Synthesis and characterization of new derivatives of 1,4-diazepinium salts

Article abstract of DOI:10.1080/00397911.2010.518332

Novel 6-aryl-1,4-diazepinium and 3-aryl-hexahydro-1H-benzo-[b-1,4]- diazepinium salts (with aryl and heteroaryl=1-quinilinio, 3,5-dimethylpyridinio, 4-phenyl phenyl, 3,4,5-trimethoxyphenyl, and 1,4-phenylene) were synthesized mostly by reactions of 1,2-di

Full text of DOI:10.1080/00397911.2010.518332

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Synthesis and Characterization of New
Derivatives of 1,4-Diazepinium Salts
A. M. Mehranpour a , S. Hashemnia a & Z. Shayan a
a Persian Gulf University , Bushehr , Iran
Published online: 31 May 2011.
To cite this article: A. M. Mehranpour , S. Hashemnia & Z. Shayan (2011) Synthesis and
Characterization of New Derivatives of 1,4-Diazepinium Salts, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 41:23, 3501-3511,
DOI: 10.1080/00397911.2010.518332
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Synthetic Communications1, 41: 3501–3511, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.518332
SYNTHESIS AND CHARACTERIZATION OF NEW
DERIVATIVES OF 1,4-DIAZEPINIUM SALTS
A. M. Mehranpour, S. Hashemnia, and Z. Shayan
Persian Gulf University, Bushehr, Iran
GRAPHICAL ABSTRACT
Abstract Novel 6-aryl-1,4-diazepinium and 3-aryl-hexahydro-1H-benzo-[b-1,4]-
diazepinium salts (with aryl and heteroaryl ¼ 1-quinilinio, 3,5-dimethylpyridinio, 4-phenyl
phenyl, 3,4,5-trimethoxyphenyl, and 1,4-phenylene) were synthesized mostly by reactions
of 1,2-diamines with 3-aryl and 3-heteroaryl-1,5-diazapentadienium salts. The ultraviolet
spectral behavior of these compounds was examined in acetonitrile. Elemental analysis,
infrared, 1H NMR, 13C NMR, and mass spectra confirmed the molecular structure of
the newly synthesized compounds.
Keywords 3-Aryl-hexahydro-1H-benzo-[b-1,4]-diazepinium salts; 3-arylvinamidinium
salts; 6-aryl-2,3-dihydro-1,4-diazepinium salts; Vilsmeier reaction
INTRODUCTION
1,4-Diazepines have attracted attention as an important class of heterocyclic
compounds in the field of drugs and pharmaceuticals.[1–6] Among these compounds,
1,4-benzodiazepines such as diazepam, oxazepam, nordiazepam, and lorazepam are
Received July 28, 2010.
Address correspondence to A. M. Mehranpour, Persian Gulf University, Bushehr 75169, Iran.
E-mail: ammehranpour@hotmail.com
3501

3502
A. M. MEHRANPOUR, S. HASHEMNIA, AND Z. SHAYAN
successfully used as drugs for the treatment of anxiety, sleep disturbance, and status
epilepticus. 1,4-Diazepines also show biological activities such as anticancer, anti-
bacterial, and antiviral activities.[7–9] Because of their broad spectrum of biological
activity, these compounds have received a great deal of attention in connection with
their synthesis.
Although many different 1,4-diazepinium derivatives have been synthesized,[10]
to the best of our knowledge, very little attention has been paid to the synthesis of
6-aryl and 6-heteroaryl-1,4-diazepinium salts.[11]
In this article, we describe the synthesis of a variety of 6-aryl and
6-heteroaryl-2,3-dihydro-1,4-diazepinium and 3-aryl-hexahydro-1H-benzo-[b-1,4]-
diazepinium salts and evaluate their structural properties on the basis of their
1
ultraviolet (UV) absorption, infrared (IR), H NMR, 13C NMR, and mass spectra.
RESULTS AND DISCUSSION
A variety of 6-aryl-2,3-dihydro-1,4-diazepinium and 3-aryl-hexahydro-1H-
benzo-[b-1,4]-diazepinium salts (with aryl and heteroaryl ¼ 1-quinilinio, 3,5-
dimethylpyridinio, 4-phenyl, 3,4,5-trimethoxyphenyl, and 1,4-phenylene) were
obtained, for the most part in good yields (see Table 1). The most used method of
preparation, exemplified in Schemes 1, 2, and 3, starts from an arylacetic acid, which
is first converted into a 3-arylvinamidinium salt by means of Vilsmeier–Arnold
Table 1. Empirical formula, elemental analyses, yields, melting points, and UV spectral data (measured in
acetonitrile) of the 6-aryl-4-diazepinium salts C, D, F, G, H, I, and K and the intermediates A, B, E, and J
Calculated found (%)
Empirical formula
(mol. mass)
Yield
(%)
Mp
(ꢀC)
kmax
(nm)
lg emax
Compound
A
C
H
N
(Mꢁ1cmꢁ1
)
(C11H10NO2)Br (188.0)
49.29 3.76
5.23
56
80
63
80
64
66
80
85
78
66
59
229
269
(49.30) (3.76) (5.31)
42.38 4.63 9.27
(41.49) (5.00) (9.01)
42.49 4.23 9.29
B
C
D
E
F
G
H
I
(C16H21N3)(ClO4)2
(453.8)
(C16H21N3)(ClO4)
(452.2)
258
337
340
4.42
4.26
(41.05) (4.91) (9.01)
41.52 5.23 10.38
(42.01) (5.24) (10.42)
(C14H21N3)(BF4)2
(405.2)
245–247
178
(C16H25N2O3)(ClO4)
(392.5)
48.92 6.37
(50.05) (6.42) (8.10)
46.35 5.28 7.72
(47.01) (6.03) (8.20)
49.17 5.93 7.17
(51.05) (6.42) (8.10)
51.86 6.04 6.72
(51.78) (6.33) (6.53)
63.38 6.04 6.95
7.13
(C14H19N2O3)(ClO4)
(362.0)
181–183 254, 360
4.02, 3.96
4.09, 4.01
4.20, 3.82
4.50, 3.93
(C16H23N2O3)(ClO4)
(390.8)
222
235
313
280
290
258, 373
257, 361
275, 361
(C18H25N2O3)(ClO4)
(416.9)
(C21H23N2)(ClO4)
(402.9)
(62.01) (6.65) (6.85)
47.84 6.42 11.16
(49.02) (6.10) (12.04)
48.23 5.67 11.25
(49.01) (5.25) (12.21)
J
(C20H32N4)(BF4)2
(502.3)
K
(C20H28N4)(BF4)2
(498.2)
281, 371
4.47, 4.38

NEW DERIVATIVES OF 1,4-DIAZEPINIUM SALTS
3503
Scheme 1. Reaction pathway to diazepinium salt C.
Scheme 2. Reaction pathway to the diazepinium salts F, G, and H.

3504
A. M. MEHRANPOUR, S. HASHEMNIA, AND Z. SHAYAN
Scheme 3. Reaction pathway to diazepinium salt K.
formylation.[12,13] This salt in turn reacts with ethane-1,2-diamine, N,N0-
dimethylethane-1,2-diamine, or cyclohexane-1,2-diamine to provide the correspond-
ing diazepinium salts.
The new 6-heteroaryl-1,4-diazepinium salt C was synthesized using a three-step
procedure as shown in Scheme 1: (i) synthesis of the N-heteroaryl acetic acid A using
the reaction between quinoline with bromoacetic acid;[14] (ii) synthesis of 3-heteroar-
ylvinamidinium salt B by Vilsmeier–Arnold formylation of A;[12,13] and (iii) synthesis
of C from B with N,N0-dimethylethane-1,2-diamine. Scheme 4 shows the preparation
of D from 1,1,5,5-tetramethyl-3-(3,5-dimethylpyridinium-1-yl)-1,5-diazapentadie-
nium bis(tetrafluoroborate)[15] by reaction with N,N0-dimethylethane-1,2-diamine.
The 1,4-diazepinium salts F, G, and H were synthesized from the 3,4,5-trimethoxy-
phenyl vinamidinium salt
E
by reaction with ethane-1,2-diamine, N,N0-
Dimethylethane-1,2-diamine, and cyclohexane-1,2-diamine, respectively (Scheme 2).
The preparation of the 1,4-diazepinium salts I and K are depicted in Schemes 5 and
3, respectively.
All diazepinium salts C, D, F, G, H, I, and K and the intermediates A, B, E,
and J are new compounds, the molecular structures of which were confirmed by
elemental analysis (Table 1), 1H NMR, 13C NMR, IR, and mass spectroscopy
(Table 2). Inspection of the data presented in Table 1 shows that the melting points
of all compounds are rather sharp, indicating the high purity of all synthesized
compounds.
1
The 13C NMR spectra of the 1,4-diazepinium salts, like the H NMR spectra,
confirm shape and charge distribution of these compounds. As for other diazepinium

NEW DERIVATIVES OF 1,4-DIAZEPINIUM SALTS
3505
Scheme 4. Reaction pathway to the diazepinium salt D.
salts,[11,16] the most striking feature of the 13C NMR spectra of the 6-aryl derivatives
is the large difference in chemical shift between the signals for C-6 (Dd ꢂ .106 ppm)
and C-5,7 (Dd ꢂ 157 ppm), indicating the strongly alternating charge density in the
conjugated vinamidinium chain, which is typical for such polymethine p-systems.[16]
The influence of the 6-aryl substituents (F, G, H, I, and K salts) on the chemical shift
of C-6 is very similar to that found for the N-aryl derivatives (C and D salts)
(Table 2). The long-wavelength UV absorption data (kmax ꢂ 340–373 and emax
values) of the 1,4-diazepinium salts C, D, F, G, H, I, and K, measured in acetonitrile,
are also depicted in Table 1. It is noteworthy that the C and D salts show only one
peak and the F, G, H, I, and K salts show two peaks attributed to the p!pꢃ transi-
tions of the salts.
Scheme 5. Reaction pathway to the diazepinium salt I.

3506

3507

3508
A. M. MEHRANPOUR, S. HASHEMNIA, AND Z. SHAYAN
CONCLUSION
Seven novel 6-aryl and 6-heteroaryl-1,4-diazepinum salts were synthesized,
mostly by reactions of 1,2-diamines with 3-aryl-1,5-diazapentadienium salts, in good
yields. The molecular structure and purity of the newly prepared compounds were
confirmed by IR, NMR, mass spectroscopy, and elemental analyses.
EXPERIMENTAL
General Methods
All reactants and chemicals were purchased from Merck or prepared according
to literature procedures. Solvents were of analytical grade.
1H NMR and 13C NMR spectra were recorded with a Bruker Avance
DRX-500. Dimethyl sulfoxide (DMSO) and deuterated chloroform (CDCl3) were
used as solvent and tetramethylsilane (TMS) as internal standard.
Mass spectral data were obtained on a Finnigan-Matt 8430 (70-eV)
spectrometer.
UV absorption spectra were recorded at room temperature in acetonitrile using
a Perkin-Elmer Lambda 25 spectrophotometer, and the IR spectra were obtained
with a Perkin-Elmer 781 spectrophotometer.
Elemental analyses with KBr discs were made with a CHN Analyzer [Flash,
1112 series (EA), Thermo Finnigan Company], and the melting points were determ-
ined on the Electrothermal 9200 apparatus.
General Experimental Procedures
N-(Hydroxycarbonylmethyl)quinolinium bromide (A). Quinoline (10.0 g,
0.08 mol) was added to 11.0 g (0.08 mol) of bromoacetic acid in 40 mL of acetonitrile.
The mixture was refluxed at 60 ꢀC for 7 h. The brown crystals of A were collected by
filtration, recrystallized from ethanol, and dried in a desiccator with P4O10.[14]
1,1,5,5-Tetramethyl-3-(1-quinolinio)-1,5-diazapentadienium
bis(per-
chlorate) (B). Phosphorus oxitrichloride (8.19 mL, 0.09 mol) was added to
16.50 mL (0.21 mol) of DMF at 0 ꢀC, and the mixture was stirred at room tempera-
ture for 30 min. N-(hydroxycarbonylmethyl)quinolinium bromide A (8.04 g 0.03 mol)
was added to this reagent. The mixture was refluxed at 75–80 ꢀC for 5 h and then set
aside in a refrigerator for 12 h. The solution was then diluted with precooled and
dried ethanol (100 mL).
A solution of 72% HClO4 (10.00 mL, 0.10 mol) in ethanol (30 mL) was added
to this solution, and the mixture was set aside in a refrigerator for 12 h. The yellow
crystals of B were collected by filtration, washed with diethyl ether, and dried in a
desiccator with P4O10.[12,13]
6-(1-Quinolinio)-2,3-dihydro-1,4-dimethyl-1H-1,4-diazepinium bis(per-
chlorate) (C). Solutions of 0.45 g (0.001 mol) of 1,1,5,5-tetramethyl-3-
(1-quinolinio)-1,5-diazapentadienium bis(perchlorate) B in 20 mL of acetonitrile
and 0.10 mL (0.001 mol) of N,N0-dimethylethane-1,2-diamine in 20 mL of acetonitrile
were added simultaneously drop by drop to boiling acetonitrile (20 mL). The

NEW DERIVATIVES OF 1,4-DIAZEPINIUM SALTS
3509
resultant solution was refluxed at 85 ꢀC for 8 h. After cooling to room temperature,
the solvent was evaporated under vacuum, and the red precipitate formed was
collected by filtration, recrystallized from dry ethanol, and dried in a desiccator with
P4O10.
6-[1-(3,5-Dimethylpyridinio)]-2,3-dihydro-1,4-dimethyl-1H-1,4-diazepinium
bis(tetrafluoroborate) (D). Solutions of 0.48 g (0.001 mol) of 1,1,5,5-
tetramethyl-3-(3,5-dimethylpyridinium-1-yl)-1,5-diazapentadienium bis(tetrafluoro-
borate)[15] in 15 mL of acetonitrile and 0.10 mL (0.001 mol) of N,N0-dimethylethane-
1,2-diamine in 15 mL of acetonitrile were added simultaneously drop by drop to boil-
ing acetonitrile (15 mL). The reaction mixture was refluxed at 85 ꢀC for 7 h. After cool-
ing to room temperature, the solvent was evaporated under vacuum, and the resultant
oily red residue was kept cold overnight. Then a small amount of dichloromethane
was added, and the precipitate formed was collected by filtration, recrystallized from
2-propanol, and dried in a desiccator with P4O10.
1,1,5,5-Tetramethyl-3-[(3,4,5-trimethoxy)phenyl]-1,5-diazapentadienium
perchlorate (E). Phosphorus oxitrichloride (1.80 mL, 0.02 mol) was added to
3.30 mL (0.04 mol) of DMF at 0 ꢀC, and the mixture was stirred at room temperature
for 30 min. 3,4,5-Trimethoxyphenyl acetic acid (purchased from Merck: 1.50 g;
0.006 mol) was added to this reagent. The mixture was refluxed at 80 ꢀC for 7 h
and then set aside in a refrigerator for 12 h. The solution was then diluted with
precooled and dried ethanol (20 mL).
A solution of 72% HClO4 (1.7 mL, 0.01 mol) in ethanol (10 mL) was added to
this solution, and the mixture was set aside in a refrigerator for 12 h. The yellow crys-
tals of salt E were collected by filtration, washed with diethyl ether, and dried in a
desiccator with P4O10.[12,13]
6-(3,4,5-Trimethoxyphenyl)-2,3-dihydro-1,4-dihydro-1H-1,4-diazepinium
perchlorate (F). Solutions of 0.39 g (0.001 mol) of 1,1,5,5-tetramethyl-3-(3,4,
5-trimethoxyphenyl)-1,5-diazapentadienium perchlorate E in 15 mL of acetonitrile
and 0.07 mL (0.001 mol) of ethane-1,2-diamine in 15 mL of acetonitrile were added
simultaneously drop by drop to boiling acetonitrile (15 mL).[17] The resultant yellow
solution was refluxed at 85 ꢀC for 5 h. After evaporating the solvent under vacuum,
an oily residue was obtained and mixed with 3 mL of dichloromethane. The resultant
gray precipitate was collected by filtration, washed with diethyl ether, and dried in a
desiccator with P4O10.
6-(3,4,5-Trimethoxyphenyl)-2,3-dihydro-1,4-dimethyl-1H-1,4-diazepinium
perchlorate (G). Solutions of 0.39 g (0.001 mol) of 1,1,5,5-tetramethyl-3-(3,4,5-
trimethoxyphenyl)-1,5-diazapentadienium perchlorate E in 15 mL of acetonitrile
and 0.10 mL (0.001 mol) of N,N0-dimethylethane-1,2-diamine in 15 mL of acetoni-
trile were added simultaneously drop by drop to boiling acetonitrile (15 mL).[17]
The resultant yellow solution was refluxed at 85 ꢀC for 5 h. After cooling, the solvent
was evaporated under vacuum, and the residue was kept cold overnight. The precipi-
tate was washed with dichloromethane, recrystallized from dry ethanol, and dried in
a desiccator with P4O10.

3510
A. M. MEHRANPOUR, S. HASHEMNIA, AND Z. SHAYAN
3-(3,4,5-Trimethoxyphenyl)-5a,6,7,8,9,9a-hexahydro-1H-benzo[b-1,4]
diazepinium perchlorate (H). Solutions of 0.39 g (0.001 mol) of 1,1,5,5-tetra-
methyl-3-(3,4,5-trimethoxyphenyl)-1,5-diazapentadienium perchlorate E in 15 mL
of acetonitrile and 0.12 mL (0.001 mol) of cyclohexane-1,2-diamine in 15 mL of acet-
onitrile were added simultaneously drop by drop to boiling acetonitrile (15 mL).[17]
The resultant yellow solution was refluxed at 83 ꢀC for 8 h. After cooling to room
temperaure, the solvent was evaporated under vacuum, and the resultant oily residue
was kept cold overnight. Then 2 mL of dichloromethane was added, and the yellow
precipitate was collected by filtration, washed with dichloromethane and n-hexane,
respectively, and dried in a desiccator with P4O10.
3-(4-Phenylphenyl)-5a,6,7,8,9,9a-hexahydro-1H-benzo[b-1,4]diazepinium
perchlorate (I). Solutions of 0.38 g (0.001 mol) of 1,1,5,5-tetramethyl-3-
(4-phenylphenyl)-1,5-diazapentadienium perchlorate[12] in 15 mL of acetonitrile
and 0.12 mL (0.001 mol) of cyclohexane-1,2-diamine in 15 mL of acetonitrile were
added simultaneously drop by drop to boiling acetonitrile (15 mL). The resultant
yellow solution was refluxed at 85 ꢀC for 7 h. After evaporating the solvent under
vacuum, an oily residue was obtained and mixed with 2 mL of dichloromethane.
The yellow precipitate was collected by filtration, washed with hot dichloromethane
and n-hexane, respectively, and dried in a desiccator with P4O10.
3,3’-(4-Phenylphenyl)bis(1,5-diazapentadienium) bis(tetrafluoroborate)
(J). Phosphorus oxitrichloride (4.10 mL, 0.045 mol) was added to 8.25 mL
(0.11 mol) of DMF at 0 ꢀC, and the mixture was stirred at room temperature for
30 min. 1,4-Phenylendiacetic acid (purchased from Merck; 1.5 g; 0.008 mol) was
added to this reagent. The mixture was refluxed at 80 ꢀC for 7 h and then set aside
in a refrigerator for 12 h. The solution was then diluted with precooled and dried
ethanol (100 mL).
A solution of 5% HBF4 (6.9 mL, 0.05 mol) in ethanol (30 mL) was added to this
solution, and the mixture was set aside in a refrigerator for 12 h. The yellow crystals
of J were collected by filtration, washed with diethyl ether, recrystallized from dry
ethanol, and dried in a desiccator with P4O10.
6,6’-(,4-Phenylphenyl) bis(2,3-dihydro-1,4-dimethyl-1H-1,4-diazepinium)
bis(tetrafluoroborate) (K). 3,30-(4-Phenylphenyl)bis(1,5-diazapentadienium) bis
(tetrafluoroborate) J (0.25 g, 0.0005 mol) in 100 mL of boiling ethanol and 0.10 mL
(0.001 mol) of N,N0-dimethylethane-1,2-diamine in 10 mL of ethanol was added sim-
ultaneously drop by drop to boiling ethanol (15 mL). The resultant yellow solution
was refluxed at 85 ꢀC for 10 h. After cooling to room temperature, the solvent was
evaporated under vacuum, and the oily residue obtained was mixed with dichloro-
methane (2 mL). The precipitate formed was collected by filtration, washed once with
diethyl ether and three times with n-hexane, and dried in a desiccator with P4O10.
ACKNOWLEDGMENT
Financial support of this work by the Research Council of the Persian Gulf
University is gratefully acknowledged.

NEW DERIVATIVES OF 1,4-DIAZEPINIUM SALTS
3511
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