Facile route for the synthesis of pyridazine derivatives: Unexpected pathway to benzothiazole, benzimidazole, and triazole derivatives

Article abstract of DOI:10.1080/00397910500328845

4-Amino-5-arylmethylidene-3-phenyl-pyridazin-6-ones 7 have been synthesized and reacted with selected nucleophile reagents such as phenyl hydrazine, semicarbazide, semithiocarbazide, cyanoacetohydrazide, 2-aminothiophenol, and 2-phenylenediamine in ethanol triethyl-amine solution. An unexpected 1-phenyl-3-arylaziridene 10, 3-aryl-5-oxo(thio)-1,2,4-triazole 21, 4-amino-3-aryl-6-hydroxy-pridazine 27, 2-arylbenzothiazole 30a-c, and 2-arylbenzimidazole 30d-f have been obtained, respectively. Also, 2-aminothiophenol and 2-phenylenediamine were reacted with N-phenylmethylidene- 2-cyanoacetohydrazide 2, affording the new 1,4-benzodiazepine derivatives 35. Copyright Taylor & Francis LLC.

Full text of DOI:10.1080/00397910500328845

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Facile Route for the Synthesis of Pyridazine
Derivatives: Unexpected Pathway to
Benzothiazole, Benzimidazole, and Triazole
Derivatives
Eman A. El Rady a
a Chemistry Department, Faculty of Science, South Valley University, Aswan,
Egypt
Published online: 21 Aug 2006.
To cite this article: Eman A. El Rady (2006): Facile Route for the Synthesis of Pyridazine Derivatives:
Unexpected Pathway to Benzothiazole, Benzimidazole, and Triazole Derivatives, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry, 36:1, 37-49
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Synthetic Communicationsw, 36: 37–49, 2006
Copyright # Taylor & Francis LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500328845
Facile Route for the Synthesis of Pyridazine
Derivatives: Unexpected Pathway to
Benzothiazole, Benzimidazole, and Triazole
Derivatives
Eman A. El Rady
Chemistry Department, Faculty of Science, South Valley University,
Aswan, Egypt
Abstract: 4-Amino-5-arylmethylidene-3-phenyl-pyridazin-6-ones 7 have been syn-
thesized and reacted with selected nucleophile reagents such as phenyl hydrazine,
semicarbazide, semithiocarbazide, cyanoacetohydrazide, 2-aminothiophenol, and
2-phenylenediamine in ethanol triethyl-amine solution. An unexpected 1-phenyl-3-
arylaziridene 10, 3-aryl-5-oxo(thio)-1,2,4-triazole 21, 4-amino-3-aryl-6-hydroxy-
pridazine 27, 2-arylbenzothiazole 30a–c, and 2-arylbenzimidazole 30d–f have been
obtained, respectively. Also, 2-aminothiophenol and 2-phenylenediamine were
reacted with N-phenylmethylidene-2-cyanoacetohydrazide 2, affording the new 1,4-
benzodiazepine derivatives 35.
Keywords: 4-Aminopyridazine, 2-aminothiophenol, phenylaziridine, N-phenylmethy-
lidene-2-cyanoacetohydrazide, 1,2,4-triazole
N-arylmethylidene-2-cyanoacetohydrazides are versatile intermediates for the
synthesis of a variety of heterocyclic systems.[1,2] In continuation of our interest
in the synthesis of polyfunctionally substituted heterocyclic compounds,[3–8]
we report herein a facile and new one-pot synthesis of the title compounds.
The reaction of known N-phenylmethylidene-2-cyanoacetohydrazide[1] 2
with aromatic aldehydes in ethanolic piperidine solution at reflux temperature
afforded a product identified as 7, as is shown in Scheme 1. The desired target
Received in the UK October 20, 2004
Address correspondence to Eman A. El Rady, Chemistry Department, Faculty of
Science, South Valley University, Aswan, Egypt. E-mail: emanelradi@hotmail.com
37

38
E. A. El Rady
Scheme 1.
was compound 4 because it contains an a,b-unsaturated ketone with cyano
function at the a-position and also contains Schiff’s moiety. The nonisolable
intermediate 4 readily cyclized via intramolecular cycloaddition of benzylic
hydrogen into cyano function to afford the pyridazine 7 via its isomers 5, 6. Pyr-
idazine 7 was obtained directly via reaction of 1 with two moles of aromatics
aldehydes under the same reaction pathway. The structures of 7a–c were
based on analytical and spectroscopic data. The IR spectra of 7a–c revealed
absorption bands at 3390–3380 and 1684–1690 cm21, assigned for amino
and carbonyl groups, respectively. The MS of 7a showed m/z at 275 (Mþ,
1
25), 247 (M–N2, 5), 171 (35), 156 (25), 130 (35). The H NMR of 7a
showed signals at 7.1–7.9 ppm for aromatic protons and at 9.3 ppm assigned
for NH2 protons. However, it thought that the new pyridazine 7 represents a
cyclic a,b-unsaturated ketone system and would undergo the classical and
known reactions of this system. So, reaction with phenyl hydrazine 8, semicar-
bazide 17a, semithiocarbazide 17b, cyanoacetohydrazide 22, 2-aminothiophe-
nol 28a, and 2-phenylendiamine 28b have been carried out.
Reaction of 7 with phenyl hydrazine 8 afforded two different products
separated by fractional crystallization from methanol. The insoluble product
showed m/z at 196 as molecular ion, whereas it revealed an absorption
band at v 3311 cm21 assigned to NH group. However, the soluble product
revealed m/z at 187 (Mþ, 80), and two intense absorption bands were
recorded at v 3356 and 1689 cm21 due to NH2 and C55O groups, respectively
(Scheme 2). It is plausible that the mechanistic pathway that accounted for the
formation of 10 and 11 is shown in Chart 1. It is seemed that the intermediate 9

Pyridazine Derivatives
39
Scheme 2.
formed via Michael addition on the activated double bond is highly unstable
and may split into two fragments, 14 and 16. A nucleophilic attack of
hydrazine nitrogen on the benzyl carbon leads to the azirdinium cation 15,
which releases a hydrogen ion to the pyridazine anion 16 to finally yield
both 10 and 11. The fragmentation patteren of the MS of both 10a and 11
may support the proposed structures. Thus, the MS of 10a showed m/z at
196 (Mþ, 100), 119 (M-Ph, 20), and 103 (M–PhNH2, 7), whereas the MS
Chart 1.

40
E. A. El Rady
of 11 revealed m/z at 187 (Mþ, 80), 171 (M–NH2, 25), and 110 (M-Ph, 30).
However, the expected products (12 or 13) have been not found.
However, semicarbazide 17a and semithiocarbazide 17b were reacted
with 7 under the same reaction conditions to yield a colorless product during
reflux. The MS showed m/z at 163 (Mþ2, 50). The IR spectrum revealed
absorption bands at n 3194 and 1688 cm21 due to NH and CO groups, respect-
ively. It is seemed that the intermediate 18 underwent breaking to yield pyri-
dazine compound 11 under the same previous mechanism, and the formed
semicarbazide cation readily undergoes intramolecular cycoladdition to the
1,2,4-triazole compound 21 as shown in Scheme 3. The 1H NMR of
21a showed signals at 6.5 and 10.3ppm due to H-3 and NH and multiplets
at 7.1–7.9 ppm for aryl protons, respectively. The mass fragmentation
pattern supports the proposed structure as revealed Mþ2 at 163 (50), 117
(M-CONH2, 100), 101 (M–H2NCONH2, 65), 93 (50), and 77 (60).
Reaction of 7 with cyanoacetohydrazide 22 is shown in Scheme 4.
Michael addition of amine function on the activated double bond yielded
the intermediate 23, which underwent splitting into the pyridazine 11 and
the nonisolable fragment 24. An intramolecular cycloaddition led to the
4-aminopyridazine derivatives 27a–c via their isomers 25, 26. The MS of
27a showed m/z at 187 (100). The IR spectrum revealed broad bands at
3350, 3335, and 3310 cm21 assigned for OH and NH2 groups, respectively.
However, the reaction of 7 with 2-aminothiophenol 28a and
2-phenyldiamine 28b afforded 2-phenylbenzothiazoles 30a–c and
Scheme 3.

Pyridazine Derivatives
41
Scheme 4.
2-phenylbenzimidazoles 30d–f, respectively, which have been previously
reported,[9] and the pyridazine compound 11 (Scheme 5). Formation of 2-aryl-
benzothiazole 30a–c and 2-arylbenzimidazole 30d–f seems to proceed from
the intermediate 29 as suggested in Chart 2. The intermediate 29 loses pyridazine
moiety 11 to yield the intermediate cation 32. An intramolecular nucleophilic
attack by the lone pair of electrons of sulfur or nitrogen atoms on the electrophilic
carbon leads to the intermediate 33, which is readily oxidized under an aerobic
conditions to give 30. The MS of 30a showed m/z at 211 (Mþ, 89) and 134
(M-Ph, 92). The expected 1,5-benzodi(thi)azepine derivatives were not isolated.
The reactivity of 2 toward 2-substituted aniline 28a, b was further inves-
tigated to prepare new seven-membered ring systems, which represent a part
of our interest.[10,11] Reaction of 2 with 2-aminothiophenol 28a in refluxing
ethanolic piperidine solution afforded 1,5-benzodiazepine derivatives 35
during reflux via intermediate 34a, which formed through addition of amine
function of 28 to the cyano function of 2. The intermediate 34 releases
hydrogen sulfide and/or ammonia under the reaction conditions to yield
finally the new 1,5-benzodiazepine derivatives 35. The MS of 35 showed
m/z at 278 (60). The IR spectrum of 35 revealed absorption bands at 3335
1
and 1680 cm21 assigned for NH2 and C55O. The H NMR of 35 showed
signals at 2.5, 7.1–7.8, 8.3, and 9.5 ppm because of CH2, aryl-H,
Ph-CH55N–, and NH2 protons, respectively. However, reaction of 2 with
2-phenylenediamine 28b under the same reaction conditions afforded the
isolated product 34b (X55NH). The MS of 34b showed MS at m/z at (295).
The IR spectrum revealed bands at v 3340, 3220, and 1680 cm21 because of
NH2, NH, and C55O groups, respectively. Repeating the reaction in
pyridine at reflux temperature afforded the same 1,5-benzodiazipine 35.
Meanwhile, boiling 34b in pyridine yielded the same 1,5-benzodiazipine 35,

42
E. A. El Rady
Scheme 5.
which showed the same spectroscopic and elemental analysis data (Scheme 6).
Thus, the intermediate 34a may release a hydrogen ion from the NH group
neighbor to the carbonyl into the thiol function to give the intermediates 40,
41, which lose a hydrogen sulfide from the transient intermediate 41,
Chart 2.

Pyridazine Derivatives
43
leading finally to 35 (Chart 3). However, elimination of hydrogen sulfide from
intermediate 36 probably formed from 34a to give the oxazepine 37 is ruled
out, since the IR spectrum showed an intense absorption band at n
1680 cm21 because of the presence of a carbonyl group.
EXPERIMENTAL
Melting points are uncorrected. The IR spectra (potassium bromide, n in
cm21) were recorded on a Pye-Unicam SP-1100 spectrophotometer.
Scheme 6.

44
E. A. El Rady
Chart 3.
1H NMR spectra (deuterodimethyl-sulfoxide, d in ppm) were run on a Varian
EM-390 spectrometer using tetramethylsilane as internal standard. Mass
spectra were recorded on a Varian MAT 311 A spectrometer, and the
elemental analyses were determined at the Micro-analytical Center, Cairo
University, Egypt.
Preparation of Compounds 7a–c
A solution of 2 (0.38 g, 1 mmol), benzaldehyde 3a (0.2 g, 1 mmol), and 0.5 mL
of piperidine in 30 mL of dry ethanol was warmed to reflux for 5 h and con-
centrated under vacuum. The solid formed after addition of cold diluted
HCl (1 mL, 20 ml H2O) was collected by filtration, washed well with 100 mL
of cold water, and crystallized from ethanol to give 7a as yellow compound.
Analogously, 2 (0.38 g, 1 mmol) was reacted with 3b to give 7b, and 3c to
afford 7c, respectively.
4-Amino-5-phenylmethylidene-3-phenyl-pyridazin-6-one
7a: Yield:
85%. Mp: 2058C, IR: n 3390 (NH2), 1684 (CO) cm21; H NMR: d 7.1–7.9
(m, 11H, Ar-H), 9.3 (s, 2H, NH2); MS (70 eV) m/z (%): 275 (Mþ, 25).
Anal. calcd. for C17H13N3O (275.31): C, 74.17; H, 4.76; N, 15.26. Found:
C, 74.47; H, 4.96; N, 15.46.
1
4-Amino-5-(4-chlorophenylmethylidene)-3-phenyl-pyridazin-6-one 7b:
1
Yield: 80%. Mp: 2208C, IR: n 3380 (NH2), 1688 (CO) cm21; H NMR: d

Pyridazine Derivatives
45
7.1–7.8 (m, 10H, Ar-H), 9.9 (s, 2H, NH2); MS (70 eV) m/z (%): 309 (Mþ, 15).
Anal. calcd. for C17H12ClN3O (309.76): C, 65.92; H, 3.90; N, 13.57. Found:
C, 65.61; H, 4.12; N, 13.27.
4-Amino-5-(4-methoxyphenylmethylidene)-3-phenyl-pyridazin-6-one
7c: Yield: 78%. Mp: 2008C, IR: n 3385 (NH2), 1690 (CO) cm21; 1H NMR: d
2.1 (s, 3H, CH3), 7.1–8.0 (m, 10H, Ar-H), 8.9 (s, 2H, NH2); MS (70 eV) m/z
(%): 305 (Mþ, 24). Anal. calcd. for C18H15N3O2 (305.34): C, 70.81; H, 4.95;
N, 13.76. Found: C, 70.50; H, 4.65; N, 13.47.
Preparation of Aziridine 10a–c and Pyridazine 11
A solution of 7 (0.38 g 1 mmol), phenylhydrazine 8 (1 mmol), and 0.2 mL of
triethylamine in 30 mL of dry ethanol was warmed to reflux for 7 h and con-
centrated under vacuum. The solid compound that formed was collected by
filtration, washed well with 5 mL of methanol, and crystallized from ethanol
to give 10a. The residue solution was poured into water and acidified with
diluted hydrochloric acid. The resulting product was filtered, washed with
50 mL of cooled water, dried, and crystallized from a mixture of methanol
and water (3 : 1) to give pyridazine 11.
1,3-Diphenylaziridene 10a: Yield: 55%. MP: 1558C, IR: n 3311 (NH)
1
cm21; H NMR: d 6.2 (d, 1H, NCH), 7.1–7.9 (m, 10H, Ar-H ), 10.3 (d, 1H,
NH); MS (70 eV) m/z (%): 196 (Mþ, 100). Anal. calcd. for C13H12N2
(196.25): C, 79.56; H, 6.16; N, 14.27. Found: C, 79.37; H, 5.86; N, 14.46.
1-Phenyl-3-(4-chlorophenyl)-aziridene 10b: Yield: 52%. Mp: 1058C,
1
IR: n 3319 (NH) cm21; H NMR: d 5.7 (d, 1H, NCH), 7.1–7.8 (m, 9H, Ar-
H ), 10.2 (d, 1H, NH); MS (70 eV) m/z (%): 230 (Mþ, 45). Anal. calcd. for
C13H11ClN2 (230.70): C, 67.68; H, 4.81; N, 12.14. Found: C, 67.41; H,
4.99; N, 12.32.
1-Phenyl-3-(4-methoxyphenyl)-aziridene 10c: Yield: 58%. Mp: 1928C,
1
IR: n 3316 (NH) cm21; H NMR: d 2.1 (s, 3H, CH3), 5.9 (d, 1H, NCH),
7.1–8.0 (m, 9H, Ar-H ), 10.1 (d, 1H, NH); MS (70 eV) m/z (%): 226 (Mþ,
24). Anal. calcd. for C14H14N2O (226.28): C, 74.31; H, 6.24; N, 12.38.
Found: C, 74.55; H, 6.47; N, 12.62.
4-Amino-3-phenyl-pyridazine-6-one 11: Yield: 22%. Mp: 2008C, IR: n
1
3356, 3340 (NH2), 1689 (CO) cm21; H NMR: d 3.3 (s, 2H, CH2), 7.1–7.9
(m, 5H, Ar-H ), 8.9 (s, 2H, NH2); MS (70 eV) m/z (%): 187 (Mþ, 80). Anal.
calcd. for C10H9N3O (187.20): C, 64.16; H, 4.85; N, 22.45. Found: C,
64.37; H, 4.99; N, 22.66.
Preparation of Compounds 21a–f
A solution of 7a (0.38 g, 1 mmol), semicarbazide 17a (0.15 g, 1 mmol), and
0.5 mL of triethylamine in 30 mL of dry ethanol was warmed to reflux for
8 h. The solid formed during reflux was collected by filtration, washed well

46
E. A. El Rady
with 5 mL of methanol, and crystallized from a mixture of ethanol/DMF
(3 : 1) to give 21a as yellow compound. The residue solution poured into
water acidified with diluted hydrochloric acid, the resulting product was
filtered and washed with cooled water, dried and crystallized from mixture
of methanol and water (3 : 1) to give 11. Analogously, 7b,c (1 mmol) was
reacted with 17a to give 21b, c, and 7a–c reacted with semithiocarbazide
17b to give 21d–f.
3-Phenyl-1,2,4-triazol-5-one 21a: Yield: 65%. Mp: 2158C, IR: n 3194
1
(NH), 1688 (CO) cm21; H NMR: d 6.5 (d, 1H, triazole-H-3), 7.1–7.9 (m,
5H, Ar-H ), 10.3 (br. d, 1H, NH); MS (70 eV) m/z (%): 163 (M þ 2, 50).
Anal. calcd. for C8H7N3O (161.16): C, 59.62; H, 4.38; N, 26.07. Found: C,
59.85; H, 4.49; N, 26.25.
3-(4-Chlorophenyl)-1,2,4-triazol-5-one 21b: Yield: 60%. Mp: 2188C,
1
IR: n 3189 (NH), 1689 (CO) cm21; H NMR: d 6.6 (d, 1H, triazole-H-3),
7.2–7.9 (m, 4H, Ar-H ), 10.3 (br. d, 1H, NH); MS (70 eV) m/z (%): 195
(Mþ, 35). Anal. calcd. for C8H6ClN3O (195.61): C, 49.12; H, 3.09; N,
21.48. Found: C, 49.33; H, 3.41; N, 21.67.
3-(4-Methoxyphenyl)-1,2,4-triazol-5-one 21c: Yield: 68%. Mp: .
1
3008C, IR: n 3189 (NH), 1686 (CO) cm21; H NMR: d 2.3 (s, 3H, CH3),
6.2 (d, 1H, triazole-H-3), 7.1–7.8 (m, 4H, Ar-H ), 10.5 (br. d, 1H, NH); MS
(70 eV) m/z (%): 191 (Mþ, 24). Anal. calcd. for C9H9N3O2 (191.19): C,
56.54; H, 4.75; N, 21.98. Found: C, 56.70; H, 4.99; N, 22.02.
3-Phenyl-1,2,4-triazol-5-thione 21d: Yield: 55%. Mp: 1508C, IR: n 3186
1
(NH) cm21; H NMR: d 6.4 (d, 1H, triazole-H-3), 7.1–7.9 (m, 5H, Ar-H ),
10.3 (br. d, 1H, NH); MS (70 eV) m/z (%): 179 (M þ 2, 59). Anal. calcd.
for C8H7N3S (177.23): C, 54.22; H, 3.98; N, 23.71. Found: C, 54.37; H,
4.02; N, 23.99.
3-(4-Chlorophenyl)-1,2,4-triazol-5-thione 21e: Yield: 60%. Mp: 1808C,
IR: n 3180 (NH) cm21; 1H NMR: d 6.3 (d, 1H, triazole-H-3), 7.1–7.9 (m, 4H,
Ar-H ), 10.6 (br. d, 1H, NH); MS (70 eV) m/z (%): 213 (M þ 2, 38). Anal.
calcd. for C8H6ClN3S (211.67): C, 45.40; H, 2.86; N, 19.85. Found: C,
45.57; H, 2.99; N, 19.99.
3-(4-Methoxyphenyl)-1,2,4-triazol-5-thione 21f: Yield: 64%. Mp:
1
1908C, IR: n 3180 (NH) cm21; H NMR: d 2.3 (s, 3H, CH3), 6.5 (d, 1H,
triazole-H-3), 7.3–7.9 (m, 4H, Ar-H ), 10.3 (br. d, 1H, NH); MS (70 eV)
m/z (%): 209 (M þ 2, 24). Anal. calcd. for C9H9N3OS (207.25): C, 52.16;
H, 4.38; N, 20.28. Found: C, 52.31; H, 4.69; N, 20.39.
Preparation of Compounds 27a–c
A solution of 7a (0.38 g, 1 mmol), cyanoacetohydrazide 22 (0.14 g, 1 mmol),
and 0.5 mL of triethylamine in 30 mL of dry ethanol was warmed to reflux for
10 h. The solid formed during reflux was collected by filtration, washed well
with 5 mL of methanol, and crystallized from DMF to give 27a as brown

Pyridazine Derivatives
47
compound. The filtrate was poured into water acidified with dilute hydro-
chloric acid, the resulting solid product which formed was collected by fil-
tration and washed well with 50 ml of cooled water, dried and crystallized
from mixture of methanol and water (3 : 1) to give 11. Analogously, 7b,c
(1 mmol) was reacted with 22 to give 27b,c.
4-Amino-6-hydroxy-3-phenyl-pyridazine 27a: Yield: 65%. Mp: 2508C,
1
IR: n 3350, 3335, 3310 (OH, NH2) cm21; H NMR: d 7.0 (s, 1H, pyrida-
zine-H-5), 7.1–7.9 (m, 6H, Ar-H þ OH ), 8.9 (s, 2H, NH2); MS (70 eV) m/z
(%): 187 (Mþ, 100). Anal. calcd. for C10H9N3O (187.20): C, 64.16; H,
4.85; N, 22.45. Found: C, 64.41; H, 4.56; N, 22.16.
4-Amino-6-hydroxy-3-(4-chlorophenyl)pyridazine 27b: Yield: 60%.
Mp: 2058C, IR: n 3330, 3318 (OH, NH2) cm21; 1H NMR: d 6.9 (s, 1H, pyr-
idazine-H-5), 7.1–7.8 (m, 5H, Ar-H þ OH ), 8.7 (s, 2H, NH2); MS (70 eV) m/
z (%): 221 (Mþ, 35). Anal. calcd. for C10H8ClN3O (221.65): C, 54.19; H, 3.64;
N, 18.96. Found:C, 54.32; H, 3.40; N, 18.67.
4-Amino-6-hydroxy-3-(4-methoxyphenyl)pyridazine 27c: Yield: 60%.
1
Mp: 2658C, IR: n 3330, 3318 (OH, NH2) cm21; H NMR: d 2.1 (s, 3H,
CH3), 6.9 (s, 1H, pyridazine-H-5), 7.1–8.0 (m, 5H, Ar-H þ OH ), 8.5 (s, 2H,
NH2); MS (70 eV) m/z (%): 217 (Mþ, 34). Anal. calcd. for C11H11N3O2
(217.23): C, 60.82; H, 5.10; N, 19.34. Found: C, 60.65; H, 5.37; N, 19.63.
Preparation of 2-Arylbenzothiazole Derivatives 30a–c
and 2-Arylbenzimdazole Derivatives 30d–f
A solution of 7 (1 mmol), 2-aminothiophenole 28a (1 mmol), and 0.1 mL of
piperidine in 30 mL of dry ethanol was warmed to reflux for 5 h. The colorless
product that formed after cooling was collected by filtration and washed well
with methanol to give 30a. The residue solution was poured into 10 mL of cold
water and 0.5 mL of diluted HCl; the resulting solid product was collected by
filtration and washed well with 20 mL of cooled water and crystallized from
methanol to give 11. Analogously, 7b, c (1 mmol) was reacted with 28a to
give 30b, c, and 7a–c reacted with 28b to give 30d–f.
1
2-Phenylbenzothiazole 30a: Yield: 45%. Mp: 2408C, H NMR: d 7.1–
7.9 (m, 9H, Ar-H ); MS (70 eV) m/z (%): 211 (Mþ, 89). Anal. calcd. for
C13H9NS (211.28): C, 73.90; H, 4.29; N, 6.63; S, 15.17. Found: C, 73.72;
H, 4.38; N, 6.53; S, 15.35.
2-(4-Chlorophenyl)-benzothiazole 30b: Yield: 38%. Mp: 2208C,
1H NMR: d 7.1–7.9 (m, 8H, Ar-H ); MS (70 eV) m/z (%): 245 (Mþ, 89).
Anal. calcd. for C13H8ClNS (245.73): C, 63.54; H, 3.28; N, 5.70; S, 13.05.
Found: C, 63.73; H, 3.60; N, 5.93; S, 13.20.
2-(4-Methoxyphenyl)-benzothiazole 30c: Yield: 40%. Mp: 1028C,
1H NMR: d 2.1 (s, 3H, CH3), 7.1–7.9 (m, 8H, Ar-H ); MS (70 eV) m/z (%):
242 (M þ 1, 80). Anal. calcd. for C14H11NSO (241.31): C, 69.68; H, 4.59;
N, 5.80; S, 13.28. Found: C, 69.99; H, 4.67; N, 5.99; S, 13.58.

48
E. A. El Rady
2-Phenylbenzimidazole 30d: Yield: 38%. Mp: 2948C, IR: n 3168 (NH)
1
cm21; H NMR: d 7.1–7.9 (m, 10H, Ar-H þ NH ); MS (70 eV) m/z (%):
195 (M þ 1, 89). Anal. calcd. for C13H10N2 (194.24): C, 80.39; H, 5.19; N,
14.42. Found: C, 80.62; H, 5.48; N, 14.82.
2-(4-Chlorophenyl)-benzimidazole 30e: Yield: 31%. Mp: 1908C, IR: n
1
3180 (NH) cm21; H NMR: d 7.0–7.8 (m, 9H, Ar-H þ NH ); MS (70 eV)
m/z (%): 229 (M þ 1, 89). Anal. calcd. for C13H9ClN2 (228.68): C, 68.28;
H, 3.97; N, 12.25. Found: C, 68.72; H, 4.68; N, 12.60.
2-(4-Methoxyphenyl)-benzimidazole 30f: Yield: 29%. Mp: 1608C, IR: n
3189 (NH) cm21; 1H NMR: d 1.9 (s, 3H, CH3), 7.1–7.9 (m, 9H, Ar-H þ NH );
MS (70 eV) m/z (%): 225 (M þ 1, 89). Anal. calcd. for C14H12N2O (224.26):
C, 74.98; H, 5.39; N, 12.49. Found: C, 74.62; H, 5.62; N, 12.63.
Preparation of Compound 34b
A solution of 2 (1 mmol), 2-phenylenediamine 28b (1 mmol), and 0.1 mL of
piperidine in 30 mL of dry ethanol was warmed to reflux for 5 h. The
colorless product that formed after triturating with 5 mL of methanol was
collected by filtration and washed well with methanol to give 34b.
Yield: 28%. Mp: 1958C, IR: n 3340 (NH2), 3220 (NH), 1680 (CO) cm21
;
1H NMR: d 3.9 (s, 2H, CH2), 7.1–7.9 (m, 11H, Ar-H þ NH ), 9.1 (s, 2H, NH2),
10.3 (s, 2H, NH2); MS (70 eV) m/z (%): 295 (Mþ, 29). Anal. calcd. for
C16H17N5O (295.35): C, 65.07; H, 5.80; N, 23.71. Found: C, 65.36; H,
5.99; N, 23.99.
Preparation of 1,5-Benzodiazepine 35
A solution of 2 (1 mmol), 2-aminothiophenole 28a (1 mmol), and 0.1 mL of
piperidine in 30 mL of dry ethanol was warmed to reflux for 4 h. The
colorless product that formed during reflux was collected by filtration and
washed well with methanol to give 35. Analogously, 2 (1 mmol) was
reacted with 28b in pyridine for 7 h to give 35.
Yield: 55 %. Mp: 2408C, IR: n 3335 (NH2), 1680 (CO) cm21; 1H NMR: d
2.5 (s, 2H, CH2), 7.1–7.9 (m, 9H, Ar-H), 8.3 (s, 1H, CH), 9.5 (s, 2H, NH2); MS
(70 eV) m/z (%): 278 (Mþ, 60). Anal. calcd. for C16H14N4O (278.32): C,
69.05; H, 5.07; N, 20.13. Found: C, 69.35; H, 5.12; N, 20.50.
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