Full text of DOI:10.1002/jccs.200200148

Journal of the Chinese Chemical Society, 2002, 49, 1035-1040
1035
Regioselectivity in Reactions of Bis-Hydrazonoyl Halides with Some
Bifunctional Heterocycles
Ahmad S. Shawali*, Magda A. Abdallah and Mohie E. M. Zayed
Department of Chemi s t r y, Faculty of Science, University of Cairo, Giza, Egypt
Bis-hydrazonoyl chloride 1 reacts regioselectively with 3-mercapto-1,2,4-triazole 2a, 2,3-dihydro-3 -
thioxo-1,2,4-triazin-5(4H)-one 2b and 2-mercaptobenzimidazole 2c to give the hitherto unknown annelated
2,3-bis-(phenylhydrazono)thiazoles 6a-c, respectively. Reactions of 1 with the methylthio derivatives of such
heterocycles afforded the annelated 3,3 -bis-(1,2,4-triazoles) 11a-c, respectively. Similar reaction of 1 with
2-phenylamino-4(3H)-pyrimidinones 4 gave 2,3-bis(phenylhydrazono)imidazo[1,2-a]pyrimidin-5(1H)-ones
16. Oxidation of 6c yielded the corresponding bis(phenylazo) derivative 15. The regiochemistry of the stud-
ied reactions is discussed.
INTRODUCTION
RESULTS AND DISCUSSION
In preceeding papers from our labo r a t o r y, it has been
shown that bis-hydrazonoyl halides 1 can be used as precur-
sors for synthesis of a variety of heterocyclic systems.1-5 In
continuation of this work, we wish to report herein the results
of our study of the reactions of 1 (Ar = C6H5) with some
heterocyclic thiones namely 1,2,4-triazole-3-thione 2a,
1,2,4-triazine-3-thione 2b, benzimidazole-2-thione 2c to-
gether with their 2-methylthio derivatives 3a-c, respectively
(Chart 1). In addition, reactions of 1 with 2-phenylamino-
6-substituted 4-pyrimidinones 4a,b (Chart 1) were also in-
vestigated. Our objective of such a study was to cast light on
the regioselectivity in the reactions of 1 with 2-4. It is worth
mentioning that in contrast to the extensive studies reported
on the reactions of monohydrazonoyl halides 5 with numer-
ous heterocycles,6-9 reactions of bis-hydrazonoyl halides of
type 1 have received much less attention.
The required bis-hydrazonoyl chloride 1,10 the thiones
2a-c11-13 and their methylthio derivatives 3a-c11,14,15 were pre-
pared by known methods. Also, 6-methyl-2-phenylamino-
4(3H)-pyrimidinone 4a was prepared by a method from the
literature.16 As 6-phenyl-2-phenylamino-4(3H)-pyrimidi-
none 4b has not been reported hitherto, it was thus prepared
in this work by reaction of 2-methylthio-6-phenyl-4(3H)-
pyrimidinone with aniline. Its structure was consistent with
its spectral (IR, 1H NMR and MS) and elemental analysis data
(see Experimental).
When 5-phenyl-1,2,4-triazole-3-thione 2a was allowed
to react with 1, either in ethanol in the presence of sodium
ethoxide at room temperature (Method A) or in refluxing
chloroform in the presence of triethylamine (Method B), it
gave, in both cases, one and the same crystalline product
whose mass spectrum [m/z 411 (M+)] and microanalysis data
were consistent with the molecular formula C22H17N7S. Such
a result indicated that the isolated product can be either one of
the two regioisomers namely 5,6-bis-(phenylhydrazono)-2-
phenylthiazolo[3,2-b][1,2,4]triazole and 5,6-bis-(phenylh y -
drazono)-3-phenylthiazolo[2,3-c][1,2,4]triazole, 6a and 7a,
respectively (Scheme I). The isolated product was assigned
the former structure 6a on the bas i s of its independent and un-
ambiguous synthesis by reaction of 1 with 1-benzoylthio-
semicarbazide 8 (Scheme I). The product obtained from the
latter reaction proved to be identical in all respects (mp.,
mixed mp., IR) with that isolated from the reaction of 2a and
1 (see Experimental). The formation of 6a rather than 7a
could be attributed to the greater nucleophilicity of N2 of
1,2,4-triazole as a result of being adjacent to a nitrogen atom,
whereas the N4 which would afford the regioisomer 7a is de-
Chart 1
ArNHN=C(Cl)-C(Cl)=NNHAr
1
R-C(X)=NNHAr
5
O
R
H
R
H
H
N
N
N
X
X
R
NHPh
R
N
4
R'
N
SCH3
R'
N
H
S
2
3
a
b
CH3
C6H5
c
a
b
2 - 3
O
R
Ph
Ph
X
N
R'
N

1036 J. Chin. Chem. Soc., Vol. 49, No. 6, 2002
Shawali et al.
due exhibits through conjugation in structures of type 6b and
11b and cross conjugation in structures of type 7b and
12b.23,24 On this basis, the two products A and B were ident i -
fied as 2,3-bis(phenylhydrazono)thiazolo[3,2-b][1,2,4]tri-
azin-7-one 6b and 3,3 -bis-(1,2,4-triazolo[4,3-b][1,2,4]tri-
azin-7(1H)-one) 11b, respectively (Scheme III). The struc-
ture of the latter product 11b was further confirmed unambig-
uously by its alternate synthesis as outlined below by reaction
of 1 with 3-methylthio-5(4H)-1,2,4-triazinone 3b (Scheme
III).
Scheme I Synthesis of 2,3-bis(phenylhydrazono) de-
rivatives of thiazolo[2,3-c][1,2,4]triazole,
thiazolo[3,2-b][1,2,4]triazin-7-one and
thiazolo[3,2-a]benzimidazole 6a-c
R
H
N
X
+
PhNHN=C(Cl)-C(Cl=NNHPh
1
R'
N
H
S
2
The reaction of 1 with 2-mercaptobenzimidazole 2c is
straightforward. Thus, treatment of 1 with 2c in chloroform
in the presence of triethylamine at room temperature afforded
a single product. As compound 2c is, in reality, symmetrical
cyclic thiourea, there is no ambiguity as to the direction of
annelation. Accordingly, the product isolated was identified
as 2,3-bis(phenylhydrazono)thiazolo[3,2-a]benzimidazole
6c (Scheme I). The structure of the latter was based on both
its spectral (mass, NMR and IR) and elemental analyses (see
Experimental). The assigned bis-hydrazone structure was
further evidenced by the oxidation of 6c. In our hands, treat-
ment of 6c with lead(IV) acetate in DMF-acetonitrile mixture
afforded the corresponding bis-(phenylazo) derivative 15
(Scheme II). The elemental analyses and the spectral data
(MS, IR, 1H- and 13C-NMR) are compatible with the assigned
structure 15. Thus, while its IR spectrum showed no absorp-
tion for the NH group, its mass spectrum revealed low inten-
sity peaks for molecular ion. Its 13C-NMR spectrum shows
the characteristic signals of the phenylazo residue as ind i -
cated in Scheme II. Also the electronic absorption spectra re-
vealed strong absorption bands assignable to the azo chromo-
phores near 500 (log 4.17) and 337 (log 4.40) nm.
R
R
NNHPh
NNHPh
N
6
N
X
R'
N
S
X
R'
N
S
PhNHN
NNHPh
7
Ph
N
Ph
H
O
NH2
S
+
1
N
N
N
S
N
H
PhNHN
NNHPh
8
6a
c
2,6,7
a
b
O
R
Ph
Ph
X
N
N
R'
activated by the neighbouring electron deficient carbon atom.
Formation of 6a rather than 7a is also in good agreement with
literature reports which indicate that reaction of 3-mercapto-
5-aryl-1,2,4-triazoles with haloketones afforded 2-aryl-1,2,4-
triazolo[3,2-b]thiadiazole derivatives.17-20
Reaction of 1 with 6-benzyl-2,3-dihydro-3-thioxo-
1,2,4-triazin-5(4H)-one 2b in ethanol in the presence of so-
dium ethoxide at room temperature gave a mixture of two
products A and B in 72 and 10% yields, respectively. Both
mass spectra and elemental analyses of these two products A
and B indicated that their molecular formulas are C24H19N7OS
and C34H24N10O2, respectively. Such data suggest that the for-
mer product A can be assigned either structure 6b or 7b
(Scheme I) whereas the second product B can have either
structure 11b or 12b (Scheme III). The IR spectra of the prod-
ucts A and B revealed their amide-I absorption bands at 1658
and 1660 cm-1, respectively. Such stretching frequencies,
while they are similar to those reported for azolo[b][1,2,4]tri-
azin-7-ones (1660-1665 cm-1),21 differ from those reported
for azolo[c][1,2,4]triazin-5-ones (1680-1690 cm-1).22 The
difference in the amide carbonyl stretching frequencies is at-
tributed to the difference in the type of conjugation exhibited
by the acylguanidine residue in such structures. Such a resi -
Scheme II Synthesis of 2,3-bis(phenylazo)thiazolo-
[3,2-a]benzimidazole 15
NNHPh
Pb(OAc)4
N
AcOH
NNHPh
N
S
6c
134
N
N
N
147
S
152.8
124
N
N N
129
133
153
15

Annelated Heterocycles via Bishydrazonoyl Halides
J. Chin. Chem. Soc., Vol. 49, No. 6, 2002 1037
Next, reactions of 1 with each of 3a-c were examined.
In our hands, such reactions, when carried out in pyridine at
reflux, afforded, in each case, one product as evidenced by tlc
analysis of the crude product. Repetition of this reaction in
refluxing ethanol in the presence of sodium ethoxide afforded
the same products. The mass spectral and the elemental anal-
ysis data of the isolated products showed that the latter are
free of sulfur and were consistent with either one of the four
possible structures 11-14 (Scheme III). Since 3c is symmetri-
cal cyclic thiourea, it follows that the two structures 11c and
12c are equivalent and that the two structures 13c and 14c are
also equivalent. In addition, the product isolated from rea c -
tion of 1 with 3b proved identical with the produ c t 11b ob-
tained above from reaction of 1 with 2b.
Table 1. Heat of Formation ( Hf) of the Isomeric Structures
11-14
- Hf , kJ. mol-1
Structure no.
a
b
c
11
12
13
14
758.37
691.27
746.71
690.33
744.48
643.44
638.20
585.04
532.40
532.40
504.80
504.80
13C NMR spectra were unsuccessful. This was due to the poor
solubility of the isolated products in most NMR solvents. Ac-
cordingly, distinction between structures 11-14 was made by
comparison of their heat of formation ( Hf). The calculations
of the Hf‘s of 11-14 were made at the AM1 level usi n g the
Hyperchem program package (version 4.0). For each struc-
ture, full geo m e t r y optimization was performed, and the en-
ergy values reported are those for the equilibrium geometries.
The results are summarized in Table 1. The data indicate that
structures 11a-c are the most stable ones. On the bas i s of this
finding and mass spectra and elemental analyses, the prod-
ucts isolated from reactions of 1 with 3a-c were assigned the
structures 11a-c, respectively. The regiochemistry in such re-
actions seems to be controlled by the basicity of the ring-
nitrogens. The overall electronic distribution in 2b or 3b re-
veals that N2 is more nucleophilic than N4 because the latter
is situated between two electron-deficient carbon atoms25 and
thus attack by N2 is more favourable and accordingly leads to
the intermediates 9 which cyclize in situ to give the respec-
tive 11 as the end products (Scheme III).
Scheme III Synthesis of 3,3 -bis(annelated 1,2,4-tri-
azoles 11a,b
3
+
1
NHPh
N
C
R
R
N
(
N
)
2
X
X
R'
N
SCH3
R'
N
SCH3
(
C=NNHPh)
2
10
9
-2 CH3SH
Ph
- 2CH3SH
N
R
N
N
N
R'
X
Ph
N
X
Finally, reactions of 1 with 2-phenylamino-6-substi-
tuted pyrimidin-4(3H)-ones 4a,b were examined. As each of
the latter pyrimidinones 4, being unsymmetrical, reaction of
each with 1 is expected to give either 2,3-dihydro-7-sub-
stituted-2,3-bis(phenylhydrazono)imidazo[1,2-a]pyrimidin-
5(1H)-one 16 or its regioisomer 2,3- dihydro-5-substituted-
2,3-bis(phenylhydrazono)imidazo[1,2-a]pyrimidin-7(1H)-
one 17 or both depending on the direction of substitution
(Scheme IV). In our hands, treatment of pyrimidinones 4a,b,
each with 1 furnished, in each case, a single product as evi -
denced by tlc analysis of the crude products. The IR spectra
of the isolated products revealed the amide carbonyl band at
1670-1676 cm-1 and their 13C NMR spectra showed the amide
carbon signals at 161-162. Such spectral data are consistent
with structure 16 and not with 17. This is because comparison
of these data with those reported for derivatives of imidazo-
[1,2-a]pyrimidin-7(1H)-one and imidazo[1,2-a]pyrimidin-
5(1H)-one ring systems I and II, respectively (Chart 2),23,24
indicates that the spectral data of the isolated products from
R
R'
N
N
N
N
R
N
X
N
N
R'
N
N
R'
X
N
Ph
Ph
12
N
N
R
R
Ph
11
Ph
N
N
N
R'
X
X
R'
N
N
N
N
R
N
N
R
N
N
R'
R
X
N
N
X
R'
N
N
Ph
Ph
14
13
a
b
3, 9-14
X
O
Ph
R
Ph
N
N
R'
Attempts to elucidate the actual structures of the prod-
ucts isolated from the reactions of 1 with 3a-c by the use of

1038 J. Chin. Chem. Soc., Vol. 49, No. 6, 2002
Shawali et al.
spectrophotometer. Microanalyses were performed by the
Microanalytical Center of Cairo University, Giza, Egypt.
The starting reagents namely bis-hydrazonoyl chloride
1,10 the thiones 2a-c,11-13 and their methylthio derivatives
3a-c11,14,15 and 2-phenylamino-6-methyl-4(3H)-pyrimidi-
none 4a16 were prepared as previously described.
Chart 2
O
O
N
O
N
NNHPh
NNHPh
N
N
N
R'
R
N
N
R
N
R
N
R'
R'
I
II
CO 165-168
CO 1656-1659 cm-1 CO 1690-1670 cm-1
16
Synthesis of 2-Phenylamino-6-phenyl-4(3H)-pyrimidinone
4b
CO 175-176
CO 161-162
CO 1670-1676 cm-1
A mixture of 2-methylthio-6-phenyl-4(3H)-pyrimidi-
none (2.17 g, 0.01 mol) and aniline (0.93 g, 0.01 mol) was
heated at 180-190 C in an oil bath for 4 h, then cooled. The
reaction mixture was poured onto crushed ice with stirring.
The precipitated solid was filtered off, dried and finally crys-
tallized from dimethylformamide to give 4b, yield 80%; m.p.
284 C (DMF), IR, (cm-1) 3100-3045, 1658, 1631; 1H NMR
( ) 6.03 (s, 1H), 7.05-8.05 (m, 10H), 8.94 (s, 1H), 10.79 (s,
1H); Anal. for C16H13N3O (263.3) Found (Calcd.): C, 73.0
(72.99); H, 4.8 (4.98); N, 15.8 (15.96) %.
the studied reactions are similar to those of derivatives of II.
On the bas i s of such similarity, the products isolated from re-
actions of 1 with 4a,b were identified as 16a,b, respectively.
This regiochemical assignment is further evidenced by its
analogy to that reported for the formation of imidazo[1,2-
a]pyrimidin-5(1H)-ones from 1,2-dibromoethane with 2-
arylamino-4(3H)-pyrimidinone derivatives.26 Had the iso-
lated products structure 17, it would be expected to observe
their ami d e carbonyl stretching bands at lower frequencies
(1650-1660 cm-1) and signal for the amide carbonyl carbon at
170-175 values.23,24
Synthesis of annelated thiazoles 6a-c
Method A
To an ethanolic sodium ethoxide solution, prepared
from sodium metal (0.115 g, 5 mmol) and absolute etha n o l
(30 mL), was added the appropriate thione 2 (5 mmol) and the
mixture was stirred. To the resulting mixture was added the
bis-hydrazonoyl chloride 1 (5 mmol) and stirring was contin-
ued for 24 h at room temperature. The excess solvent was
then distilled under reduced pressure and the mixture was
cooled. The solid that was precipitated was filtered off,
washed with water and dried. Crystallization from dimethyl-
formamide-ethanol mixture gave the fused thiazole deriva-
tives 6. The physical constants of the products 6a-c prepared
are presented bel o w.
Scheme IV Synthesis of 2,3-bis(phenylhydrazono)-
imidazo[1,2-a]pyrimidin-5(1H)-ones 16
O
NHPh
N
O
N
N
1
+
NH
NHPh
R
N
N
N
R
Ph NHPh
16
4
O
R
4, 16, 17
N
a
b
Ph
CH3
R
N
N
C6H5
Method B
N
N
NHPh
To a mixture of equimolar quantities of 1 and the appro-
priate 2 (5 mmol each) in chloroform (30 mL) was added
triethylamine (0.7 mL, 5 mmol) and the resulting mixture was
refluxed 5 h. Workup of the reaction mixture as above gave
the products 6 identical in all respects with those obtained by
method-A.
PhNH
17
EXPERIMENTAL SECTION
Melting points were determined in open capillary tubes
Compound 6a: Yield 60%; m.p. 244 C (EtOH/DMF),
1
IR, (cm-1) 3321-3161; H NMR ( ) 6.73-8.22 (m, 15H),
and are uncorrected. The IR spectra were recorded on a Pye-
1
Unicam SP300 instrument. The H- and 13C-NMR spectra
9.56 (s, 1H), 12.83 (s, 1H); MS. m/z (%) 411 (M+, 27), 236
(19), 206 (5), 177 (11), 132 (9), 118 (9), 104 (36), 91 (25), 77
(100), 65 (38), 51 (38). Anal. for C22H17N7S (411.5) Found
(Calcd.): C, 63.90 (64.22); H, 4.10 (4.16); N, 23.70 (23.83)
%.
were recorded for solutions in deuterated chloroform or
dimethylsulfoxide with a Varian Gemi n i spectrometer usi n g
TMS as an internal standard. Mass spectra were obtained in a
GCMS-Q1000-EX spectrometer. Electronic absorption spec-
tra were obtained usi n g a Shimadzu UV and Visible 3101 PC
Compound 6b:Yield 72%; m.p. 240 C (DMF), IR,

Annelated Heterocycles via Bishydrazonoyl Halides
J. Chin. Chem. Soc., Vol. 49, No. 6, 2002 1039
(cm-1) 3220, 3180, 1699; 1H NMR ( ) 4.1 (s, 2H), 6.8-8.1 (m,
15H), 10.4 (s, 1H), 11.6 (s, 1H); MS. m/z (%) 454 (M+, 12),
347 (8), 328 (7), 229 (10), 219 (13), 206 (7), 145 (6), 117
(18), 105 (14), 91 (65), 86 (15), 77 (100), 65 (31), 51 (46).
Anal. for C24H19N7OS (453.5) Found (Calcd.): C, 63.30
(63.56); H, 4.10 (4.22); N, 21.40 (21.62) %.
collected, washed with water, dried and finally crystallized
from dimethylformamide-water to give the corresponding
11. The physical constants of the products 11a-c prepared are
given below.
Compound 11a: Yield 48%; m.p. 232-233 C (DMF/
H2O), 1H NMR ( ) 7.15-8.3 (m); MS. m/z (%) 520 (M+, 52),
285 (10), 261 (5), 103 (100), 91 (27), 77 (51), 64 (7), 51 (15).
Anal. for C30H20N10 (520.5) Found (Calcd.): C, 68.80
(69.22); H, 3.30 (3.87); N, 26.60 (26.91) %.
Compound 6c: Yield 75%; m.p. 260 C (EtOH/DMF),
1
IR, (cm-1) 3294-3180; H NMR ( ) 6.91-8.3 (m, 14H),
10.57 (s, 1H), 11.1 (s, 1H); MS. m/z (%) 384 (M+, 32), 292
(18), 206 (5), 186 (5), 150 (6), 134 (8), 105 (59), 92 (18), 77
(100), 65 (22), 51 (18). Anal. for C21H16N6S (384.4) Found
(Calcd.): 65.50 (65.61); H, 4.10 (4.19); N, 21.70 (21.86).
Compound 11b: Yield 60%; m.p. 284-286 C (EtOH/
DMF), IR, (cm-1) 1660; 1H NMR ( ) 4.1 (s, 4H), 7.0-8.2 (m,
20H); MS. m/z (%) 605 (M+, 5), 487 (14), 371 (28), 345 (12),
302 (7), 116 (33), 91 (100), 77 (31), 64 (26), 51 (31). Anal. for
C34H24N10O2 (604.6) Found (Calcd.): C, 67.20 (67.54); H,
3.90 (4.00); N, 23.00 (23.17) %.
Oxidation of 6c
To a stirred solution of 6c (3.84 g, 0.01 mole) in dry
dimethylformamide-acetonitrile (15 mL each) was added
lead tetraacetate (0.012 mole) and the resulting mixture was
further stirred for 24 h. The mixture was then poured onto
cold wat e r. The crude solid that precipitated was filtered off,
dried and finally crystallized from DMF-water to give pure
bis-azo derivative 15.
Compound 11c: Yield 43%; m.p. > 300 C (DMF/
H2O), MS. m/z (%) 467 (M+, 49), 378 (89), 259 (59), 207
(70), 169 (19), 144 (17), 130 (19), 103 (100), 91 (60), 77 (97),
65 (66), 51 (53). Anal. for C28H18N8 (466.5): Found (Calcd.):
C, 72.00 (72.09); H, 3.90 (3.89); N, 23.90 (24.20) %.
Compound 15: Yield 40%; m.p. 200 C (DMF/H2O),
1H NMR ( ) 7.28-8.27 (m); MS. m/z (%) 382 (M+, 15), 292
(5), 259 (6), 134 (7), 121 (9), 105 (32), 90 (7), 77 (100), 65
(7), 51 (20). Anal. for C21H14N6S (382.4) Found (Calcd.): C,
65.70 (65.95); H, 3.50 (3.69); N, 21.70 (21.97) %.
Synthesis of 2,3-dihydro-1-phenyl-2,3-bis-(phenyl-
hydrazono)-7-substituted-imidazo[1,2-a]pyrimidin-5(1H)-
ones 16a,b
To an ethanolic sodium ethoxide solution, prepared
from sodium metal (0.115 g, 5 mmol) and absolute etha n o l
(30 mL), was added the appropriate 2-phenylaminopyri-
midinone 4 (5 mmol) and the mixture was stirred. To the re-
sulting mixture was added bis-hydrazonoyl chloride 1 (5
mmol) and stirring was continued for 24 h at room tempera-
ture. The excess solvent was then distilled under reduced
pressure and the mixture was cooled. The solid that was
formed was filtered off, washed with water and dried. Crys-
tallization from dimethylformamide-ethanol mixture gave
the fused imidazole derivative 16. The physical constants of
the products 16a,b prepared are presented bel o w.
Alternate Synthesis of thiazolo[3,2-b][1,2,4]triazole 6a
To a stirred solution of equimolar quantities of 1-ben-
zoylthiosemicarbazide 8 and bishydrazonoyl chloride 1 (5
mmol each) in ethanol (30 mL) was added triethylamine (1.4
mL, 10 mmol). The mixture was stirred at room temperature
for 24 h. The solid that precipitated duri n g this period was fil-
tered off, washed with water and dried. Crystallization from
dimethylformamide-ethanol mixture gave 6a in 60% yield
(1.23 g), mp. 244 C. The isolated product proved identical in
all respects (mp., mixed mp. and IR) with 6a that was isolated
above from the reaction of 1 and 2a.
Compound 16a: Yield 76%; m.p. 178 C; (EtOH/
DMF), IR, (cm-1) 3319, 3157, 1670, 1647; 1H NMR ( ) 2.13
(s, 3H), 6.03 (s, 1H), 6.72-7.59 (m, 15H), 10.71 (s, 1H), 12.81
(s, 1H); MS. m/z (%) 436 (M+ +1, 27), 435 (M+, 25), 343 (14),
270 (18), 107 (43), 93 (100), 92 (31), 77 (80). Anal. for
C25H21N7O (435.5) Found (Calcd.): C, 69.00 (68.95); H, 4.70
(4.86); N, 22.30 (22.51) %.
Synthesis of 3,3 -Bis(annelated [1,2,4]triazoles) 11
To an ethanolic sodium ethoxide solution, prepared
from sodium metal (0.115 g, 5 mmol) and absolute etha n o l
(30 mL), was added methylthio derivative 3 (5 mmol) while
stirring the mixture. To the latter was added the bishydrazo-
noyl chloride 1 (5 mmol) and the reaction mixture was
refluxed till methanethiol ceased to evolve (15 h). The excess
solvent was distilled und e r reduced pressure and the reaction
mixture was cooled. The solid that formed upon cooli n g was
Compound 16b: Yield 90%; m.p. 280 C (EtOH/
DMF), IR, (cm-1) 3200, 3150, 1676, 1650; 1H NMR ( ) 6.53
(s, 1H), 6.84-7.92 (m, 20H), 11.05 (s, 1H), 12.76 (s, 1H); MS.
m/z (%) 497 (M+, 52), 405 (23), 129 (18), 105 (18), 77 (100).
Anal. for C30H23N7O (497.5) Found (Calcd.): C, 72.40

1040 J. Chin. Chem. Soc., Vol. 49, No. 6, 2002
Shawali et al.
Chem. 1971, 744, 88.
(72.42); H, 4.50 (4.66); N, 19.60 (19.71) %.
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