Studies on enaminonitriles: A new synthesis of 1,3-substituted pyrazole-4-carbonitrile

Article abstract of DOI:10.1002/jhet.5570420623

3-Diethylaminoacrylonitrile (1) reacts with hydrazonyl halides (2a-d) to yield 1,3-disubstituted pyrazole-4-carbonitriles 5a-d. The acetyl 1-p-chlorophenylpyrazole-4-carbonitrile (5a) condensed with hydrazine hydrate to yield the bishydrazone 10 and with

Full text of DOI:10.1002/jhet.5570420623

Sep-Oct 2005
Studies on Enaminonitriles: a New Synthesis of
1185
1,3-Substituted Pyrazole-4-carbonitrile
1
1
Said Ahmed Soliman Ghozlan , Ismail Abdelshafy Abdelhamid ,
2
1
Hatem Moustafa Gaber and Mohamed Hilmy Elnagdi*
1
Department of Chemistry, Faculty of Science, Cairo University, Giza, A.R. Egypt; e.mail: shelmy@access.com.eg
2
National Organization for Drugs Control and Research (NODCAR), P.O. Box 29, Cairo, A.R. Egypt
Received October 18, 2004
3-Diethylaminoacrylonitrile (1) reacts with hydrazonyl halides (2a-d) to yield 1,3-disubstituted pyrazole-
4-carbonitriles 5a-d. The acetyl 1-p-chlorophenylpyrazole-4-carbonitrile (5a) condensed with hydrazine
hydrate to yield the bishydrazone 10 and with dimethylformamide dimethylacetal to yield 1-aryl-3-(3-
dimethylamino)acryloyl pyrazole-4-carbonitrile (11). This enamine reacts with hydrazine hydrate to yield
the pyrazolylpyrazole (12) and with naphthoquinone to yield the 3-naphthofuranoyl pyrazole 13. The pyra-
zolyl pyridine derivative 14 was obtained upon treatment of 11 with acetylacetone in the presence of ammo-
nium acetate. Compound 11 was coupled with p-chlorobenzene diazonium chloride to yield the hydrazone
16 that was coupled further with p-chlorobenzenediazonium chloride to yield the formazane 18.
J. Heterocyclic Chem., 42, 1185 (2005).
Introduction.
Scheme 1
Functionally substituted enamines are versatile reagents
and their chemistry has received in the last fifteen years
considerable attention [1-4]. In our previous work aimed at
exploring synthetic potentialities of enaminones [5-12] we
have reported 1,3-dipolar cycloaddition of nitrileimines to
enaminones to yield pyrazoles [13,14]. This reaction was
then utilized to prepare several novel pyrazoles and
tetrazines [15].
In conjunction of this work we investigated the reaction
of enaminonitriles with nitrileimines. We have found that
3-diethylaminoacrylonitrile 1, the preparation of which
has been described in the literature [16], reacts readily with
nitrileimines, generated in situ from hydrazonyl halides
2a-e and triethylamine, to yield products of addition across
the double bond affording cycloadducts that subsequently
aromatized via diethylamine elimination to yield pyra-
zoles. Two structures seemed possible for these pyrazoles
(cf. 5 and 6) depending on regioorientation of the cycload-
dition. Thus cycloadduct 3 would afford 5 while
cycloadduct 4 would yield 6.
1
13
H NMR and C NMR enabled assignment of struc-
1
ture 5 for these reaction products. Thus H NMR, taking
5a as a typical example, showed pyrazole ring proton sig-
nal at δ 9.42 ppm, which can only be interpreted for pyra-
zole H-5. Pyrazole H-4 should appear at a much higher
field. Simulated spectra for both structures proposed H-4
in compound 6 to appear at δ 7.35 ppm while H-5 in com-
13
pound 5 at 8.17 ppm. C NMR adds further evidence.
Thus taking again 5a as typical example pyrazole C-4
appeared at δ 92.9 ppm. If the reaction product was 6
again the carbon should appear at much lower field.
Spectral simulation for 5 and 6 showed C-4 in 5 to
expected at δ 98.33 ppm while in isomeric 6 this carbon
would be expected at δ 108.69 ppm. In an attempt to con-
vert 5a into amino pyrazolo[3,4-c]pyrimidine 9 via inter-
mediate 8a, only the bishydrazone 10 was obtained.
Condensation with phenylhydrazine afforded only the
phenylhydrazone 8b, which could not be further cyclised.
Compound 5a condensed with dimethylformamide
dimethylacetal to yield the trans enaminone 11 as H
NMR revealed trans olefinic protons at δ 5.86 and δ 7.71
1

1186
S. A. S. Ghozlan, I. A. Abdelhamid, H. M. Gaber and M. H. Elnagdi
Scheme 2
Vol. 42
ppm as two doublets with J = 16 Hz. The enaminone 11
reacted readily with hydrazine hydrate to yield the pyra-
zolylpyrazole 12. Typical for the recently reported behav-
ior of enaminones, Compound 11 reacted with naphtho-
quinone to yield naphthofuranylpyrazole 13.
Reaction of 11 with acetylacetone in refluxing acetic
acid and in presence of ammonium acetate has afforded
a pyrazolopyridine derivative that may be formulated
Scheme 3

Sep-Oct 2005
Studies on Enaminonitriles: a New Synthesis of 1,3-Substituted Pyrazole-4-carbonitrile
1187
1-(4-Nitrophenyl)-3-phenyl-1H-pyrazole-4-carbonitrile (5c).
This compound was obtained in 70 % yield, mp: 168 -170 °C;
as 14 or isomeric 15. Structure 14 is assigned for the
product based on presence of pyridyl ring protons as
doublets at δ 8.36 and δ 9.56 ppm with J = 8 Hz. If the
reaction product is 15 one would expect [17,18] pyridyl
ring protons to have much smaller coupling constant
(J = 3-4 Hz).
Similar to reported behavior of enaminones [19] com-
pound 11 also coupled with benzenediazonium chloride to
yield the arylhydrazono derivative 16 that could be
cyclised into pyrazolylcinnoline 17 on heating with con-
centrated sulphuric acid. Further coupling with 16 gave the
coupling product 18. Attempts to convert 5b into a pyra-
zolopyridazine derivative via reaction with hydrazine
hydrate afforded only hydrazide 19.
-1
+
1
IR (KBr): ν 2224 cm (CN); MS (EI): m/z (%) = 290 (M ); H
NMR (DMSO-d ): δ = 8.47 (d, 2H, H o- to NO ), 8.23 (d, 2H, H
6
2
m- to NO ), 7.58-7.60 (m, 2H, Ph H-3), 7.6-8.3 (m, 3H, Ph H-
2
13
2,H4), 9.66 (pyrazole H); C NMR (DMSO-d ): δ = 94.6 (C-4
pyrazole), 115.7 (CN), 120.1, 121.5, 126.5, 128.8, 129.5, 133.6,
135.2 (C-5 pyrazole), 147.8, 155.2 ppm (C-3 pyrazole).
6
Anal. Calcd. for C H N O (290.28): C, 66.20; H, 3.47; N,
16 10
4 2
19.30. Found: C, 66.19; H, 3.42; N, 19.32.
1-(4-Chlorophenyl)-4-cyano-1H-pyrazole-3-carboxylic Acid
Phenylamide (5d).
This compound was obtained in 55 % yield, mp: 236-238 °C;
-1
IR (KBr): ν 3300 (NH), 2241.1 cm (CN); MS (EI): m/z (%) =
+
1
322/324 (M ); H NMR (DMSO-d ): δ = 7.15-8.09 (m, 9H, Ar
6
H), 9.491 (s, 1H, pyrazole H), 10.46 (s, 1H, NH, D O exhabge).
2
Anal. Calcd. for C H N ClO (322.76): C, 63.26; H, 3.44; N,
17.36. Found: C, 63.23; H, 3.45; N, 17.38.
EXPERIMENTAL
17 11
4
The melting points were determined on a Stuart melting
point apparatus and are uncorrected. The IR spectra were
recorded as KBr pellets using a FTIR unit Bruker-vector 22
General Procedure for Preparation of Compounds 8b and 10.
A mixture of 3-acetyl-1-(4-chloro-phenyl)-1H-pyrazole-4-car-
bonitrile 5a (10 mmol) and phenylhydrazine and/or hydrazine
hydrate (10 mmol) is refluxed in DMF for 2 hrs. The reaction
mixture is then poured on water. The crude product was collected
and crystallized from an ethanol/DMF mixture.
1
13
spectrophotometer. The H and C NMR spectra were
recorded in DMSO-d and CDCl as solvent at 200 or 300
6
3
MHz on a Varian Gemini NMR spectrometer using TMS as
internal standard. Chemical shifts are reported in δ units
(ppm). Mass spectra were measured on a Shimadzu GMMS -
QP-1000 EX mass spectrometer at 70 eV. The elemental
analyses were performed at the microanalytical center, Cairo
University.
1-(4-Chlorophenyl)-3-[1-(phenylhydrazono)-ethyl]-1H-pyra-
zole-4-carbonitrile (8b).
This compound was obtained in 79 % yield, mp: 190 °C; IR
(KBr): ν 3348.4 (NH), 2232.2 (CN); MS (EI): m/z (%) = 335/337
+
1
(M ); H NMR (DMSO-d ): δ = 2.28 (s, 3H, CH ), 6.72-7.84 (m,
6
3
General Procedure for Preparation of 5a-d.
13
9H, Ar H), 9.26(s, 1H, pyrazole H), 9.61 (s, 1H, NH); C NMR
A mixture of enaminonitrile 1 (10 mmol), hydrazonyl halide
(DMSO-d ): ν = 12.06 (CH ), 90.1 (C-4 pyrazole), 113.2 (C-3
6
3
2a-d (10 mmol), Et N (10 mmol) in ethanol (20 ml) was refluxed
3
pyrazole), 114.7 (CN), 119.7, 120.5, 128.9, 129.6, 131.8, 133.8,
136.4 (CH aromatic), 137.2 (C-5 pyrazole), 145.3 (CH aromatic),
153.8 (C=N).
for 4 h. The solvent was evaporated under vacuo and the crude
product was collected and crystallized from ethanol.
Anal. Calcd. for C H N Cl (335.80): C, 64.38; H, 4.20; N,
20.86. Found: C, 64.41; H, 4.23; N, 20.83.
3-Acetyl-1-(4-chlorophenyl)-1H-pyrazole-4-carbonitrile (5a).
18 14 5
This compound was obtained in 72 % yield, mp: 207 °C; IR
-1
Preparation of 1-[1-(4-Chlorophenyl)-3-cyano-1H-pyrazol-4-yl]-
ethanone Azine (10).
(KBr): ν 2238 (CN), 1688 cm (CO); MS (EI): m/z (%) =
+
1
245/247 (M ); H NMR (DMSO-d ): δ = 2.57 (s, 3H, CH CO),
6
3
13
7.62- 7.93 (m, 4H, Ar-H), 9.42 ppm (s, 1H, pyrazole H);
C
This compound was obtained in 70 % yield, mp: 320 °C; IR
NMR (DMSO-d ): δ = 26.5 (CH ), 92.9 (C-4 pyrazole), 112.6
+
6
3
(KBr): ν = 2230.3 (CN); MS (EI): m/z (%) = 487.35/489 (M );
(CN), 121.57, 129.9, 133.1, 136.9, (CH aromatic), 137.5 (C-5
pyrazole), 151.2 (C-3 pyrazole ), 191.6 (CO) ppm.
1
H NMR (DMSO-d ): δ = 2.5 (s, 6H, 2CH ), 7.90 – 8.12 (m, 8H,
6
3
Ar H), 9.70 (s, 2H, CH pyrazole).
Anal. Calcd. for C H C1N O (245.67): C, 58.67; H, 3.28; N,
12
8
3
Anal. Calcd. for C H N Cl (487.35): C, 59.15; H, 3.31; N,
24 16 8 2
17.10. Found: C, 58.62; H, 3.30; N, 17.08.
22.99. Found: C, 59.20; H, 3.28; N, 22.89.
Ethyl 1-(4-Chlorophenyl)-4-cyano-1H-pyrazole-3-carboxylate
(5b).
Preparation of 1-(4-Chlorophenyl)-3-((E)-3-dimethylamino-
acryloyl)-1H-pyrazole-4-carbonitrile (11).
This compound was obtained in 66 % yield, mp: 178- 180 °C;
A mixture of 5a and DMFDMA was refluxed in xylene for 3 hrs.
The solvent was removed by evaporation under vacuo. The solid
product was then crystallized from ethanol to give 5a in 75 % yield,
mp: 190 °C; IR (KBr): ν = 3092, 3031 (CH olephinic), 2234 (CN),
-1
IR (KBr): ν 2236 (CN), 1725.4 cm (CO); MS (EI): m/z (%) =
+
1
275/277 (M ); H NMR (DMSO-d ): δ = 2.26 (t, 3H, CH , J=7
6
3
Hz), 4.34 (q, 2H, CH , J=7 Hz) 7.61- 7.85 (m, 4H, Ar H), 9.48
2
13
+
1
ppm (s, 1H, pyrazole H); C NMR (DMSO-d6): δ = 14.0 (CH ),
1642 (CO); MS (EI): m/z (%) = 300/302 (M ); H NMR (DMSO-
3
61.72 (CH ), 95.4 (C-4 pyrazole), 112.1 (CN), 121.5, 129.8,
d ): δ = 2.92 (s, 6H, 2CH ), 5.86 (d, 1H, olephinic H, J=16 Hz), 7.61-
2
6
3
133.1, 136.7, (CH aromatic), 137.0 (C-5 pyrazole), 144.7 ppm
(C-3 pyrazole), 159.2 (CO).
7.95 (m, 4H, Ar H), 7.71 (d, 1H, olephinic H, J=16 Hz), 9.34 (s, 1H,
13
CH pyrazole); C NMR (DMSO-d ): δ = 45.6 (CH ), 93.2, 94.1 (C-
6
3
Anal. Calcd. for C H ClN O (275.70): C, 56.64; H, 3.66;
4 pyrazole), 114.7 (CN), 119.7, 122.2, 130.6, 133.3 (C-5 pyrazole),
13 10
3 2
N, 15.24. Found: C, 56.65; H, 3.61; N, 15.28.
137.4, 137.4, 138.1, (C-3 pyrazole), 155.2 (N-C=C), 180.5 (CN).

1188
S. A. S. Ghozlan, I. A. Abdelhamid, H. M. Gaber and M. H. Elnagdi
Vol. 42
Anal. Calcd. for C H N ClO (300.75) : C, 59.91; H, 4.36; N,
18.63. Found: C, 59.89; H, 4.33; N, 18.65.
mp: 217 °C; IR (KBr): δ 3420 (NH), 2238 (CN), 1704 (CO),
15 13
4
+
1
1643 (CHO); MS (EI): m/z (%) = 411 (M ); H MNR (DMSO-
d ): δ = 7.38-7.95 (m, 8H, Ar H), 7.79 (s, 1H, pyrazole H), 9.52
6
Preparation of 1-(4-Chlorophenyl)-1H,1’H-[3,3]bipyrazolyl-4-
carbonitrile (12).
(s, 1H, CHO), 9.93 (s, 1H, NH, D O exchange).
2
Anal. Calcd. for C H C1 N O (412.24): C, 55.36; H, 2.69;
19 11
2 5 2
A mixture of enaminone (11) with hydrazine hydrate was
refluxed in DMF (25 mL) for 3 h. The reaction mixture was then
poured on water. The solid that formed was collected by filtration
and crystallized from ethanol and DMF to give 12 in 78 % yield,
mp: 310 °C; IR (KBr): ν 2232 (CN); MS (EI): m/z (%) = 269/271
N, 16.99. Found: C, 55.25; H, 2.73; N, 17.12.
Preparation of 3-(6-Cinnoline-3-carbonyl)-1-(4-chlorophenyl)-
1H-pyrazole-4-carboxylic Acid Amide (17).
Hydrazonal 16 was heated in H SO for 15 minutes. The reac-
2
4
+
1
(M ); H NMR (DMSO-d ): δ = 7.60-8.10 (m, 4H, aromatic H),
tion mixture is poured on water. The solid that formed was col-
lected by filtration and crystallized from ethanol. This compound
was obtained as yellow a powders in a yield of 80%, mp: 265 °C;
IR (KBr): ν 3420.2, 3331.7 (NH), 1659.8, 1621 (CO); MS (EI):
6
8.28 (m, 1H, CH pyrazole), 8.98 (d, 1H, CH pyrazole), 9.38 (s,
1H, CH pyrazole), 13.27 (s, 1H, NH, D O exchange).
2
Anal. Calcd. for C H C1N (269.70): C, 57.90; H, 2.99; N
13
8
5
+
1
25.97. Found: C, 57.81; H, 2.86; N, 26.13.
m/z (%) = 411/413 (M ); H NMR (DMSO-d ): δ = 7.41-8.13
6
(m, 7H, Ar H), 9.12 (s, 1H, pyrazole H), 9.14 (s, 1H, cinnoline
H), 13.61 (s, 2H, NH).
1-(4-Chlorophenyl)-3-(5-hydroxynaphtho[1,2-b]furan-3-car-
bonyl)-1H-pyrazole-4-carbonitrile (13).
Anal. Calcd. for C H C1 N O (412.24): C, 55.36; H, 2.69;
19 11
2 5 2
A mixture of enaminone (11) and naphthoquinone was
stirred in acetic acid and left over night at room temperature.
The reaction mixture is poured on water. The solid that formed
was collected by filtration and crystallized from ethanol and
DMF. This compound was obtained as brown crystals in 83 %
yield, mp: 312 °C; IR (KBr): ν 3415 (OH), 2239 (CN), 1705.7
N, 16.99. Found: C, 55.45; H, 2.81; N, 16.85.
Preparation of 3-{2-(4-Chlorophenylazo)-2-[(4-chlorophenyl)-
hydrazono]-acetyl}-1-(4-chloro-phenyl)-1H-pyrazole-4-carboni-
trile (18).
A cold solution of aryldiazonium salt (20 mmol) was prepared
by adding a solution of sodium nitrite (1.5 g into 10 mL H O) to a
+
1
(CO); MS (EI): m/z (%) = 413/415 (M ); H NMR (DMSO-
2
d ): δ = 7.58-8.28 (m, 9H, Ar H), 9.41 (s, 1H, pyrazole), 9.56
cold solution of arylamine hydrochloride (20 mmol of arylamine in
10 mL concentrated HCl) with stirring. The resulting solution of
aryldiazonium salt was then added to a cold solution of pyrazole
(11) in ethanol (50 mL) containing sodium acetate (2 g). The mix-
ture was stirred and the solid product was collected by filtration
and crystallized from ethanol to give 82 % yield of 18, mp: 282 °C;
IR (KBr): ν 3448 (NH), 2239 (CN), 1711 (CO); MS (EI): m/z (%)
6
13
(s, 1H, furan H), 10.34 (s, 1H, OH); C NMR (DMSO-d ): δ
6
= 95.4 (C-4 pyrazole), 101.1, 114.5 (CN), 120.2, 120.8, 121.7,
122.7, 124.2, 124.6, 125.9, 128.4, 130.6, (CH aromatic), 133.9
(C-5 pyrazole), 137.8, 138.1 (C-3 pyrazole), 145.1, 151.9,
152.9, 155.4, 180.1 (CO).
Anal. Calcd. for C H C1N O (413.82): C, 66.76; H, 2.92;
23 12
3 3
+
1
N, 10.15. Found: C, 66.82; H, 2.96; N, 10.09.
= 521/523/525 (M ); H NMR (DMSO-d ): δ = 6.53-7.98 (m,
6
12H, Ar H), 8.80 (s, 1H, CH pyrazole), 9.51 (S, 1H, NH).
Preparation of 3-(5-Acetyl-6-methylpyridin-2-yl)-1-(4-
chlorophenyl)-1H-pyrazole-4-carbonitrile (14).
Anal. Calcd. for C H C1 N O (522.78): C, 55.14; H, 2.70;
24 14
3 7
N, 18.75. Found: C, 55.23; H, 2.79; N, 18.63.
A mixture of enaminone (11) and acetyl acetone was refluxed
in acetic acid and ammonium acetate for 2 hrs. The reaction mix-
ture is poured on water. The solid that formed was collected by
filtration and crystallized from ethanol. This compound was
obtained as yellow crystals in 82 % yield, mp: 220-222 °C; IR
(KBr): ν 2236.2 (CN), 1679.7 (CO); MS (EI): m/z (%) = 336/338
Preparation of 1-(4-Chlorophenyl)-4-cyano-1H-pyrazole-3-car-
boxylic Acid Hydrazide (19).
A mixture of pyrazole ester 5b and hydrazine hydrate was
refluxed in dimethylformamide (DMF) for 3 hr. The reaction
mixture is poured on water. The solid that formed was collected
by filtration and crystallized from an ethanol-DMF mixture. This
compound was obtained as yellow powders in 85% yield, mp:
+
1
(M )., H NMR (DMSO-d ): δ = 2.63 (s, 3H, CH ), 3.30 (s, 3H,
6
3
CH ), 7.64-8.04 (m, 4H, Ar H), 8.36 (d, 1H, pyridine H, J= 8),
3
13
9.47 (s, 1H, pyrazole H), 9.56 (d, 1H, pyridine H, J= 8);
C
322 °C; IR (KBr): ν 3290-3131.6 (NH ), 2244.8(CN), 1704.9
2
NMR (DMSO-d ): δ = 25.1 (CH ), 30.4 (CH ), 93.7 (C-4 pyra-
+
1
6
3
3
(CO); MS (EI): m/z (%) = 261/263 (M ); H NMR (DMSO-d ):
6
zole), 114.5 (CN), 118.6, 121.1, 122.4, 130.6, 133.3 (C-5 pyra-
zole), 138.1, 139.6, 150.4 (C-3 pyrazole), 152.3, 158.1, 201.1
(C=O).
δ = 5.96 (s, 2H, NH ) 7.66-7.96 (m, 4H,Ar H), 9.48 (s, 1H, pyra-
2
zole H), 11.190 (s, 1H, NH).
Anal. Calcd. for C H C1N O (261.67): C, 50.49; H, 3.08; N,
11
8
5
Anal. Calcd. for C H C1N O (336.78): C, 64.20; H, 3.89; N,
18 13
4
26.76. Found: C, 50.41; H, 3.18; N, 26.81.
16.64. Found: C, 64.29; H, 3.91; N, 16.72.
Acknowledgment.
Preparation of 1-(4-Chlorophenyl)-3-{2-[(4-chlorophenyl)-
hydrazono]-3-oxo-propionyl}-1H-pyrazole-4-carbonitrile (16).
H. Gaber is grateful to ICSC-World Laboratory, Switzerland
for a research grant to him at Nucleic Acid Center, Department of
Chemistry, University of Southern Denmark, Odense M,
Denmark. We are thankful for all the facilities provided to this
fellowship.
A cold solution of aryldiazonium salt (10 mmol) was prepared
by adding a solution of sodium nitrite (0.7 g into 10 mL H O) to
2
a cold solution of arylamine hydrochloride (10 mmol of ary-
lamine in 5 mL concentrated HCl) with stirring. The resulting
solution of aryldiazonium salt was then added to a cold solution
of enaminone (11) in ethanol (50 mL) containing sodium acetate
(1 g). The mixture was stirred and the solid product was collected
by filtration and crystallized from ethanol to yield 82 % of 16,
REFERENCES AND NOTES
[1] S. Patai, Ed (the chemistry of enamines), J. Wiley and Sons,

Sep-Oct 2005
Studies on Enaminonitriles: a New Synthesis of 1,3-Substituted Pyrazole-4-carbonitrile
1189
New York, (1994).
[11] M. A. Al-Shiekh, A. M. Salah El-Din, E. A. Hafez, and M. H.
Elnagdi, J. Heterocyclic Chem., 41, 647 (2004).
[2] B. Stanovnik, J. Heterocyclic Chem., 36, 1581, (1999).
[3] A. Winter and N. Risch, Synlett, 1, 1959 (2003).
[4] K. M. Davis and B. K. Carpenter, J. Org. Chem., 61, 4617
[12] F. M. A. El-Taweel, and M. H. Elnagdi, J. Heterocyclic Chem.,
38, 981 (2001).
(1996).
[5] K. M. Al-Zaydi, E.A. Hafez and M. H. Elnagdi, J. Chem.
Res.(S), 154, (2000).
[6] M. M. Abdel- Khalik and M.H. Elnagdi, Synthetic Commun.,
32, 159 (2002).
[13] M. A. Al-Shiekh, A. M. Salah El-Din, E.A. Hafez, and M. H.
Elnagdi, J. Chem., Res., 174 (2004).
[14] A. A. Elassar and A. A. El-Khair, Tetrahedron, 59, 8463 (2003).
[15] M. M. Abdel-Khalik, M. H. Elnagdi, S. M. Agamy, Synthesis,
1166 (2000).
[7] F. Al-Omran, N. Al-Awadi, A. A. El-Khair and M. H. Elnagdi,
Org. Prep. Proced. Ind., 29, 285 (1997).
[8] A. Al-Anezi, B. Al-Saleh and M. H. Elnagdi, J. Chem. Res. (S).,
4 (1997).
[16] L. Rene, J. Poncet, and G. Auzou, Synthesis, 419 (1986).
[17] R. M. Silverstien and F. X. Webster, Spectrometric
Identification of organic compounds, 6 Ed., John Wiely & Sons., Inc.
th
(1998).
[9] S. Al-Mousawi, M. M. Abdel-Khalik, E. John and M. H.
Elnagdi, J. Heterocyclic Chem., 40, 689 (2003).
[10] S. Almazroa, M. H. Elnagdi, and A. M. Salah El-Din J.
Heterocyclic Chem., 41, 267 (2004).
[18] M. M. Abdel-Khalik, S. M. Agamy and M. H. Elnagdi, Z.
Naturforsch, 55b, 1211 (2000).
[19] F. Al-Omran, M. M.Abdel-Khalik, A. A. El-Khair and M. H.
Elnagdi, Synthesis, 91 (1997).