Microwave-induced synthesis of 2-aminoimidazolines under neat conditions

Article abstract of DOI:10.1080/00397910902739896

2-Aminoimidazolines were synthesized by the nucleophilic substitution reaction of 2-methylmercapto-4,5-dihydroimidazole hydroiodide with various amine compounds under neat conditions. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910902739896

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Microwave-Induced Synthesis
of 2-Aminoimidazolines Under
Neat Conditions
Murat Genc a & Süleyman Servi b
a Department of Chemistry , Faculty of Science and
Art, University of Adiyaman , Adiyaman, Turkey
b Department of Chemistry , Faculty of Science and
Art, University of Firat , Elazig, Turkey
Published online: 12 Aug 2009.
To cite this article: Murat Genc & Süleyman Servi (2009) Microwave-Induced Synthesis
of 2-Aminoimidazolines Under Neat Conditions, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 39:18,
3263-3277, DOI: 10.1080/00397910902739896
To link to this article: http://dx.doi.org/10.1080/00397910902739896
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Synthetic Communications1, 39: 3263–3277, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910902739896
Microwave-Induced Synthesis of
2-Aminoimidazolines Under Neat Conditions
Murat Genc1 and Su¨leyman Servi2
1Department of Chemistry, Faculty of Science and Art,
University of Adiyaman, Adiyaman, Turkey
2Department of Chemistry, Faculty of Science and Art,
University of Firat, Elazig, Turkey
Abstract: 2-Aminoimidazolines were synthesized by the nucleophilic substitution
reaction of 2-methylmercapto-4,5-dihydroimidazole hydroiodide with various
amine compounds under neat conditions.
Keywords: 2-Aminoimidazolines, microwave irradiation, neat reaction
INTRODUCTION
2-Aminoimidazolines are important heterocyclic compounds included in
the various classes of pharmacological agents and play important roles in
biochemical processes. They are a class of compounds that are very
promising in the treatment of many diseases such as psychiatric disorders,
opiate withdrawal, Parkinson’s and Alzheimer’s diseases, as well as
Huntington’s chorea. These compounds are already used in medical
practice and their development is still in progress.[1–4]
Microwave-assisted organic synthesis (MAOS) has emerged as a
powerful technique to promote the rapid preparation of new compounds
and drug development candidates. The combination of solvent-free
conditions and microwave irradiation (MWI) leads to large reductions
Received November 13, 2008.
Address correspondence to Suleyman Servi, Faculty of Science and Arts,
¨
Department of Chemistry, Firat University, Elazig 23169, Turkey. E-mail:
sservi@firat.edu.tr
3263

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M. Genc and S. Servi
in reaction times and enhancements in conversions and sometimes in
selectivity, with several advantages of the ecofriendly approach.[5] Neat
synthesis is another interesting technique in MAOS. The neat reaction
method completely eliminates the use of solvent during the course of
the reaction. This facilitates accomplishing the desired product with
minimal amounts of by-products and almost without solvents. The other
advantages of this approach are that no expenses are incurred for the
purchase and disposal or recovery of solvent.[6–9]
In continuation of our work on the microwave-assisted synthesis of
2-aminoimidazolines, we thought it worthwhile to synthesize 2-aminoimi-
dazolines under microwave irradiation (MWI) conditions, which can be
used to develop new experimental methods. The aim of this study is to
synthesize substituted 2-aminoimidazolines under MWI conditions, using
different precursors than those previously reported.[10,11]
RESULTS AND DISCUSSION
A few conventional methods to synthesize 2-aminoimidazolines from the
corresponding aromatic amines have been reported in the literature. In
these methods, yields of reaction are not very high and the reactions
involve generally long process.[12–17] Furthermore, because of side
reactions and large volumes of organic solvents, these protocols produce
significant quantities of chemical wastes.
Two different methods for microwave-assisted, solvent-free synthesis
of 2-aminoimidazolines are available in literature, and these methods
were developed in our previous studies. In the first work, we reported
microwave-assisted synthesis in solvent-free conditions of several new
2-aminoimidazolines from dimethyl N-aryldithioimidocarbonates and
ethylenediamine.[10] In the subsequent study, 2-aminoimidazolines were
synthesized from a one-pot reaction of aromatic or hetero-aromatic
amines with imidazolidine-2-thione.[11]
2-Methylmercapto-4,5-dihydroimidazole hydroiodide (compound 1)
was used as the starting reagent in this study. The synthesis of 2-
aminoimidazolines was performed by refluxing these compounds in
methanol for 8 h following the conventional method. The yields of the
products are 39–80% with this method.
In our endeavor to develop an environmentally benign synthesis
that gets rid of the use of solvent, an attempt was made to synthesize
2-aminoimidazolines under neat reaction conditions. Test reactions were
carried out to modify of the conventional method to microwave-assisted
neat reaction conditions. The heating ability of compound 1 and sub-
stituted amines were investigated under MWI conditions. Neither

Microwave-Induced Synthesis of 2-Aminoimidazolines
3265
Figure 1. Profile of rise in temperature under microwave irradiation by modu-
lation of emitted power for the reaction of benzyl amine with compound 1
(compound 1=amine ¼ 1:2).
2-methylmercapto-4,5-dihydroimidazole hydroiodide nor amines reached
the needed temperature. When 1 mol of compound 1 and 2 mol of amine
were mixed and irradiated with MW at 10 W, the temperature reached
130–135ꢀC in a very short time (Fig. 1). We tried several reactions under
MWI at 10 W and 25 W. The greatest yields were obtained with 10 W in
5 min.
When a 2=1 molar ratio of amine and 2-methylthioimidazoline
hydroiodide were used both to increase nucleophilic capability of amines
and to increase heat transfer with MWI, the product yields significantly
increased. 2-Aminoimidazolines were obtained with excellent yields in a
2=1 reactive ratio using 10 W for 5 min at 130–135ꢀC for the neat reaction
conditions. The data of the different reactions are summarized in Table 1.
Table 1. Reaction of benzylamine with compound 1 under microwave irradiation
Applied power (W)
Temperature (ꢀC)
Reaction time (min)
Yield (%)
10
10
10
10
25
25
145–150
140–145
130–135
120–125
120–125
100–105
5
5
5
10
10
10
83
89
91
85
79
87

3266
M. Genc and S. Servi
We observed that when a 1=1 molar ratio of amine and 2-methylmer-
capto-4,5-dihydroimidazole hydroiodide was used, the yields of the
products decreased and a significant amount of compound 1 did not react
in these reactions. Because 2-aminoimidazolines have physical features
similar to compound 1, 2-aminoimidazolines were very difficult to isolate
from the reaction mixture. When the reaction was completed, the crude
product was purified by precipitating with hexane, except for 5i and
5k. These compounds were purified by using column chromatography,
eluting with 1=1 acetonitrile and dichloromethane (v=v). Optical rota-
tions of chiral-2-aminoimidazolines were measured in CHCl3 solution,
but optical rotation was not observed for compound 5k. Compounds
3a–d were described in the literature.[18,19] All of the spectroscopic data
of the other compounds are in full agreement with their structures.
CONCLUSION
A new microwave-assisted synthesis of 2-aminoimidazolines has been
achieved under neat reaction conditions from commercially available mate-
rials. It is especially important to point out that no organic solvent was used
at any time in the neat reaction except for the purification step. Neat reac-
tants were subjected to MWI to give the required products in excellent
yield. This environmentally friendly method provides various advantages,
such as good yields, fast reaction times, and neat reaction conditions.
EXPERIMENTAL
General
All reagents were of commercial quality, and solvents were used without
further purification. Infrared (IR) spectra were determined on a Perkin-
Elmer Spectrum One Fourier transform-infrared (FT-IR) spectrometer.
NMR spectra were recorded on Bruker 300-MHz and 400-MHz spectro-
meters. Chemical shift d are reported in parts per million relative to
CHCl3 (1H d ¼ 7.27), CDCl3 (13C d ¼ 77.0), and dimethylsulfoxide
(DMSO) (1H d ¼ 2.51 and 3.36 for water present in DMSO), DMSO-d6
(13C d ¼ 39.51), and tetramethylsilane (TMS) as internal standard. Col-
umn chromatography was carried out on silica gel 60 (40–63 mM).
Thin-layer chromatography (TLC) was carried out on aluminum sheets
precoated with silica gel 60 F254 (Merck). Melting points (uncorrected)
were determined with the Electrothermal IA 9100 apparatus. Optical
rotations were measured with a Perkin-Elmer polarimeter. The reactions
were carried out with single mode CEM Discover Labmate instrument

Microwave-Induced Synthesis of 2-Aminoimidazolines
3267
(producing continuous irradiation at 2450 MHz), which has an in situ
magnetic stirrer, irradiation monitored by PC computer, IR measure-
ment, and continuous feedback temperature control.
General Procedure
The mixture of chiral or nonchiral amines (2 mmol) and 2-methylmercapto-
4,5-dihydroimidazole hydroiodide (1 mmol) were placed in a 50-mL,
one-necked flask. The mixture was irradiated in the microwave cavity at
10 W for 5 min at 130–135ꢀC.
Caution: The noxious gas CH3SH evolves during the synthesis, and it
should be trapped with a concentrated aqueous solution of NaOH and
then destroyed with sodium hypochlorite.
The crude product was dissolved in chloroform (2 mL), and then hex-
ane (30 mL) was added. The precipitate was filtered off and dried under
vacuum. The crude products were purified by crystallization from appro-
priate solvents. The synthesis of compounds 3a–g and 5a–i were pre-
sented in Scheme 1. Physicochemical data for the achiral (3a–g) and
chiral (5a–k) 2-aminoimidazolines are given in Tables 2 and 3.
Data
Cyclohexyl-(4,5-dihydro-1H-imidazol-2-yl)amine hydroiodide (3a)
1
Colorless; IR (neat): t; 3276, 3200, 2935, 2848, 1662, 1596. H NMR
(300 MHz, CDCl3): d 1.33–2.01 (m, 11H), 3.73 (s, 4H, imidazoline
N-CH2), 7.11 (br, 2H, NH), 7.46 (d, J ¼ 8.4 Hz, 1H, þNH). Anal. calcd.
for C9H18N3I (295.16): C, 36.62; H, 6.15; N, 14.24. Found: C, 36.73; H,
6.09; N, 14.48.
Scheme 1. Synthesis of 2-aminomidazolines at neat reaction conditions.

3268

3269

3270

3271

3272
M. Genc and S. Servi
Piperidin-1-yl-(4,5-dihydro-1H-imidazol-2-yl)amine hydroiodide (3b)
Colorless; IR (neat): t; 3231, 2945, 2853, 1662, 1601. 1H NMR (300 MHz,
CDCl3): d 1.65 (m, 6H, piperidine CH2), 2.83 (br, 4H, piperidine N-CH2),
3.76 (m, 4H, imidazoline N-CH2), 6.48 (s, 1H, NH), 7.35 (s, 1H, NH),
8.93(s, 1H, þNH). Anal. calcd. for C8H17N4I (296.15): C, 32.44; H,
5.79; N, 18.92. Found: C, 32.53; H, 5.86; N, 18.76.
Morpholin-4-yl-(4,5-dihydro-1H-imidazol-2-Yl)amine
hydroiodide (3c)
1
Colorless; IR (neat): t; 3301, 3212, 2988, 2821, 1662, 1604. H NMR
(300 MHz, CDCl3): d 3.00 (s, 4H, morpholine N-CH2), 3.84 (m, 8H, imi-
dazoline N-CH2 and morpholine O-CH2), 6.92 (s, 1H, NH), 7.39 (s, 1H,
NH), 9.13 (s, 1H, þNH). Anal. calcd. for C7H15N4OI (298.12): C, 28.20;
H, 5.07; N, 18.79. Found: C, 28.26; H, 5.16; N, 18.84.
Benzyl-(4,5-dihydro-1H-imidazol-2-yI)amine hydroiodide (3d)
1
Colorless; IR (neat): t; 3310, 3211, 3060, 2939, 1668, 1597; H NMR
(300 MHz, DMSO-d6): d 3.63 (s, 4H, imidazoline N-CH2), 4.40 (s, 2H,
benzylic CH2), 7.29–7.42 (m, 5H, Ar-H), 8.25 (br, 3H, NH and þNH).
13C NMR (75 MHz, DMSO-d6): d 42.54, 45.76, 127.26, 127.58, 128.57,
136.97, 159.33. Anal. calcd. for C10H14N3I (303.02): C, 39.62; H, 4.65;
N, 13.86. Found: C, 39.77; H, 4.72; N, 13.91.
(2-Chlorobenzyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (3e)
1
Colorless; IR (neat): t; 3271, 3215, 3070, 2961, 1660, 1604; H NMR
(300 MHz, DMSO-d6): d 3.62 (s, 4H, imidazoline N-CH2), 4.44 (s, 2H,
benzylic CH2), 7.51–7.33 (m, 4H, Ar-H), 8.51 (br, 3H, NH and þNH).
Anal. calcd. for C10H13ClN3I (336.98): C, 35.58; H, 3.88; N, 12.45.
Found: C, 35.65; H, 3.91; N, 12.56.
(4-Methoxybenzyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (3f)
Colorless;IR(neat):t3275,3215,3068,2934,1660,1610;1HNMR(300 MHz,
DMSO-d6): d 3.59 (s, 4H, imidazoline N-CH2), 3.79 (s, 3H, OCH3), 4.28 (s,
2H, benzylic CH2), 6.94 (d, J ¼ 8.7 Hz, 2H, Ar-H), 7.25 (d, J ¼ 8.4 Hz

Microwave-Induced Synthesis of 2-Aminoimidazolines
3273
2H, Ar-H), 8.16 (br, 3H, NH and þNH). Anal. calcd. for C11H16N3OI
(333.03): C, 39.65; H, 4.84; N, 12.61. Found: C, 39.69; H, 4.94; N, 12.66.
(4-Methylbenzyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (3g)
1
Colorless; IR (neat): t; 3284, 3198, 3073, 2922, 1664, 1595; H NMR
(300 MHz, DMSO-d6): d 2.27 (s, 3H, CH3), 3.59 (s, 4H, imidazoline
N-CH2), 4.31 (s, 2H, benzylic CH2), 7.25 (s, 4H, Ar-H), 8.50 (br, 3H,
NH and þNH). Anal. calcd. for C11H16N3I (317.17): C, 41.66; H, 5.08;
N, 13.25. Found: C, 41.73; H, 5.17; N, 13.33.
(R)-(1-Cyclohexylethyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5a)
20
Colorless; ½aꢁD ꢂ2.7 (c 3.28, CHCl3); IR (neat): t 3301, 3250, 2969, 1671,
1
1589; H NMR (400 MHz, CDCl3): d 1.57 (d, J ¼ 6.8 Hz, 3H, CH3),
1.86–1.17 (m, 11H, CH and CH2), 3.74 (m, 5H, imidazoline N-CH2
and N-CH), 7.23 (br, 1H, NH), 7.35 (br, 1H, NH), 7.43(d, J ¼ 9.6 Hz,
1H, þNH). 13C NMR (100 MHz, CDCl3): d 18.03, 26.00, 28.62, 40.96
42.46, 43.01, 55.44, 55.47, 158.97. Anal. calcd. for C11H22N3I (323.22):
C, 40.88; H, 6.86; N, 13.00. Found: C, 40.97; H, 6.92; N, 13.11.
(S)-(1-Cyclohexylethyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5b)
20
Colorless; ½aꢁD þ0.7 (c 3.18, CHCl3); IR (neat): t; 3306, 3254, 2969, 2841,
1671, 1589. 1H NMR (300 MHz, CDCl3): d 1.24 (d, J ¼ 6.6 Hz, 3H, CH3),
1.58–1.41 (m, 11H, CH and CH2), 3.72 (m, 5H, imidazoline N-CH2 and
N-CH), 7.23 (br, 1H, NH), 7.35 (br, 1H, NH), 7.45 (d, J ¼ 9.6 Hz, 1H,
þNH). 13C NMR (75 MHz, CDCl3): d 18.03, 26.00, 28.62, 40.96 42.46,
43.01, 55.44, 55.47, 158.97. Anal. calcd. for C11H22N3I (323.22): C,
40.88; H, 6.86; N, 13.00. Found: C, 40.79; H, 6.79; N, 13.09.
(R)-(1-Phenylethyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5c)
20
Colorless; ½aꢁD þ7.4 (c 3.08, CHCl3); IR (neat): t; 3262, 3206, 3064, 2974,
1666, 1593; 1H NMR (300 MHz, CDCl3): d 1.6 (d, J ¼ 6.9 Hz, 3H, CH3),
3.66 (s, 4H, imidazoline N-CH2), 5.03 (p, J ¼ 6.9 Hz, 1H, CH), 6.8 (br, 2H,
NH), 7.32 (m, 3H, Ar-H), 7.49 (d, J ¼ 8.1 Hz, 2H, Ar-H), 8.24 (d,

3274
M. Genc and S. Servi
J ¼ 7.2 Hz, 1H, þNH). 13C NMR (75 MHz, CDCl3): d 23.79, 42.59, 54.12,
125.35, 128.36, 128.39, 141.34, 159.78. Anal. calcd. for C11H16N3I (317.17):
C, 41.66; H, 5.08; N, 13.25. Found: C, 41.62; H, 5.17; N, 13.34.
(S)-(1-Phenylethyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5d)
20
Colorless; ½aꢁD ꢂ2.5 (c 3.36, CHCl3); IR (neat): t 3266, 3187, 3064, 2974,
1657, 1593; 1H NMR (300 MHz, CDCl3): d 1.54 (d, J ¼ 6.6 Hz, 3H, CH3),
3.59 (s, 4H, imidazoline N-CH2), 5.07 (q, J ¼ 6.6, 1H, CH), 7.10 (br, 2H,
NH), 7.22 (m, 3H, Ar-H), 7.62 (d, J ¼ 7.1 Hz, 2H, Ar-H), 8.10 (s, 1H,
þNH). Anal. calcd. for C11H16N3I (317.17): C, 41.66; H, 5.08; N,
13.25. Found: C, 41.78; H, 6.19; N, 13.23.
(R)- (1-Phenyl-propyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5e)
20
Colorless; ½aꢁD þ2.5 (c 3.36, CHCl3); IR (neat): t; 3262, 3202, 3060, 2965,
1666, 1597; 1H NMR (300 MHz, CDCl3): d 0.97 (t, J ¼ 7.2 Hz, 3H, CH3),
1.90 (m, 2H, CH2), 3.67 (s, 4H, imidazoline N-CH2), 4.08 (q, J ¼ 6.6 Hz,
1H, CH), 6.74 (br, 2H, NH), 7.32–7.16 (m, 5H, Ar-H), 8.28 (s, 1H, þNH).
13C NMR (75 MHz, CDCl3): d 10.70, 30.06, 42.58, 59.95, 126.79, 128.86,
140.01, 159.12. Anal. calcd. for C12H18N3I (331.20): C, 43.52; H, 5.48; N,
12.69. Found: C, 43.66; H, 5.51; N, 12.80.
(R)-[1-(4-Methoxyphenyl)ethyl](4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5f)
20
Colorless; ½aꢁD þ6.0 (c 3.57, CHCl3); IR (neat): t 3262, 3189, 3068, 2831,
1666, 1610; 1H NMR (300 MHz, CDCl3): d 1.58 (d, J ¼ 6.6 Hz, 3H, CH3),
3.52 (s, 4H, imidazoline N-CH2), 3.78 (s, 3H, OCH3), 5.03 (q, J ¼ 6.6 Hz,
1H, CH), 6.78–6.86 (m, 4H, ArH þ 2NH), 7.4 (d, J ¼ 8.7 Hz, 2H, Ar-H),
8.17 (s, 1H, þNH). 13C NMR (75 MHz, CDCl3): d 23.79, 42.56, 53.58,
55.38, 114.07, 127.24, 133.30, 158.51, 159.25. Anal. calcd. for C12H18N3OI
(347.20): C, 41.51; H, 5.23; N, 12.10. Found: C, 41.72; H, 5.33; N, 12.22.
(S)-[1-(4-Methoxyphenyl)ethyl](4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5g)
20
Colorless; ½aꢁD ꢂ2.8 (c 3.33, CHCl3); IR (neat): t 3262, 3189, 3068, 2831,
1
1668, 1610; H NMR (300 MHz, CDCl3): d 1.58 (d, J ¼ 6.6 Hz, 3H, CH3),

Microwave-Induced Synthesis of 2-Aminoimidazolines
3275
3.65 (s, 4H, imidazoline N-CH2), 3.78 (s, 3H, OCH3), 4.98 (q, J ¼ 6.3 Hz, 1H,
CH), 6.87–6.78 (m, 4H, ArHþ 2NH), 7.4 (d, J ¼ 8.4 Hz, 2H, Ar-H), 8.18 (s,
1H, þNH). 13C NMR (75MHz, CDCl3): d 23.81, 42.57, 53.63, 55.39, 114.31,
127.33, 133.08, 158.88, 159.29. Anal. calcd. for C12H18N3OI (347.20): C,
41.51; H, 5.23; N, 12.10. Found: C, 41.59; H, 5.31; N, 12.19.
(R)-[1-(4-Chlorophenyl)ethyl]-(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5h)
20
Colorless; ½aꢁD þ2.8 (c 3.57, CHCl3); IR (neat): t 3262, 3189, 3060, 2982,
1664, 1593; 1H NMR (300 MHz, CDCl3): d 1.59 (d, J ¼ 6.6 Hz, 3H, CH3),
3.69 (s, 4H, imidazoline N-CH2), 5.09 (p, J ¼ 6.6 Hz, 1H, CH), 7.12 (br,
2H, NH), 7.28–7.50 (m, 4H, Ar-H), 8.24 (d, J ¼ 7.2 Hz, 1H, þNH). 13C
NMR (75 MHz, CDCl3): d 23.48, 42.59, 53.51, 127.81, 128.86, 139.77,
158.73. Anal. calcd. for C11H15ClN3I (351.61): C, 37.57; H, 4.30;
N, 11.95. Found: C, 37.77; H, 4.41; N, 12.06.
(R)-(1-Naphthalen-2-yl-ethyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5i)
20
Colorless; ½aꢁD þ7.7 (c 2.98, CHCl3); IR (neat): t 3262, 3185, 3056, 2974,
1660, 1597; 1H NMR (400 MHz, CDCl3): d 1.64 (d, J ¼ 6.8 Hz, 3H, CH3),
3.45 (s, 4H, imidazoline N-CH2), 5.19 (q, J ¼ 6.8 Hz, 1H, CH), 7.16 (br,
2H, NH), 7.28–8.1 (m, 7H, Ar-H), 8.27 (d, J ¼ 7.6 Hz, 1H, þNH). Anal.
calcd. for C15H18N3I (367.23): C, 49.06; H, 4.94; N, 11.44. Found: C,
49.13; H, 5.09; N, 11.56.
(S)-(1-Naphthalen-2-yl-ethyl)(4,5-dihydro-1H-imidazol-2-yl)amine
hydroiodide (5k)
20
Colorless; oily; ½aꢁD not determined; IR (neat): t 3262, 3181, 3051, 2974,
1660, 1597; 1H NMR (300 MHz, CDCl3): d 1.65 (d, J ¼ 6.9 Hz, 3H, CH3),
3.45 (s, 4H, imidazoline N-CH2), 5.20 (q, J ¼ 6.9 Hz, 1H, CH), 7.16 (br,
2H, NH), 7.28–8.1 (m, 7H, Ar-H), 8.26 (d, J ¼ 7.8 Hz, 1H, þNH). Anal.
calcd. for C15H18N3I (367.23): C, 49.06; H, 4.94; N, 11.44. Found:
C, 49.15; H, 5.06; N, 11.51.
ACKNOWLEDGMENTS
We are indebted to the the Scientific and Technological Research Council
of Turkey (TUBITAK, Project Number 105T419) for financial support
of this work.

3276
M. Genc and S. Servi
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