Enaminones as building blocks in organic synthesis: A novel route to polyfunctionally substituted benzonitriles, pyridines, eneylbenzotriazoles and diazepines

Article abstract of DOI:10.1002/jhet.5570400205

An efficient synthesis of enaminones 1a-c is reported. Compounds 1a-c reacted with diethyl-3-amino-2-cyanopenten-1,5-dicarboxylate (3) to yield the benzonitriles 6. On the other hand, the reaction of 1a-c with 3-amino-2-cyano-2-pentene dinitrile (7) affor

Full text of DOI:10.1002/jhet.5570400205

Enaminones as Building Blocks in Organic Synthesis:
a Novel Route to Polyfunctionally Substituted
Mar-Apr 2003
225
Benzonitriles, Pyridines, Eneylbenzotriazoles and Diazepines
*
Abu Zeid A. Hassanien [a] , Said A. S. Ghozlan [b] and Mohamed H. Elnagdi [b]
[a] Department of Chemistry, Faculty of Education, Suez Canal University, Arish, Egypt.
[b] Department of Chemistry, Faculty of Science, Cairo University, Egypt.
Received September 19, 2002
An efficient synthesis of enaminones 1a-c is reported. Compounds 1a-c reacted with diethyl-3-amino-2-
cyanopenten-1,5-dicarboxylate (3) to yield the benzonitriles 6. On the other hand, the reaction of 1a-c with
3-amino-2-cyano-2-pentene dinitrile (7) afforded a mixture of benzonitriles 10 and pyridines 9. The reaction
of 1a-c with 3-aminocrotononitrile 11 has afforded the 4-substituted-3-cyano-2-methylpyridines 15a-c. The
reaction of ethylene diamine with 1a-c afforded 5-substituted-2,3-dihydro-1H-[1,4]diazepines 18a-c. On the
other hand, 1a-c reacted with o-phenylenediamine to yield the 4-(2-aminopheynlamino)-substituted
enaminones 21. Compounds 21 could be converted into the benzotriazolylenones 22 on treatment with
sodium nitrite in acetic acid solution.
J. Heterocyclic Chem., 40, 225 (2003).
Scheme 1
In conjunction to pervious interest in exploring synthetic
potential of enaminones [1-5] we report on synthesis and
reactivity of 1a-c. Although 1a-c has been prepared earlier
from reaction of methyl ketones with DMFDMA in
refluxing toluene [5] yields of 1a-c under these conditions
never exceeded 40%. Trials to adopt other literature
procedure [6] of reacting methyl ketones with DMFDMA in
refluxing acetic acid afforded in our hands only trimers 2a-c
which has recently been obtained on refluxing 1a-c in AcOH
[7,8]. Now we report 70-80% yield synthesis of 1a-c via
refluxing a mixture of methyl ketones with little excess of
DMFDMA (1:1.2 mole) for six hours in absence of solvent.
Compounds 1, so formed reacted with diethyl 3-amino-
2-cyanopenten-1,5-dicarboxylate (3) to yield products of
condensation via dimethylamine elimination. These were
assigned structure 6 and are assumed to be formed via
intermediates 4 and 5.
well, structure 15 is established based on H-5, 6 coupling
of pyridine which showed a value of 4 Hz, if the reaction
product is 13 one would expect these protons to have
J ~ 9Hz. [9].
On the other hand, reaction of 3-amino-2-cyano-2-
pentene dinitrile (7) with 1a afforded a mixture of two
products. These were identified as 9 and 10 based on
spectral data. Compounds 9 and 10 are assumed to be
formed via the common intermediate 8, which either losses
water to yield 9 or cyclize via addition of electron rich
double bond in 8 to the cyano group to give 10. But in case
of 1b,1c only compound 9 could be isolated.
The reaction of ethylenediamine with 1a-c in refluxing
ethanol afforded the diazepene 18 via the nonisolable
intermediate 17.
On the other hand, the reaction of 1a-c with o-phenyl-
enediamine afforded products of condensation via
dimethylamine elimination. These were assigned cis struc-
1
ture 21 rather than trans structure 20 based on H NMR
which revealed signals for cis olefinic protons at δ 6.04
and δ 8.40 ppm, (J = 9 Hz). The predominance of this form
may be due to fixation by hydrogen bonding. Attempted
cyclisation of 21 into diazepene derivatives failed under a
The reaction of 1a-c with 3-aminocrotononitrile 11
afforded the pyridine derivative 15 via the intermediates
14, but not 12. Although this reaction can afford 13 as

226
A. Z. A. Hassanien, S. A. S. Ghozlan and M. H. Elnagdi
Vol. 40
Scheme 2
Ethyl 2-Amino-5-aroyl-3-cyano-4-hydroxybenzoate (6a-c).
A mixture of enaminone 1a-c (0.01 mol), ethyl cyanoacetate
dimer (0.01 mol) and few drops of triethylamine in 1,4-dioxan
(20 ml) was refluxed for 8-12 h. After removel of the solvent, the
residue was chromatographed on silica gel using EtOAc/CHCl
4:1 as eluent.
3
Ethyl 2-Amino-5-benzoyl-3-cyano-4-hydroxybenzoate (6a).
This compound was obtained in yield (63%), mp. 205 °C; ir
-1
(KBr) νmax/cm : 3430 (OH), 3420 (NH ), 2985 (CH aliph),
2
+
2187 (CN), 1710 (CO, ester), 1658 (CO); ms: m/z = 310 (M ,
13.5%); H nmr (dimethyl sulfoxide-d ): δ (ppm) = 1.34 (t, 3H,
1
6
J = 7.5 Hz, CH ), 4.10 (q, 2H, J = 7.5 Hz, CH ), 6.03 (b, 2H,
3
2
NH ), 7.14-7.83 (m, 6H, H-Ar), 13.1 (s, 1H, OH).
2
Anal. Calcd. for C H N O : C, 65.80; H, 4.51, N, 9.03%.
17 14
2 4
Found C, 65.50; H, 4.50; N, 9.30.
Scheme 3
Ethyl 2-Amino-3-cyano-4-hydroxy-5-(p-methylbenzoyl)ben-
zoate (6b).
This compound was obtained in yield (58%), mp 220 °C; ir
-1
(KBr) νmax/cm : 3450 (OH), 3422 (NH ), 2958 (CH aliph),
2
1
2195 (CN), 1708 (CO, ester), 1645 (CO); H nmr (dimethyl sul-
foxide-d ): δ (ppm) = 1.41 (t, 3H, J = 7.5 Hz, CH ), 1.73 (s, 3H,
6
3
CH ), 4.32 (q, 2H, J = 7.5 Hz, CH ), 5.93 (b, 2H, NH ), 7.13-
3
2
2
7.72 (m, 5H, H-Ar), 12.91 (s, 1H, OH).
Anal. Calcd. for C H N O : C, 66.66; H, 4.93, N, 8.64%.
18 16
2 4
Found C, 66.60; H, 4.80; N, 8.80.
Varity of conditions. However, diazotization afforded the
trans enaminone 22, which was also obtained from
reaction of benzotriazole 23 with 1a-c.
Ethyl 2-Amino-3-cyano-4-hydroxy-5-(4-methoxybenzoyl)ben-
zoate (6c).
This compound was obtained in yield (53%), mp 195 °C; ir
Scheme 4
-1
(KBr) νmax/cm : 3465 (OH), 3435 (NH ), 2982 (CH aliph),
2
+
2190 (CN), 1715 (CO, ester), 1638 (CO); ms: m/z = 340 (M ,
35%). H nmr (dimethyl sulfoxide-d ): δ (ppm) = 1.34 (t, 3H, J =
1
6
7 Hz, CH ), 3.56 (s, 3H, OCH ), 4.41 (q, 2H, J = 7 Hz, CH ),
3
3
2
5.83 (s, 2H, NH ), 7.03-7.71 (m, 5H, H-Ar), 12.62 (s, 1H, OH).
2
Anal. Calcd. for C H N O : C, 63.52; H, 4.70, N, 8.23%.
18 16
2 5
Found C, 63.50; H, 4.80; N, 8.10.
Preparation of Compounds (9a-c) and 10.
General Procedure.
To a solution of enaminones 1a-c (0.01 mol) in absolute
ethanol (30 ml) and malononitrile dimer (0.01 mol) a few drops
of piperidine were added. The mixture was refluxed for 7-9 h.
The solvent was evaporated under reduced pressure, and the
solid product so formed was collected by filtration washed
several time with water dried and recrytallized from benzene in
case of 9a,c and 10 and ethanol in case of 9b, compound 9a and
10 were separated by fractional crystallization from benzene to
afforded insoluble 10 (23%) and soluble 9 (35%) which
precipitate on cooling.
EXPERIMENTAL
2-[3-Cyano-6-phenylpyridin-2-(1H)-ylidene]malononitrile (9a).
This compound was obtained in yield (35%), mp 315 °C; ir
Melting points are uncorrected. IR spectra were recorded with
FTIR-8201 PC spectrophotometer Shimadzu. H-NMR spectra
were obtained on a Varian Germini 200 MHz spectrometer in
-1
1
(KBr) νmax/cm : 3340 (NH), 2210, 2187 (3CN); ms: m/z = 244
+
1
(M , 100%); H nmr (dimethyl sulfoxide-d ): δ (ppm) =
6
7.51-7.80 (m, 5H, H-Ar), 8.31 (d, 1H, J = 6Hz, 4 H-pyridine),
8.63 (d, 1H, J = 6 Hz, 5H-pyridine), 10.72 (s, 1H, NH).
DMSO-d as solvent and TMS as an internal reference. Mass spec-
6
tra were performed on a Shimadzu GCMS-QP-1000 EX using the
direct inlet system and EI + QI MSLMRUPLR. Microanalysis
were performed by the Microanalytical Unit at Cairo University.
Anal. Calcd. for C H N : C, 73.77; H, 3.27, N, 22.95%.
15
8 4
Found C, 74.0; H, 3.20; N, 23.10.

Mar-Apr 2003
Enaminones as Building Blocks in Organic Synthesis
227
2-[3-Cyano-6-(p-tolyl)pyridin-2-(1H)-ylidene]malononitrile
(dimethyl sulfoxide-d ): δ (ppm) = 2.83 (s, 3H, CH ), 3.56 (s,
6 3
(9b).
3H, OCH ), 7.35-7.89 (m, 4 H, H-Ar), 8.04 (d, 1H, J = 4 Hz, H-5
3
pyridine), 8.08 (d, 1H, J = 4 Hz, H-6 pyridine).
This compound was obtained in yield (55%), mp 298 °C; ir
Anal. Calcd. for C H N O C, 75.0; H, 5.35, N, 12.50%.
-1
14 12 2
(KBr) νmax/cm : 3330 (NH), 2989 (CH aliph), 2215, 2195
Found C, 75.0; H, 5.40; N, 12.60.
Preparation of compounds (18a-c) and (21a-c).
General Procedure.
+
1
(3CN); ms: m/z = 258 (M , 100%). H nmr (dimethyl sulfoxide-
d ): δ (ppm) = 2.41 (s, 3H, CH ), 7.31-7.71 (m, 4H, H-Ar), 8.42
6
3
(d, 1H, J = 8Hz, 4H-pyridine), 8.59 (d, 1H, J = 8Hz, 5H-pyri-
dine), 10.13 (b, 1H, NH)
A mixture of enaminones 1a-c (0.01 mol) and ethylene
diamine or o-phenylene diamine (0.01 mol) in absolute ethanol
(30 ml) was refluxed for 5-8 h. The solvent was partially
removed and the solid product so formed was collected on cool-
ing and recrytallized from ethanol.
Anal. Calcd. for C H N : C, 74.41; H, 3.87, N, 21.70%.
Found C, 74.50; H, 3.60; N, 21.90.
16 10
4
2-[3-Cyano-6-(p-methoxyphenyl)pyridin-2-(1H)-ylidene]mal-
ononitrile (9c).
This compound was obtained in yield (93%), mp 315 °C; ir
5-Phenyl-1,2,3-trihydro[1,4]diazepine (18a).
-1
(KBr) νmax/cm : 3305 (NH), 2984 (CH aliph), 2218, 2192
1
This compound was obtained in yield (85%), mp 192 °C; ir
(3CN); H nmr (dimethyl sulfoxide-d ): δ (ppm) = 3.54 (s, 3H,
6
-1
(KBr) νmax/cm : 3310 (NH), 2985 (CH aliph); ms: m/z = 172
OCH ), 7.13-7.82 (m, 4H, H-Ar), 8.31 (d, 1H, J = 8Hz, 4 H-pyri-
3
+
1
(M , 86%); H nmr (deuteriochloroform): δ (ppm) = 3.34 (t, 4H,
dine), 8.71 (d, 1H, J = 6 Hz, 5 H-pyridine), 10.64 (s, 1H, NH).
J = 6.4, 2CH ), 5.7 (d, 1H, J = 8 Hz, H-6), 6.73 (d, 1H, J = 8 Hz,
2
Anal. Calcd. for C H N O: C, 70.07; H, 3.64, N, 20.43%.
16 10
4
H-7), 7.15-7.75 (m, 5H, H-Ar), 10.46 (b, 1H, NH).
Found C, 70.20; H, 3.40; N, 20.60.
Anal. Calcd. for C H N : C, 76.74; H, 6.97, N, 16.27%.
11 12
2
6-Benzoyl-1,3-diamino- -2,4-dicyanobenzene (10).
Found C, 76.70; H, 6.90; N, 16.30.
This compound was obtained in yield (23%), mp 325 °C; ir
5-(p-Tolyl)-1,2,3-trihydro[1,4]diazepine (18b).
This compound was obtained in yield (80%), mp 200 °C; ir
-1
(KBr) νmax/cm : 3490, 3340, 3230 (NH ), 2218 (2CN), 1647
2
+
1
(CO); ms: m/z = 262 (M , 52%), H nmr (dimethyl sulfoxide-d ):
6
-1
(KBr) νmax/cm : 3340 (NH), 2985 (CH aliph); ms: m/z = 186
δ (ppm) = 6.35 (b, 2H, NH ), 7.35-7.86 (m, 6H, H-Ar), 8.72 (b,
2
+
1
(M , 38%); H nmr (deuteriochloroform): δ (ppm) = 2.38 (s, 3H,
CH ), 3.42 (t, 4H, J = 6.4 Hz, CH ), 5.6 (d, 1H, J = 8 Hz, H-6),
2H, NH ).
2
3
2
Anal. Calcd. for C H N O: C, 68.70; H, 3.81, N, 21.37%.
15 10
4
6.80 (d, 1H, J = 8 Hz, H-7), 7.23 (d, 2H, J = 8 Hz, H-Ar), 7.46 (d,
2H, J = 8 Hz, H-Ar), 10.36 (b, 1H, NH).
Found C, 68.60; H, 3.90; N, 21.30.
4-Aryl-2-methylpyridine-3-carbonitrile (15a-c).
General Procedure.
Anal. Calcd. for C H N : C, 77.41; H, 7.52, N, 15.05%.
12 14
2
Found C, 77.50; H, 7.40; N, 15.10.
5-(p-Methoxyphenyl)-1,2,3-trihydro[1,4]diazepine (18c).
This compound was obtained in yield (82%), mp 183 °C; ir
A mixture of each compound 1a-c (0.01 mol) and acetonitrile
dimer 12 (0.015 mol) was refluxed in ethanol (30 ml) in presence
of sodium ethoxide (0.01 mol) for 3-6 h. The solvent was
removed and the residue was chromatographed on silica gel
using EtOAc/petroleum ether 60-80 (3:7) as eluent. The product
was crystallized from ethanol.
-1
(KBr) νmax/cm : 3339 (NH), 2985 (CH aliph); ms: m/z = 202
+
1
(M , 53%). H nmr (deuteriochloroform): δ = 3.46 (d, 4H,
2CH ), 3.80 (s, 3H, OCH ), 5.83 (d, 1H, J = 8 Hz, H-6), 6.83 (d,
2
3
1H, J = 6 Hz, H-7), 7.19 (d, 2H, J = 8 Hz, H-Ar), 7.93 (d, 2H, J =
8 Hz, H-Ar), 10.32 (b, 1H, NH).
3-Cyano-2-methyl-4-phenylpyridine (15a).
Anal. Calcd. for C H N O: C, 71.28; H, 6.93, N, 13.86%.
12 14
2
This compound was obtained in yield (67%), mp 135 °C; ir
Found C, 71.40; H, 7.10; N, 13.80.
-1
(KBr) νmax/cm : 2923 (CH aliph), 2221 (CN); ms: m/z = 194
(Z)-3-(2-Aminoanilino)-1-phenylprop-2-en-1-one (21a).
+
1
(M , 100%); H nmr (dimethyl sulfoxide-d ): δ (ppm) = 2.84 (s,
6
3H, CH ), 7.21-7.91 (m, 5H, H-Ar), 8.07 (d, 1H, J = 4 Hz, H-5-
pyridine), 8.17 (d, 1H, J = 4 Hz, H-6 pyridine).
This compound was obtained in yield (78%), mp 145 °C; ir
3
-1
(KBr) νmax/cm : 3450, 3320 (NH , NH), 2985 (CH aliph), 1640
2
+
1
Anal. Calcd. for C H N : C, 80.41; H, 5.15, N, 14.43%.
(CO); ms: m/z = 238 (M , 65%); H NMR (deuteriochloroform):
13 10
2
Found C, 80.50; H, 5.10; N, 14.30.
δ = 3.77 (d, 2H, NH exchangable), 6.04 (d, 1H, J = 9 Hz,
2
CH-vinyl), 6.62-7.72 (m, 9H, H-Ar), 8.2 (d, 1H, J = 9 Hz,
CH-vinyl), 12.13 (b, 1H, NH exchangeable).
3-Cyano-2-methyl-4-(p-tolyl)pyridine (15b).
This compound was obtained in yield (62%), mp 143 °C; ir
Anal. Calcd. for C H N O: C, 75.63; H, 5.88, N, 11.76%.
15 14
2
-1
(KBr) νmax/cm : 2989 (CH aliph), 2218 (CN); ms: m/z = 208
Found C, 75.60; H, 5.80; N, 11.80.
+
1
(M , 100%). H nmr (dimethyl sulfoxide-d ): δ (ppm) = 2.21 (s,
6
(Z)-3-(2-Aminoanilino)-1-(p-tolyl)prop-2-en-1-one (21b).
This compound was obtained in yield (80%), mp 205 °C; ir
3H, CH ), 2.89 (s, 3H, CH ), 7.1-7.83 (m, 4H, H-Ar), 8.03 (d,
3
3
1H, J = 4 Hz, H-5 pyridine), 8.06 (d, 1H, J = 4 Hz, H-6 pyridine).
Anal. Calcd. for C H N : C, 80.76; H, 5.76, N, 13.46%.
-1
(KBr) νmax/cm : 4450, 3340 (NH , NH), 2985 (CH aliph),
2
14 12
2
+
1
1638 (CO); ms: m/z = 252 (M , 43%); H NMR (deuterio-
chloroform): δ = 2.42 (s, 3H, CH ), 3.77 (s, 2H, NH
Found C, 80.60; H, 5.60; N, 13.50.
3
2
3-Cyano-2-methyl-4-(p-methoxyphenyl)pyridine (15c).
This compound was obtained in yield (65%), mp 128 °C; ir
exchangable), 6.04 (d, 1H, J = 9 Hz, CH-vinyl), 6.79-7.89 (m,
8H, H-Ar), 8.17 (d, 1H, J = 9 Hz, CH-vinyl),, 12.19 (b, 1H,
NH exchangeable).
-1
1
(KBr) νmax/cm : 2998 (CH aliph), 2215 (CN); H nmr

228
A. Z. A. Hassanien, S. A. S. Ghozlan and M. H. Elnagdi
Vol. 40
Anal. Calcd. for C H N O: C, 76.19; H, 6.34, N, 11.11%.
Found C, 76.20; H, 7.20; N, 11.20.
(E)-3-(1H-1,2,3-Benzotriazol-1-yl)-1-(p-tolyl)prop-2-en-1-one
(22b).
16 16
2
This compound was obtained in yield (56%), mp 122 °C; ir
(Z)-3-(2-Aminoanilino)-1-(p-methoxyphenyl)prop-2-en-1-one
(21c).
-1
(KBr) νmax/cm : 2985 (CH aliph), 1648 (CO); ms: m/z = 263
+
1
(M , 38%); H nmr (deuteriochloroform): δ = 2.31 (s, 3H, CH ),
3
This compound was obtained in yield (78%), mp 185-186
7.12-7.78 (m, 9H, H-Ar, vinyl-H), 8.62 (d, 1H, J = 9 Hz,
CH-vinyl)
-1
°C; ir (KBr) νmax/cm : 4460, 3340 (NH , NH), 2995
2
+
1
(CH aliph), 1641 (CO); ms: m/z = 268 (M , 38%); H nmr
(deuteriochloroform): δ = 3.54 (s, 3H, OCH ), 3.75 (s, 2H,
Anal. Calcd. for C H N O: C, 73.00; H, 4.94, N, 15.96%.
16 13
3
3
Found C, 73.10; H, 4.90; N, 15.90.
NH exchangable), 6.10 (d, 1H, J = 9 Hz, CH-vinyl),
2
(E)-3-(1H-1,2,3-Benzotriazol-1-yl)-1-(p-methoxyphenyl)prop-2-
en-1-one (22c).
6.78-7.94 (m, 8H, H-Ar), 8.4 (d, 1H, J = 9 Hz, CH-vinyl),
12.30 (b, 1H, NH exchangeable).
Anal. Calcd. for C H N O : C, 71.64; H, 5.97, N, 10.44%.
Found C, 71.60; H, 5.90; N, 10.50.
This compound was obtained in yield (63%), mp 143 °C; ir
16 16
2 2
-1
(KBr) νmax/cm : 2983 (CH aliph), 1650 (CO); ms: m/z = 279
+
1
(M , 25%); H nmr (deuteriochloroform): δ = 3.56 (s, 3H, OCH ),
3
Preparation of (E)-1-Aryl-3-(1H-1,2,3-benzotriazol-1-yl)-prop-
2-en-1-one 22a-c.
7.10-7.81 (m, 9H, H-Ar, vinyl-H), 8.93 (d, 1H, J = 9 Hz, CH-vinyl).
Anal. Calcd. for C H N O : C, 68.81; H, 4.65, N, 15.05%.
16 13
3 2
Found C, 68.80; H, 4.70; N, 15.10.
General Procedure.
Method A:
REFERENCES AND NOTES
A solution of glacial acetic acid (10 ml) was added dropwise
to a stirred suspension of 22a-c (0.01 mol) and sodium nitrite
(0.015 mol) in water (2 ml) at room temperature for 3 h, the
precipitate was collected by filtration and recrystallized from
ethanol.
[*]
To whom correspondence should be addressed:
E-mail: abuzeid5@hotmail. com.
[1] J. V. Greenhill, Chem. Soc. Revs. 6, 277 (197), and references
cited therein.
[2] A. Al-Anezi, B. Al-Saleh and M. H. Elnagdi, J. Chem. Res.
(S) 4, (M) 0116 (1997).
[3] F. M. A. El-Taweel and M. H. Elnagdi, J. Heterocyclic Chem.,
38, 981 (2001).
[4] B. Al-Saleh, N. Al-Awadi, H. Al-Kanderi, M. M. Abdel-
Khalik and M. H. Elnagdi, J. Chem. Res. (S) 16, (M) 201 (2000).
[5] K. M. Al-Zaydi, E. A. Hafez and M. H. Elnagdi, J. Chem. Res.
(S) 4, (M) 510 (2000).
[6] F. Al-Omran, N. Al-Awadi, A. Abou El-Kair and
M. H. Elnagdi, Org. Preparation and Procedures International, 29(3)
285 (1997).
[7] S. Tseng, J. W. Wpstein, H. J. Brabander and G. Franscisco,
J. Heterocyclic Chem., 24, 837 (1987).
[8] M. M. Abdel-Khalik and M. H. Elnagdi, Synthetic Commun.,
32 (2) 159 (2002).
Method B:
The same experimental described above for preparation 18a-c
by using benzotriazole (0.01 mole) instead of ethylene diamine.
The solid formed crystallized from ethanol.
(E)-3-(1H-1,2,3-Benzotriazol-1-yl)-1-phenylprop-2-en-1-one
(22a).
This compound was obtained in yield (53%), mp 134 °C; ir
-1
(KBr) νmax/cm : 2989 (CH aliph), 1649 (CO); ms: m/z = 249
+
1
(M , 10%); H nmr (deuteriochloroform): δ = 7.12-7.83 (m, 10H,
H-Ar, vinyl-H), 8.51 (d, 1H, J = 9 Hz, CH-vinyl).
Anal. Calcd. for C H N O: C, 72.28; H, 4.41, N, 16.86%.
[9] B. Al-Saleh, M. M. Abdel-Khalik, A. Eltoukhy and
M. H. Elnagdi, J. Heterocyclic Chem., 39, 1035 (2002).
15 11
3
Found C, 72.30; H, 4.50; N, 16.70.