An efficient one-pot strategy for the synthesis of triazole-fused 1,4-benzodiazepinones from n-substituted 2-azidobenzamides

Article abstract of DOI:10.1055/s-0033-1339346

A catalyst-free, one-pot strategy for the synthesis of 1,2,3-triazole-fused 1,4-benzodiazepinone derivatives from N-substituted 2-azidobenzamides and propargyl bromide, in the presence of a base, is reported. The products are formed in good to excellent y

Full text of DOI:10.1055/s-0033-1339346

PAPER
▌2619
paper
An Efficient One-Pot Strategy for the Synthesis of Triazole-Fused
1,4-Benzodiazepinones from N-Substituted 2-Azidobenzamides
Triazole-Fused 1,4-Benzodiazepinones
K. C. Majumdar,* Sintu Ganai
Department of Chemistry, University of Kalyani, Kalyani 741235, West Bengal, India
Fax +91(33)25828282; E-mail: kcm@klyuniv.ac.in
Received: 18.04.2013; Accepted after revision: 10.06.2013
a diverse range of 1,2,3-triazole-fused pharmacophores.9
Many research groups have employed the Huisgen 1,3-di-
polar cycloaddition of azides with alkynes10 for the syn-
thesis of bicyclic, polycyclic and triazole-fused nitrogen-
containing heterocycles.11 Various approaches toward the
preparation of 1,4-benzodiazepine derivatives have also
been reported.12 Akritopoulou-Zanze et al.13 have report-
ed a two-step synthesis of fused triazole derivatives via al-
kyne–azide cycloadditions of substrates obtained from
Ugi reactions of isocyanides and o-azidobenzaldehyde.
Hemming and co-workers14 reported the synthesis of tri-
azolobenzodiazepines and pyrrolobenzodiazepines using
an intramolecular 1,3-dipolar cycloaddition in a multistep
process. Furthermore, Chowdhury15 has described an
approach for the synthesis of 1,2,3-triazolo[1,5-
a][1,4]benzodiazepin-6-ones and 1,2,3-triazolo[1,5-
a][1,5]benzodiazocin-7-ones through Sonogashira cou-
pling of an aryl iodide with 2-amino-N-methyl-N-(prop-2-
ynyl)benzamide or its homologue, followed by in situ di-
azotization, azidation and cycloaddition reactions. The
Lemrova16 group have reported a solid-phase synthesis of
Abstract: A catalyst-free, one-pot strategy for the synthesis of
1,2,3-triazole-fused 1,4-benzodiazepinone derivatives from N-sub-
stituted 2-azidobenzamides and propargyl bromide, in the presence
of a base, is reported. The products are formed in good to excellent
yields via N-alkylation followed by a 1,3-dipolar cycloaddition.
Key words: fused triazole, azide–alkyne cycloaddition, 1,4-benzo-
diazepinones, N-substituted 2-azidobenzamides, catalyst-free
The benzodiazepine core is considered to be a privileged
structure in medicinal chemistry, and has attracted consid-
erable attention as a ligand for various bioreceptors.1 1,4-
Benzodiazepines play important roles as anti-anxiety and
antihistaminic agents.2 Benzodiazepines with fused 1,2,3-
triazole and tetrazole rings have also gained popularity
due to their potent biological activity.3 Tricyclic fused
benzodiazepines such as flumazenil (1),4 diazepinone (2)5
and estazolam (3)6 have achieved clinical success in the
treatment of central nervous system disorders (Figure 1).
18F-Labelled compound 1 is a useful ligand for positron
emission tomography.7 Furthermore, the tetracyclic ben-
zodiazepine, bretazanil (4), has shown activity in the treat-
ment of central nervous system disorders and against
neurodegenerative diseases.8
1,2,3,4-tetrahydrobenzo[e][1,4]diazepin-5-ones
polystyrene resin. A domino approach for the synthesis of
polyfunctionalized and tricyclic fused diben-
using
zo[b,e][1,4]diazepin-1-one and pyrrole derivatives was
reported by Jiang and co-workers.17 Finally,
O
Me
N
Van der Eycken18
has
synthesized
triazolo[1,5-
F
N
O
a][1,4]benzodiazepinones by employing a post-Ugi cop-
per-catalyzed tandem azide–alkyne cycloaddition and
Ullmann coupling strategy. They used o-bromobenzalde-
hyde, an amine, an isocyanide, and propiolic acid deriva-
tives for the synthesis of the Ugi-product. However, the
majority of these protocols require the use of very expen-
sive reagents or ligands. In continuation of our efforts to
synthesize potentially bioactive heterocycles,19 we
planned to develop a simple protocol for the preparation
of triazole-fused 1,4-benzodiazepinones by employing a
1,3-dipolar cycloaddition reaction. The results of this
study are reported herein.
N
N
N
CO2Et
CO2Et
N
N
2
1
O
Br
Ph
N
Cl
N
N
H
N
N
CO2t-Bu
N
N
4
3
The starting materials, N-substituted 2-azidobenzamides
6a–g, were prepared from 2-azidobenzoic acid (5), which
was converted into the corresponding benzoyl chloride
derivative by treatment with thionyl chloride. This was
followed by reaction with the appropriate amine under
phase-transfer catalysis conditions, using tetrabutylam-
monium hydrogen sulfate (TBAHS) as the catalyst and
potassium carbonate as the base, to afford benzamides
6a–g in 80–90% yields (Scheme 1).
Figure 1 Examples of biologically active fused benzodiazepinones
As a result, considerable interest has been generated in the
development of new and more efficient synthetic routes to
SYNTHESIS 2013, 45, 2619–2625
Advanced online publication: 31.07.2013
0
0
3
9
-
7
8
8
1
1
4
3
7
-
2
1
0
X
DOI: 10.1055/s-0033-1339346; Art ID: SS-2013-Z0299-OP
© Georg Thieme Verlag Stuttgart · New York

2620
K. C. Majumdar, S. Ganai
PAPER
6a, R1 = Ph (82%)
Table 1 Optimization of the Intramolecular Azide–Alkyne [3+2]
Cycloadditiona
6b, R1 = 4-MeC6H4 (88%)
6c, R1 = 2,4-Me2C6H3 (85%)
6d, R1 = 4-ClC6H4 (81%)
6e, R1 = 4-MeOC6H4 (80%)
6f, R1 = 4-AcC6H4 (90%)
6g, R1 = 4-MeO2CC6H4 (88%)
O
COOH
O
(i)
NHR1
Ph
O
N
(ii)
N3
Ph
N3
solvent, base
temp
5
N
H
Br
+
N
N3
Scheme 1 Preparation of 2-azidobenzamides 6a–g. Reagents and
conditions: (i) 5, SOCl2, DMF, reflux, 2 h; (ii) R1NH2, TBAHS (cat.),
CH2Cl2, K2CO3 (aq), r.t., 4 h.
N
N
6a
7a
8a
Entry
Solvent
Base
Temp
(°C)
Time
(h)
Yield
(%)b
Compound 6a was selected as a model substrate to opti-
mize the reaction conditions. The reaction at room tem-
perature between azidobenzamide 6a and propargyl
bromide (7a) in N,N-dimethylformamide, using potassi-
um carbonate as the base, did not afford the desired cy-
clized product 8a (Table 1, entry 1). However, on heating
the reaction mixture to 70 °C, product 8a was obtained in
a very satisfactory 89% yield within five hours (Table 1,
entry 2). The reaction using copper(I) iodide as a catalyst
gave a similar yield (85%) of the product (Table 1, entry
3). Using other bases such as cesium carbonate (Cs2CO3),
triethylamine or sodium carbonate did not lead to any im-
provement in the yield of the cyclized product (Table 1,
entries 4–6). No reaction occurred in the absence of a base
(Table 1, entry 7). The use of other solvents including di-
methyl sulfoxide (DMSO), N,N-dimethylacetamide
(DMA), 1,4-dioxane, acetonitrile, toluene and acetone re-
sulted in no improvement in the yield of the cyclized prod-
uct (Table 1, entries 8–13); N,N-dimethylacetamide and
acetonitrile afforded the desired product in moderate 72%
and 50% yields, respectively. Thus, N,N-dimethylform-
amide proved to be the best solvent for this cycloaddition.
1
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMSO
DMA
K2CO3
K2CO3
K2CO3
Cs2CO3
Et3N
r.t.
12
5
5
5
7
5
7
5
5
5
5
5
5
0
2
70 °C
70 °C
70 °C
70 °C
70 °C
70 °C
70 °C
70 °C
70 °C
70 °C
70 °C
reflux
89
85
82
80
74
0
3c
4
5d
6
Na2CO3
–
7
8
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
<50
72
43
50
30
36
9
10
11
12
13
1,4-dioxane
MeCN
toluene
acetone
a All reactions were carried out using 6a (1 equiv), 7a (1.5 equiv) and
base (1.5 equiv).
b Yield of isolated product.
From these control experiments, the optimized conditions
were established as follows: reaction of the N-substituted-
2-azidobenzamide (1 equiv) with the alkyne (1.5 equiv)
and K2CO3 (1.5 equiv) in DMF at 70 °C for five–six
hours. These conditions were then applied in the reactions
of substrates 6b–f and the results are summarized in Table
2.
c CuI (10 mol%) was used as the catalyst.
d Et3N (3 equiv) was used as the base.
product, via formation of the intermediate 1,5-regioiso-
mer 10 (Scheme 2).
In conclusion, we have developed a simple, one-pot ap-
proach for the synthesis of 1,2,3-triazole-fused 1,4-benzo-
diazepinone derivatives with potential biological activity
via intramolecular Huisgen 1,3-dipolar cycloadditions.
The protocol is mild and catalyst-free, occurs at ambient
temperature, and the products are simple to isolate in high
yields.
Two mechanistic paths (A or B) can be considered for the
formation of products 8. Path A involves N-alkylation of
the amide moiety by nucleophilic attack of the benzamide
6 on the propargyl bromide 7, in the presence of the base,
to form intermediate 9. This subsequently undergoes in-
tramolecular azide–alkyne cycloaddition to yield the tri-
azole-fused 1,4-benzodiazepinone 8. The alternative
mechanism, path B, takes place through initial formation
of the bromomethyl-1,2,3-triazole intermediate 11 via an
intermolecular azide–alkyne cycloaddition of propargyl
bromide with the azide group of benzamide 6, followed by
intramolecular coupling of the bromomethyl group of the
triazole with the amide moiety to give product 8. As it is
well known that the reaction is both rapid and exclusively
1,4-directing, it is more likely that the process follows
path A rather than path B. If the reaction had followed
path B, it would have been expected to afford some di-
Silica gel [Rankem (India), 60–120 and 230–400 mesh] was used
for column chromatography. Silica gel G [CDH (India), silica gel
GF-254] was used for TLC. Petroleum ether (PE) refers to the frac-
tion boiling between 60–80 °C. Melting points were determined in
open capillary tubes using a metal bath apparatus from Sunbeam
(India) and are uncorrected. IR spectra were recorded on a Perkin-
Elmer L 120-000A spectrometer. 1H and 13C NMR spectra were re-
corded on Bruker DPX 400 and 300 spectrometers in CDCl3 with
TMS as the internal standard. Mass spectrometry was accomplished
using a Q-TOF Micro™ instrument at the Indian Institute of Chem-
ical Biology (Kolkata). HRMS were recorded on a Q-TOF Micro
and oligomerized by-products, along with the desired YA263 instrument at the Indian Association for the Cultivation of
Science (Kolkata). CHN analyses were recorded on a Perkin-Elmer
2400 series II CHN analyzer at the University of Kalyani.
Synthesis 2013, 45, 2619–2625
© Georg Thieme Verlag Stuttgart · New York

PAPER
Triazole-Fused 1,4-Benzodiazepinones
2-Azidobenzoic Acid (5)
2621
Table 2 Azide–Alkyne [3+2] Cycloaddition Reactions with Various
Substratesa
2-Aminobenzoic acid (10 g, 72.99 mmol) was added to a beaker
containing H2O (45 mL) and concd H2SO4 (15 mL), and cooled to
0 °C. A soln of NaNO2 (6 g, 87.58 mmol) in H2O (30 mL) was add-
ed dropwise at 0 °C over 30 min. Next, an ice-cold soln of NaN3
(5.7 g, 87.58 mmol) in H2O (30 mL) was added with stirring and the
mixture was heated at 80 °C over a period of 30 min. After cooling,
the resulting precipitate was collected, washed with cold H2O (10
mL) and dried under reduced pressure to afford 2-azidobenzoic acid
(5) (7.37 g, 45.21 mmol, 62%). The peaks at 2109 and 2137 cm–1 in
the IR spectrum confirmed the presence of the azide group.
O
O
R1
R1
N
R2
N
H
Br
N
N
N3
R2
6
8
N
Entry 2-Azidobenzamide
Alkyne
Time Product Yield
(h)
(%)b
2-Azido-N-phenylbenzamide (6a); Typical Procedure
1
2
3
4
5
6
7
8
6a (R1 = C6H5)
7a (R2 = H)
5
8a
8b
8c
8d
8e
8f
89
82
86
83
94
90
95
91
2-Azidobenzoic acid (5) (500 mg, 3.07 mmol) was added to a
round-bottomed flask and treated with SOCl2 (2 mL) and DMF (1
drop). The resulting mixture was heated at reflux temperature for 2
h and then evaporated under reduced pressure to yield the corre-
sponding 2-azidobenzoyl chloride. To a stirred soln of the 2-azido-
benzoyl chloride in CH2Cl2 (20 mL) was added a mixture of aniline
(428 mg, 4.60 mmol) and TBAHS (78 mg, 5 mol%) in CH2Cl2 (20
mL). A soln of K2CO3 (635 mg, 4.60 mmol) in H2O (10 mL) was
added dropwise and the mixture was stirred vigorously for 4 h. After
completion of the reaction (monitored by TLC), the organic layer
was separated and washed with H2O (2 × 20 mL) and brine (20 mL),
dried over anhyd Na2SO4 and filtered. The filtrate was concentrated
and the crude residue purified by column chromatography over sil-
ica gel (PE–EtOAc, 1:9) to give compound 6a (598 mg, 2.512
mmol, 82%) as a white solid.
6a (R1 = C6H5)
7b (R2 = Me) 6
6b (R1 = 4-MeC6H4)
7a (R2 = H)
5
6
5
5
5
5
6c (R1 = 2,4-Me2C6H3) 7a (R2 = H)
6d (R1 = 4-ClC6H4) 7a (R2 = H)
6e (R1 = 4-MeOC6H4) 7a (R2 = H)
6f (R1 = 4-MeCOC6H4) 7a (R2 = H)
6g (R1 = 4-MeCO2C6H4)7a (R2 = H)
8g
8h
a Reaction conditions: 2-azidobenzamide 6 (1 equiv), alkyne 7 (1.5
equiv), K2CO3 (1.5 equiv), DMF, 70 °C.
Mp 102–104 °C; Rf = 0.50 (15% EtOAc–PE).
IR (KBr): 3288, 2134, 2098, 1651, 1325, 1302, 754 cm–1.
b Yield of isolated product.
1H NMR (400 MHz, CDCl3): δ = 7.14–7.30 (m, 3 H, ArH), 7.37 (t,
J = 8.0 Hz, 2 H, ArH), 7.46–7.57 (m, 1 H, ArH), 7.67 (d, J = 7.2 Hz,
2 H, ArH), 8.23 (d, J = 8.0 Hz, 1 H, ArH), 9.28 (s, 1 H, NH).
13C NMR (100 MHz, CDCl3): δ = 118.5, 120.6, 124.6, 125.5, 129.1,
132.6, 132.8, 136.9, 138.0, 162.6.
O
R1
N
N3
O
R1
R2
9
N
O
N
N
NHR1
R2
R2
N
+
Br
N3
8
7
6
O
N
O
N
NHR1
R2
NHR1
or
Br
N
Br
N
R2
N
11
N
10
1,5-regioisomer
1,4-regioisomer
Scheme 2 Mechanistic rationalization for the formation of compounds 8
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 2619–2625

2622
K. C. Majumdar, S. Ganai
PAPER
HRMS (ESI): m/z [M + H]+ calcd for C13H11N4O: 239.0933; found:
239.0878.
13C NMR (100 MHz, CDCl3): δ = 55.5, 114.2, 118.4, 122.3, 125.3,
125.4, 131.1, 132.5, 132.6, 136.8, 156.7, 162.4.
MS (ESI): m/z = 269 (100%) [M + H]+.
2-Azido-N-p-tolylbenzamide (6b)
Starting from 2-azidobenzoic acid (5) (500 mg, 3.07 mmol) and p-
toluidine (492 mg, 4.60 mmol), compound 6b was isolated as a
white solid (680 mg, 2.69 mmol, 88%).
Anal. Calcd for C14H12N4O2: C, 62.68; H, 4.51; N, 20.88. Found: C,
62.82; H, 4.54; N, 20.97.
N-(4-Acetylphenyl)-2-azidobenzamide (6f)
Mp 82–84 °C; Rf = 0.52 (15% EtOAc–PE).
IR (KBr): 3332, 2138, 2105, 1644, 1327, 811, 746 cm–1.
1H NMR (400 MHz, CDCl3): δ = 2.47 (s, 3 H, CH3), 7.31 (d, J = 8.4
Hz, 2 H, ArH), 7.37–7.44 (m, 2 H, ArH), 7.69 (d, J = 8.4 Hz, 3 H,
ArH), 8.38 (dd, J = 8.4, 1.6 Hz, 1 H, ArH), 9.38 (s, 1 H, NH).
13C NMR (100 MHz, CDCl3): δ = 21.0, 118.5, 120.5, 125.3, 125.4,
129.5, 132.3, 132.6, 134.2, 135.4, 136.8, 162.6.
MS (ESI): m/z = 253 (100%) [M + H]+.
Starting from 2-azidobenzoic acid (5) (500 mg, 3.07 mmol) and 1-
(4-aminophenyl)ethanone (621 mg, 4.60 mmol), compound 6f was
isolated as a light yellow solid (773 mg, 2.76 mmol, 90%).
Mp 153–155 °C; Rf = 0.47 (15% EtOAc–PE).
IR (KBr): 3330, 2134, 2105, 1671, 1651, 1274, 754 cm–1.
1H NMR (400 MHz, CDCl3): δ = 2.61 (s, 3 H, COCH3), 7.29 (d,
J = 8.0 Hz, 1 H, ArH), 7.33 (t, J = 8.0 Hz, 1 H, ArH), 7.60 (t, J = 8.0
Hz, 1 H, ArH), 7.81 (d, J = 8.0 Hz, 2 H, ArH), 8.00 (d, J = 8.0 Hz,
2 H, ArH), 8.28 (d, J = 8.0 Hz, 1 H, ArH), 9.62 (s, 1 H, NH).
Anal. Calcd for C14H12N4O: C, 66.65; H, 4.79; N, 22.21. Found: C,
66.72; H, 4.61; N, 22.35.
13C NMR (100 MHz, CDCl3): δ = 26.5, 118.5, 119.7, 124.6, 125.6,
129.8, 132.7, 133.1, 133.3, 137.0, 142.3, 162.8, 197.0.
MS (ESI): m/z = 281 (100%) [M + H]+.
2-Azido-N-(2,4-dimethylphenyl)benzamide (6c)
Starting from 2-azidobenzoic acid (5) (500 mg, 3.07 mmol) and 2,4-
dimethylaniline (556 mg, 4.60 mmol), compound 6c was isolated as
a gray solid (693 mg, 2.60 mmol, 85%).
Anal. Calcd for C15H12N4O2: C, 64.28; H, 4.32; N, 19.99. Found: C,
64.41; H, 4.27; N, 20.09.
Mp 134–136 °C; Rf = 0.48 (15% EtOAc–PE).
IR (KBr): 3223, 2133, 2094, 1642, 1299, 754 cm–1.
1H NMR (400 MHz, CDCl3): δ = 2.32 (s, 3 H, CH3), 2.35 (s, 3 H,
CH3), 7.05 (d, J = 8.0 Hz, 2 H, ArH), 7.25–7.32 (m, 2 H, ArH), 7.55
(t, J = 8.0 Hz, 1 H, ArH), 7.90 (d, J = 8.0 Hz, 1 H, ArH), 8.29 (d,
J = 8.0 Hz, 1 H, ArH), 9.15 (s, 1 H, NH).
13C NMR (100 MHz, CDCl3): δ = 18.2, 20.9, 118.4, 123.1, 125.5,
127.3, 131.1, 132.7, 132.8, 134.8, 162.4.
MS (ESI): m/z = 267 (100%) [M + H]+.
Methyl 4-(2-Azidobenzamido)benzoate (6g)
Starting from 2-azidobenzoic acid (5) (500 mg, 3.07 mmol) and
methyl 4-aminobenzoate (695 mg, 4.60 mmol), compound 6g was
isolated as a white solid (799 mg, 2.70 mmol, 88%).
Mp 138–140 °C; Rf = 0.46 (15% EtOAc–PE).
IR (KBr): 3310, 2138, 1708, 1668, 1277, 751 cm–1.
1H NMR (400 MHz, CDCl3): δ = 3.92 (s, 3 H, COOCH3), 7.28 (d,
J = 8.0 Hz, 1 H, ArH), 7.32 (t, J = 8.0 Hz, 1 H, ArH), 7.59 (t, J = 8.0
Hz, 1 H, ArH), 7.78 (d, J = 8.4 Hz, 2 H, ArH), 8.06 (d, J = 8.4 Hz,
2 H, ArH), 8.26 (d, J = 8.0 Hz, 1 H, ArH), 9.57 (s, 1 H, NH).
Anal. Calcd for C15H14N4O: C, 67.65; H, 5.30; N, 21.04. Found: C,
67.81; H, 5.43; N, 20.97.
13C NMR (100 MHz, CDCl3): δ = 52.0, 118.5, 119.6, 124.7, 125.6,
125.9, 130.9, 132.8, 133.2, 136.9, 142.1, 162.7, 166.6.
MS (ESI): m/z = 297 (100%) [M + H]+.
2-Azido-N-(4-chlorophenyl)benzamide (6d)
Starting from 2-azidobenzoic acid (5) (500 mg, 3.07 mmol) and 4-
chloroaniline (586 mg, 4.60 mmol), compound 6d was isolated as a
white solid (676 mg, 2.48 mmol, 81%).
Anal. Calcd for C15H12N4O3: C, 60.81; H, 4.08; N, 18.91. Found: C,
60.78; H, 4.01; N, 19.09.
Mp 150–152 °C; Rf = 0.51 (15% EtOAc–PE).
IR (KBr): 3310, 2125, 2090, 1650, 1286, 820, 756 cm–1.
5-Phenyl-4H-benzo[f][1,2,3]triazolo[1,5-a][1,4]diazepin-6(5H)-
one (8a); Typical Procedure
Benzamide 6a (100 mg, 0.42 mmol) was dissolved in DMF (5 mL)
in a sealable tube and then treated with alkyne 7a (0.06 mL, 0.63
mmol). K2CO3 (87 mg, 0.63 mmol) was added, the tube was stop-
pered, and the mixture was stirred at 70 °C for 5 h. After completion
of the reaction (monitored by TLC), the mixture was allowed to cool
and H2O (10 mL) was added. The mixture was extracted with EtO-
Ac (3 × 20 mL) and the combined organic layer washed with H2O
(4 × 10 mL), dried (Na2SO4), filtered and concentrated. The crude
residue was purified by column chromatography over silica gel
(PE–EtOAc, 4:1) to afford product 8a as a white solid (103 mg,
0.373 mmol, 89%).
1H NMR (400 MHz, CDCl3): δ = 7.27–7.29 (m, 2 H, ArH), 7.34 (d,
J = 8.4 Hz, 2 H, ArH), 7.57 (t, J = 7.6 Hz, 1 H, ArH), 7.65 (d,
J = 8.8 Hz, 2 H, ArH), 8.34 (d, J = 7.6 Hz, 1 H, ArH), 9.34 (s, 1 H,
NH).
13C NMR (100 MHz, CDCl3): δ = 118.5, 121.8, 124.8, 125.4, 129.0,
129.1, 129.5, 132.5, 133.0, 136.5, 136.9, 162.7.
MS (ESI): m/z = 273 (100%) [35Cl, M + H]+, 275 (32%) [37Cl, M +
H]+.
Anal. Calcd for C13H9ClN4O: C, 57.26; H, 3.33; N, 20.55. Found:
C, 57.33; H, 3.19; N, 20.68.
Mp 98–100 °C; Rf = 0.48 (30% EtOAc–PE).
IR (KBr): 1645, 1492, 1399, 757, 698 cm–1.
2-Azido-N-(4-methoxyphenyl)benzamide (6e)
Starting from 2-azidobenzoic acid (5) (500 mg, 3.07 mmol) and 4-
methoxyaniline (566 mg, 4.60 mmol), compound 6e was isolated as
a gray solid (658 mg, 2.45 mmol, 80%).
1H NMR (400 MHz, CDCl3): δ = 4.84 (s, 2 H, NCH2), 7.21–7.46
(m, 5 H, ArH), 7.62 (t, J = 7.6 Hz, 1 H, ArH), 7.74–7.77 (m, 2 H,
ArH, one singlet is overlapped), 8.06 (d, J = 8.0 Hz, 1 H, ArH), 8.11
(d, J = 7.6 Hz, 1 H, ArH).
13C NMR (100 MHz, CDCl3): δ = 43.3, 120.1, 122.6, 126.2, 127.1,
127.8, 128.8, 129.2, 130.7, 132.7, 133.2, 134.6, 143.5, 165.9.
Mp 130–132 °C; Rf = 0.50 (15% EtOAc–PE).
IR (KBr): 3343, 2140, 2104, 1637, 1248, 1029, 822 cm–1.
1H NMR (400 MHz, CDCl3): δ = 3.81 (s, 3 H, OCH3), 6.90 (d,
J = 8.8 Hz, 2 H, ArH), 7.23–7.28 (m, 2 H, ArH), 7.53 (t, J = 8.0 Hz,
1 H, ArH), 7.57 (d, J = 8.8 Hz, 2 H, ArH), 8.22 (d, J = 8.0 Hz, 1 H,
ArH), 9.18 (s, 1 H, NH).
HRMS (ESI): m/z [M + H]+ calcd for C16H13N4O: 277.1089; found
277.1101.
Synthesis 2013, 45, 2619–2625
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Triazole-Fused 1,4-Benzodiazepinones
2623
3-Methyl-5-phenyl-4H-benzo[f][1,2,3]triazolo[1,5-a][1,4]diaze-
pin-6(5H)-one (8b)
Starting from compound 6a (100 mg, 0.42 mmol) and alkyne 7b
(0.07 mL, 0.63 mmol), compound 8b was isolated as a white solid
(100 mg, 0.34 mmol, 82%).
1H NMR (400 MHz, CDCl3): δ = 4.82 (s, 2 H, NCH2), 7.20 (d,
J = 8.8 Hz, 2 H, ArH), 7.40 (d, J = 8.2 Hz, 2 H, ArH), 7.61 (t,
J = 8.0 Hz, 1 H, ArH), 7.75 (d, J = 7.6 Hz, 1 H, ArH), 7.79 (s, 1 H,
ArH), 8.05 (d, J = 8.2 Hz, 1 H, ArH), 8.12 (d, J = 8.2 Hz, 1 H, ArH).
13C NMR (100 MHz, CDCl3): δ = 43.2, 122.7, 127.2, 127.6, 129.3,
129.8, 130.7, 132.7, 133.4, 133.5, 134.4, 140.9, 165.9.
Mp 100–102 °C; Rf = 0.50 (30% EtOAc–PE).
IR (KBr): 1642, 1491, 1407, 755 cm–1.
1H NMR (400 MHz, CDCl3): δ = 2.38 (s, 3 H, CH3), 4.75 (s, 2 H,
NCH2), 7.23–7.25 (m, 2 H, ArH), 7.35 (t, J = 7.2 Hz, 1 H, ArH),
7.45 (t, J = 7.2 Hz, 2 H, ArH), 7.59 (t, J = 7.6 Hz, 1 H, ArH), 7.73
(t, J = 7.6 Hz, 1 H, ArH), 8.04 (d, J = 8.4 Hz, 1 H, ArH), 8.15 (d,
J = 7.6 Hz, 1 H, ArH).
13C NMR (100 MHz, CDCl3): δ = 10.1, 43.1, 122.4, 126.2, 127.2,
127.8, 129.0, 129.6, 131.6, 132.6, 133.1, 133.2, 139.2, 142.7, 166.1.
MS (ESI): m/z = 291 (100%) [M + H]+.
MS (ESI): m/z = 311 (100%) [35Cl, M + H]+, 313 (32%) [37Cl, M +
H]+.
Anal. Calcd for C16H11ClN4O: C, 61.84; H, 3.57; N, 18.03. Found:
C, 61.96; H, 3.66; N, 17.98.
5-(4-Methoxyphenyl)-4H-benzo[f][1,2,3]triazolo[1,5-a][1,4]di-
azepin-6(5H)-one (8f)
Starting from compound 6e (100 mg, 0.373 mmol) and alkyne 7a
(0.05 mL, 0.560 mmol), compound 8f was isolated as a white solid
(103 mg, 0.336 mmol, 90%).
Anal. Calcd for C17H14N4O: C, 70.33; H, 4.86; N, 19.30. Found: C,
70.45; H, 4.92; N, 19.41.
Mp 162–164 °C; Rf = 0.45 (30% EtOAc–PE).
IR (KBr): 1654, 1509, 1402, 1257, 756 cm–1.
5-p-Tolyl-4H-benzo[f][1,2,3]triazolo[1,5-a][1,4]diazepin-6(5H)-
one (8c)
Starting from compound 6b (100 mg, 0.397 mmol) and alkyne 7a
(0.06 mL, 0.595 mmol), compound 8c was isolated as a white solid
(99 mg, 0.341 mmol, 86%).
1H NMR (200 MHz, CDCl3): δ = 3.83 (s, 3 H, OCH3), 4.80 (s, 2 H,
NCH2), 6.94 (d, J = 9.2 Hz, 2 H, ArH), 7.15 (d, J = 9.2 Hz, 2 H,
ArH), 7.63 (t, J = 8.8 Hz, 1 H, ArH), 7.73–7.79 (m, 2 H, ArH one
singlet is overlapped), 8.06 (d, J = 8.8 Hz, 1 H, ArH), 8.17 (d,
J = 8.8 Hz, 1 H, ArH).
13C NMR (50 MHz, CDCl3): δ = 43.6, 55.6, 114.8, 122.6, 127.4,
129.2, 130.6, 132.6, 132.7, 133.1, 134.7, 135.4, 140.1, 158.9, 166.2.
MS (ESI): m/z = 307 (100%) [M + H]+.
Mp 162–164 °C; Rf = 0.51 (30% EtOAc–PE).
IR (KBr): 1659, 1398, 1332, 759 cm–1.
1H NMR (200 MHz, CDCl3): δ = 2.38 (s, 3 H, CH3), 4.82 (s, 2 H,
NCH2), 7.13 (d, J = 7.6 Hz, 2 H, ArH), 7.24 (d, J = 8.0 Hz, 2 H,
ArH), 7.62 (t, J = 7.6 Hz, 1 H, ArH), 7.74 (s, 1 H, ArH), 7.76 (d,
J = 7.6 Hz, 1 H, ArH), 8.06 (d, J = 8.0 Hz, 1 H, ArH), 8.16 (d,
J = 7.6 Hz, 1 H, ArH).
13C NMR (50 MHz, CDCl3): δ = 21.1, 43.4, 122.6, 126.0, 127.7,
129.2, 130.2, 130.6, 132.7, 132.8, 133.1, 134.9, 137.9, 140.1, 166.0.
MS (ESI): m/z = 291 (100%) [M + H]+.
Anal. Calcd for C17H14N4O2: C, 66.66; H, 4.61; N, 18.29. Found: C,
66.81; H, 4.75; N, 18.32.
5-(4-Acetylphenyl)-4H-benzo[f][1,2,3]triazolo[1,5-a][1,4]diaze-
pin-6(5H)-one (8g)
Starting from compound 6f (100 mg, 0.357 mmol) and alkyne 7a
(0.05 mL, 0.535 mmol), compound 8g was isolated as a white solid
(108 mg, 0.339 mmol, 95%).
Anal. Calcd for C17H14N4O: C, 70.33; H, 4.86; N, 19.30. Found: C,
70.49; H, 4.94; N, 19.27.
Mp 178–180 °C; Rf = 0.46 (30% EtOAc–PE).
IR (KBr): 1686, 1666, 1600, 1380, 1270, 752 cm–1.
5-(2,4-Dimethylphenyl)-4H-benzo[f][1,2,3]triazolo[1,5-
a][1,4]diazepin-6(5H)-one (8d)
Starting from compound 6c (100 mg, 0.376 mmol) and alkyne 7a
(0.06 mL, 0.564 mmol), compound 8d was isolated as a white solid
(95 mg, 0.31 mmol, 83%).
1H NMR (400 MHz, CDCl3): δ = 2.62 (s, 3 H, COCH3), 4.90 (s, 2
H, NCH2, ArH), 7.41 (d, J = 8.2 Hz, 2 H, ArH), 7.64 (t, J = 8.0 Hz,
1 H, ArH), 7.77 (s, 1 H, ArH), 7.79 (d, J = 7.6 Hz, 1 H, ArH), 8.03
(dd, J = 8.7, 0.8 Hz, 2 H, ArH), 8.07 (d, J = 8.4 Hz, 1 H, ArH), 8.18
(dd, J = 8.4, 0.8 Hz, 1 H, ArH).
13C NMR (100 MHz, CDCl3): δ = 26.7, 43.0, 122.7, 126.0, 126.8,
129.3, 129.7, 130.8, 132.6, 132.7, 133.5, 134.2, 136.0, 146.3, 165.8,
196.9.
Mp 130–132 °C; Rf = 0.48 (30% EtOAc–PE).
IR (KBr): 1660, 1489, 1396, 1333, 757 cm–1.
1H NMR (400 MHz, CDCl3): δ = 2.04 (s, 3 H, CH3), 2.36 (s, 3 H,
CH3), 4.75 (s, 2 H, NCH2), 6.98 (s, 1 H, ArH), 7.12 (d, J = 8.4 Hz,
2 H, ArH), 7.691 (td, J = 8.0, 1.2 Hz, 1 H, ArH), 7.694 (s, 1 H,
ArH), 7.78 (td, J = 8.0, 1.2 Hz, 1 H, ArH), 8.06 (d, J = 8.2 Hz, 1 H,
ArH), 8.17 (d, J = 8.0 Hz, 1 H, ArH).
MS (ESI): m/z = 319 (100%) [M + H]+.
Anal. Calcd for C18H14N4O2: C, 67.91; H, 4.43; N, 17.60. Found: C,
68.01; H, 4.52; N, 17.67.
Methyl 4-{6-Oxo-4H-benzo[f][1,2,3]triazolo[1,5-a][1,4]diaze-
pin-5(6H)-yl}benzoate (8h)
Starting from compound 6g (100 mg, 0.337 mmol) and alkyne 7a
(0.05 mL, 0.506 mmol), compound 8h was isolated as a white solid
(103 mg, 0.308 mmol, 91%).
13C NMR (100 MHz, CDCl3): δ = 17.9, 21.1, 43.2, 122.7, 126.5,
127.3, 128.2, 129.2, 130.6, 132.0, 132.6, 133.2, 134.9, 138.9, 139.5,
165.6.
MS (ESI): m/z = 305 (100%) [M + H]+.
Anal. Calcd for C18H16N4O: C, 71.04; H, 5.30; N, 18.41. Found: C,
71.22; H, 5.38; N, 18.52.
Mp 122–124 °C; Rf = 0.45 (30% EtOAc–PE).
IR (KBr): 1719, 1647, 1604, 1385, 1284, 754 cm–1.
5-(4-Chlorophenyl)-4H-benzo[f][1,2,3]triazolo[1,5-a][1,4]diaz-
epin-6(5H)-one (8e)
Starting from compound 6d (100 mg, 0.367 mmol) and alkyne 7a
(0.05 mL, 0.551 mmol), compound 8e was isolated as a white solid
(107 mg, 0.345 mmol, 94%).
1H NMR (400 MHz, CDCl3): δ = 3.94 (s, 3 H, COOCH3), 4.89 (s, 2
H, NCH2), 7.38 (dd, J = 8.4, 1.6 Hz, 2 H, ArH), 7.64 (t, J = 7.6 Hz,
1 H, ArH), 7.79 (td, J = 7.6, 1.2 Hz, 2 H, ArH), 8.08–8.18 (m, 4 H,
ArH).
13C NMR (100 MHz, CDCl3): δ = 43.1, 52.4, 122.8, 125.9, 127.1,
129.3, 129.4, 130.8, 131.0, 132.7, 132.8, 133.7, 134.2, 146.2, 165.8,
166.1.
Mp 94–96 °C; Rf = 0.49 (30% EtOAc–PE).
IR (KBr): 1647, 1492, 1408, 754 cm–1.
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 2619–2625

2624
K. C. Majumdar, S. Ganai
PAPER
MS (ESI): m/z = 335 (100%) [M + H]+.
(7) Donohue, A. R.; Dannals, R. F. Tetrahedron Lett. 2009, 50,
7271.
Anal. Calcd for C18H14N4O3: C, 64.66; H, 4.22; N, 16.76. Found: C,
64.54; H, 4.17; N, 16.88.
(8) (a) Basolo, L.; Beccalli, E. M.; Borsini, E.; Gianluigi
Broggini, G.; Maisaa Khansaa, M.; Rigamonti, M. Eur. J.
Org. Chem. 2010, 1694. (b) Patel, N.; Chambers, C. S.;
Hemming, K. Synlett 2009, 3043. (c) Broggini, G.; Marchi,
I. D.; Martinelli, M.; Paladino, G.; Pilati, T.; Terraneo, A.
Synthesis 2005, 2246. (d) Hunkeler, W. Chimia 1993, 47,
141.
Acknowledgment
We thank CSIR (New Delhi) and UGC (New Delhi) for financial
assistance. S.G. is grateful to CSIR (New Delhi) for his research fel-
lowship and K.C.M. is thankful to UGC (New Delhi) for a UGC
Emeritus fellowship. We also thank DST (New Delhi) for providing
FT-IR and Bruker NMR (400 MHz) spectrometers, a UV/Vis spec-
trophotometer and a Perkin-Elmer CHN Analyzer.
(9) (a) Sahoo, S.; Veliyath, S. K.; Mahendra Kumar, C. B. Int. J.
Res. Pharm. Sci. 2012, 3, 326. (b) Majumdar, K. C.; Ray, K.
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Anderson, D. J.; Barbachyn, M. R.; Emmert, D. E.; Garmon,
S. A.; Graber, D. R.; Grege, K. C.; Hester, J. B.; Hutchinson,
D. K.; Morris, J.; Reischer, R. J.; Ford, C. W.; Zurenko, G.
E.; Hamel, J. C.; Schaadt, R. D.; Stapert, D.; Yagi, B. H.
J. Med. Chem. 2000, 43, 953. (d) Palhagen, S.; Canger, R.;
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Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.SnuIomprifgtooatrinSugpIoi
nnfomartit
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Triazole-Fused 1,4-Benzodiazepinones
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Synthesis 2013, 45, 2619–2625