Synthesis of novel benzo-substituted macrocyclic schiff bases containing two triazole rings

Article abstract of DOI:10.1002/jhet.5570440636

(Chemical Equation Presented) A synthesis of a series of novel macrocyclic Schiff bases containing two triazole rings 10a,b, 11a,b, 34-37 in good yields by heating the appropriate bis-amines 1f, 6a,b, 31 with the corresponding bis-aldehydes 2, 9a,b, 29 in

Full text of DOI:10.1002/jhet.5570440636

Nov-Dec 2007
1475
Synthesis of Novel Benzo-Substituted Macrocyclic Schiff Bases
Containing Two Triazole Rings
Ahmed H. M. Elwahy* and Ghada S. Masaret
Department of Chemistry, Faculty of Applied Science, Umm Al-Qura University
Makkah Almukkarramah, P. O. Box 6503 unit 25, Saudi Arabia
e-mail: aelwahy@hotmail.com, Fax no.: 0096625542673
Received September 30, 2006
X
O
O
X
CHO
CHO
O
O
Acetic acid
+
N
N
N
N
High dilution
NH2
N
NH2
N
S
S
R
R
S
R
R
S
N
N
N
N
Y
N
N
N
N
Y
,
R = H, Ph, PhCH2, X, Y = (CH2)2, (CH2)3,
,
MeO
CH3
N
A synthesis of a series of novel macrocyclic Schiff bases containing two triazole rings 10a,b, 11a,b, 34-
37 in good yields by heating the appropriate bis-amines 1f, 6a,b, 31 with the corresponding bis-aldehydes
2, 9a,b, 29 in refluxing acetic acid under high dilution conditions was described. Attempts to synthesize
macrocyclic Schiff bases containing pyridine and two triazole rings were also described.
J. Heterocyclic Chem., 44, 1475 (2007).
additional donor group (O, S, P, etc.) and this makes
them good candidates for metal ion complexation and
for mimicking biological systems. Alternatively they
can be obtained by template effect; this procedure
directly gives the designed complexes in high yield and
INTRODUCTION
Macrocyclic compounds have attracted increasing
interest owing to their role in the understanding of
molecular processes occurring in biochemistry,
material science, catalysis, encapsulation, activation,
transport phenomena, and hydrometallurgy [1-16].
Moreover, they have been shown to exhibit important
applications including selective ion separation
and detection, molecular recognition, biological
applications as well as many other interesting
applications in diverse fields of supramolecular
chemistry [17-24]. Many ligands have been designed to
mimic the function of natural carriers in recognizing
and transporting specific metal ions, anions or neutral
molecules and in understanding and reproducing the
catalytic activity of metal co-enzymes and proteins [1-
24]. In particular, macrocyclic Schiff bases have
received much attention because they can be obtained
by simple self-condensation of suitable formyl- or
keto- and primary amine-precursors [25]. They can be
functionalized by inserting appropriate groups in the
aliphatic and/or aromatic chains of the formyl- or keto-
and amine-precursors. They generally can contain
in
a satisfactory purity grade. Moreover, these
complexes can undergo transmetallation reactions
when reacted with a different metal salt allowing the
formation of the free ligand. Reduction of the free
ligands as well as their complexes can give rise to the
formation of the corresponding polyamine derivatives.
These reduced compounds are less sensitive to
hydrolysis and more flexible and contain NH groups
which may be further functionalized by appropriate
synthetic procedures. They can be also linked to an
appropriate support (e.g. silica) giving rise to modified
catalysts or modified surfaces, bearing well defined
molecular assemblies [26].
In continuation of our interest in synthesizing
novel macrocyclic ligands, we report here on our
attempts to synthesize novel macrocyclic Schiff
bases upon which fused triazole and pyridine units
and contain N, O and S as donor atoms in the
macrocyclic ring.

1476
A. H. M. Elwahy and G. S. Masaret
Vol 44
Scheme 1
N
N
N
N
X
O
O
R
N
N
S
S
N
N
R
N
N
N
N
X
CHO
OHC
2
S
S
R
R
N
N
Acetic acid/ high dilution
O
O
NH2
NH2
Compd
R
X
1a, 3a
1b, 3b
1c, 3c
1d, 3d
1e, 3e
1f
(CH2)2
(CH2)3
(CH2)3
(CH2)4
(CH2)4
(CH2)2
H
Ph
PhCH2
Ph
PhCH2
Ph
1a-f
3a-d
coordinating moiety were reported to play an important
role on the selective binding of charged or neutral species
[28-35]. We first studied an alteration of the arrangement
of the donor atoms in the macro ring by attachment of the
1,3-xylyl unit to the triazole part. Thus, 1,3-bis(4-amino-
1,2,4-triazol-3-ylsulfanylmethyl)benzenes 6a-c were
prepared in 68-75% yield from 4-amino-1,2,4-triazole-3-
thione derivatives 4a-c by reaction with 1,3-
bis(bromomethyl)benzene 5 in ethanol/water mixture
containing potassium hydroxide. The 1H-NMR of the
reaction mixture indicates the absence of the
corresponding N-alkylated products. The exclusive
formation of 6 is in accordance with previous results
RESULTS AND DISCUSSION
Recently we reported the synthesis of macrocyclic
Schiff bases 3a-d by cyclocondensation of the appropriate
bis(carbonyl) ethers 2 with the corresponding bis(amines)
1a-f in glacial acetic acid under high dilution conditions
(Scheme 1) [27].
In this study we intended to make structure variations
within the ligand 3 in an attempt to improve their binding
properties. These structure variations involve the number
of donor atoms in the macrocyclic ring, their relative
position and the size of the chelating rings. These factors
together with the flexibility and the shape of the
Scheme 2
CHO
N
N
N
N
N
N
N
N
Br
Br
N
N
5
7
Ph
N
N
S
S
N
N
Ph
R
N
SH
S
EtOH /H2O
KOH
R
N
S
N
R
Acetic Acid
CH
CH
NH2
NH2
NH2
6a-c
4a-c
Y
8
a, R = H
O
O
Acetic Acid
b, R = Ph
-
c, R = PhCH2
CHO OHC
9a,b
N
N
N
N
Y
R
R
N
N
S
S
N
N
R
a
-(CH2)2-
-(CH2)3-
H
Ph
b
O
O
Y
10a,b

Nov-Dec 2007 Synthesis of Novel Benzo-Substituted Macrocyclic Schiff Bases Containing Two Triazole Rings
1477
which confirm the preferential alkylation of 4-substituted-
1,2,4-triazole-3-thiones on sulfur [36-44]. The reactivity
of the bis amines 6a-c towards aromatic aldehydes was
investigated by reaction of 6b with benzaldehyde in
refluxing acetic acid. As expected the corresponding
benzylideneamino derivative 8 was obtained in 48%
yield. On the other hand, the reaction of 6a with 1,2-bis(2-
formylphenoxy)ethane (9a) [45,46] in refluxing acetic
acid under high dilution conditions afforded the
corresponding macrocyclic Schiff base 10a in 48% yield.
Similarly, 6b reacted with 9b to give the target molecule
10b in 56% yield (Scheme 2).
We also studied the insertion of an additional 1,3-xyly
unit into the macrocyclic ring 10a,b instead of the
ethylene or the propylene moieties aiming at studying the
effect of rigidity provided by these groups on the ability
of the ligands to form stable complexes compared to other
macrocyclic analogues. Thus, under similar conditions
6a,b reacted with 2 to give the corresponding macrocyclic
Schiff base 11a,b in 55% and 61% yields, respectively.
group with 2-chloroacetylchloride to give the correspond-
ing chloroacetoxy macrocycles 13 followed by reaction
with a series of secondary amines (Scheme 3) [47].
On the other hand, Elwahy and Abbas attempted the
incorporation of a pyridine ring as a subcyclic unit in the
macrocycle 3 [27]. Such nitrogen heterocycles can
participate in complexation through their soft donor
atoms. They reacted 1, ꢀ-bis(4-amino-1,2,4-triazole-3-yl-
sulfanyl)alkanes
1
with 2,6-bis(2-formylphenoxy-
methyl)pyridine 15 in refluxing acetic acid under high
dilution conditions aiming at synthesizing the correspond-
ing novel macrocycles 17. Unfortunately, the reaction did
not lead to the formation of 17 and gave instead the 2,6-
bis[benzo(b)furan-2-yl]pyridine 16. The formation of the
latter proceeds via interamolecular cyclocondensation of
the aldehydic group with the active methylene groups
(Scheme 4).
We now studied the synthesis of isomeric structure of
17 by insertion of the pyridine moiety in the triazole part
as outlined in Scheme 5. Thus, 2,6-bis(4-amino-1,2,4-
triazol-3-ylsulfanylmethyl)pyridine derivatives 19a-c
were prepared in 60-78% yield by reacting the appropriate
4-amino-1,2,4-triazole-3-thione derivatives 4a-c with 1,3-
bis(bromomethyl)pyridine 18 in ethanol/water mixture
containing potassium hydroxide. Unfortunately repeated
attempts to react 19b with 1,3-bis(2-formylphenoxy-
methyl)propane 9b in refluxing acetic acid under high
dilution conditions did not lead to the formation of pure
sample of the expected macrocyclic Schiff base 20. The
1H NMR (DMSO) of the reaction products indicates the
presence of a mixture of each of the corresponding Schiff
base 20 and another product which may be characterized
as the condensed heteromacrocycle 21 but we are still
unable to isolate pure samples of each of them. The
presence of a mixture of the products 20, 21 was
confirmed by the presence of a characteristic signal for
the aldimine H-atom HC=N at ꢁ 9.22 ppm [27, 40]
together with the appearance of additional multiplet
signals at ꢁ 4.19-5.47 characteristic for the OCH2 protons
as well as the aliphatic CH-S and CH-N protons of the
N
N
N
N
R
N
N
S
S
N
N
R
R
a
b
H
Ph
O
O
11a,b
We now attempted another structure variation of ligand
3 by insertion of additional donor atoms aiming at
increasing their binding abilities. In this respect, Abbas
recently reported the synthesis of macrocyclic Schiff
bases 14 with additional donating sidearm from the
hydroxyl macrocycle 12 by first acylation of the hydroxy
Scheme 3
Y
O
N
OCOCH2Cl
O
O
OH
O
O
S
O
S
O
S
O
S
N
N
N
N
N
N
N
N
N
N
N
N
S
S
R
R
R
R
R
R
N
N
N
N
N
N
N N
X
N
N
N N
X
X
14
13
12
R = Ph, PhCH2, X = (CH2)3, (CH2)4, Y = CH2, O

1478
A. H. M. Elwahy and G. S. Masaret
Vol 44
Scheme 4
N
Acetic acid
O
O
16
N
N
N
N
N
O
O
X
+
R
S
S
R
N
N
X
N N
N
N
OHC
CHO
R
R
S
S
NH2
NH2
N
N
N
N
1
15
O
O
N
R = H, Ph, PhCH2, X = (CH2)n, n = 2,3,4
17
Scheme 5
N
N
N N
N
Y
R
R
S
S
N
N
N
N
N
N
O
O
N
N
N
S
+
R
S
R
N
N
CHO OHC
NH2
NH2
O
O
19a-c
Y
a, R = H
b, R = Ph
c, R = PhCH2
20
9b
-
X = (CH2)3
R = Ph, X = (CH2)3
+
KOH/EtOH
N
N
N
N
S
S
N
N
N
N
N
R
R
+
HN
NH
HS
R
N
N
O
O
Br
Br
NH2
X
18
4a-c
21
R = Ph, X = (CH2)3
new formed six membered ring in the 1H NMR spectrum.
These multiplet signals assumes the generation of
asymmetric center in this molecule.
benzylideneamino carbon under the acidic reaction
conditions.
The unsuccessful incorporation of pyridine rings into the
macroring 3 prompted us to study the synthesis of modified
derivatives of these macrocycles with additional donor atoms
as outlined in Scheme 7. Thus, the dibromo compound 27
was prepared from 25 by first formylation of p-cresol in the
presence of base to give the corresponding diol, which was
selectively methylated with dimethyl sulfate to give diol 26.
The two hydroxymethyl groups of 26 were converted with
PBr3 to the bromomethyl derivative 27 in quantitative yield
[49,50]. The methyl groups in the divergent 4-position of the
benzene rings serve as blocking group that prevent unwanted
substitution reaction from occurring during synthesis.
It is noteworthy to mention that we successfully
synthesized the condensed hetero- macrocycles 23 by
reacting 1,2-bis(4-amino-1,2,4-triazole-3-ylsulfanylmethyl)-
quinoxalines 22 with the appropriate bis(carbonyl)ethers
9a-c in refluxing acetic acid under high dilution
conditions [48]. In the last reaction no traces of the
corresponding macrocyclic Shiff bases 24 could be
isolated from the reaction mixture (Scheme 6). The
reaction can proceed via initial formation of the
corresponding non isolated macrocyclic Schiff base 24
followed by reaction of the methylene group with the

Nov-Dec 2007 Synthesis of Novel Benzo-Substituted Macrocyclic Schiff Bases Containing Two Triazole Rings
1479
Scheme 6
N
O
N
O
N
N
N
N
S
S
N
N
R
R
HN
NH
9a-c
Y
Acetic acid
23
N
S
N
S
N
N
N
N
high dilution
R
R
N
N
N
N
S
NH2
NH2
22
N
N
N N
S
R
R
N
N
N
N
O
O
Y
24
Y = (CH2)n, n = 2-4
R = H, Ph, PhCH2, p-MeOC6H4-
Scheme 7
CH3
CH3
CH3
1) HCHO/KOH
PBr3
2) Me2SO4/NaOH
OMe
OH OMe OH
Br
OMe Br
27
25
26
Scheme 8
CH3
OK
CH3
CH3
CHO
4b
N
N
N
N
28
O
OMe O
OMe
Ph
S
S
Ph
KOH
N
N
DMF
CHO OHC
Br
OMe Br
31
EtOH/H2O
NH2
NH2
29
27
NO2
CHO
Acetic acid
Acetic acid
4b
32
CH3
CH3
N
N
N N
OMe
Ph
Ph
S
S
N
N
N
N
O
OMe O
HS
N
N
N
N
SH
Ph
Ph
N
N
N N
NO2
NO2
30
33

1480
A. H. M. Elwahy and G. S. Masaret
Vol 44
Compound 27 serves as starting material for the synthesis
of each of the novel bis(aldehyde) 29 as well as the
bis(amines) 31. Thus, reaction of 27 with the potassium
salt 28 (obtained upon treatment of salicylaldehyde with
ethanolic potassium hydroxide) in refluxing DMF
afforded 2-methoxy-5-methyl-1,3-bis(2-formylphenoxy-
methyl)benzene 29 in 91% yield. On the other hand,
reaction of 27 with 4b in ethanol/water mixture containing
potassium hydroxide afforded the corresponding 2-
methoxy-5-methyl-1,3-bis(4-amino-1,2,4-triazol-3-yl-
sulfanyl)benzene 31 in 75% yield. The reactivity of the
latter towards condensation with aromatic aldehydes was
first investigated by reaction with 4-nitrobenzaldehyde 32
in refluxing acetic acid and as a result the expected
bis(benzylideneamino) derivative 33 was successfully
obtained in 65% yield. We have also investigated the
reactivity of the bis(aldehyde) 29 towards condensation
with 4-amino-5-phenyltriazole-3-thione 4b in refluxing
acetic acid. As expected the corresponding condensation
product 30 could be successfully isolated in 79% yield
(Scheme 8).
The synthetic utility of the novel bis aldehyde 29 and
the bis amine 31 as building blocks for novel macrocyclic
Schiff bases containing 4-methylanisole group incorpo-
rated into the ring system by substitution in their 2,6-
positions was now investigated. Thus, cyclocondensation
of 29 with 1,2-bis(4-amino-5-phenyl-3-ylsulfanyl)ethane
(1f) in glacial acetic acid under high dilution conditions
gave the corresponding macrocyclic Schiff base 34 in
71% yield as outlined in (Scheme 9).
The insertion of an additional 1,3-xylyl unit into the
macrocyclic ring 34 instead of the ethylene moiety was
also investigated. Thus, under similar conditions each of
6a,b reacted with 29 to give the corresponding
macrocyclic Schiff bases 35a,b in 61% and 76% yields,
respectively. Furthermore, the macrocyclic Schiff base 36
which is isomeric to 35b could also synthesized in 70%
yield by cyclocondensation of 2 with 31 in refluxing
acetic acid. We could also synthesize the novel
macrocyclic Schiff base 37 with two 4-methylanisole
groups incorporated into the ring system in 77% yield by
cyclocondensation of 29 with 31 in refluxing acetic acid
under high dilution conditions (Scheme 10).
Scheme 9
In conclusion, we prepared a new series of 1,3-bis(4-
amino-1,2,4-triazol-3-ylsulfanyl) benzene derivatives and
utilized them successfully as key intermediates for the
synthesis of novel macrocyclic Schiff bases upon which
fused triazole units and contain N, O and S inside the
macrocyclic ring as donor atoms. We expect this should
improve the binding abilities of the new macrocycles
compared to their corresponding analogues where the
additional donor atoms can effectively participate in the
coordination and lead to higher cation-binding. Moreover,
fusion of different coordinating entities (i.e. a Schiff base
N
N
N N
S
Ph
S
Ph
N
N
N
N
Acetic acid
high dilution
1f
29
+
O
OMe O
CH3
34
Scheme 10
6a
6b
29
29
+
+
+
+
2
31
29
31
Acetic acid
high dilution
Acetic acid
high dilution
Acetic acid
high dilution
CH3
CH3
N
N
N
N
N
N
N N
N
N
N N
R
R
S
S
OMe
N
N
N
Ph
Ph
S
S
OMe
N
N
N
N
Ph
Ph
S
S
N
N
N
N
N
O
OMe O
O
OMe O
O
O
CH3
CH3
35a, R = H
35b, R = Ph
36
37

Nov-Dec 2007 Synthesis of Novel Benzo-Substituted Macrocyclic Schiff Bases Containing Two Triazole Rings
1481
gave crude 6c which was crystallized from diluted acetic acid as
colorless crystals (75%), mp 200 °C; ir: NH2 3335, 3196 cm-1; 1H
nmr (DMSO-d6): ꢀ 4.06 (s, 4H, CH2-Ph), 4.30 (s, 4H, S-CH2),
5.81 (s, 4H, NH2), 7.20-7.39 ppm (m, 14H, ArH's); ms: m/z (%)
514 (M+, 2), 421 (0.67), 321 (6.3), 273 (0.78), 206 (100), 116
(17.6). Anal. Calcd for C26H26N8S2 (514.68): C, 60.68; H, 5.09;
N, 21.77. Found: C, 60.70; H, 5.40; N, 22.10.
and crown-ether moiety) into a unique ligand can give rise
to very interesting systems capable of multiple selective
and/or different metal ions recognition processes.
Furthermore the incorporation of additional aromatic and
heterocyclic moieties into the macroring should provide
the rigidity required to improve the stability of their
complexes. The present paper also gives
a brief
1,3-Bis(4-amino-1,2,4-triazol-3-ylsulfanylmethyl)pyridine
(19a). With the use of the general procedure 4a and 18 gave
crude 19a which was crystallized from ethanol as colorless
description of some of our recent contribution to the
utility of the cyclocondensation reactions under high
dilution conditions as an efficient route to a large number
of macrocyclic Schiff bases which of high interest in the
fields of supramolecular chemistry, molecular recognition
and organic synthesis.
crystals (60%), mp 203 C; ir: NH2 3258, 3157 cm-1; H nmr
(DMSO-d6): ꢀ 4.45 (s, 4H, S-CH2), 6.07 (s, 4H, NH2), 7.36-7.73
(m, 3H, pyridine H's), 8.43 ppm (s, 2H, triazole H) ppm; ms:
m/z (%) 335 (M+, 1.8), 320 (3.71), 287 (0.9), 236 (2.5), 204
(15), 175 (4.1), 137 (9.5), 116 (100). Anal. Calcd for C11H13N9S2
(335.42): C, 39.39; H, 3.91; N, 37.58. Found: C, 39.20; H, 3.60;
N, 37.80.
°
1
EXPERIMENTAL
1,3-Bis(4-amino-5-phenyl-1,2,4-triazol-3-ylsulfanylmethyl)-
pyridine (19b). With the use of the general procedure 4b and 18
gave crude 19b which was crystallized from acetic acid/ethanol
(1:1) as colorless crystals (78%), mp 212 °C; ir: NH2 3316, 3361
All melting points are uncorrected. IR spectra (KBr) were
recorded on a Perkin-Elmer 1430 spectrophotometer. NMR
spectra were measured with a Varian Mercury 300 (300 MHz 1H
NMR, 75 MHz 13C NMR) spectrophotometer and chemical
shifts are given in ppm from TMS. Mass spectra were recorded
on a GC MS-QP1000 EX (70 eV) or MS 5988 (15 eV)
spectrometers. Elemental analyses were carried out at the
Microanalytical Centre, Cairo University. 4-Aminotriazole-3-
thione derivatives 4 were prepared as reported [51]. 1,3-Bis-
(bromomethyl)benzene and 2,6-bis-(bromomethyl)pyridine were
used as purchased from Aldrich.
1
cm-1; H nmr (DMSO-d6): ꢀ 4.53 (s, 4H, S-CH2), 6.15 (s, 4H,
NH2), 7.43-8.01 ppm (m, 13H, ArH'S, pyridine H's); 13C nmr
(DMSO-d6): ꢀ 37.37 (SCH2), 121.84, 126.98, 127.77, 128.41,
129.57, 137.55, 152.83, 154.07, 156.47 ppm (Aromatic C's,
pyridine C's); ms: m/z (%) 487 (M+, 0.53), 402 (2.3), 393 (4.6),
342 (2.7), 291 (2.5), 177 (92), 145 (100); Anal. Calcd for
C23H21N9S2 (487.62): C, 56.65; H, 4.34; N, 25.85. Found: C,
56.70; H, 4.60; N, 25.70.
1,3-Bis(4-amino-5-benzyl-1,2,4-triazol-3-ylsulfanylmethyl)-
pyridine(19c). With the use of the general procedure 4c and 18
gave crude 19c which was crystallized from ethanol as colorless
Synthesis of 1,3-Bis(4-amino-1,2,4-triazol-3-ylsulfanylmethyl)-
benzenes (6a-c), 31 and 2,6-Bis(4-amino-1,2,4-triazol-3-ylsul-
fanylmethyl)pyridines 19a-c.
crystals (71%), mp 206 C; ir: NH2 3250, 3158 cm-1; H nmr
(DMSO-d6): ꢀ 4.06 (s, 4H, CH2-Ph), 4.39 (s, 4H, S-CH2), 5.87
(s, 4H, NH2), 7.12-7.65 ppm (m, 13H, ArH'S, pyridine H's); ms:
m/z (%) 515 (M+, 0.4), 500 (0.9), 453 (0.6), 346 (0.4), 296 (7.0),
206 (100), 117 (18.4). Anal. Calcd for C25H25N9S2 (515.67): C,
58.23; H, 4.89; N, 24.45. ound: C, 57.90; H, 5.10; N, 24.20.
2-Methoxy-5-methyl-1,3-bis(4-amino-1,2,4-triazol-3-ylsul-
fanylmethyl)benzene (31). With the use of the general
procedure 4b and 27 gave crude 31 which was crystallized from
°
1
General Procedure. To a solution of 4a-c (50 mmol) in
aqueous ethanol (50 ml, 50%) containing KOH (50 mmol) was
added the appropriate dibromo compounds 5, 18, 27 (25 mmol).
The reaction mixture was heated under reflux for 1 h. The
solvent was then removed in vacuo and the remaining solid was
collected and crystallized from the proper solvent to give
colorless crystals of compounds 6a-c, 19a-c and 31.
2,6-Bis(4-amino-1,2,4-triazol-3-ylsulfanylmethyl)benzene
(6a). With the use of the general procedure 4a and 5 gave crude
6a which was crystallized from ethanol as colorless crystals
°
ethanol as colorless crystals (75%), mp 195-197 C; ir: NH2
3308, 3165 cm-1; 1H nmr (DMSO-d6): ꢀ 2.21 (s, 3H, CH3C6H2),
3.89 (s, 3H, OCH3), 4.42 (s, 4H, SCH2), 6.16 (s, 4H, NH2), 7.23-
8.03 ppm (m, 12H, ArH's); 13C nmr (DMSO-d6): ꢀ 20.33
(CH3C6H2), 30.19 (S-CH2), 62.13 (O-CH3), 126.89, 127.77,
128.25, 128.47, 129.63, 130.13, 130.93, 133.25, 153.17, 154.13
ppm (Aromatic C's); ms: m/z (%) m/z 530 (M+, 6.6), 515 (7.2),
499 (3.2), 483 (14), 468 (21), 324 (71.8), 292 (66), 190 (100),
147 (86.1). Anal. Calcd for C26H26N8OS2 (530.68): C, 58.85; H,
4.94; N, 21.12. Found: C, 58.60; H, 5.20; N, 21.40.
°
1
(68%), mp 183 C; ir: NH2 3322, 3110 cm-1; H nmr: (DMSO-
d6): ꢀ 4.35 (s, 4H, S-CH2), 6.03 (s, 4H, NH2), 7.25-7.43 (m, 4H,
ArH's), 8.45 ppm (s, 2H, triazole H); ms: m/z (%) 334 (M+, 8.5),
280 (2), 219 (43.9), 171 (2.7), 135 (11.1), 116 (100); Anal.
Calcd for C12H14N8S2: (334.43): C, 43.11; H, 4.22; N, 33.51.
Found: C, 43.30; H, 3.90; N, 33.70.
2,6-Bis(4-amino-5-phenyl-1,2,4-triazol-3-ylsulfanylmethyl)-
benzene (6b). With the use of the general procedure 4b and 5
gave crude 6b which was crystallized from acetic acid as
colorless crystals (77%), mp 198 °C; ir: NH2 3245, 3134 cm-1; 1H
nmr (DMSO-d6): ꢀ 4.42 (s, 4H, S-CH2), 6.09 (s, 4H, NH2), 7.29-
7.99 ppm (m, 4H, ArH's); 13C nmr (DMSO-d6): ꢀ 35.05 (SCH2),
126.88, 127.77, 128.13, 128.46, 128.56, 129.62, 137.68, 153.02,
154.09 ppm (Aromatic C's, triazoleC's); ms: m/z (%) 486 (M+,
0.9), 471 (1.1), 339 (0.46), 295 (0.81), 259 (3.9), 192 (100), 121
(21). Anal. Calcd for: C24H22N8S2 (486.63): C, 59.24; H, 4.56; N,
23.03. Found: C, 59.40; H, 4.30; N, 23.00.
Synthesis of 2-methoxy-5-methyl-1,3-bis(2-formylphenoxy-
methyl)benzene (29). A solution of the potassium salt of
salicylaldehyde 28 (20 mmol) and the dibromo compound 27
(10 mmol) in DMF (20 ml) was heated under reflux for 5 min.
during which potassium chloride was precipitated. The solution
was concentrated to small volume (ca. 2 ml) and then cold water
(ca. 10 ml) was added. The solid obtained was collected and
crystallized from acetic acid as pale yellow crystals of 29 (91%),
mp 137.5-138 °C; ir: CHO 2853, 2755 cm-1; 1H nmr (DMSO-d6):
ꢀ 2.29 (s, 3H, CH3C6H2), 3.78 (s, 3H, OCH3), 5.25 (s, 4H,
OCH2), 7.09-7.76 (m, 10H, ArH's), 10.40 ppm (s, 2H, CHO);
2,6-Bis(4-amino-5-benzyl-1,2,4-triazol-3-ylsulfanylmethyl)-
benzene (6c). With the use of the general procedure 4c and 5

1482
A. H. M. Elwahy and G. S. Masaret
Vol 44
13C nmr (DMSO-d6): ꢀ 20.36 (CH3C6H2), 62.56 (O-CH3), 65.42
(O-CH2), 113.76, 120.81, 124.50, 127.79, 129.03, 130.57,
133.44, 136.12, 154.25, 160.47 (Aromatic C's), 188.87 ppm
(C=O); ms: m/z (%) 390 (M+, 5), 332 (6.3), 293 (9.8), 250 (7),
197 (11.9), 148 (62), 97 (88.5), 71 (100). Anal. Calcd for
C24H22O5 (390.44): C, 73.83; H, 5.68. Found: C, 74.00; H, 5.60.
Synthesis of the Bis-Schiff Bases 8, 33. To a solution of the
appropriate bis amines 6b and 31 (20 mmol) in glacial acetic
acid (15 ml) was added the corresponding aromatic aldehydes 7,
32. The reaction mixture was heated under reflux for 1 h and the
solvent was then removed in vacuo. The remaining solid was
collected and crystallized from the proper solvent to give
crystals of 8 and 33.
1H nmr (DMSO-d6): ꢀ 4.26 (s, 4H, S-CH2), 4.56 (s, 4H, OCH2),
6.97-7.71 (m, 12H, ArH's), 8.76 ppm (s, 2H, triazole H's); ms: m/z
(%) 568 (0.1), 406 (0.1), 332 (0.6), 264 (26.7), 204 (22.3), 146
(100), 91(50). Anal. Calcd for C28H24N8O2S2 (568.69): C, 59.14;
H, 4.25; N, 19.70. Found: C, 59.20; H, 4.40; N, 19.60.
28,32-Metheno-3,23-diphenyl-12,13-dihydro-14H,27H,33H-
bis[1,2,4]-triazolo[4,3-f:3,4-q]dibenzo[b,u]-1,23-dioxa-5,6,18,
19-tetraaza-8,16-dithiacyclohexacosine (10b). With the use of
the general procedure 6b and 9b gave crude 10b which was
°
crystallized from ethanol as colorless crystals (66%), mp 244 C;
1H nmr (DMSO-d6): ꢀ 1.91 (s, 3H, CH3C6H2), 2.20 (quintet, 2H, J =
6.0 Hz, OCH2CH3), 4.10 (s, 4H, OCH2), 4.32 (t, 4H, J = 6.0 Hz,
OCH2), 7.08-7.91 (m, 22H, ArH's), 9.10 ppm (s, 2H, CH=N); 13C
nmr (DMSO-d6): ꢀ 20.98 (OCH2CH3), 37.87 (S-CH2), 64.96 (O-
CH2), 113.23, 119.69, 121.12, 126.55, 126.97, 127.90, 128.46,
128.61, 129.17, 129.91, 134.95, 136.52, 145.46, 151.65, 158.63,
162.16, 171.92 ppm (Aromatic C's, triazole C's, CH=N); ms: m/z
(%) 735 (M++1, 0.1), 691 (0.1), 579 (0.2), 445 (0.3), 402 (0.8), 313
(2.5), 278 (46), 160 (100). Anal. Calcd for C41H34N8O2S2 (734.91):
C, 67.01; H, 4.66; N, 15.25. Found: C, 67.30; H, 4.80; N, 14.90.
13,17,32,36-Dimetheno-12H,18H,27H,31H-bis[1,2,4]tria-
zolo[4,3-f:3,4-q]dibenzo[b,u]-1,23-dioxa-5,6-18,19-tetraaza-
8,16-dithiacyclotricontin (11a). With the use of the general
procedure 6a and 2 gave crude 11a which was crystallized from
acetic acid as colorless crystals (55%), mp 231 °C; 1H nmr
(DMSO-d6): ꢀ 4.35 (s, 4H, SCH2), 5.26 (s, 4H, OCH2), 7.07-7.76
(m, 16H, ArH's), 8.89 (s, 2H, CH=N), 9.08 ppm (s, 2H, triazole
H' s); 13C nmr (DMSO-d6): ꢀ 35.38 (S-CH2), 70.02 (O-CH2),
113.87, 120.41, 121.16, 125.66, 126.97, 128.35, 128.48, 129.27,
129.38, 133.98, 136.56, 137.34, 138.81, 147.63, 155.47, 157.81
ppm (Aromatic C's, triazole C's, CH=N); ms: m/z (%) 644 (0.9),
577(29), 551 (26.9), 423 (8), 368 (23), 313 (100), 264 (73), 129
(59.4), 98 (77.3). Anal. Calcd for C34H28N8O2S2 (644.79): C,
63.34; H, 4.38; N, 17.38. Found: C, 63.10; H, 4.50; N, 17.10.
13,17,32,36-Dimetheno-3,27-diphenyl-12H,18H,31H,37H-
bis[1,2,4]triazolo[4,3-f:3,4-q]dibenzo[b,u]-1,23-dioxa-5,6,18,
19-tetraaza-8,16-dithiacyclotricontin (11b). With the use of
the general procedure 6b and 2 gave crude 11b which was
crystallized from acetic acid as colorless crystals (61%), mp
1,3-Bis[(4-benzylideneamino-5-phenyl-1,2,4-triazolo-3-yl)-
sulfanylmethyl]benzene (8). With the use of the general
procedure 6b and 7 gave crude 8 which was crystallized from
1
benzene/n-pentane as yellow crystals (48%), mp 98-100°C; H
nmr (DMSO-d6): ꢀ 4.34 (s, 4H, S-CH2), 7.22-7.84 (m, 24H, ArH's),
8.73 ppm (s, 2H, CH=N). Anal. Calcd for C38H30N8S2 (662.85): C,
68.86; H, 4.56; N, 16.91. Found: C, 68.70; H, 4.20; N, 16.90.
2-Methoxy-5-methyl-1,3-bis{[4-p-(nitro)benzylideneamino-
5-phenyl-1,2,4-triazolo-3-ylsulfanyl]methyl}benzene (33).
With the use of the general procedure 31 and 32 gave crude 33
which was crystallized from ethanol as as colorless crystals
°
1
(65%), mp 117 C; H nmr (DMSO-d6): ꢀ 2.0 (s, 3H, CH3C6H2),
3.64 (s, 3H, OCH3), 4.29 (s, 4H, SCH2), 6.94-8.37 (m, 20H,
ArH's), 8.96 ppm (s, 2H, CH=N); ms: m/z (%) 796 (4.6), 613
(4.18), 551(21.76), 496 (12.6), 339 (22.2), 239 (40.2), 185
(25.1), 131(51.5), 96 (31.8), 57 (100). Anal. Calcd for
C40H32N10O5S2 (796.90): C, 60.29; H, 4.05; N, 17.58. Found: C,
60.40; H, 4.30; N, 17.70.
Synthesis of 2-Methoxy-5-methyl-1,3-Bis{2-[(5-phenyl-3-
sulfanyl-1,2,4-triazol-4-yl)-1-azavinyl]phenoxymethyl}benzene
(30). To a solution of each of 29 (20 mmol) in glacial acetic acid
(15 ml) was added a solution of 4-aminotriazole-3-thione 4b (40
mmol). The reaction mixture was heated under reflux for 1 h and
the solvent was then removed in vacuo. The remaining solid was
collected and crystallized from ethanol to give 30 as colorless
°
1
crystals (79%), mp 142 C; H nmr (DMSO-d6): ꢀ 2.0 (s, 4H,
CH3), 3.79 (s, 3H, OCH3), 5.26 (s, 4H, O-CH2), 7.09-7.97 (m,
22H, ArH's), 10.24 (s, 2H, CH=N), 14.16 ppm (s, 2H, SH); ms:
m/z (%) 738 (M+, 0.3), 737 (0.3), 691 (0.4), 610 (0.4), 508 (0.5),
406 (0.7), 278 (2.7), 149 (97), 97 (100). Anal. Calcd for
C40H34N8O3S2 (738.90): C, 65.02; H, 4.64; N, 15.17. Found: C,
65.30; H, 4.80; N, 15.30.
1
251°C; H nmr (DMSO-d6): ꢀ 4.43 (s, 4H, S-CH2), 5.24 (s, 4H,
OCH2), 6.6-7.9 ppm (m, 26H, ArH's), 9.05 (s, 2H, CH=N); ms:
m/z (%) 796 (0.1), 792 (0.1), 747 (0.2), 690 (0.2), 559 (0.4), 456
(1.8), 398 (15.4), 280 (100), 222 (42), 104 (70.3). Anal. Calcd
for C46H36N8O2S2 (796.98): C, 69.33; H, 4.55; N, 14.06. Found:
C, 69.30; H, 4.80; N, 13.80.
13,17-Metheno-15-methyl-34-methoxy-3,27-diphenyl-31,32-
dihydro-12H,18H-bis[1,2,4]triazolo[4,3-f:3,4-l]dibenzo[b,p]-
1,18-dioxa-5,6,13-14-tetraaza-30,33-dithiacyclopentacosine
(34). With the use of the general procedure 1f and 29 gave crude 34
which was crystallized from ethanol as colorless crystals (71%),
mp 247-250 C; H nmr (DMSO-d6): ꢀ 2.30 (s, 3H, CH3C6H2),
3.46 (s, 4H, SCH2), 3.77 (s, 3H, OCH3), 5.17 (s, 4H, OCH2), 7.16-
7.95 (m, 20H, ArH's), 9.04 ppm (s, 2H, CH=N); ms: m/z (%) 764
(M+, 2.8), 733 (0.3), 713 (4.8), 552 (11.5), 368 (36.2), 269 (43.5),
135 (100). Anal. Calcd for C42H36N8O3S2 (764.94): C, 65.95; H,
4.74; N, 14.65. Found: C, 65.70; H, 4.50; N, 14.60.
Synthesis of the Macrocyclic Bis-Schiff Bases 10a, b, 11a, b
and 34-37.
General procedure. To a solution of the appropriate bis
aldehydes 2, 9a, b and 29 (10 mmol) in glacial acetic acid (50
ml) was added a solution of the appropriate bis amines 1f, 6a, b
and 31 (10 mmol) in glacial acetic acid (50 ml). The reaction
mixture was then heated under reflux for 2 h. The solution was
concentrated to small volume (ca. 2 ml) and then cold water (ca.
15 ml) was added. The precipitate obtained was collected and
recrystallized from the proper solvent to give crystals of 10a, b,
11a, b and 34-37.
°
1
13,17,32,36-Dimetheno-15-methyl-37-methoxy-12H,18H,
27H,31H-bis[1,2,4-]triazolo[4,3-f:3,4-q]dibenzo[b,u]-1,23-
dioxa-5,6,18,19-tetraaza-8,16-dithiacyclotricontin (35a).
With the use of the general procedure 6a and 29 gave crude 35a
which was crystallized from acetic acid/ethanol (1:1) as
27,31-Metheno-12,13-dihydro-26H,32H-bis[1,2,4]triazolo-
[4,3-f:3,4-q]dibenzo[b,u]-1,23-dioxa-5,6,18,19-tetraaza-8,16-
dithiacycloopentacosine (10a). With the use of the general
procedure 6a and 9a gave crude 10a which was crystallized from
°
colorless crystals (61%), mp 186 C; 1H nmr (DMSO-d6): ꢀ 2.03
°
acetic acid/ethanol (1:1) as colorless crystals (48%), mp 230 C;

Nov-Dec 2007 Synthesis of Novel Benzo-Substituted Macrocyclic Schiff Bases Containing Two Triazole Rings
1483
[5] Okawa, H.; Furutachi, H.; Fenton, D. E. Coord. Chem. Rev.
1998, 174, 51.
[6] Fenton, D. E.; Okawa, H. Chem. Ber., 1997, 130, 433.
(s, 3H, CH3C6H2), 3.70 (s, 3H, OCH3), 4.21 (s, 4H, SCH2), 5.19
(s, 4H, OCH2), 7.09-7.77 (m, 14H, ArH's), 8.81 (s, 2H, CH=N),
9.04 ppm (s, 2H, triazole H' s); ms: m/z (%) 689 (M++1, 0.7),
685 (0.8), 632 (1.2), 551 (13.2), 323 (6.8), 313 (62), 239 (41),
171 (30), 129 (77), 72 (100). Anal. Calcd for C36H32N8O3S2
(688.84): C, 62.77; H, 4.68; N, 16.27. Found: C, 63.00; H, 4.60;
N, 16.40.
[7] Collinson, S. R., Fenton, D. E. Coord. Chem. Rev. 1996, 148,
19.
[8] Fenton, D.E. Pure Appl. Chem. 1986, 58, 1437.
[9] Lindoy, L. F. The chemistry of Macrocyclic Ligand
Complexes, Cambridge University, Cambridge, UK, 1989.
[10] Lindoy, L. F. Pure Appl. Chem. 1989, 61, 1575.
[11] Lindoy, L. F. In : R. M. Izatt, J. J. Christensen (Eds.),
Synthesis of Macrocycle: The Design of Selective Complexing Agents,
Wiley, NY, 1987, p. 53.
13,17,32,36-Dimetheno-3,27-diphenyl-15-methyl-37-meth-
oxy-12H,-18H,27H,31H-bis[1,2,4]triazolo[4,3-f:3,4-q]dibenzo-
[b,u]-1,23-dioxa-5,6,18,19-tetraaza-8,16-dithiacyclotricontin
(35b). With the use of the general procedure 6b and 29 gave
crude 35b which was crystallized from ethanol as colorless
[12] Guerriero, P.; Tamburini, S.; Vigato, P. A. Coord. Chem.
Rev., 1995, 139, 17.
°
1
crystals (76%), mp 155-157 C; H nmr (DMSO-d6): ꢀ 2.03 (s,
3H, CH3C6H2), 3.71 (s, 3H, OCH3), 4.32 (s, 4H, S-CH2), 5.24 (s,
4H, OCH2), 7.13-7.98 (m, 24H, ArH's), 9.15 ppm (s, 2H,
CH=N); 13C nmr (DMSO-d6): ꢀ 20.27 (CH3C6H2), 37.72 (S-
CH2), 62.50 (O-CH3), 65.30 (O-CH2), 113.75, 120.24, 121.49,
126.66, 127.13, 127.84, 128.02, 128.56, 128.64, 128.72, 128.89,
129.48, 129.89, 133.42, 134.89, 136.62, 145.73, 151.92, 153.52,
158.53, 161.18 ppm (Aromatic C's, triazole C's, CH=N); ms:
m/z (%) 840 (M+, 0.7), 837 (0.9), 811 (0.7), 797 (0.8), 558
(15.9), 381 (25.6), 280 (100). Anal. Calcd for C48H40N8O3S2
(841.04): C, 68.55; H, 4.79; N, 13.32. Found: C, 68.70; H, 4.80;
N, 13.10.
[13] Murray, K. S. In: A. G. Sikes (Ed.), Advances in Inorganic
Chemistry, vol. 43, Academic Press, S. Diego, USA, 1995, p.261.
[14] Cooper, S. R. In “Crown Compounds: Towards future
Applications'' ed. S.R. Cooper, VCH, United Kingdom, UK, 1992.
[15] Melson, G. A. (Ed.), Coordination Chemistry of Macrocyclic
Compounds, Plenium Press, New York, 1979.
[16] Martell, A.; Penitka, J.; Kong, D. Coord. Chem. Rev. 2001,
216-217, 55.
[17] Gokel, G. W. Comprehensive Supramolecular Chemistry,
Vol. 1, Elsevier Science Ltd., 1996.
[18] Vögtle, F. Comprehensive Supramolecular Chemistry, Vol.
2, Elsevier Science Ltd., 1996.
[19] Hamilton, A. D. In: A. R. Katritzky, C. W. Rees (Eds.),
Comprehensive Heterocyclic Chemistry, Vol. 7, Pergamon Press, 1984,
pp. 731–761.
[20] Gokel, G. W.; Freder, M. F.; In: Katritzky, A. R.; Rees, C.
W.; Scriven, E. F. V. (Eds.), Comprehensive Heterocyclic Chemistry II,
Vol. 9, Pergamon Press, 1996, pp. 863–892;
[21] Krakowiak, K. E.; Bradshaw, J. S.; Zamecka-Krakowiak, D.
J. Chem. Rev. 1989, 89, 929–972.
[22] Habata, Y.; Akabori, S.; Bradshaw, J. S.; Izatt, R. M. Ind.
Eng. Chem. Res. 2000, 39 3465.
[23] Elwahy, A. H. M. J. Heterocycl. Chem. 2003, 40, 1.
[24] Gokel, G. W.; Leevy, W. M.; Weber, M. E. Chem. Rev. 2004,
104, 2723.
[25] Vigato, P. A.; Tamburini, S. Coord. Chem. Rev. 2004, 248,
1717.
[26] Bradshaw, J. S.; Krakowiak, K. E.; Tarbet, B. J.; Bruening,
R. L.; Biernat, J. F.; Bochenska, M.; Izatt, R. M.; Christensen, J. J. Pure
Appl. Chem. 1989, 61, 1619.
13,17,32,36-Dimetheno-3,27-diphenyl-34-methyl-38-meth-
oxy-12H,18H,31H,37H-bis[1,2,4]triazolo[4,3-f:3,4-q]dibenzo-
[b,u]-1,23-dioxa-5,6,18,19-tetraaza-8,16-dithiacyclotricontin
(36). With the use of the general procedure 2 and 31 gave crude
36 which was crystallized from ethanol as colorless crystals
°
(71%), mp 210-212 C; 1H nmr (DMSO-d6): ꢀ 1.99 (s, 3H,
CH3C6H2), 3.63 (s, 3H, OCH3), 4.42 (s, 4H, S-CH2), 5.22 (s, 4H,
OCH2), 7.07-7.94 (m, 24H, ArH's), 8.98 ppm (s, 2H, CH=N);
13C nmr (DMSO-d6): ꢀ 19.89 (CH3C6H2), 32.12 (S-CH2), 62.29
(O-CH3), 69.65 (O-CH2), 113.65, 119.97, 121.49, 126.52,
127.07, 127.78, 128.07, 128.61, 128.71,129.89, 129.89, 131.77,
133.64, 134.88, 136.20, 136.26, 136.77, 145.68, 151.88, 154.73,
158.28, 160.45 ppm (Aromatic C's, triazole C's, CH=N); ms:
m/z (%) 841 (M++1, 3.1), 656 (4%), 604 (12), 578 (49), 481
(8.6), 367 (20.8), 313(100), 239 (40.7), 69 (73). Anal. Calcd for
C48H40N8O3S2 (841.04): C, 68.55; H, 4.79; N, 13.32. Found: C,
68.50; H, 4.50; N, 13.00.
[27] Elwahy, A. H. M.; Abbas, A. A. Tetrahedron, 2000, 56,
885.
13,17,32,36-Dimetheno-3,27-diphenyl-15,34-dimethyl-37,38-
dimethoxy-12H,18H,31H,37H-bis[1,2,4]triazole[4,3-f:3,4-q]-
dibenzo[b,u]-1,23-dioxa-5,6,18,19-tetraaza-8,16-dithiacyclo-
tricontin (37). With the use of the general procedure 29 and 31
gave crude 37 which was crystallized from benzene/n-pentane as
colorless crystals (78%), mp 154 °C; 1H nmr (DMSO-d6): ꢀ 1.93,
2.09 (2s, 6H, CH3C6H2), 3.41, 3.70 (2s, 6H, OCH3), 4.32 (s, 4H,
SCH2), 5.20 (s, 4H, OCH2), 7.16-7.99 ppm (m, 22H, ArH's),
9.14 (s, 2H, CH=N); ms: m/z (%) 884 (M+, 0.1), 799 (0.1), 652
(0.1), 554 (0.1), 480 (0.1), 386 (0.5), 279 (11.9), 167 (27.8), 149
(100). Anal. Calcd for C50H44N8O4S2 (885.09): C, 67.85; H, 5.01;
N, 12.66. Found: C, 68.10; H, 4.90; N, 12.50.
[28] Beer, P. D.; Smith, D. K. In Karlin, K. D. (Ed)., Prog. Inorg.
Chem. Vol. 39, John Wiley & Sons, New York, USA, 1982, p. 1.
[29] Beer, P. D.; Smith, D. K.; In Karlin, K. D. (Ed)., Prog.
Inorg. Chem. Vol. 39, John Wiley & Sons, New York, USA, 1997, p. 1.
[30] McKee, V. In: Sikes, A. G. (Ed.), Adv. Inorg. Chem. Vol. 40,
Academic Press, Diego, S.; USA, 1993, p. 323.
[31] Nelson, J.; Mckee, V.; Morgan, G. In: Karlin, K. D. (Ed.),
Prog. Inorg. Chem. Vol. 47, John Wiley & Sons, New York, USA,
1998, p. 167.
[32] Brooker, S. Coord. Chem. Rev. 2001, 222, 33.
[33] Inone, Y.; Gokel, G. W. (Eds.) Cation Binding by
Macrocycles, Marcel Dekker Inc., New York, USA, 1990.
[34] Branchi, A.; Bowman-James, K.; Garcia-Espaꢀa, E. (Eds.),
Supramolecular Chemistry of Anions, Wiely-VCH, New York, USA,
1997.
REFERENCES
[35] Amendola, V.; Fabbrizzi, L.; Mangano, C., Poggi, P. A.;
Taglietti, A. Coord. Chem. Rev. 2001, 219-221, 821.
[36] Elwahy, A. H. M.; Abbas, A. A.; Kassab, R. M. Heteroatom
Chem. 2003, 14, 551.
[1] Curtis, N. F. Coord. Chem. Rev. 1968, 3, 3.
[2] Busch, D. H. Science, 1971, 171, 241.
[3] Nelson, S. M. Pure Appl. Chem. 1980, 52, 2461.
[4] Alexander, V. Chem Rev. 1995, 95, 273.
[37] Elwahy, A. H. M.; Abbas, A. A.; Ahmed, A. A. M. J.
Heterocycl. Chem. 2005, 42, 233.

1484
A. H. M. Elwahy and G. S. Masaret
Vol 44
[38] Chande, M. S.; Karnik, B. M. J. Ind. Chem. Soc. 1990, 67,
683.
864.
[45] Ibrahim, Y. A.; Elwahy, A. H. M.; Elkareish, G. M. M. J.
[39] El-Emam, A. A. Sulfur letters 1991, 12, 201.
Chem. Res (S), 1994, 414; J. Chem. Res. (M), 1994, 2321.
[46] Ibrahim, Y. A.; Elwahy, A. H. M.; Abbas, A. A. J. Chem.
Res. (S), 1998, 548; J. Chem. Res. (M), 1998, 2501.
[47] Abbas, A. A. Tetrahedron, 2004, 60, 1541.
[48] Elwahy, A. H. M.; Abbas, A. A.; Kassab, R. M. Synthesis
2002, 260.
[49] Ito, K.; Ohba, Y.; Sone, T. Heterocycles 1999, 51, 2203.
[50] Trost, B. M.; Yeh, V. S. C.; Ito, H.; Bremeyer, N. Org. Lett.
2002, 4, 2621.
[40] Elwahy, A. H. M.; Abbas, A. A.; Ibrahim, Y. A. J. Chem.
Res. (S), 1996, 182; J. Chem. Res. (M), 1996, 1066.
[41] Polya, J. B. In Comprehensive Heterocyclic Chem., Elsevier:
New York, 1984, Vol. 5, pp. 7333.
[42] Chande, M. S.; Athalye, S. S. Synth. Commun. 1999, 29,
1711.
[43] El-Emam, A. A.; Moustafa, M. A.; El-Subbagh, H. I.; El-
Ashmawy, M. B. Monatsh Chem. 1990, 121, 221.
[44] Holla, B. S.; Kalluraya, B. Ind. J. Chem. Sect B. 1988, 27,
[51] Hoggarth, E. J. Chem. Soc. 1952, 4811.