Novel intramolecular cyclization of pyrazolone ketene S,N-acetals for the construction of methylsulfanylpyrazolo-[4,3-b]pyridines

Article abstract of DOI:10.1081/SCC-120014787

A novel and efficient method for the synthesis of 6-substituted-7,7a-dihydro-1,7a-dimethyl-7-imino-2-phenyl-1H-pyrazolo[4, 3-b]pyridin-3(2H)-ones via the reaction of 4-amino-2,3-dimethyl-1-phenylpyrazolin-5-one with ketene dithioacetals and ethoxy-methylenemalononitrile or ethyl ethoxymethylene-cyanoacetate followed by intramolecular cyclization of the products has been investigated.

Full text of DOI:10.1081/SCC-120014787

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NOVEL INTRAMOLECULAR CYCLIZATION OF
PYRAZOLONE KETENE S,N-ACETALS FOR THE
CONSTRUCTION OF METHYLSULFANYLPYRAZOLO- [4,3-
b]PYRIDINES
Galal H. Elgemeie a , Ali M. Elzanate b , Ahmed H. Elghandour b & Sayed A. Ahmed b
a Department of Chemistry , Faculty of Science , Helwan University , Ain-Helwan, Cairo,
Egypt
b Department of Chemistry , Faculty of Science , Cairo University (Bani Suef Branch) , Bani
Suef, Egypt
Published online: 22 May 2009.
To cite this article: Galal H. Elgemeie , Ali M. Elzanate , Ahmed H. Elghandour & Sayed A. Ahmed (2002)
NOVEL INTRAMOLECULAR CYCLIZATION OF PYRAZOLONE KETENE S,N-ACETALS FOR THE CONSTRUCTION OF
METHYLSULFANYLPYRAZOLO- [4,3-b]PYRIDINES, Synthetic Communications: An International Journal for Rapid Communication
of Synthetic Organic Chemistry, 32:22, 3509-3517, DOI: 10.1081/SCC-120014787
To link to this article: http://dx.doi.org/10.1081/SCC-120014787
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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 22, pp. 3509–3517, 2002
NOVEL INTRAMOLECULAR
CYCLIZATION OF PYRAZOLONE
KETENE S,N-ACETALS FOR
THE CONSTRUCTION
OF METHYLSULFANYLPYRAZOLO-
[4,3-b]PYRIDINES
Galal H. Elgemeie,1, Ali M. Elzanate,2
*
Ahmed H. Elghandour,2 and Sayed A. Ahmed2
1Department of Chemistry, Faculty of Science, Helwan
University, Ain-Helwan, Cairo, Egypt
2Department of Chemistry, Faculty of Science, Cairo
University (Bani Suef Branch), Bani Suef, Egypt
ABSTRACT
A
novel and efficient method for the synthesis of
6-substituted-7,7a-dihydro-1,7a-dimethyl-7-imino-2-phenyl-
1H-pyrazolo[4,3-b]pyridin-3(2H)-ones via the reaction of
4-amino-2,3-dimethyl-1-phenylpyrazolin-5-one with ketene
dithioacetals and ethoxy-methylenemalononitrile or ethyl
ethoxymethylene-cyanoacetate followed by intramolecular
cyclization of the products has been investigated.
Key Words: Intramolecular cyclization; Ketene S,N-acetals;
Pyrazolo[4,3-b]pyridines; Unsaturated nitriles; 4-Aminoanti-
pyrine
*Corresponding author. E-mail: rughe@rusys.eg.net or elgemeie@hotmail.com
3509
DOI: 10.1081/SCC-120014787
Copyright & 2002 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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3510
ELGEMEIE ET AL.
During the course of our studies directed toward exploring the
synthetic potential of ketene dithioacetals for synthesizing new classes of
novel antimetabolites,[1–3] we have recently reported different successful
approaches for synthesis of mercaptopurine and thioguanine analogues by
the reaction of ketene dithioacetals with diazoles containing amino and
active methylene functions.[4,5] In an extension of this work, the present
paper describes a novel synthesis of 5-methylthio-6-substituted-7-imino-
1,7a-dimethyl-2-phenylpyrazolo[4,3-b]pyridin-3(2H)-ones by the intra-
molecular cyclization of pyrazolone ketene N,S-acetals. Thus, it has been
found that both [bis(methylthio)-methylene]malononitrile 2a and ethyl
2-cyano-3,3-bis(methylthio)acrylate 2b was reacted with 4-amino-2,3-
dimethyl-1-phenylpyrazolin-5-one 3 in refluxing ethanol containing catalytic
amounts of piperidine to afford the corresponding pyrazolone ketene N,S-
acetal derivatives 4a,b (Sch. 1). The structures of 4 were established on the
basis of their elemental analysis and spectral data (IR, 1H NMR, 13C NMR,
and MS). The analytical data for 4a revealed a molecular formula
C16H15N5OS (Mþ¼ 326). The 1H NMR spectrum revealed a band at ꢀ
2.69 ppm assignable to the SCH3 group, a multiplet at ꢀ 7.32–7.53 ppm
assigned to aromatic protons and a broad singlet at ꢀ 9.65 ppm assignable
to an NH group. The 13C NMR spectrum was characterized by a signal at ꢀ
15.59 ppm attributed to SCH3 carbon and two signals at ꢀ 106.81 and
112.57 ppm attributed to two CN carbons. Moreover, signals appeared at
ꢀ ¼ 130.38, 134.51, and 173.11 ppm corresponding to C-3, C-4, and C-5,
respectively. Attempted cyclization of the compounds 4 in boiling ethanolic
hydrochloric acid resulted in the formation of a colorless product, two poss-
ible isomeric structures, 5 and 6, for which were considered according to the
1
molecular weight (by mass spectra). The H NMR spectrum revealed an
imine function (D2O exchangeable) and three different methyl protons
indicating that the methyl group at C-3 was not involved in the cyclization.
The pyrazolo[4,3-b]pyridine structure 6a,b was therefore suggested for the
reaction product and not the pyrazolo[4,3-b]azapine structure 5. In order to
investigate the scope of this reaction further and to establish whether the
reaction of ketene dithioacetals with 4-amino-pyrazol-3(2H)-5-one could be
extended to provide a general approach to 5-methylthiopyrazolo[4,3-b]pyr-
idines, we studied the reaction of 4-amino-2,3-dimethyl-pyrazolin-5-one 3
with other functionalized ketene dithioacetals. Thus, compound 3 reacts
with ketene dithioacetals 7 in refluxing ethanol containing catalytic amounts
of piperidine to yield the acyclic structures 8 (Sch. 2). The latter undergo
smoothly intramolecular cyclization on refluxing in ethanolic hydrochloric
acid to afford the corresponding 5-methylthio-6-substituted-pyrazolo[4,3-b]-
pyridines 9. The structures of 9 were established and confirmed on the basis
of their elemental analysis and spectral data (MS, IR, 1H NMR, and

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METHYLSULFANYLPYRAZOLO[4,3-b]PYRIDINES
3511
Scheme 1.
13C NMR). The 13C NMR spectrum of 9a was characterized by these signals
for three methyl carbons at 18.64 (CH3), 20.26 (SCH3), and 32.96 (N–CH3)
ppm. Compounds 8 bearing methylthio group and other latent functional
substituent were found useful for the synthesis of pyrazole derivatives. Thus,
it has been found that the reaction of pyrazolone ketene N,S-acetals 8 with
substituted hydrazines in refluxing ethanol gives the corresponding amino-
pyrazole derivatives 10 in good yields. The structures of 10 were established
on the basis of their elemental analysis and spectra data (MS, IR, 1H NMR,
and 13C NMR). The analytical data for 10a indicated a molecular formula
C15H17N7O2 (Mþ ¼ 328) and 1H NMR spectrum contained a multiplet
at ꢀ ¼ 7.32–7.54 ppm assigned to the aromatic protons, two broad singlets at

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3512
ELGEMEIE ET AL.
Scheme 2.
ꢀ ¼ 6.16 and 7.25 ppm assignable for two NH2 groups and a broad band at
ꢀ ¼ 11.14 ppm assignable to an NH group. Similarly, 4-amino-2,3-dimethyl-
pyrazolin-5-one 3 reacted with ethoxy-methylenemalononitrile 11a or ethyl
ethoxymethylenecyanoacetate 11b in refluxing ethanol to give the corre-
sponding N-substituted-aminopyrazoles 12, which undergoes intramolecu-
lar cyclization under the same conditions to give the corresponding
pyrazole[4,3-b]pyridines 13a,b (Sch. 3). The structures of compounds 13
were established on the basis of their elemental analysis and spectral data.
Thus, the mass spectrum of 13a was compatible with the molecular formula
1
C15H13N5O. The H NMR spectrum of 13a revealed two different methyl

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METHYLSULFANYLPYRAZOLO[4,3-b]PYRIDINES
3513
Scheme 3.
protons indicating that the methyl group at C-3 was not involved in the
cyclization, a pyridine proton at 7.22 ppm and an imine proton at 6.11 ppm.
The 13C NMR spectrum was characterized by two signals at 18.26 and
35.30 ppm corresponding to two methyl carbons.

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3514
ELGEMEIE ET AL.
In summary, we have achieved a regiospecific synthesis of interesting
6-substituted-pyrazolo[4,3-b]pyridines by intramolecular cyclization of
pyrazolone ketene N,S-acetals. The compounds obtained seems promising
as high potential antimetabolite agents.
EXPERIMENTAL
All melting points are uncorrected. The IR spectra were obtained
1
(KBr, disk) on a Perkin Elmer/1650 FT-IR instrument. The H NMR spec-
tra were measured on a Varian 400 MHz spectrometer for solutions in
(CD3)2SO with SiMe4 as an internal standard. Mass spectra were recorded
on a Varian MAT 112spectrometer. Analytical data were obtained from the
Microanalytical Data Center at Cairo University.
1-Phenyl-2,3-dimethyl-4-(substituted-methylthioethylene)amino-pyrazo-
lin-5-ones 4a,b; 8a,b. General procedure: A mixture of ketene dithioacetals
2a,b or 7a,b (0.01 mol) and 4-aminoantipyrine 3 (0.01 mol) was refluxed in
ethanol in the presence of catalytic amount of pipridine for 30 min. The
formed solid product was collected and recrystallized from ethanol.
4a: Pale yellow crystals, (from ethanol), m.p. 240ꢀC (yield 90%);
ꢁ
max/cmꢁ1 (KBr) 3548 (NH), 2203 (2CN), 1655 cmꢁ1 (CO); [ꢀH(CD3)2SO]
2.22 (s, 3H, CH3), 2.69 (s, 3H, SCH3), 3.13 (s, 3H, N–CH3), 7.32–7.53 (m,
5H, C6H5), 9.65 (s, 1H, NH); ꢀC 10.19 (CH3), 15.59 (SCH3), 35.84 (N–CH3),
106.81 (CN), 112.57 (CN), 123.63–129.27 (phenyl carbons), 130.38 (C-3),
134.51 (C-4), 151.14 (C-7), 160.08 (C-8), 173.11 (C-5); m/z 326 (Found: C,
59.32, H, 4.41, N, 21.32; Calcd: for C16H15N5OS: C, 59.08, H, 4.62,
N, 21.54%). 4b: Pale yellow crystals, (from ethanol), m.p. 148ꢀC
(yield 85%); ꢁmax/cmꢁ1 (KBr): 3163 (NH), 2203 (CN), 1670 (CO);
[ꢀH (CD3)2SO] 1.25 (t, 3H, CH3), 2.19 (s, 3H, CH3), 2.54 (s, 3H, SCH3),
3.12(s, 3H, N–CH ), 4.23 (q, 2H, CH2), 7.23–7.49 (m, 5H, C6H5), 10.63 (s,
3
1H, NH); (Found: C, 58.23, H, 5.52, N, 15.31. Calcd: for C18H20N4O3S: C,
58.06, H, 5.38, N, 15.05%). 8a: Yellow crystals, (from ethanol), m.p. 196ꢀC
(yield 85%); ꢁmax/cmꢁ1(KBr), 3408, 3308, and 3213 (NH2, NH), 2214 (CN),
1689 (CO), 1647 (CO); [ꢀH (CD3)2SO] 2.31 (s, 3H, CH3), 2.39 (s, 3H, SCH3),
3.09 (s, 3H, N–CH3), 7.34–7.53 (m, 5H, C6H5), 8.82(s, 2H, NH 2), 9.63 (s,
1H, NH); ꢀC 10.00 (CH3), 16.48 (SCH3), 35.34 (N–CH3), 102.28 (CN),
112.77 (C-3), 120.45 (C-4), 124.43–129.22 (phenyl carbons), 133.98 (C-7),
147.48 (C-8), 159.69 (C-9), 167.84 (C-5); m/z 342(Found: C, 55.80, H, 4.63,
N, 20.11. Calcd: for C16H17N5O2S: C, 55.98, H, 4.96, N, 20.41%). 8b:
Yellow crystals, (from ethanol), m.p. 249ꢀC (yield 85%); ꢁmax/cmꢁ1 (KBr)
3408, 3308, and 3224 (NH2, NH), 2210 (CN), 1690 (CO); [ꢀH (CD3)2SO]
2.22 (s, 3H, CH3), 2.65 (s, 3H, SCH3), 3.24 (s, 3H, N–CH3), 7.33–7.58

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METHYLSULFANYLPYRAZOLO[4,3-b]PYRIDINES
3515
(m, 5H, C6H5), 9.72(s, 2H, NH 2); m/z 358 (Found: C, 53.15, H, 4.82, N,
19.64. Calcd: for C16H17N5OS2: C, 53.48, H, 4.74, N, 19.50%).
6-Substitued-5-methylthio-7,7a-dihydro-1,7a-dimethyl-7-imino-2-phenyl-
pyrazolo[4,3-b]pyridin-3-ones 6a,b; 9a,b. General procedure: A solution of
each of 4a,b or 8a,b (0.01 mol) in ethanol (30 mL) was treated with concen-
trated hydrochloric acid (1 mL). The reaction mixture was heated under
reflux for 30 min and then evaporated under reduced pressure, the resulting
solid products was collected by filtration and recrystallised from ethanol.
6a: Colorless crystals, (from ethanol), m.p. 260ꢀC (yield 60%);
ꢁ
max/cmꢁ1 (KBr) 3308 (N, 2215 (CN), 1706 (CO); [ꢀH (CD3)2SO] 2.25 (s,
3H, CH3), 2.48 (s, 3H, SCH3), 2.97 (s, 3H, N–CH3), 5.00 (s, 1H, ¼NH),
7.23–7.37 (m, 5H, C6H5); m/z 326 (Found: C, 59.11, H, 4.53, N, 21.67.
Calcd: for C16H15N5OS: C, 59.08, H, 4.62, N, 21.54%). 6b: colorless
crystals, (from ethanol), m.p. 155ꢀC (yield 60%); ꢁmax/cmꢁ1 (KBr) 3311
(NH), 1710 (CO); [ꢀH (CD3)2SO] 1.34 (t, 3H, CH3), 2.34 (s, 3H, CH3),
2.54 (s, 3H, SCH3), 3.11 (s, 3H, N–CH3), 4.32(q, 2H, CH 2), 6.09 (s, 1H,
¼NH), 7.23–7.40 (m, 5H, C6H5); (Found: C, 58.09, H, 5.66, N, 15.41. Calcd:
for C18H20N4O3S: C, 58.06, H, 5.38, N, 15.05%). 9a: Yellow crystals, (from
ethanol), m.p. 224ꢀC (yield 80%); ꢁmax/cmꢁ1 (KBr) 3373, 3322 and 3190
(NH2, NH), 1739 (CO), 1671 (CO); [ꢀH (CD3)2SO] 2.08 (s, 3H, CH3), 2.25 (s,
3H, SCH3), 3.27 (s, 3H, N–CH3), 6.01 (s, 1H, ¼NH), 7.03–7.29 (m, 5H,
C6H5), 7.45 (s, 2H, NH2); ꢀC 18.64 (CH3), 20.26 (SCH3), 32.96 (N–CH3),
105.55 (C-7a), 107.45 (C-4a), 123.59–128.99 (phenyl carbons), 140.92 (C-5),
145.86 (C-6), 160.14 (C-7), 166.32(C-8), 172.42(C-3); (Found: C, 55.77, H,
4.59, N, 20.33. Calcd: for C16H17N5O2S: C, 55.98, H, 4.96, N, 20.41%). 9b:
Yellow crystals, (from ethanol), m.p. 180ꢀC (yield 60%); ꢁmax/cmꢁ1 (KBr)
3360, 3310 and 3209 (NH2, NH), 1715 (CO); (Found: C, 53.35, H, 4.62, N,
19.64. Calcd: for C16H17N5OS2: C, 53.48, H, 4.74, N, 19.50%).
1-Phenyl-2,3-dimethyl-4-(substitutedpyrazolyl)-aminopyrazolin-5-one deri-
vatives 10a–d. General procedure: A mixture of compounds 8a–b (0.01 mol)
and hydrazine hydrate (0.01mol) or phenylhydrazine was refluxed in ethanol
in the presence of catalytic amount of pipridine for 1 h. After cooling of the
reaction mixture the solid product was filtered off and recrystallized from
ethanol.
10a: Yellow crystals, (from ethanol), m.p. over 300ꢀC (yield 85%);
ꢁ
max/cmꢁ1 (KBr) 3433, 3369 and 3213 (NH2, NH), 1686 (CO), and 1629
(CO); [ꢀH (CD3)2SO] 2.39 (s, 3H, CH3), 3.37 (s, 3H, N–CH3), 6.16 (s, 2H,
NH2), 7.25 (s, 2H, NH2), 7.32–7.54 (m, 5H, C6H5), 11.45 (s, 1H, NH); m/z
328 (Found: C, 55.23, H, 5.11, N, 29.82. Calcd: for C15H17N7O2: C, 55.05,
H, 5.20, N, 29.97%). 10b: Yellow crystals, from ethanol, m.p. 250ꢀC yield
80%. ꢁmax/cmꢁ1 (KBr) 3400, 3325 and 3200 (NH2, NH), 1680 (CO);
(Found: C, 52.14, H, 4.82, N, 24.53%). Calcd: for C15H17N7OS, C, 52.48,

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3516
ELGEMEIE ET AL.
H, 4.96, N, 24.49. 10c: Yellow crystals, (from ethanol), m.p. 222ꢀC (yield
90%); ꢁmax/cmꢁ1 (KBr) 3430, 3300 and 3203 (NH2, NH), 1680 (CO), 1690
(CO); (Found: C, 62.33, H, 5.35, N, 24.11. Calcd: for C21H21N7O2: C, 62.53,
H, 5.21, N, 24.32%). 10d: Yellow crystals, (from ethanol), m.p. 200ꢀC yield
90%; ꢁmax/cmꢁ1 (KBr) 3415, 3320 and 3217 (NH2, NH), 1670 (CO); m/z 422
(Found: C, 60.41, H, 5.25, N, 20.23. Calcd: for C21H21N7OS: C, 60.14, H,
5.01, N, 20.05%).
1-Phenyl-2,3-dimethyl-4-(substitutedacrylonitrile)amino-pyrazolin-5-
ones 12a–b. General procedure: A mixture of ethoxymethylene–malono-
nitrile 11a or ethyl ethoxymethylenecyanoacetate 11b (0.01 mol) was
refluxed with 4-aminoantipyrine 3 (0.01 mol) in ethanol in the presence
of catalytic amount of piperidine for 1 h. The formed solid product was
collected by filtration and recrystallized from ethanol.
12a: Buff crystals, (from ethanol), m.p. 240ꢀC (yield 75%); ꢁmax/cmꢁ1
(KBr), 2210 (CN), 2190 (CN), 1660 (CO); [ꢀH (CD3)2SO] 2.27 (s, 3H, CH3),
3.13(s, 3H, N–CH3), 7.32–7.53 (m, 5H, C6H5), 7.90 (s, 1H, ¼CH), 10.45 (s,
1H, NH); ꢀC 10.19 (CH3), 34.98 (N–CH3), 104.57 (CN), 109.25 (CN),
119.05–129.22 (phenyl carbons), 124.34 (C-3), 134.51 (C-4), 147.38 (C-7),
151.13 (C-8), 160.08 (C-5); m/z 280 (Found: C, 64.22, H, 4.81, N, 25.32.
Calcd: for C15H13N5O: C, 64.52, H, 4.66, N, 25.09%). 12b: white crystals,
(from ethanol), m.p. 130ꢀC (yield 85%); ꢁmax/cmꢁ1 (KBr) 3320 (NH), 1706,
1685 (2CO); [ꢀH (CD3)2SO] 1.25(t, 3H, CH3), 2.18 (s, 3H, CH3), 3.11 (s, 3H,
N–CH3), 4.22 (q, 2H, CH2), 7.26–7.48 (m, 6H, C6H5 and CH), 10.63 (s, 1H,
NH); m/z 328 (Found: C, 52.01, H, 5.11, N, 17.55. Calcd: for C17H18N4O3:
C, 52.58, H, 5.52, N, 17.18%).
6-Substituted-7,7a-dihydro-1,7a-dimethyl-7-imino-2-phenyl-Pyrazolo-
[4,3-b]pyridin-3-ones 13a,b. General procedure: Compounds 12a,b
(0.01 mole) in ethanol (30 mL) was treated with concentrated hydrochloric
acid (1 mL). The reaction mixture was heated under reflux for 1 h and then
evaporated under reduced pressure. The resulting solid product was
collected by filtration and recrystallized from ethanol.
13a: Colorless crystals, (from ethanol), m.p. 285ꢀC (yield 65%);
ꢁ
max/cmꢁ1 (KBr) 3320 (NH), 2215 (CN), 1670 (CO); [ꢀH (CD3)2SO] 2.39
(s, 3H, CH3), 2.50 (s, 3H, N–CH3), 6.11 (s, 1H, ¼NH), 7.22 (s, 1H, pyridine-
H); 7.36–7.47 (m, 5H, C6H5); ꢀC 18.26 (CH3) 35.30 (N–CH3), 104.01 (CN),
106.01 (C-7a), 122.32 (C-4a), 125.56–128.18 (phenyl carbons), 140.94 (C-5),
145.74 (C-6), 161.33 (C-7), 167.40 (C-3); Found: C, 64.22, H, 4.81, N, 25.32.
Calcd: for C15H13N5O: C, 64.52, H, 4.66, N, 25.09%) 13b: Colorless crys-
tals, (from ethanol), m.p. 160ꢀC (yield 85%); ꢁmax/cmꢁ1 (KBr) 3420 (NH),
1695, 1670 (2CO); [ꢀH (CD3)2SO] 1.37 (t, 3H, CH3), 2.34 (s, 3H, CH3), 2.54
(s, 3H, N–CH3), 4.32(q, 2H, CH 2), 6.09 (s, 1H, ¼NH); 7.21–7.28 (m, 3H,
phenyl-H); 7.32(s, 1H, pyridine-H); 7.36–7.40 (m, 2H, phenyl-H); m/z 326

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METHYLSULFANYLPYRAZOLO[4,3-b]PYRIDINES
3517
(Found: C, 52.01, H, 5.11, N, 17.55. Calcd: for C17H18N4O3: C, 52.58, H,
5.52, N, 17.18%)
REFERENCES
1. Elgemeie, G.E.H.; Elghandour, A.H.; Elzanate, A.M.; Ahmed, S.A.
J. Chem. Soc. Perkin Trans. 1. 1997, 3285.
2. Elgemeie, G.E.H.; Elghandour, A.H.; Elzanate, A.M.; Masoud, W.A.
J. Chem. Research(S) 1998, 164.
3. Elgemeie, G.E.H.; Elghandour, A.H.; Elzanate, A.M.; Ahmed, S.A.
J. Chem. Research(S) 1998, 162.
4. Elgemeie, G.E.H.; Elghandour, A.H.; Elzanate, A.M. J. Chem.
Research(S) 1996, 340.
5. Elgemeie, G.E.H.; El-Ezbawy, S.R.; Ali, H.A.; Mansour, A.K. Bull.
Chem. Soc. Japan 1994, 67, 738.
Received in the UK July 23, 2001

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