 12.08 mmol) to give white crystals of 3a. Yield: 4.2 g, 84%, mp: 124-125 ◦ C.
IR(cm−1)ν =1697 (NCN), 1 H-NMR (DMSO-d6)δ: 1.94 (quin., 2H, J =4.2 Hz, NCH2 CH2 CH2 N), 3.31 (t,
4H, J =4.5 Hz, NCH2 CH2 CH2 N), 4.81 (s, 4H, CH2 C5 H4 N), 7.38, 7.47, 7.88 and 8.61 (m, 8H, CH2 C5H4 N),
8.79 (s, 1H, 2-CH). 13 C-NMR (DMSO-d6)δ: 19.0 and 43.7 (NC H2C H2C H2 N), 59.3 (C H2 C5 H4 N), 123.6,
124.1, 138.1, 150.3, 154.5 (CH2C5 H4 N), 155.7 (2-C H). Anal. Calcd for C16 H19 N4 PF6 : C, 46.60, H, 4.61, N,
13.59. Found: C, 46.33, H, 4.65, N, 13.28.
1,3-Di(3-picolyl) tetrahydropyrimidinium hexafluorophosphate (3b). This compound was pre-
pared in the same way as 2a from 1,2-bis(3-picolylamino)propane (3.33 g, 13.00 mmol), CH(OEt)3 (3 mL), and
NH4 PF6 (2.12 g, 13.00 mmol) to give white crystals of 3b.
Yield: 4.7 g, 88%, mp: 245-246 ◦ C. IR(cm−1)ν =1670 (NCN), 1 H-NMR (DMSO-d6)δ: 1.89 (quin.,
2H, J =4.5 Hz, NCH2 CH2 CH2 N), 3.22 (t, 4H, J =4.5 Hz, NCH2 CH2 CH2 N), 4.71 (s, 4H, CH2 C5 H4 N),
329

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Picolyl substituted N -heterocyclic carbene/palladium..., B. YIGIT, et al.,
7.45, 7.86, 8.58 and 8.65 (m, 8H, CH2 C5H4 N), 8.82 (s, 1H, 2-CH). 13 C-NMR (DMSO-d6)δ: 18.8 and 42.8
(NC H2C H2C H2 N), 55.9 (C H2 C5 H4 N), 124.5, 130.5, 136.8, 150.3, 150.4 (CH2C5 H4 N), 154.7 (2-C H). Anal.
Calcd for C16 H19 N4 PF6 : C, 46.60, H, 4.61, N, 13.59. Found: C, 46.47, H, 4.44, N, 13.24.
1,3-Di(4-picolyl) tetrahydropyrimidinium hexafluorophosphate (3c). This compound was pre-
pared in the same way as 2a from 1,2-bis(4-picolylamino)propane (3.04 g, 11.87 mmol), CH(OEt)3 (3 mL), and
NH4 PF6 (1.93 g, 11.84 mmol) to give white crystals of 3c.
Yield: 4.4 g, 90%, mp: 209-210 ◦ C. IR(cm−1)ν =1702 (NCN), 1 H-NMR (DMSO-d6)δ: 1.97 (quin.,
2H, J =4.2 Hz, NCH2 CH2 CH2 N), 3.26 (t, 4H, J =4.5 Hz, NCH2 CH2 CH2 N), 4.73 (s, 4H, CH2 C5 H4 N),
7.43 and 8.62 (d, 8H, J =4.5 Hz, CH2 C5H4 N), 8.79 (s, 1H, 2-CH). 13 C-NMR (DMSO-d6)δ: 18.8 and 43.3
(NC H2C H2C H2 N), 57.1 (C H2 C5 H4 N), 123.5, 143.8, 150.7 (CH2C5 H4 N), 155.6 (2-C H). Anal. Calcd for
C16 H19 N4 PF6 : C, 46.60, H, 4.61, N, 13.59. Found: C, 46.30, H, 4.56, N, 13.43.
General procedure for the Heck coupling reactions
Pd(OAc)2 (1.0 mmol%), 1,3-dialkylimidazolinium salts 2a-d, or 1,3-dialkyltetrahydropyrimidinium salts 3a-c
(2 mmol%), aryl bromide (1.0 mmol), styrene (1.5 mmol), K2 CO3 (2 mmol), water (3 mL), and DMF (3 mL)
were added to a small Schlenk tube and the mixture was heated at 90 ◦ C for 3 h. At the conclusion of the
reaction, the mixture was cooled, extracted with ethyl acetate–hexane (1:5), filtered through a pad of silica
gel with copious washing, concentrated, and purified by flash chromatography on silica gel. The purity of the
compounds was checked by NMR and yields are based on aryl bromide.
Results and discussion
Condensation of ethylendiamine or 1,3-propandiamine with aldehydes in ethanol gave Schiff bases in high
yields. Reduction of the resulting Schiff bases with NaBH4 leads to N, Nꢀ -dialkylethan-1,2-diamines and
N, Nꢀ -dialkylpropan-1,3-diamines.
As shown in the Scheme, 1,3-dialkylimidazolinium salts 2 and 1,3-dialkyltetrahydropyrimidinium salts 3
were easily synthesized in high yields from N, Nꢀ -dialkylethan-1,2-diamines, N, Nꢀ -dialkylpropan-1,3 -diamines,
triethyl ortoformate, and ammonium hexafluorophosphate. The salts are soluble in the common polar solvents
ethanol and dichloromethane and are stable under air and in the presence of moisture. The structures of 2 and 3
were determined by their spectroscopic data and elemental analyses (see Experimental section). The 13 C-NMR
spectra of 2a-d and 3a-c show only a singlet (165.5 ppm(2a), 160.6 ppm(2b), 159.1 ppm(2c), 160.1 ppm(2d),
155.7 ppm(3a), 157.7 ppm(3b), and 155.6 ppm(3c)) for the imino carbon and (52.9 ppm(2a), 52.5 ppm(2b),
49.2 ppm(2c), 50.5 ppm(2d), 59.3 ppm(3a), 55.9 ppm(3b), and 57.1 ppm(3c)) for benzylic carbon. The 1 H-
NMR spectra of imidazolinium and tetrahydropyrimidinium salts further supported the assigned structures.
The resonances of the C(2)-H were observed as a sharp singlets at δ= 8.50, 8.89, 8.74, 8.78, 8.79, 8.82, 8.79
ppm for 2a-d and 3a-c, respectively. The IR data for imidazolinium 2a-d and tetrahydropyrimidinium 3a-c
salts clearly indicate the presence of the –C=N- group with a ν (C=N) vibration at 1658, 1664.3, 1664.0, 1666,
1679, 1670, and 1702 cm−1 for 2a-d and 3a-c, respectively. These NMR and IR values were similar to other
1,3-dialkylimidazolinium and 1,3-dialkyltetrahydropyrimidinium salts.34
330

˙ ˘ ˙
Picolyl substituted N -heterocyclic carbene/palladium..., B. YIGIT, et al.,
N
N
-
+)
N
PF6
N
N
N
N
N
N
+)
N
-
N
PF6
-
+)
PF6
2a
N
2b
3a
NH4PF6
+
CH(OEt)3
N
N
N
N
N
+)
N
-
N
PF6
-
+)
PF6
+
N
NHR
(H2C)n
NHR
1
3b
2c
N
N
N
N
-
-
+)
PF6
+)
N
PF6
N
N
N
2d
Scheme. Synthesis of 1,3-dialkylimidazolinium and 1,3-dialkyltetrahydropyrimidinium salts.
3c
The Pd-catalyzed Heck reaction between aryl halides and alkenes is a very useful method for forming
natural products, drug design, and organic synthesis.35,36 The choice of bases and solvents is usually important
for achieving an efficient cross coupling reaction. The widely used solvents such as DMF, DMSO, toluene,
dioxane, THF, and CH3 CN had remarkable effects on the coupling reaction. For optimal reaction conditions,
the Pd(OAc)2 -catalyzed cross coupling of bromobenzene with styrene was employed as the model reaction using
ligand 2a at 90 ◦ C, as the bases CsCO3 , K2 CO3 , K3 PO4 , and t-BuOK were tested. The coupling reactions
of aryl bromides and styrene were carried out in DMF/H2 O (3:3 mL) with 1 mol% Pd(OAc)2 , 2 mol% 2 or
3, and 2 equiv. K2 CO3 for 3 h at 90 ◦ C. The results are summarized in Table. Control experiments indicate
331

˙ ˘ ˙
Picolyl substituted N -heterocyclic carbene/palladium..., B. YIGIT, et al.,
Table. The Heck coupling reaction of aryl bromides with styrene.
Pd(OAc)2 , LHX
DMF/H2O , K2CO3
LHX Yield (%)
Br
R
+
R
Entry
1
R
COCH3
COCH3
COCH3
COCH3
COCH3
COCH3
COCH3
CHO
CHO
CHO
CHO
CHO
CHO
CHO
H
2a
2b
2c
2d
3a
3b
3c
2a
2b
2c
2d
3a
3b
3c
2a
2b
2c
2d
3a
3b
3c
2a
2b
2c
2d
3a
3b
3c
2a
2b
2c
2d
3a
3b
3c
92
98
96
97
97
94
95
85
94
89
92
96
91
88
83
80
89
82
90
84
91
72
74
81
79
71
73
75
82
79
80
74
76
73
75
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
H
H
H
H
H
H
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
Reaction conditions: R-C6 H4 Br-p1.0 mmol, styrene 1.5 mmol, K2 CO3 2.0 mmol, Pd(OAc)2 1% (molar ratio), 2a-d,
3a-c 2% (molar ratio), water (3 mL)/DMF (3 mL), 90 ◦ C, 3 h. Yields are based on aryl bromide. All reactions were
monitored by GC, and the compound purity was checked by NMR.
332

˙ ˘ ˙
Picolyl substituted N -heterocyclic carbene/palladium..., B. YIGIT, et al.,
that the coupling reaction did not occur in the absence of 2a. Under these reaction conditions, a wide range
of aryl bromides bearing electron-donating or electron-withdrawing groups react with styrene, affording the
coupled products in excellent yields (Table, entries 2, 12, 21, 24 and 29). Enhancements in activity, although
less significant, are also observed employing 4-bromobenzaldehyde instead of 4-bromoacetophenone (entries 1-7
and 8-14, respectively). However, chloroarenes do not react under standard conditions, and yields are typically
<6%.
Conclusion
We synthesized 1,3-dialkylimidazolinium and 1,3-dialkyltetrahydropyrimidinium hexafluorophosphate salts and
investigated their catalytic activity in Heck coupling reactions. The procedure is simple and efficient for various
types of aryl bromides and does not require an induction period. The advantage of the catalyst is that it has
low-loading capabilities, and it is useable in air. Detailed investigations focusing on imidazolidin-2-ylidene and
benzimidazolin-2-ylidene substituent effects, functional group tolerance, and catalytic activity in this and other
coupling reactions are ongoing.
Acknowledgements
¨
˙
¨ ˙
We thank the Scientific and Technological Research Council of Turkey TUBITAK/CNRS, TUBITAK (107T419),
˙
TBAG-U/181 (106T716), and Ino¨nu¨ University Research Fund (BAP 2007/29) for financial support of this work.
References
1. Trost, B. M.; Verhoeven, T. R. Organopalladium Compounds in Organic Synthesis and in Catalysis. In Compre-
hensive Organometallic Chemistry. Wilkinson, G.; Stone, F. G. A.; Abel, E. W. Eds., Pergamon: Oxford, 1982.
2. Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457-2483.
3. Tietze, L. F.; Petersen, S. Eur. J. Org. Chem. 2001, 9, 1619-1624.
4. Cianga, I.; Ya˘gci Y. Eur. Polymer J. 2002, 38, 695-703.
5. Busacca, C. A.; Eriksson, M. C.; Fiaschi, R. Tetrahedron Lett. 1999, 40, 3101-3104.
6. Miller, J. A.; Farrell, R. P. Tetrahedron Lett. 1998, 39, 7275-7278.
7. Suzuki, A. J. Organomet. Chem. 2002, 653, 83-90.
8. Xu, L.; Chen, W.; Xiao. J. J. Mol. Catal. A. 2002, 187, 189-193.
9. Herrmann, W. A. in Cornils, B.; Herrmann, W. A. (Eds). Applied Homogeneous Catalysis with Organometallic
Compounds. VCH, Weinheim, 1996.
10. Lappert, M. F. J. Organomet. Chem. 1988, 358, 185-213.
11. Bourissou, D.; Guerret, O.; Gabbai, F. B.; Bertrand, G. Chem. Rev. 2000, 100, 39-92.
12. Herrmann, W. A.; Wescamp, T.; B¨ohm, V. P. M. Adv. Organomet. Chem. 2001, 48, 1-69.
13. B¨ohm, V. P. W.; Gst¨ottmayr, C. W. K.; Wescamp, T.; Herrmann, W. A. J. Organomet. Chem. 2000, 595, 186-190.
333

˙ ˘ ˙
Picolyl substituted N -heterocyclic carbene/palladium..., B. YIGIT, et al.,
14. McGuinness, D. S.; Cavell, K. J. Organometallics. 2000, 19, 741-748.
¨
15. Ozdemir, I.; Yi˘git, M.; C¸etinkaya, E.; C¸etinkaya, B. Appl. Organometal. Chem. 2006, 20, 187-192.
˙
¨
16. C¸ etinkaya, B.; Ozdemir, I.; Bruneau, C.; Dixneuf, P. H. J. Mol. Catal. A. 1997, 118, L1-L4.
˙
¨
˙
17. Ozdemir, I.; Yi˘git, B.; C¸etinkaya, B.; Ulku¨ D.; Tahir, M. N.; Arıcı, C. J. Organomet Chem., 2001, 633, 27-32.
¨
¨
18. C¸ etinkaya, B.; Ozdemir, I.; Dixneuf, P. H. J. Organomet. Chem. 1997, 534, 153-158.
˙
19. Scholl, M.; Ding, S.; Lee, C. W.; Grubbs, R. H. Org. Lett. 1999, 1, 953-956.
¨
˙
20. C¸ etinkaya, B.; Demir, S.; Ozdemir, I.; Toupet, L.; S´emeril, D.; Bruneau, C.; Dixneuf, P. H. New. J. Chem. 2001,
25, 519-521.
¨
21. C¸ etinkaya, B.; Demir, S.; Ozdemir, I.; Toupet, L.; S´emeril, D.; Bruneau, C.; Dixneuf, P. H. Chem. Eur. J. 2003,
˙
9, 2323-2330.
22. Agnelli, F.; Sulikowski G. A. Tetrahedron Lett.; 1998, 39, 8807-8810.
23. Kondo, Y.; Shilai, M.; Uchiyama, M.; Sakamoto, T. J. Am. Chem. Soc. 1999, 121, 3539-3540.
24. Sakamoto, T.; Kondo, Y.; Masumoto, K.; Yamanaka, H. J. Chem. Soc. Perkin Trans. 1. 1994, 3, 235-236.
25. Carfagna, C.; Musco, A.; Sallese, G.; Santi, R.; Fiorani, T. J. Org. Chem. 1991, 56, 261-263.
26. Kondo, Y.; Inamoto, K.; Uchiyama, M.; Sakamoto, T. Chem. Commun. 2001, 2704-2705.
¨
27. Yi˘git, M.; Yi˘git, B.; Ozdemir, I.; C¸etinkaya, E.; C¸etinkaya, B. Appl. Organometal. Chem. 2006, 20, 322-327.
˙
28. Saba, S.; Brescia, A.; Kaloustian, M. K. Tetrahedron Lett. 1991, 32, 5031-5034.
29. C¸ etinkaya, E.; Hitchcock, P. B.; Jasim, H. A.; Lappert, M. F.; Spyropoulos, K. J. Chem. Soc. Perkin Trans. 1.
1992, 5, 561-567.
¨
30. Yi˘git, M.; Ozdemir, I.; C¸etinkaya, E.; C¸etinkaya, B. Trans. Met. Chem. 2007, 32, 536-540.
˙
¨
31. Yi˘git, M.; Ozdemir, I.; C¸etinkaya, E.; C¸etinkaya, B. Heteroatom Chem. 2005, 16, 461-465.
˙
¨
32. Yi˘git, M.; Ozdemir, I.; C¸etinkaya, B.; C¸etinkaya, E. J. Mol. Catal. A. 2005, 241, 88-92.
˙
¨
˙
33. Ozdemir, I.; Yi˘git, M.; Yi˘git, B.; C¸etinkaya, B.; C¸etinkaya, E. J. Coord. Chem. 2007, 60, 2377-2384.
¨
34. Ozdemir, I.; Gu¨rbu¨z, N.; G¨ok, Y.; C¸ etinkaya, B. Heteroatom Chem. 2008, 19, 82-86.
˙
35. Beletskaya, I. P.; Cheprakov, A. V. Chem. Rev. 2000, 100, 3009-3066.
36. Phan, N. T. S.; Van Der Sluys M.; Jones, C. W. Adv. Synth. Catal. 2006, 348, 609-679.
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