One-pot synthesis of thiazolo[3,2-α]pyridine derivatives catalysed by ionic liquids

Article abstract of DOI:10.3184/174751912X13282820029367

A green method for the synthesis of thiazolo[3,2-α]pyridine derivatives via the coupling of malononitrile, an aryl aldehyde and methyl thioglycolate in an ionic liquid has been developed. The advantages of this protocol are that it is non-toxic, no by-products are formed, short reaction times are required and high yields are obtained. Thiazolo [3,2-a]pyridines have important biological and medical applications.

Full text of DOI:10.3184/174751912X13282820029367

162 RESEARCH PAPER
MARCH, 162–165
JOURNAL OF CHEMICAL RESEARCH 2012
One-pot synthesis of thiazolo[3,2-a]pyridine derivatives catalysed by
ionic liquids
Hai-Liang Chen and Hong-Yun Guo*
College of Chemical Engineering and Materials, Zhejiang University ofTechnology, Hangzhou 310014, P. R. China
A green method for the synthesis of thiazolo[3,2-α]pyridine derivatives via the coupling of malononitrile, an aryl
aldehyde and methyl thioglycolate in an ionic liquid has been developed. The advantages of this protocol are that
it is non-toxic, no by-products are formed, short reaction times are required and high yields are obtained. Thiazolo
[3,2-α]pyridines have important biological and medical applications.
Keywords: one-pot synthesis, ionic liquids, thiazolo[3,2-a]pyridine
Thiazolo[3,2-α]pyridines are an important class of compounds
possessing notable biological activites including the inhibition
of beta-amyloid production,1 potent CDK2-cyclin A inhibition,2
α-glucosidase inhibitor,3 potent uterine stimulation,4 together
with antibacterial and antifungal activities.5,6 Therefore, the
synthesis of thiazolo[3,2-α]pyridines has attracted much
attention, and numerous procedures have been developed7,8.
However these methods all have drawbacks, so the attempts to
develop green and facile approaches are important.
Recently, room temperature ionic liquids have attracted
interest due to their unique properties including non-volatility,
high ionic conductivity, nonflammability, high thermal stability,
wide electrochemical window and their recyclable uses. Ionic
liquids have been used in organic reactions such as the Frie-
del–Crafts reaction,9 Diels–Alder reaction,10 Heck reaction,11
Pechmann condensations,12 Biginelli reaction,13 Beckmann
rearrangement14 and other reactions.15 As part of our research
on thiazolo[3,2-α]pyridine derivatives, we report a green syn-
thesis of these compounds by coupling malononitrile, aromatic
aldehydes and methyl thioglycolate in an ionic liquid.
First, the three-component reaction of benzaldehyde (1a,
2 mmol), malononitrile (2, 2 mmol) and methyl thioglycolate
(3, 1 mmol)was carried out in different solvents in the pres-
ence of HEAA(2-hydroxyethylammonium acetate) under
conventional heating and the reaction was followed by TLC.
As shown in Table 1, various solvents were screened for
their efficiency in the reaction. Among them, ethanol:H2O
was superior to other solvents and was chosen for the further
investigations of the reaction.
The optimised reaction conditions were then tested for
the construction of a library with 14 aldehydes and two aceto-
nitrile derivatives (malonitrile and ethyl cyanoacetate). The
corresponding fused thiazolo[3,2-α]pyridine derivatives were
obtained in good yields. The aldehydes, acetonitrile deriva-
tives and methyl thioglycolate were all commercially available
materials. The results are summarised in Table 2.
This procedure was applied to aryl aldehydes with either
electron-donating groups(hydroxyl, alkoxyl) or electron-
withdrawing groups(nitro, halide) and heterocyclic aldehydes.
It can be seen from Table 2 that the electronic effect of the
Scheme 1
* Correspondent. E-mail: guohy63@163.com

JOURNAL OF CHEMICAL RESEARCH 2012 163
Table 1 Reaction conditions optimisation for the synthesis of
In conclusion we have developed an efficient protocol for
the synthesis at highly functionalised thiazolo[3,2-α]pyridine
derivatives which are of great interest because of their biologi-
cal activity. The procedure has several advantages including
higher yields, shorter reaction time, no side-product, minimal
environmental impact, and is a useful and attractive method for
the synthesis of those compounds.
4a
Entry Solvent
Temp./°C)
Time/h
Yielda/%
1
2
acetonitrile
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
60
4
trace
66
piperidine
H2O
3
3
3
34
4
DMF
0.5
0.5
0.5
0.5
0.5
0.5
0.5
70
5
Glycol
55
6
EtOH
76
Experimental
7
EtOH:H2O=1:1
EtOH:H2O=1:1
EtOH:H2O=1:1
EtOH:H2O=1:1
82
Melting points were determined with a X-4 microscopic melting-point
apparatus and were uncorrected. IR spectra were recorded on a Nexus
670 spectrometer in KBr. 1H NMR were measured on a Bruker
Avance-II 500 MHz spectrometer using TMS as internal standard and
DMSO-d6 as solvent.
8
83
9
80
86
10
100
81
a Isolated yield.
The synthesis of HEAA was carried out by a similar method to the
literature.16 The ionic liquid was formed quantitatively and in high
purity as assessed by 1H NMR. All other chemicals (AR grade) were
commercially available and were used without further purification.
substituted benzaldehydes play an important role in the reac-
tion. Substrates bearing electron-withdrawing groups have
higher reactivity (higher yields and shorter reaction time) than
those bearing electron-donating groups. In this investigation,
all the products were characterised by m.p.., IR, 1H NMR.
Finally, we examined the ionic liquid (HEAA). Because
of the possible toxicity of organic catalytic agents, we chose
the ionic liquid (HEAA) to catalyse the reaction. Therefore,
we tested the recovery and reuse of the ionic liquid. As shown
in Table 3, the ionic liquid HEAA could be successfully recov-
ered and reused four times without any notable loss in catalytic
activity.
A plausible mechanism for the formation of compounds 4 is
suggested in Scheme 2. Firstly, the nucleophilic addition of
methyl thioglycolate 3 to the acetonitrile derivative 2 yielded
the intermediate 5, which was converted to the thiazolinone
derivatives 6 via intramolecular dehydration. Then, the inter-
mediate 6 underwent a Michael addition with 7 which was
formed from Knoevenagel condensation of 1 and 2. After
the open-chain intermediate 8 was formed, a series of intramo-
lecular cyclisations and isomerisations occurred to form com-
pound 10. Finally, compound 4 was formed by another Michael
addition between 1 and 10.
Synthesis of thiazolo[3,2-α]pyridine derivatives 4; general procedure
The mixture of the aromatic aldehyde 1 (2 mmol), malononitrile 2
(2 mmol), methyl thioglycolate 3 (1 mmol), HEAA (0.1 mmol) in
EtOH:H2O=1:1 (5 mL) was stirred at 80 °C for the appropriate time
(monitored by TLC). After the reaction was finished, the mixture was
cooled and poured into ice water (10 mL). The product was collected
by filtration and recrystallised from EtOH. The filtrate was extracted
with diethyl ether several times to retrieve the HEAA for subsequent
use.
5-Amino-2,3-dihydro-3-oxo-7-phenyl-2-(phenylmethylene)-7H-
thiazolo[3,2-a]pyridine-6,8-dicarbonitrile, (4a): Yellow powder; m.p.
249–250 °C (lit.17 245–248 °C); IR (KBr) νmax: 3422, 3320, 3236,
2982, 2940, 2208, 1730, 1661 cm−1; 1H NMR (DMSO-d6, 500 MHz)
δ: 4.56 (s, 1H, pyridine-4 H), 7.34 (m, 1H, ArH), 7.38 (m, 4H, ArH),
7.50 (m, 1H, ArH), 7.52 (s, 2H, NH2-H), 7.56 (m, 2H, ArH), 7.63 (m,
2H, ArH), 7.82 (s, 1H, olefin-H).
5-Amino-2,3-dihydro-7-(4-methylphenyl)-2-[(4-methylphenyl)
methylene]-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile
(4b): Yellow powder; m.p. 239–240 °C (lit.18 239–240 °C); IR (KBr)
νmax: 3420, 3380, 3270, 2960, 2940, 2200, 1740, 1650 cm−1; 1H NMR
(DMSO-d6, 500 MHz) δ: 2.32 (s, 3H, CH3-H), 2.38 (s, 3H, CH3-H),
4.55 (s, 1H, pyridine-4 H), 7.21 (d, 2H, ArH, J = 7.2 Hz), 7.28 (d, 2H,
ArH, J = 7.2 Hz), 7.40–7.41 (m, 2H, NH2-H), 7.54 (d, 4H, ArH,
J = 7.2 Hz), 7.82 (s, 1H, olefin- H).
5-Amino-2,3-dihydro-7-(4-nitrophenyl)-2-[(4-nitrophenyl)
methylene]-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile
(4c): Yellow powder; m.p. 259–261 °C (lit.18 255–257 °C; IR (KBr)
νmax: 3380, 3282, 3075, 2855, 2204, 2198, 1727, 1656, 1561, 1520,
1410, 1339, 1169, 845 cm−1; 1H NMR (DMSO-d6, 500 MHz) δ: 4.94
(s, 1H, pyridine-4 H), 7.69 (s, 2H, NH2-H), 7.76 (d, 2H, ArH, J =
8.8 Hz), 7.94 (d, 2H, ArH, J = 8.8 Hz), 8.00 (s, 1H, olefin-H), 8.30 (d,
2H, ArH, J = 8.8 Hz), 8.34 (d, 2H, ArH, J = 8.8 Hz).
Table 2 Synthesis of thiazolo[3,2-α]pyridine derivatives 4
using HEAA as catalyst in ethanol
Entry Ar
X
Products Time/h Yielda/%
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
C6H5-
CN
CN
CN
CN
CN
CN
CN
CN
CN
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
0.5
0.7
1.5
0.4
1.0
1.5
0.5
0.5
1.5
0.6
0.5
0.5
3
89
90
78
86
76
77
91
86
73
82
84
79
78
NR
77
73
4-CH3-C6H4-
4-NO2-C6H4-
2-Cl-C6H4-
4-Cl-C6H4-
4- OCH3-C6H4-
4-F-C6H4-
4-OH-C6H4-
3-Br-C6H3-
4-OH-3-OCH3-C6H3- CN
2,4- Cl2-C6H3-
2-NO2-C6H4-
2-Furyl-
5-Amino-7-(2-chlorophenyl)-2-[(2-chlorophenyl)methylene]-2,
3-dihydro-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile (4d):
Yellow powder; m.p. 293–295 °C (lit.19 293–295 °C); IR (KBr) νmax
:
3434, 3402, 3270, 2960, 2956, 2212, 1742, 1650 cm−1; 1H NMR
(DMSO-d6, 500 MHz) δ: 4.48 (s, 1H, pyridine-4 H), 6.68 (s, 2H, NH2-
H), 7.24 (d, 2H, ArH, J = 8.5 Hz), 7.40 (d, 2H, ArH, J = 8.5 Hz),
7.47–7.53 (d, 4H, ArH, J = 8.5 Hz), 7.80 (s, 1H, olefin-H).
5-Amino-7-(4-chlorophenyl)-2-[(4-chlorophenyl)methylene]-2,
CN
CN
CN
CN
COOEt
COOEt
3-dihydro-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile (4e):
Yellow powder; m.p. 254–255 °C (lit.19 253–254 °C); IR (KBr) νmax
:
3382, 2925, 2208, 1718, 1654, 1617, 1560, 1336, 1092, 823 cm−1;
1H NMR (DMSO-d6, 500 MHz) δ: 4.69 (s, 1H, pyridine-4 H), 7.47
(d, 2H, ArH, J = 8.6 Hz), 7.51 (d, 2H, ArH, J = 8.6 Hz), 7.65 (d, 4H,
ArH, J = 8.6 Hz), 7.71 (d, 2H, ArH, J = 8.6 Hz)7.60 (s, 2H, NH2-H),
7.87 (s, 1H, olefin-H).
n-Butyl-
4-Cl-C6H4-
4-F-C6H4-
12
5
5.5
a Isolated yield.
5-Amino-2,3-dihydro-7-(4-methoxyphenyl)-2-[(4-methoxyphenyl)
methylene]-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile(4f):
Yellow powder; m.p. 242–243 °C (lit.19 243–244 °C); IR (KBr) νmax
:
Table 3 Studies on the reuse of HEAA in the preparation of
3463, 3350, 2982, 2950, 2208, 1720, 1662 cm−1; 1H NMR (DMSO-d6,
500 MHz) δ: 3.78 (s, 3H, CH3-H), 3.85 (s, 3H, CH3-H), 4.54 (s, 1H,
pyridine-4 H), 6.95 (d, 2H, ArH, J = 8.9 Hz), 7.15 (d, 2H, ArH, J =
8.9 Hz), 7.54 (d, 2H, ArH, J = 8.9 Hz), 7.63 (d, 2H, ArH, J = 8.9 Hz),
7.31-7.34 (m, 2H, NH2-H), 7.82 (s, 1H, olefin-H).
4a
Round
1
2
3
4
5
Yield (%)
93
91
88
85
83

164 JOURNAL OF CHEMICAL RESEARCH 2012
Scheme 2
5-Amino-7-(4-fluorophenyl)-2-[(4-fluorophenyl)methylene]-2,
5-Amino-2,3-dihydro-7-(4-hydroxy-3-methoxyphenyl)-2-[(4-
hydroxy-3-methoxyphenyl)methylene]-3-oxo-7H-thiazolo[3,
2-a]pyridine-6,8-dicarbonitrile (4j): Blackish green powder, m.p.
277–278 °C (lit.1 278–279 °C); IR (KBr) νmax: 3400, 3370, 3250, 2910,
2880, 2175, 1734, 1620 cm−1; 1H NMR (DMSO-d6, 500 MHz) δ: 3.78
(s, 3H, CH3-H), 3.84 (s, 3H, CH3-H), 4.47 (s, 1H, pyridine-4 H), 6.78
(d, 2H, ArH, J = 8.3 Hz), 6.93 (d, 1H, ArH, J = 8.3 Hz), 7.00 (d, 1H,
ArH, J = 8.3 Hz), 7.11 (d, 1H, ArH, J = 8.3 Hz), 7.27 (d, 1H, ArH,
J = 8.3 Hz), 7.53 (s, 2H, NH2-H), 7.78 (s, 1H, olefin-H), 9.07 (s, 1H,
OH-H), 10.08 (s, 1H, OH-H).
3-dihydro-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile (4g):
Yellow powder; m.p. 255–257 °C (lit.18 255–257 °C); IR (KBr) νmax
:
3420, 3379, 3270, 2940, 2936, 2200, 1740, 1660 cm−1; 1H NMR
(DMSO-d6, 500 MHz) δ: 4.67 (s, 1H, pyridine-4 H), 7.24–7.27 (t, 2H,
ArH, J = 8.9 Hz), 7.42–7.46 (t, 2H, ArH, J = 8.9 Hz), 7.58 (s, 2H,
ArH), 7.74–7.77 (m, 2H, ArH) 7.48–7.50 (m, 2H, NH2-H), 7.89 (s,
1H, olefin-H).
5-Amino-2,3-dihydro-7-(4-hydroxyphenyl)-2-[(4-hydroxyphenyl)
methylene]-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile
(4h): Black powder; m.p 269–270 °C (lit.1 271–272 °C); IR (KBr)
νmax: 3430, 3415, 3270, 2950, 2930, 2208, 1743, 1637 cm−1; 1H NMR
(DMSO-d6, 500 MHz) δ: 4.46 (s, 1H, pyridine-4 H), 6.76–6.78 (d, 2H,
ArH, J = 8.6 Hz), 6.96–6.98 (d, 2H, ArH, J = 8.7 Hz), 7.51–7.54 (t,
4H, ArH), 7.18–7.19 (d, 2H, NH2-H), 7.76 (s, 1H, olefin-H), 9.51 (s,
1H, OH-H), 10.42 (s, 1H, OH-H).
5-Amino-7-(2,4-dichlorophenyl)-2-[(2,4-dichlorophenyl)methylene
]-2,3-dihydro-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile
(4k): Yellow powder; m.p. >300 °C (lit.1 >300 °C); IR (KBr) νmax
:
3400, 3380, 3273, 2910, 2883, 2195, 1738, 1647 cm−1; 1H NMR
(DMSO-d6, 500 MHz) δ: 5.10 (s, 1H, pyridine-4 H), 7.54–7.56 (m,
2H, ArH, J = 8.4 Hz), 7.62 (d, 2H, ArH, J = 8.4 Hz) 7.68 (d, 2H, ArH,
J = 8.4 Hz), 7.69–7.71 (m, 1H, olefin-H), 7.90–7.91 (m, 2H, NH2-H).
5-Amino-2,3-dihydro-7-(2-nitrophenyl)-2-[(2-nitrophenyl)
methylene]-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile (4l):
Brown powder, m.p. 246–248 °C (lit.1 245–246 °C); IR (KBr) νmax: 3480,
3454, 3267, 2960, 2940, 2213, 1740, 1670 cm−1; 1H NMR (DMSO-d6,
500 MHz) δ: 5.18 (s, 1H, pyridine-4 H), 7.61–7.63 (m, 1H, ArH,
J = 8.5 Hz), 7.65 (s, 2H, NH2-H), 7.68–7.85 (m, 3H, ArH, J = 8.5 Hz),
7.91-8.25 (m, 3H, ArH, J = 8.5 Hz), 8.25 (s, 1H, ArH), 8.26-8.26 (m,
1H, olefin-H).
5-Amino-7-(3-bromophenyl)-2-[(3-bromophenyl)methylene]-2,
3-dihydro-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile (4i):
Yellow powder; m.p. 261–263 °C (lit.1 261–262 °C); IR (KBr) νmax
:
3411, 3393, 3358, 2963, 2960, 2200, 1752, 1650 cm−1; 1H NMR
(DMSO-d6, 500 MHz) δ: 4.68 (s, 1H, pyridine-4 H), 7.36 (d, 1H, ArH,
J = 8.3 Hz), 7.44 (d, 1H, ArH, J = 7.8 Hz), 7.54 (d, 2H, ArH,
J = 8.3 Hz), 7.61–7.64 (t, 3H, ArH, J = 8.3 Hz), 7.70 (d, 2H, NH2-H),
7.85 (s, 1H, ArH), 7.91 (s, 1H, olefin-H).

JOURNAL OF CHEMICAL RESEARCH 2012 165
2
3
S. Vadivelan, B.N. Sinha, S.J. Irudayam and S.A.R.P. Jagarlapudi, J. Chem.
Inf. Model., 2007, 47, 1526.
H. Park, K.Y. Hwang, K.H. Oh, Y.H. Kim, J.Y. Lee and K. Kim, Bioorg.
5-amino-7-(2-furanyl)-2-(2-furanylmethylene)-2,3-dihydro-3-oxo-
7H-thiazolo[3,2-a]pyridine-6,8-dicarbonitrile (4m): Yellow powder;
m.p. 266-268 °C (lit. 21 266–268 °C); IR (KBr) νmax: 3403, 3306, 3229,
1
2213, 1720, 1620 cm−1; H NMR (DMSO-d6, 500 MHz) δ: 4.62 (s,
Med. Chem., 2008, 16, 284.
4
5
F.M. Manhi and G.A. Soliman, Chem. Abstr., 1993, 121, 50029.
G. El-Hag Ali, A. Khalil, R. Lamphon and A. El-Maghraby, Phosphorus,
Sulfur Silicon Relat. Elem., 2005, 180, 1909.
1H, pyridine-4 H), 6.36–6.39 (m, 2H, NH2-H), 6.64–6.67 (m, 3H, furan-
H), 6.88–7.58 (m, 3H, furan-H), 7.77 (m, 1H, olefin-H).
5-amino-7-(4-chlorophenyl)-2-[(4-chlorophenyl)methylene]-2,
3-dihydro-3-oxo-7H-Thiazolo[3,2-a]pyridine-6,8-dicarboxylic acid
6,8-diethyl ester (4o): Yellow powder; m.p. 230–231 °C (lit.20 230–
231 °C); IR (KBr) νmax: 3430, 3387, 3320, 2910, 2883, 2195, 1738,
1647 cm−1; 1H NMR (DMSO-d6, 500 MHz) δ: 1.19–1.22 (t, 3H,
CH3-H), 1.25–1.28 (t, 3H, CH3-H), 4.07–4.11 (t, 2H, CH2-H), 4.19–
4.23 (m, 2H, CH2-H), 4.91 (s, 1H, pyridine-4 H), 7.15 (d, 2H,
ArH, J = 8.6 Hz), 7.19 (d, 2H, ArH, J = 8.6 Hz), 7.45 (d, 2H, ArH,
J = 8.6 Hz), 7.56 (d, 2H, ArH, J = 8.6 Hz), 7.70 (s, 1H, olefin-H), 8.69
(s, 2H, NH2-H).
6
7
8
9
A.A. El-Maghraby, G.A.M. El-Hag Ali, A.H.A. Ahmed and M.S.A.
El-Gaby, Phosphorus, Sulfur Silicon Relat. Elem., 2002, 177, 293.
F. Shi, C.M. Li, M. Xia, K.J. Miao, Y.X. Zhao, S.J. Tu, W.F. Zheng,
G. Zhang and N. Ma Bioorg. Med. Chem., 2009, 19, 5565.
F.F. Abdel-latif, Y.S. Mohammed, H. Abdel-ghani, E.Kh. Ahmed and
E.H. El-gawish, Phosphorus, Sulfur, Silicon, 1993, 78, 251.
L. He, G.H. Tao, W.S. Liu, Xiong, W. Xiong, T. Wang and Y. Kou, Chin.
Chem. Lett., 2006, 17, 321.
10 T. Fischer, A. Sethi, T. Welton and J. Woolf. Tetrahedron Lett., 1999, 40,
793.
5-Amino-7-(4-fluorophenyl)-2-[(4-fluorophenyl)methylene]-2,3-
dihydro-3-oxo-7H-thiazolo[3,2-a]pyridine-6,8-dicarboxylic acid 6,8-
diethyl ester (4p): Yellow powder; m.p. 225–226 °C (li.20 226–267 °C);
IR (KBr) νmax: 3390, 3382, 3200, 2916, 2874, 2210, 1743, 1650 cm−1;
1H NMR (DMSO-d6,500MHz) δ: 1.18–1.21 (t, 3H, CH3-H), 1.25–1.28
(t, 3H, CH3-H), 4.07–4.11 (m, 2H, CH2-H), 4.18–4.24 (m, 2H, CH2-
H), 4.92 (s, 1H, pyridine-4 H), 6.90–6.93 (t, 2H, ArH, J = 8.7 Hz),
7.17–7.21(dd, 4H, ArH, J1 = 8.0, J2 = 1.9 Hz), 7.63–7.65 (m, 2H,
ArH), 7.72 (s, 1H, olefin-H), 8.68 (s, 2H, NH2-H).
11 H. Hagiwara, Y. Shimizu, T. Hoshi, T. Suzuki, M. Ando, K. Ohkubo and
C. Yokoyama, Tetrahedron Lett., 2001, 42, 4349.
12 M.K. Potdar, S.S. Mohile and M.M. Salunkhe, Tetrahedron Lett., 2001, 42,
9285.
13 J. Peng and Y. Deng, Tetrahedron Lett., 2001, 42, 5917.
14 X. X. Xu, Z.L. Wei and X. Bo, Chin. J. Org. Chem., 2006, 3, 354.
15 B. Wang, Y. Gu, C. Luo, T. Yang, L. Yang and J. Suo, Tetrahedron Lett.,
2004, 45, 3417.
16 X.L. Yuan, S.J. Zhang and X.M. Lu, J. Chem. Eng. Data, 2007, 52, 596.
17 H.M. Al-Matar, K.D. Khalil, H. Meier, H. Kolshorn and M. H. Elnagdi,
Arkivoc, 2008, 288.
Received 12 December 2011; accepted 20 January 2012
Paper 1100988 doi: 10.3184/174751912X13282820029367
Published online: 22 March 2012
18 A.A. El-Maghraby, A.M. Gameel, E.H. Ali, A.H.A. Ahmed and M.S.A.
El-Gaby, Phosphorus, Sulfur Silicon, 2002, 177, 293.
19 F.F. Abdel-latif, Y.S. Mohammed, H. Abdel-ghani, E.Kh. Ahmed and E.H.
El-gawish. Phosphorus, Sulfur, Silicon, 1993, 78, 251.
20 M.H. Elnagdi, M.R.H. Elmoghayar, A.H.H. Elghandour and K. U. Sadek,
Egypt. Sulfur Lett., 1989, 9, 109.
References
1
M.J. Mullan, D. Paris and P. Bakshi, WO 2008070875, 2008, Chem. Abstr.
2008, 149, 45259.
21 M.H. Elnagdi, M.R.H. Elmoghayar, A.H.H. Elghandour and K.U. Sadek,
Coll. Czech. Chem. Commun., 1990, 55, 745.

Copyright of Journal of Chemical Research is the property of Science Reviews 2000 Ltd. and its content may
not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written
permission. However, users may print, download, or email articles for individual use.