A convenient one-pot three component approach to synthesis of highly substituted iminothiazolines

Article abstract of DOI:10.3987/COM-08-11453

An efficient one-pot three component method was developed for the synthesis of highly substituted 2-iminothizolines by the reaction of isothiocyanates, primary amines and α-bromoketones in ambient temperature. The reaction produced the desired products in a completely regioselective manner in excellent yields (78-94%). The Japan Institute of Heterocyclic Chemistry.

Full text of DOI:10.3987/COM-08-11453

HETEROCYCLES, Vol. 75, No. 11, 2008
2825
HETEROCYCLES, Vol. 75, No. 11, 2008, pp. 2825 - 2833. © The Japan Institute of Heterocyclic Chemistry
Received, 26th May, 2008, Accepted, 3rd July, 2008, Published online, 7th July, 2008. COM-08-11453
A CONVENIENT ONE-POT THREE COMPONENT APPROACH TO
SYNTHESIS OF HIGHLY SUBSTITUTED IMINOTHIAZOLINES
Heshmat Allah Samimi, Manouchehr Mamaghani,* and Khalil Tabatabaeian
Department of Chemistry, Faculty of Sciences, University of Guilan, P. O. Box
41335-1914, Rasht, Iran
E-mail: m-chem41@guilan.ac.ir
Abstract – An efficient one-pot three component method was developed for the
synthesis of highly substituted 2-iminothizolines by the reaction of
isothiocyanates, primary amines and α-bromoketones in ambient temperature. The
reaction produced the desired products in a completely regioselective manner in
excellent yields (78-94%).
INTRODUCTION
Iminothiazolines are significant group of organic compounds which have attracted a great deal of
attention in organic synthesis due to their diverse biological activities such as bactericidal,1 analgesicidal,2
fungicidal,3 insecticidal,4 anti HIV,5 anti-inflammatory,6 vasodilator and antihypertensive,7
anticonvulsant,8 anthelmintic,9 plant growth regulatory and antifungal activities,10 pifithrin (Pft-α), skin
whitening agent (KHG22394)11 and fungitoxicity against rice blast.12
Several methods have been developed for the synthesis of iminothiazoline moity which include,
N-alkylation of aminothiazoles,13 solid- phase strategy,14 the condensation of carbonyl compounds with
thioureas and 1,3-disubstituted thioureas using 1,1′-(ethan-1,2-diyl)dipyridinium bistribromide
(EDPBT),15 reaction of N-monoalkylated thiaoureas with 3-bromomethyl-2-cyanocinnmonitrile,
microwave-assisted reaction,16 cycloaddition reaction,17 by ring transformation of 2-(thiocyanomethyl)-
aziridines,18 the reaction of benzoyl-3-phenylthioureas with bromine and enolizable ketones in the
presence of triethylamine,19 reaction of N-propargylaniline with acylisothiocyannates, reaction of
α-haloketones with N-benzoyl-N′-arylthioureas or N,N′-disubstituted thioureas.20 The main disadvantages
with most of these procedures are harsh reaction conditions, difficult workup, low yields, high reaction
time and in the case of using unsymmetrical disubstituted thioureas low regioselectivity.
In spite of synthesis of numerous substituted 2-iminothiazolines and evaluation of their biological
activities, only a few fully substituted iminothiazolines have been synthesized and examined for their
biological properties.

2826
HETEROCYCLES, Vol. 75, No. 11, 2008
These observations prompted us to synthesize a series of new, highly substituted aryl- and
alkylimino-thiazolines via a convenient one-pot three component reaction under ambient temperature.
RESULTS AND DISCUSSION
As a continuation of our research devoted to the development of new methodologies in the synthesis of
heterocyclic compounds,21 in a search for a suitable protocol for the synthesis of 2-iminothiazoline ring
system, as potential drug candidates possessing interesting biological activities, at mild reaction
conditions using readily accessible reagents, we employed a simple one-pot three component pathway
(Scheme 1). In this approach, the reaction of isothiocyanates (1a-j) and primary amines (2a-j) in ethanol,
followed by the addition of α-bromoketones (3a-j) at ambient temperature, produced the desired
2-iminothiazoline (4a-j) as sole products in excellent yields (78-94%) (Table 1).
R2
Br
N
Ph
S
R1
R3
O
R1
R2
N
S
3a-j
R1NCS + R2NH2
N
N
H
H
1a-j
2a-j
Ph
R3
4a-j
Scheme 1
In this approach the condensation of dissymmetric thioureas (via in situ formation from isothiocyanate
and amine), and α-bromo ketone produced only one regio-isomer of iminothiazolines (4a-j) (Table 1).
Table 1. One-pot three component synthesis of iminothiazolines 4a-j
Entry
R1
R2
R3
Time (h)
Yield (%)a
mp (ºC)
a
b
c
d
e
f
Et
Me
Me
Me
Et
Et
PhCH2CH2
PhCH2CH2
PhCH2CH2
4-Me-C6H4-
4-Me-C6H4-
Bn
Ph
Me
H
7
9
8
9
9
9
8
8
8
9
81
93
78
87
92
91
94
89
92
88
146-148
140-142
121-122
106-107
105-107
88-90
Ph
Me
Ph
Me
Me
Ph
H
Et
g
h
i
Et
198-200
146-148
138-139
122-124
Bn
Bn
Bn
Ph
Ph
j
Ph
a. Isolated yield

HETEROCYCLES, Vol. 75, No. 11, 2008
2827
Since the spectral data (e.g., NMR, IR, and elemental analysis) for the structural assignment of
iminothiazolines with dissymmetrically substituted nitrogens were not conclusive, X-ray crystallographic
22
analysis was conducted on the hydrobromide salt of 4b to verify product structure. As shown in the
ORTEP plots of 4b (Figure 1), the bulky phenethyl group resides on imino nitrogen. The result of X-ray
analysis clearly confirms the stereoelectronic controlling nature of the reaction.
Figure 1. ORTEP plots of 4b
In this reaction, under kinetic control sulfur from thiourea (formed in situ), attacks the carbon bearing Br
(3a-j), then cyclization takes place by nucleophilic addition of N to the carbonyl group and finally
dehydration of the intermediate thus formed, furnishes the desired 2-imino-thiazolines (4a-j). In this
approach formation of two regio-isomers (4a-j, 5a-j) is possible but under the reaction condition used
only one regio-isomer is formed (4a-j). In all the reactions carried out for the synthesis of
2-iminothiozolines no trace of imidazole-2-thione (6) (Figure 2), which could have been the result of
initial attack of nitrogen from in situ formed thioureas to the carbon bearing Br (3a-j), was detected.
R1
R1
N
R4
R2
N
N
S
S
N
Ph
Ph
R3
R2
5a-j
6
Figure 2
According to the literature report this type of products are formed by the reaction of N,N′-dialkylthioureas
o
with 3-hydroxy-2-butanone in boiling 1-hexanol (bp 157 C).23 We examined this reaction by reacting
o
N,N′-dialkylthioureas in boiling 2-ethylhexanol(bp 185 C) (Scheme 2). The reaction cleanly produced

2828
HETEROCYCLES, Vol. 75, No. 11, 2008
the related imidazole-2-thiones (9a, 9b) in 20 h as sole products in high yields. These results also revealed
that replacement of Br as better leaving group with OH in the α-haloketone, completely changes the
reaction pathway.
In order to assign the right structure of the regio-isomers obtained, the synthesis of 4g was conducted
using the method reported by De Kimpe and co-workers13 (Scheme 3). Spectral properties of the product
S
O
S
R
R
reflux
N
N
Me
R
R
+
Me
N
N
2-ethylhexanol
20 h
H
H
OH
Me
Me
7
8
9a 84%
9b 77%
a
R= Et
b
R= Bn
Scheme 2
(4g) from this reaction was identical the one obtained from our approach. With respect to the spectral data
from 4a, 4b and 4g (Figure 3) and the results of X-ray analysis, full structural assignments of all the
NH2
O
S
EtOH/Et3N
heat, 3h
Me
N
S
+
Ph
H2N
NH2
10
Br
Ph
Me
EtOH/EtI
heat, 15h
NH
N
Ph
Et
EtOH/BnCl
heat, 5h
Et
N
S
N
S
Ph
Me
Ph
Me
4g
Scheme 3
1
synthesized regio-isomers were possible (Table 1). It is quite evident from the H NMR data (Figure 3)
that CH2 protons attached to the ring nitrogen compared with those on imino nitrogen are observed in
relatively downfields. This may also be explained by the result of X-ray analysis of hydrobromide salt of
4b (Figure 1) which confirms the more basic nature of exocyclic imino nitrogen.

HETEROCYCLES, Vol. 75, No. 11, 2008
2829
CONCLUSION
In summary this research work describes an efficient and facile synthesis of highly substituted
2-iminothiazolines by one-pot three component reaction in a completely regio-selective reaction in
ambient temperature with excellent yields (78-94%). The research in this respect for the synthesis of
fused ring iminothiazolines is under way.
3.1 ppm
3.1 ppm
3.3 ppm
3.4 ppm
3.2 ppm
3.7 ppm
N
N
N
3.5 ppm
3.5 ppm
N
S
N
S
3.7 ppm
N
S
4b
4c
4d
1.1 ppm
3.7 ppm
1.3 ppm
3.8 ppm
3.8 ppm
1.2 ppm
4.3 ppm
1.2 ppm
N
N
N
1.3 ppm
3.1 ppm
N
N
S
N
S
N
S
4.6 ppm
S
N
4e
4a
4f
4g
N
N
N
5.0 ppm
5.0 ppm
N
S
5.1 ppm
N
S
N
S
4h
4j
4i
Figure 3. 1H NMR chemical shifts of various alkyl groups attached to N
EXPERIMENTAL
1H NMR spectra were obtained on a Bruker DRX-500 and those of 13C NMR spectra on a Bruker
DRX-125 Avance spectrometer. FT-IR spectra were recorded on a Shimadzu FT-IR-8400S spectrometer.
Chemical shifts of 1H and 13C NMR spectra were expressed in ppm in downfield from tetramethylsilane.
Melting points were measured on a Buchi melting point B-540 instrument and are uncorrected. Elemental
analyses were made by a Carlo-Erba EA1110CNNO-S analyzer and agreed with the calculated values.
All the chemicals were purchased from Merck and used without further purification.

2830
HETEROCYCLES, Vol. 75, No. 11, 2008
General procedure for synthesis of iminothiazoles via three component reaction
To a solution of alkyl or arylamine (1 mmol) in EtOH (10 mL), isothiocyanate (1 mmol) was added
and the reaction mixture was stirred at rt for 3 h. To the resulting reaction mixture 2-bromoketone (3)
(1mmol) was added and stirring was continued for 3-6 h. The mixture was concentrated with evaporation
under reduced pressure, washed with aqueous Na2CO3 (10%) and extracted with CH2Cl2 (3x10 mL). The
organic phase was evaporated and the residue dissolved in EtOH, addition of water gave
2-iminothiazolines (4) as white precipitate with 78-94% yields. Pure products of 4b, 4d, 4e and 4g were
obtained by recrystalization from mixed H2O/EtOH/DMSO (10:3:3).
General procedure for synthesis of thiazol-2-thione (9a and 9b)
To a solution of N,N′-diethyl(or dibenzyl)thiourea (2 mmol) in 2-ethylhexanol (7 mL),
3-hydroxy-2-butanone (0.17 g, 2 mmol) was added. The reaction was heated under reflux for 20 h.
Purification of the mixture by column chromatography (silica gel, EtOAc-hexane: 1/4) provided
thiazol-2-thione 9a (mp 120-122 °C) and 9b (mp 114-116 °C ) in 84 and 77 % yields, respectively.
1
4a. Yield 81%, white solid, mp 146-148 °C, H-NMR (CDCl3, 500 MHz): δ 1.1 (s, 3H), 1.3 (s, 3H), 3.1
(s, 2H), 3.7 (s, 2H), 7.0-8.1 (m, 10H); 13C-NMR (CDCl3, 125 MHz): 13.0, 17.5, 24.6, 49.0, 110.3, 121.1,
127.7, 128.6, 128.9, 129.3, 130.8, 130.9, 138.1, 152.3, 158.5; IR (KBr, cm-1): 3035, 2960, 1610, 1590,
1450, 1375, 750, 700. Anal. Calcd for C19H20N2S (308.44): C, 73.99; H, 6.54; N, 9.08. Found: C, 73.69;
H, 6.82; N, 9.15.
4b. Yield 93%, white solid, mp 140-142 °C, 1H-NMR (CDCl3, 500 MHz): δ 2.15 (s, 3H), 3.29 (t, 2H, J =
7.3 Hz), 3.70 (s, 3H), 3.70 (t, 2H, J = 7.3 Hz), 7.26-7.28 (m, 3H), 7.32-7.37 (m, 4H), 7.54-7.59 (m, 3H);
13C-NMR (CDCl3, 125 MHz): 12.6, 34.9, 38.0, 50.8, 115.2, 127.2, 127.3, 127.8, 129.2, 129.5, 130.0,
131.2, 138.1, 138.5, 167.0; IR (KBr, cm-1): 3030, 2950, 1620, 1590, 1435, 1377, 780, 757, 700, 500.
Anal. Calcd for C19H20N2S (308.44): C, 73.99; H, 6.54; N, 9.08. Found: C, 74.10; H, 6.44; N, 9.15.
4c. Yield 78%, white solid, mp 121-122 °C, 1H NMR (CDCl3, 500 MHz): δ 3.10 (t, 2H, J = 5.9 Hz), 3.35
(s, 3H), 3.64 (t, 2H, J = 5.9 Hz), 5.92 (s, 1H), 7.27 (m, 1H), 7.35 (d, 3H, J = 4.4 Hz), 7.39 (dd, 2H, J =
7.3, 2.3 Hz), 7.49 (dd, 2H, J = 4.6, 3.9 Hz); 13C-NMR (CDCl3, 125 MHz): 34.4, 36.7, 51.2, 112.2, 127.5,
127.8, 128.8, 129.2, 129.7, 130.1, 131.7, 138.2, 138.2, 165.4; IR (KBr, cm-1): 3050, 2965, 2920, 2880,
1634, 1580, 1500, 1450, 1381, 1251, 700. Anal. Calcd for C19H22N2S ( 310.46): C, 73.51; H, 7.14; N,
9.02. Found: C, 73.37; H, 7.05, N, 9.22.
1
4d. Yield 87%, white solid, mp 106-107 °C, H-NMR (CDCl3, 500 MHz): δ 3.11 (t, 2H, J = 5.96 Hz),
3.19 (s, 3H), 3.52 (t, 2H, J = 5.96 Hz), 7.05 (dd, 2H, J = 5.9, 1 Hz), 7.13 (m, 3H), 7.30 (m, 1H), 7.34 (dd,
13
2H, J = 5.6, 2.1 Hz), 7.40 (d, 4H, J = 6.7 Hz), 7.48 (m, 3H); C NMR (CDCl3, 125 MHz): 33.2, 37.8,

HETEROCYCLES, Vol. 75, No. 11, 2008
2831
57.4, 126.4, 126.8, 128.1, 128.2, 128.7, 128.8, 129.1, 129.4, 129.6, 129.7, 130.8, 132.0, 133.2, 135.9,
141.1, 158.8; IR (KBr, cm-1): 3100, 2990, 1620, 1400, 1350, 757, 690. Anal. Calcd for C26H30N2S
(402.59): C, 77.57; H, 7.51; N, 6.96. Found: C, 77.50; H, 7.57; N, 6.87.
4e. Yield 92%, white solid, mp 105-107 °C, 1H-NMR (CDCl3, 500 MHz): δ 1.73 (t, 3H, J = 7 Hz), 1.93
(s, 3H), 2.38 (s, 3H), 3.78 (q, 2H, J = 7 Hz), 7.03 (d, 2H, J = 6.4 Hz), 7.18 (d, 2H, J = 8.0 Hz), 7.36 (dd,
13
2H, J = 7.6, 1.3 Hz), 7.48-7.53 (m, 3H); C-NMR (CDCl3, 125 MHz): 13.0, 49.0, 106.3, 121.5, 128.7,
128.9, 130.0, 130.2, 131.0, 132.1, 134.3, 149.8, 158.6.; IR (KBr, cm-1): 3057, 2968, 2918, 2862, 1634,
1580, 1502, 1439, 1381, 1251, 705. Anal. Calcd for C19H20N2S (308.44): C, 73.99; H, 6.54; N, 9.08.
Found: C, 73.87; H, 6.64; N, 9.13.
4f. Yield 91%, white solid, mp 88-90 °C, 1H-NMR (CDCl3, 500 MHz): δ 1.19 (t, 2H, J = 7 Hz), 2.34 (s,
3H), 3.80 (q, 2H, J = 7 Hz), 6.9 (m, 2H), 7.05 (m, 5H), 7.15 (s, 1H), 7.16 (s, 1H), 7.35 (m, 2H), 7.45 (m,
13
3H); C-NMR (CDCl3, 125 MHz): 11.6, 12.8, 36.0, 115.8, 121.0, 126.3, 127.1, 127.8, 128.1, 128.8,
129.1, 129.4, 129.9, 120.1, 130.4, 133.4, 137.0, 162.3; IR (KBr, cm-1): 3050, 2980, 1620, 1580, 1500,
1420, 1380, 1320, 1200, 1080, 820, 750, 690, 500; Anal. Calcd for C24H22N2S (370.50): C, 77.80; H,
5.98; N, 7.56. Found: C, 77.75; H, 5.99; N, 7.60.
1
5g. Yield 94%, white solid, mp 198-200 °C, H-NMR (CDCl3, 500 MHz): δ 1.24 (t, 3H, J = 7 Hz), 2.04
13
(s, 3H), 4.27 (q, 2H, J = 7 Hz), 4.70 (s, 2H), 7.25 (m, 2H), 7.36 (m, 3H), 7.5-7.6 (m, 5H).; C-NMR
(CDCl3, 125 MHz): 12.1, 13.7, 43.9, 50.1, 116.0, 127.3, 128.4, 128.7, 128.8, 129.5, 130.2, 130.8, 134.2,
137.6, 165.4; (KBr, cm-1): 3020, 2985, 2985, 2820, 1580, 1490, 1440, 1350, 1330, 1240, 1010, 750, 690.
Anal. Calcd for C20H23N2S (323.48): C, 74.26; H, 7.17; N, 8.66. Found: C, 74.30; H, 7.20, N, 8.76.
1
4h. Yield 89%, white solid, mp 146-148 °C, H-NMR (CDCl3, 500 MHz): δ 1.97 (s, 3H), 5.00 (s, 2H),
13
7.06-7.10 (m, 3H), 7.11-7.15 (m, 4H), 7.22-7.25 (m, 3H), 7.36-7.42 (m, 5H); C-NMR (CDCl3, 125
MHz): 13.0, 49.0, 107.3, 122.1, 123.3, 127.4, 127.7, 128.6, 129.0, 129.3, 129.8, 130.8, 130.9, 134.9,
138.1, 152.3, 159.5; IR (KBr, cm-1): 3067, 3024, 2921, 1626, 1604, 1578, 1489, 1380, 1321, 1147, 815,
694, 658. Anal. Calcd for C23H20N2S (356.48): C, 77.49; H, 5.65; N, 7.86. Found: C, 77.60; H, 5.66; N,
7.97.
4i. Yield 92%, white solid, mp 138-139 °C, 1H-NMR (CDCl3, 500 MHz): δ 5.06 (s, 2H), 6.98 (d, J = 5.35
Hz, 2H), 7.11 (m, 6H), 7.17 (m, 5H), 7.27 (d, 1H, J = 7.2 Hz), 7.36 (t, 2H, J = 7.3 Hz), 7.43 (m, 4H); 13C-
NMR (CDCl3, 125 MHz): 48.8, 122.0, 123.5, 127.1, 127.5, 127.6, 128.2, 128.7, 128.7, 129.3, 129.7,
129.9, 131.2, 131.5, 132.6, 135.2, 138.0, 152.1; IR (KBr, cm-1): 3060, 2926, 2854, 1620, 1585, 1440,
1377, 1325, 1195, 1074, 757, 694. Anal. Calcd for C28H22N2S (418.55): C, 80.35; H, 5.30; N, 6.69.
Found: C, 80.30; H, 5.35; N, 6.61.
1
4j. Yield 88%, white solid, mp 122-124 °C, H-NMR (CDCl3, 500 MHz): δ 5.13 (s, 2H), 5.83 (s, 1H)
7.07-7.13 (m, 5H), 7.22-7.30 (m, 5H), 7.39 (t, 4H, J = 8.2 Hz), 7.40 (d, 1H, J = 7.3 Hz). 13C-NMR (CDCl3,

2832
HETEROCYCLES, Vol. 75, No. 11, 2008
125 MHz): 48.5, 95.9, 121.5, 123.0, 127.1, 127.2, 128.3, 128.5, 129.0, 129.1, 129.4, 131.7, 137.5, 140.4;
IR (KBr, cm-1): 3096, 3056, 3025, 1588, 1563, 1490, 1445, 1385, 1234, 176, 765, 730, 707, 698. Anal.
Calcd for C23H22N2S (358.5): C, 77.06; H, 6.19; N, 7.81. Found: C, 77.16; H, 6.09; N, 7.85.
ACKNOWLEDGEMENTS
We are thankful to Research Council of University of Guilan for the partial support of this work.
REFERENCES (AND NOTES)
1. D. L. Garmaise, C. H. Chambers, and R. C. Mecral, J. Med. Chem., 1968, 11, 1205; M. Omar, E.-D. S.
Shams, A. Ghobashy, and M. Khalil, Eur. J. Med. Chem., 1981, 16, 77; A. El-Khamry, S. El-Nagdy,
M. Habashy, and F. El-Bassiouny, Pharmazie, 1989, 44, 312; G. B. Chandrakant and J. G. Naresh,
Bioorg. Med. Chem., 2004, 12, 2151.
2. V. S. Misra and A. Saxena, J. Indian Chem. Soc., 1970, 47, 23; K. A. El Rashood and S. M. Bayoni,
Sulfur Lett., 1991, 13, 151.
3. B. C. Dash and G. N. Mahapatra, J. Proc. lnst. India, 1967, 34, 178; H. Tripathy, M. K. Das, B. Sahu,
and G. N. Mahapatra, J. Indian Chem. Soc., 1973, 50, 417; A. Mohsen, E. Omar, and N. H. Eshba, J.
Pharm. Sci.,1984, 73, 1166.
4. F. Nagasaki, T. Yamada, E. Takahashi, Y. Kitagaya, and R. Hatano, Jpn. Kokai Tokkyo Koho JP 63,
250, 371 (88,250,371) (C1.CO7D277/42), 18 Oct. 1988, Appl. 87/82,455. 03 Apr. 1987) (Chem.
Abstr., 1989, 110, 192810y).
5. N. Masuda, O. Yamamato, M. Fujii, T. Ohgami, J. Fujiyasu, T. Kontani, A. Moritomo, M. Orita, H.
Kurihara, H. Koga, H. Nakahara, S. Kageyama, M. Ohta, H. Inoue, T. Hatta, H. Suzuki, K. Sudo, Y.
Shimizu, E. Kodama, M. Matsuoka, M. Fujiwara, T. Yokota, S. Shigeta, and M. Baba, Bioorg. Med.
Chem., 2004, 12, 6171; ibid., 2005, 13, 949.
6. S. Plescia, M. L. Bajardi, D. Raffa, C. Daidone, M. Matera, A. Caruso, and N. Amico-Roxas, Eur. J.
Med. Chem., 1986, 21, 291; S. Plescia, G. Daidone, L. Ceraulo, M. L. Bajardi, and R. Anigo,
Farmaco Ed. Sci., 1984, 39, 120.
7. M. D,hooghe, A. Waterinckx, and N. De Kimpe, J. Org. Chem., 2005, 70, 227.
8. A. K. Chaturvedi and S. S. Pamar, Znd. J. Pharm., 1972, 34, 72.
9. V. S. Misra, P. N. Gupta, R. Pandey, C. Nath, and G. P. Gupta, Pharmazie, 1980, 35, 400.
10. H. Yu, L. Shao, and J. Fang, J. Organometal. Chem., 2007, 692, 991.
11. N. Pietrancosta, A. Moumen, R. Dono, P. Lingor, V. Planchamp, F. Lamballe, M. Bahar, J.-L. Kraus,
and F. Maina, J. Med. Chem., 2006, 49, 3645; X. X. Zhu, Q. S. Yu, R. G. Culter, C. W. Culmsee, H.
W. Holloway, D. K. Lahiri, M. P. Mattson, and N. H. Greig, J. Med. Chem., 2002, 45, 5090.
12. H.-G. Hahn, K. D. Nam, S. H. Shin, and H. Mah, Korean, J. Pestic. Sci., 2001, 5, 13.

HETEROCYCLES, Vol. 75, No. 11, 2008
2833
13. N. De Kimpe, M. Boelens, and J.-P. Declercq, Tetrahedron, 1993, 49, 3411.
14. O. S. Wolfbeis and H. Junek, Monatsh. Chem., 1979, 1387.
15. S. Murru, C. B. Singh, V. Kavala, and B. K. Patel, Tetrahedron, 2008, 64, 1931.
16. S. Kasmi, J. Hamelin, and H. Benhaoua, Tetrahedron Lett., 1998, 39, 8093.
17. F. Tittelbach, S. Vieth, and M. Schneider, Eur. J. Org. Chem., 1998, 515.
18. M. D,hooghe, A. Waterinckx, and N. De Kimpe, J. Org. Chem., 2005, 70, 227.
19. C. B. Singh, S. Murru, V. Kavala, and B. K. Patel, Org. Lett., 2006, 8, 5397; R.-Sh. Zeng, J.-P. Zou,
S.-J. Zhi, J. Chen, and Q. Shen, Org. Lett., 2003, 5, 1657.
20. A. Bijev and P. Prodanova, Synth. Commun., 2006, 3095; A. Manaka, T. Ishii, K. Takahashi, and M.
Sato, Tetrahedron Lett., 2005, 46, 419; Y. L. Zborovskii, V. V. Orysyk, A. A. Dobosh, V. I. Staninets,
V. V. Pirozhenko, and A. N. Chernega, Chem. Heterocycl. Comp., 2003, 39, 1099; J. Schmeyers and
G. Kaupp, Tetrahedron, 2002, 58, 7241; B. C. Dash and B. B. Nandi, J. Indian Chem. Soc., 1979, 56,
70; H. Beyer and G. Ruhling, Chem. Ber., 1956, 89, 1473; A. Hantzsch and H. Weber, Chem.
Ber.,1887, 20, 3118; Z. Bartoszewski and Z. Jerzmanovska, Roczniki Chem., 1961, 38, 919; M. J.
Korhoda and A. B. Bojarska, Polish J. Chem., 1984, 58, 447.
21. K. Tabatabaeian, M. Mamaghani, N. Mahmoodi, and A. Khorshidi, J. Mol. Catal. A, 2007, 270, 112;
H. Adibi, H. A. Samimi, and M. Beygzadeh Catal. Commun., 2007, 8, 2119; K. Tabatabaeian, M.
Mamaghani, N. Mahmoodi, and A. Khorshidi, Can. J. Chem., 2006, 84, 1541; M. Mamaghani, K.
Tabatabaeian, M. Mirzaeinejad, and M. Nikpassand, J. Iranian Chem. Soc., 2006, 3, 89; M.
Mamaghani, M. R. Yazdanbakhsh, A. Badrian, H. Valizadeh, and H. A. Samimi, Lett. Org. Chem.,
2005, 2, 721; M. Mamaghani, K. Tabatabaeian, A. Ghanadzadeh, and F. Habibi, Tetrahedron Lett.,
2003, 44, 4775.
22. X-Ray Structural Center (XRSC), Chemistry and Material Sciences Division of Russian Academy of
Sciences (RAS), Institute of Organoelement Compounds (INEOS) of RAS, Moscow, Russia.
23. A. M. Ward, Org. Synthesis, Coll. Vol. 2, 159 (1943).