Synthesis of 2-aminomethylpiperidine ruthenium(II) phosphine complexes and their applications in transfer hydrogenation of aryl ketones

Article abstract of DOI:10.1002/aoc.2924

The complex trans,cis-[RuCl₂(PPh₃)₂(ampi)] (2) was prepared by reaction of RuCl₂(PPh₃)₃ with 2-aminomethylpiperidine(ampi) (1). [RuCl₂(PPh ₂(CH₂)_nPPh₂)(ampi) (n = 3, 4, 5)] (3-5) were synthesized by displacement of two PPh₃ with chelating phosphine ligands. All complexes (2-5) were characterized by ¹ H, ¹³C, ³¹P NMR, IR and UV-visible spectroscopy and elemental analysis. They were found to be efficient catalysts for transfer hydrogen reactions. Copyright

Full text of DOI:10.1002/aoc.2924

Full Paper
Received: 3 June 2012
Revised: 7 August 2012
Accepted: 14 August 2012
Published online in Wiley Online Library: 15 October 2012
(wileyonlinelibrary.com) DOI 10.1002/aoc.2924
Synthesis of 2-aminomethylpiperidine ruthenium(II)
phosphine complexes and their applications in
transfer hydrogenation of aryl ketones
Hayati Türkmen*
The complex trans,cis-[RuCl2(PPh3)2(ampi)] (2) was prepared by reaction of RuCl2(PPh3)3 with 2-aminomethylpiperidine(ampi)
(1). [RuCl2(PPh2(CH2)nPPh2)(ampi) (n = 3, 4, 5)] (3–5) were synthesized by displacement of two PPh3 with chelating phosphine
ligands. All complexes (2–5) were characterized by 1 H, 13C, 31P NMR, IR and UV-visible spectroscopy and elemental analysis.
They were found to be efficient catalysts for transfer hydrogen reactions. Copyright © 2012 John Wiley & Sons, Ltd.
Keywords: 2-aminomethylpiperidine; transfer hydrogenation; phosphine complexes; ruthenium(II) complexes
ruthenium(II) complexes [RuCl2(ampi)(phosphine)] (ampi= 2-ami-
nomethylpiperidine; phosphine = PPh3, PPh2(CH2)nPPh2; n = 3,4,5).
Introduction
Owing to their high remarkable performance in the transfer
hydrogenation (TH) of aryl ketones, ruthenium(II) complexes
are receiving intensive attention.[1,2] Ruthenium, rhodium and
iridium complexes efficiently catalyze the TH of polar substrates
such as ketones from H2 donors such as 2-propanol and formic
acid,[3,4] but they are found to be minimally active in the
presence of H2. The ligands applied to TH feature various combi-
nations of nitrogen, phosphorus and N-heterocyclic carbene
as donor atoms.[5–7] Monotosylated diamines are among the
most effective in terms of catalyst performance.[1a,1c,3]
In ampi, the reduced pyridine (NH) produces an N^N ligand with
stronger s-donation than ampy. It extends this approach to phos-
phine ruthenium complexes with pyridine-based bidentate N^N
ligands and compares their efficiencies in TH reactions.
The ’NH effect’, which involves the bifunctional action of M-H/
N-H groups to attack apolar bonds in the outer coordination
sphere, has been studied extensively experimentally.[8,9] The
effect of the N-H group was observed by the fact that metal hyr-
ide amine systems that lacked N-H were found to be less active
and so more forcing conditions were required for hydrogenation
of aryl ketones. In view of the ability of ruthenium(II) species to
act as efficient catalysts in the TH reaction, the catalytic activity
of N^N-chelating complexes has been studied. On the other
hand, diphosphine ligands (PP) are well known for their good
chelating capabilities with transition metals, which could adjust
the stability, reactivity and catalytic performances of their com-
plexes.[10] They are identified by the presence of two phosphine
ligands joined by a backbone, and are usually chelating. The
use of chelate phosphines with many bridging groups giving
long flexible chains has different effects. The most widely used
diphosphine ligands are the bis(diphenylphosphino)alkanes,
Ph2P(CH2)nPPh2, binap and biphep (Figure 1).[11] Numerous differ-
ent ruthenium–PP systems bearing NN (NN= 1,2-diamine, ampy),
CNN (6-(4-methylphenyl)-2-pyridyl)methylamine) are known.[12] Af-
ter Noyori published the remarkable finding that Ru–binap/diamine
complexes are exceptionally active catalysts for the hydrogenation
of aryl ketones, many efforts have been made to design highly effi-
cient catalysts.[12,13] Baratta and co-workers reported a number of
Ru(II) complexes bearing the 2-aminomethylpyridine (ampy)[12]
and examined their excellent ability to catalyze the reduction of
ketones. Here, this study reports the preparation of some neutral
Figure 1. Examples of Phosphine ligands.
Results and Discussion
Synthesis and Characterization of Complexes
Previous studies have shown that diphosphine and diamine
ligands act in a cooperative manner to improve activity with
these facts in mind.[12] In this work, ruthenium(II) complexes
bearing 2-aminomethylpiperidine and various phosphines were
prepared and investigated (Scheme 1). Therefore, it is logical
to include the ampi ligand in the [RuCl2(PP)(diamine)] system.
Treatment of RuCl2(PPh3)3 with ampi in dichloromethane at room
temperature gives the derivative 2 of trans,cis configuration,
isolated in 79% yield. In the 31P{1 H} NMR spectrum, consistent
with ampy complex,[6b] two doublets at d = 44.2 and 40.6 ppm
with 2 J(P,P) = 31.7 Hz were observed (Table 1). Furthermore, in
*
Correspondence to: Hayati Türkmen, Department of Chemistry, Ege University,
35100 Bornova-Izmir, Turkey. E-mail: hayatiturkmen@hotmail.com
Department of Chemistry, Ege University, 35100, Bornova-Izmir, Turkey
Appl. Organometal. Chem. 2012, 26, 731–735
Copyright © 2012 John Wiley & Sons, Ltd.

H. Türkmen
NH2
NH
1
RuCl2(PPh3)3
Ph2P
Ph2P
Ph2P
Ph2P
Ph2P
Ph2P
Cl
Ru
Cl
Cl
Cl
Ru
Cl
Cl
Cl
Cl
NH2
NH
NH2
NH
NH2
NH
NH2
NH
PPh3
PPh3
Ru
Ru
2
3
4
5
Scheme 1. Synthesis of the neutral (ampi)ruthenium phosphine complexes
Table 1. Comparison of selected spectroscopic data of complexes 2–5
Complex
n
N–H (cm–1
)
31P NMR (ppm); J(P,P) (Hz)
UV-visible (nm)
2
3
4
5
3202, 3266
40.6, 44.2; 31.7
40.8, 56.8; 36.9
40.0, 54.2; 36.9
37.6, 58.2; 38.3
416, 405, 314, 302, 279, 254, 215
521, 463, 325, 274, 252, 248, 243
473, 430, 376, 371, 354, 280, 275,
469, 428, 376, 361, 325, 266
3203, 3264, 3337
3208, 3266, 3344
3228, 3263, 3343
the 1 H NMR spectrum ampi ligand displays diastereotopic
geminal protons at d = 3.45 and 3.40 ppm to (J(HH) = 0.8 Hz). cis,
cis-[RuCl2(PPh2(CH2)nPPh2)(ampi); n = 3–5] 3–5 have been
obtained by reaction of PPh2(CH2)nPPh2 (n = 3–5) and ampi with
RuCl2(PPh3)3 in toluene at 110 ꢀC. The 31P{1 H} NMR spectroscopy
study of 3 shows two doublets at d = 56.8 and 40.8 ppm with 2 J(P,
P) = 36.9 Hz. Similarly, 31P{1 H} NMR spectra of 4, 5 exhibit doub-
lets at d = 54.2 and 40.0 ppm with 2 J(P,P) = 36.9 Hz, and d = 58.2
and 37.6ppm with 2 J(P,P) = 38.3Hz, respectively. It is worth point-
ing out that the trans/cis isomerization of the diphosphino com-
plexes [RuCl2(PPh2(CH2)4PPh2)(NN) has been observed by James
et al. when NN is a dipyridine type ligand, whereas with
ethylenediamine or with pyridine the trans derivatives are thermo-
dynamically favored. [14]
IR spectra of the ruthenium complexes 2–5 show many bands of
varying intensities within 4000–400 cmÀ1(Table 1). Assignment
of each individual band to a specific vibration has not been
attempted. The IR spectra of compounds 2-5 displayed absorption
bands at 3130–3344 cmÀ1 due to N-H. The IR features of 4 are
mostly similar to 5.
Catalytic Studies
Bifunctional catalysis works extremely well also in TH of ketones
using RuCl2(PP)(diamine) pre-catalysts.[11b] Besides binap, other
biaryl and related phosphines are suitable and, while many
diamines with at least one N-H group are effective, ampy and
CNN often give the best performance. All [RuCl2(PP)(ampi)] com-
plexes (2–5) were studied for the TH of acetophenone to give
phenylethanol in 2-propanol at 82 ꢀC. As shown in Table 2 com-
plexes 3–5 bearing the diphospine (PPh2(CH2)nPPh2, n = 3, 4, 5)
show a significantly higher activity compared to 2, with two
PPh3 ligands. The highest catalytic activity has been observed
with complex 5 bearing the diphosphine PPh2(CH2)4PPh2 and
ampi, leading to 99% conversion of ketone in 5 min (turnover
frequency (TOF) = 2640 hÀ1). This result agrees with the data
reported by Lindner et al. and Morris et al. on the RuCl2(PP)(1,2-di-
amine) complexes, which show moderate activity in TH.[15] Le
Page and James reported that even in the absence of transition
metal complex acetophenone is quantitatively reduced within
24 h in refluxing 2-propanol containing NaOH.[16]
Studies performed by Morris showed that the base is necessary
for obtaining cis-RuH/-NH2 species which are involved in catalytic
cycle.[17] The effects of bases, catalyst loading and reaction times
on TH of acetophenone with 2-propanol using complex 5 as a
ruthenium source were surveyed. As shown in Table 3, among
The electronic spectra of 2–5 in dichloromethane at room
temperature showed medium-intensity bands around the 521–
405 nm region due to metal-to-ligand charge transfer transitions
(MLCT) and intense n–p*, p–p* ligand-centered transitions bands
with maxima in the 376–215 nm region (Table 1)
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Copyright © 2012 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2012, 26, 731–735

Transfer hyrogenation of aryl ketones with ruthenium complexes
Table 2. Catalytic activity for transfer hydrogenation of acetophenone catalyzed by Ru(II) complexes (2–5)
Entry
RuII
Time (min)
Yield (%)
TOF (hÀ1 a
)
1
2
3
4
2
3
4
5
30
5
80
85
98
99
1090
2340
2490
2640
5
5
[S]/[cat.] = 100, 82 ꢀC, KOH, in IPA. TOF = mol molÀ1 hÀ1
aBased on 2 min conversion.
.
organic and inorganic bases examined, it has been found that
KOH is the most efficient (entry 1); other bases, such as NaOH,
K2CO3, K3PO4, Et3N and pyridine (py), were slightly less efficient
(entries 2–5).
metal–alkoxide complex (inner sphere mechanism) or a metal
amide species when an NH2 functionality is present( outer sphere
mechanism).[18] In all these systems containing amine ligands,
the presence of the NH2 function has been proven to be crucial
for achieving a highly efficient TH of ketones.
As in previous studies,[7b,c] the best results were obtained with
KOH, whereas other bases required longer reaction times. When
catalyst loading decreased from 1% to 0.001%, a much lower yield
was obtained (entries 7 and8). To test catalyst performance at
lower temperatures, the transfer hydrogenation of acetophenone
was determined from 25 to 82 ꢀC. Temperature-dependent stud-
ies between 25 and 50 ꢀC allowed moderate yields (entries 9
and 10).
Conclusion
A comparative study on ruthenium(II) complexes bearing differ-
ent phosphine and ampi ligands was investigated in transfer
hydrogenation of ketones. The ampi is a well-suited bidentate li-
gand neutral Ru(II) complex for catalyzing transfer hydrogenation.
The electron-donating NH and NH2 groups increase activity in TH.
This ligand offers extra hydrogen bonds near the metal center.
The high catalytic activity of these [RuCl2(phosphine)(ampi)]
can be ascribed to an Ru-NH2 linkage, which is involved in
hydrogen-bonding interactions with the ketone and alcohol,
and to the flexible ampi system that appears crucial for access
of the substrate to the ruthenium center. The synthesis of rho-
dium and iridium complexes with the ampi ligand is in progress
in our laboratories.
To further explore the effectiveness of catalyst 5 on other
substrates, 4-chloroacetophenone, 2-chloroacetophenone,
4-aminoacetophenone, 4-bromoacetophenone and 4-methox-
yacetophenone, were also investigated under identical condi-
tions; the results are summarized in Table 4. Commercially
available ampi ligand shows a particularly high acceleration
effect in TH catalyzed by Ru(II) complexes in 2-propanol (IPA).
The TH of ketones catalyzed by transition metal complexes
is generally conceived to occur via metal hydride species
that deliver the hydride ligand to the substrate, affording a
Table 3. Screening of bases and reaction conditions
Entry
5%
Base
Temperature (ꢀC)
Yield (%)
1
2
1
1
KOH
NaOH
K3PO4
K2CO3
Et3N
py
82
82
82
82
82
82
82
82
50
25
99
87
54
63
22
27
60
23
47
24
3
1
4
1
5
1
6
1
7
0.01
0.001
1
KOH
KOH
KOH
KOH
8
9
10
01
Catalytic condition: substrate (1 mmol), base (0.1 mmol), IPA (5 ml), 5 min.
Appl. Organometal. Chem. 2012, 26, 731–735
Copyright © 2012 John Wiley & Sons, Ltd.
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H. Türkmen
Table 4. Conversion of alternative substrate using complex
5.
Entry
R
Conversion (%)a
TOF (hÀ1 b
)
1
2
3
4
5
6
H
99
94
99
96
85
62
2640
2610
2700
2610
2400
1770
4-Cl
2-Cl
4-NH2
4-Br
4-OCH3
aCatalytic condition: substrate (1 mmol), 5 (0.01 mmol), KOH (0.1 mmol), IPA (5 ml), 5 min. Conversion determined by GC and NMR analysis. [S]/
[cat.] = 100, TOF = mol molÀ1 hÀ1
bBased on 2 min conversion.
.
numbering of C atoms): d 137.5, 136.2 (d, JC–P = 36.2 Hz, ipso-C,
PC6H5), 135.3, 134.7 (d, JC–P = 9.9Hz, m-C PC6H5), 132.3, 131.0 (d,
Experimental
All solvents and chemicals were used as received without any
further treatment unless noted otherwise. Starting compounds
and reagents were obtained from Merck, Fluka, Alfa Aesar and
Acros Organics; 2-aminomethylpiperidine, PPh2(CH2)nPPh2 (n = 3,
4, 5) were obtained from Alfa Aesar and solvents such as dichloro-
methane, 2-propanol, diethyl ether, toluene, hexane and pentane
were obtained from Merck and Ridel de Haen. [RuCl2(PPh3)3] was
prepared according to the literature.[19] Elemental analyses were
performed on a PerkinElmer PE 2400 elemental analyzer. 1 H, 13C
{H}, HMQC, HMQC and 31P{1 H} NMR spectra were recorded on
a Varian AS 400 Mercury instrument. As solvent, CDCl3 was
employed. Chemical shifts (d) are given in ppm and coupling
constants (J) in Hz. FT-IR spectra were recorded on a PerkinElmer
spectrum 100 series. Conversions on transfer hydrogenation of aryl
ketones were determined using GC and NMR.
J
C–P = 2.3Hz, p-C, PC6H5), 127.8, 127.2(d, JC–P = 8.4Hz, o-C PC6H5),
62.2 (C2), 53.8 (C7), 50.9 (C6), 48.6 (C3), 29.8 (C4), 24.0 (C5). 31P{1 H}
NMR (162 MHz, CDCl3): d 44.2 (d, J = 31.7 Hz), 40.6 (d, J = 31.7 Hz).
IR(CH2Cl2): 564, 978, 1041, 1082, 1163, 1268, 1364, 1402, 1434,
1675, 1738, 2224, 2927, 3202 cmÀ1. Anal. Calcd for C42H44Cl2N2P2Ru
(M: 810.73): C, 62.22; H, 5.47; N, 3.46; Found: C, 62.29; H, 5.44; N,
3.51%.
Synthesis of cis-[Ru(PPh2(CH2)3PPh2)(ampi)Cl2] (3)
[RuCl2(PPh3)3] (1.221 g, 1 mmol), PPh2(CH2)3PPh2 (0.412 g, 1 mmol),
and 2-aminomethylpiperidine (0.114 g, 1 mmol) were added to
10ml toluene. The mixture was refluxed for 2 h and cooled to room
temperature, and addition of pentane afforded a yellow precipitate.
After filtration the product was washed with pentane and diethyl
ether. Yield 0.56 g, 80%. 1 H NMR (400 MHz, CDCl3): d 8.20 (m, 2 H,
P(C6H5)2), 7.86 (m, 2 H, P(C6H5)2) , 7.56 (m, 2 H, P(C6H5)2) 7.47–7.26
(m, 14 H, P(C6H5)2), 4.25–3.59 (m, 2 H, H7), 3.04 (m, 1 H, H2),
2.73–2.66 (m, 2 H, H6), 2.38–2.31 (m, 2 H, H3), 2.11–1.87 (m, 4 H, H,
PPh2(CH2)3PPh2), 1.68–1.61 (m, 2 H, H4), 1.34–1.18 (m, 2 H, H5),
0.40–0.21 (m, 2 H, PPh2(CH2)3PPh2). 13C{H} NMR 100 MHz, CDCl3)
(see Figure 2 for the numbering of C atoms): d 145.2, 143.5 (d,
Figure 2. The numbering of 2-aminomethylpiperidine ligand
Synthesis of trans,cis-[Ru(PPh3)2(ampi)Cl2] (2)
J
C–P = 34.1 Hz, ipso-C, PC6H5), 138.3, 136.9 (d, JC–P = 7.6 Hz, m-C
PC6H5), 134.3, 133.0 (d, JC–P = 2.0 Hz, p-C, PC6H5), 129.2, 128.4
(d, JC–P = 8.8 Hz, o-C PC6H5), 56.8 (C2), 53.0 (C7), 51.3 (C6), 49.5
(C3), 39.8 (PPh2(CH2)3PPh2), 27.6 (C4), 24.0 (C5). 31P{1 H} NMR
(162 MHz, CDCl3): d 56.8 (d, J = 36.9 Hz), 40.8 (d, J = 36.9 Hz). IR
(CH2Cl2): 515, 655, 698, 745, 790, 971, 1044, 1090,1149, 1228,
To a suspension of [RuCl2(PPh3)3] (1.221 g, 1 mmol) in dichloro-
methane (10 ml) was added 2-aminomethylpiperidine, 1 (0.114g,
1 mmol), and the resulting solution was mixed for 1 h at room
temperature. The brown solution thus obtained was filtered to
remove any solid impurities, and the filtrate was concentrated to
half its volume. The concentrated solution was saturated with
diethyl ether and placed in a refrigerator for crystallization. Slowly,
a microcrystalline product separated, which was filtered off,
washed with diethyl ether and dried in vacuo. Yield 0.64 g, 79%.
1 H NMR (400 MHz, CDCl3): d 7.69–6.97 (m, 30 H, P(C6H5)3), 5.29
(d, J = 0.8 Hz, H7), 3.09 (m, 1 H, H2), 3.06 and 2.91 (m, 1 H, H6), 2.74
and 2.61 (m, 2 H, H3), 1.79 and 1.62 (m, 2 H, H4), 1.38 and 1.25
(m, 2 H, H5). 13C{H} NMR 100 MHz, CDCl3) (see Figure 2 for the
1314, 1433, 1595, 1738, 2924, 3055, 3131, 3203,3244, 3337cmÀ1
Anal. Calcd for C33H40Cl2N2P2Ru (M: 698.60): C, 56.73; H, 5.77; N,
4.01; Found: C, 56.63; H, 5.84; N, 4.01%.
.
Synthesis of cis-[Ru(PPh2(CH2)4PPh2)(ampi)Cl2] (4)
Prepared by following the procedure for 3 by using [RuCl2(PPh3)
3] (1.221 g, 1 mmol), PPh2(CH2)4PPh2 (0.426 g, 1 mmol) and
2-aminomethylpiperidine 0.114 g, 1 mmol). Yield 0.51 g, 74%. 1 H
NMR (400 MHz, CDCl3): d 1 H NMR (400 MHz, CDCl3): d 8.09
(m, 2 H, P(C6H5)2), 7.89 (m, 2 H, P(C6H5)2) , 7.66 (m, 2 H, P(C6H5)2),
7.37–7.07 (m, 14 H, P(C6H5)2), 4.25–4.15 (m, 2 H, H7), 3.19 (m, 1 H,
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Transfer hyrogenation of aryl ketones with ruthenium complexes
H2), 3.03–2.89 (m, 2 H, H6), 2.77–2.53 (m, 2 H, H3), 2.26–1.69
(m, 5 H, H4, PPh2(CH2)4PPh2), 1.68–1.61 1.34-0.98 (m, 2 H, H5),
0.35–0.23 (m, 4 H, PPh2(CH2)4PPh2). 13C{H} NMR 100 MHz,CDCl3)
(see Figure 2 for the numbering of C atoms): d 144.8, 141.5 (d,
O. Soltani, M. A. Ariger, H. V´azquez-Villa, E. M. Carreira, Org. Lett.,
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J
C–P = 30.2 Hz, ipso-C, PC6H5), 137.3, 135.3 (d, JC–P = 7.0 Hz, m-C
PC6H5), 133.5, 132.0 (d, JC–P = 2.0 Hz, p-C, PC6H5), 129.0, 126.0 (d,
C–P = 9.0 Hz, o-C PC6H5), 58.7 (C2), 53.9 (C7), 50.1 (C6), 49.5 (C3),
39.8, 30.5, (PPh2(CH2)4PPh2), 27.7 (C4), 24.5 (C5), 21.9, 18.8 (PPh2
(CH2)4PPh2). 31P{1 H} NMR (162 MHz, CDCl3):
54.2 (d,
J
d
J = 36.7 Hz), 40.0 (d, J = 36.7 Hz). IR(CH2Cl2): 523, 696, 743, 956,
998, 1021, 1087, 1188, 1266, 1432, 1481, 1560, 2927, 3050, 3208,
3266, 3344 cmÀ1. Anal. Calcd for C34H42Cl2N2P2Ru (M: 712.63): C,
57.30; H, 5.94; N, 3.93; Found: C, 57.33; H, 5.87; N, 4.00%.
Synthesis of cis-[Ru(PPh2(CH2)5PPh2)(ampi)Cl2] (5)
Prepared by following the procedure for 3 by using [RuCl2(PPh3)3]
(1.221 g, 1 mmol), PPh2(CH2)5PPh2 (0.441 g, 1 mmol) and 2-amino-
methylpiperidine 0.114g, 1 mmol). Yield 0.49 g, 68%. 1 H NMR
(400 MHz, CDCl3): d 7.58 (m, 2 H, P(C6H5)2), 7.49 (m, 2 H, P(C6H5)2),
7.33 (m, 2 H, P(C6H5)2), 7.17–6.99 (m, 14 H, P(C6H5)2), 3.48–3.35
(m, 2 H, H7), 3.15 (m, 1 H, H2), 3.05–2.90 (m, 2 H, H6), 2.87–2.63
(m, 2 H, H3), 2.36–1.58 (m, 7 H, H4, PPh2(CH2)5PPh2), 1.48–1.30,
1.24–0.98 (m, 2 H, H5), 0.44–0.20 (m, 4 H, PPh2(CH2)5PPh2). 13C{H}
NMR 100 MHz,CDCl3) (see Figure 2 for the numbering of C atoms):
d 143.0, 140.3 (d, JC–P = 32.2 Hz, ipso-C, PC6H5), 135.8, 135.3 (d,
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J
C–P = 8.4 Hz, m-C PC6H5), 134.5, 130.9 (s, p-C, PC6H5), 128.6,
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21.0, 18.5 (PPh2(CH2)5PPh2). 31P{1 H} NMR (162 MHz, CDCl3):
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744, 956,1022, 1087, 1188, 1405, 1432, 1482, 1560, 2928, 3007,
3060, 3228, 3263, 3343 cmÀ1. Anal. Calcd for C35H44Cl2N2P2Ru
(M: 726.66): C, 57.85; H, 6.10; N, 3.86; Found: C, 57.80; H, 5.99; N,
3.90%.
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Hydrogen Transfer Catalytic Experiments
The tested complex (0.01 mmol) was dissolved in a solution of
KOH (0.1 mmol), and 2-propanol (5 ml) in a Schlenk tube. The
solution was heated to 82 ꢀC for 30 min. Subsequently, substrate
(1 mmol) was added with an Eppendorf pipette. The reaction
progress was monitored by GC and 1 H NMR spectra. Yields were
determined by GC for an average of three runs.
Acknowledgements
Financial support was from Ege University (Project 2010-FEN-046).
I thank Dr S. Astley at Ege University Chemistry Department for
reading the manuscript and Mr Salih Günnaz For NMR analyses.
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