Trichloroisocyanuric Acid Mediated High-Yielding Synthesis of N -Acylbenzotriazoles under Mild Reaction Conditions

Article abstract of DOI:10.1055/s-0037-1611724

N -Acylbenzotriazoles are achieved in good yields from the corresponding carboxylic acids by using only 0.35 equivalent of trichloroisocyanuric acid and 1.2 equivalents of PPh ₃. The salient features of the developed reaction path include an ec

Full text of DOI:10.1055/s-0037-1611724

SYNTHESIS
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0
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© Georg Thieme Verlag Stuttgart · New York
2019, 51, A–H
paper
A
de
M. Singh et al.
Paper
Synthesis
Trichloroisocyanuric Acid Mediated High-Yielding Synthesis of
N-Acylbenzotriazoles under Mild Reaction Conditions
Mala Singh
Anoop S. Singh
O
Nidhi Mishra
3
N
N
PPh3
Cl
Anand K. Agrahari
Vinod K. Tiwari*
O
O
N
0
0
0
0-
0
0
0
1-9
2
4
4-8
8
8
9
N
N
O
N
O
N
H
OH
+
Department of Chemistry, Institute of Science, Banaras Hindu
University, Varanasi 221005, India
tiwari_chem@yahoo.co.in
N
N
31 examples
yields up to 92%
Vinod.Tiwari@bhu.ac.in
This manuscript is dedicated to the (Late) Prof. Alan R. Katritzky
for his contributions to benzotriazole chemistry.
Received: 23.11.2018
Accepted after revision: 10.01.2019
Published online: 20.02.2019
the respective halides by reacting trichloroisocyanuric acid
with PPh3 in refluxing anhydrous acetonitrile.24 This meth-
od was further explored by Jang et al. to develop an alterna-
tive method for secondary amides.25 Later on, Rodrigues et
al. reported a one-pot conversion of carboxylic acids to the
corresponding amides and esters by reacting trichloroiso-
cyanuric acid and triphenylphosphine in the presence of a
carboxylic acid followed by the addition of amines or alco-
hols, respectively, in the presence of triethylamine.26 How-
ever, the method was surprisingly not explored with ben-
zotriazole as amine. Recently, we have developed a new ap-
proach for the synthesis of N-acylbenzotriazoles by reacting
DOI: 10.1055/s-0037-1611724; Art ID: ss-2018-z0786-op
Abstract N-Acylbenzotriazoles are achieved in good yields from the
corresponding carboxylic acids by using only 0.35 equivalent of tri-
chloroisocyanuric acid and 1.2 equivalents of PPh3. The salient features
of the developed reaction path include an economic, facile, base-free,
and equally useful method in milligram to gram scale.
Key words N-acylbenzotriazole, coupling reaction, trichloroiso-
cyanuric acid
27
The interesting chemical behavior of benzotriazole moi-
ety makes it one of the most successful synthetic tools in
organic synthesis.1 It can be easily introduced to any mole-
cule and can be substituted even more easily by suitable
groups. It is compatible with many functional groups and
shows high stability in various chemical environments. Be-
sides this, easy availability, low cost, and nontoxic nature of
benzotriazole moiety enhance the economic and environ-
ment friendly nature of chemical reactions employing ben-
zotriazole methodology.1–3 Recently, N-acylbenzotriazole
derivatives have emerged as an alternative to acid chlorides
in N-, O-, S-, and C-acylations under mild and neutral con-
ditions for the synthesis of amides, acid azides, peptides,
oxazolines, esters, diketones, and thiazolines.4–17 Further-
more, long time stability on storage, moisture insensitivity,
and physical state (generally solid) also make it a suitable
substitute of acid chlorides for the common laboratory re-
actions.18 Various synthetic methods are well documented
in literature to convert carboxylic acids into N-acylben-
zotriazoles, such as, the use of thionyl chloride with 3.5
equivalents of 1H-benzotriazole (BtH); BtH with EDC or
DCC; 1-(methanesulfonyl)benzotriazole/Et3N; BtH with
I2/PPh3 or TCT/PPh3; or BtH with tosyl chloride and a base19–23
(Scheme 1). Hiegel et al. successfully converted alcohols to
carboxylic acid with BtH-NBS/PPh3 and furthermore, the
method has been successfully extended with the use of
BtH-I2/PPh3 for the synthesis of glycoconjugated N-acylben-
zotriazoles.28 Very recently, we explored 2,2′-dipyridyl di-
sulfide/PPh3 with BtH for an easy access of N-acylbenzotri-
azoles from the corresponding carboxylic acids (Scheme
1).29
O
Previous methods:
O
(a) BtH/SOCl2 (4:1), DCM
(b) NBS, PPh3, BtH, DCM
(c) I2, PPh3, BtH, Et3N, DCM
(d) BtSO2R, Et3N,THF, reflux
(e) EDC/or DCC, BtH, DCM
(f) PySSPy, PPh3, BtH, DCM
N
N
OH
N
This Work:
alkyl, aryl,
glycosyl
TClCA, PPh3, BtH, DCM, r.t
Scheme 1 Previous and present work form our group to convert car-
boxylic acid into N-acylbenzotriazoles
All these reported methods have one or more limita-
tions, such as harsh conditions, use of expensive reagents,
and low reaction yields. Thus, in continuation to these ef-
forts, herein we introduce the use of trichloroisocyanuric
acid/PPh3 as a suitable reagent for the synthesis N-acylbenzo-
triazoles.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

B
M. Singh et al.
Paper
Synthesis
To establish trichloroisocyanuric acid (TClCA)/triphenyl-
phosphine (PPh3) as a reagent for the transformation of car-
boxylic acids into corresponding N-acylbenzotriazoles, a
prototype reaction was conducted with the optimized con-
ditions of our previously reported work:27 Reaction of 1.0
equivalent of benzoic acid with 1.2 equivalents of 1H-ben-
zotriazole in the presence of 1.2 equivalents of TClCA and
1.2 equivalents of PPh3 in anhydrous dichloromethane. The
mixture was stirred for 10 hours at room temperature and
the resultant mass was purified by column chromatography
(SiO2) to afford N-benzoylbenzotriazole (2a) in 92% yield
(Scheme 2).
Table 1 Reaction Optimization Studya
O
O
TCICA (x equiv), PPh3 (x equiv)
OH
N
N
BtH (x equiv), anhyd solvent
N
1a
2a
Entry
TClCA (equiv) PPh3 (equiv) BtH (equiv) Solventb
Yield (%)c
1
2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.0
1.5
2.0
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.0
1.5
2.0
0.8
1.0
1.0
1.0
1.0
1.0
1.0
1.0
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DMF
THF
91
90
91
73
92
90
79
87
91
92
80
92
60
trace
70
73
91
36
1.0
3
0.5
4
0.25
0.4
O
5
O
TClCA (1.2 equiv), PPh3 (1.2 equiv)
BtH (1.2 equiv)
6
0.35
0.3
N
N
OH
DCM, 0 °C
N
7
1a
2a
8
0.35
0.35
0.35
0.35
0.35
0.35
0.35
0.35
0.35
0.35
0.35
Scheme 2 Prototype reaction for the synthesis of N-benzoylbenzotri-
azole (2a)
9
10
11
12
13
14
15
16
17
18
After establishing TClCA/PPh3 as a reagent for the syn-
thesis of N-acylbenzotriazoles, we intended to find out op-
timized conditions for high product yields with minimal re-
agent amounts. For this, investigation was started by cali-
brating the amount of trichloroisocyanuric acid and found
that 0.35 equivalent affords high yields of N-acylbenzotri-
azoles. Then the loading of PPh3/BtH was also checked and
it was observed that there is no change in yields above 1.0
equivalent amount. Cyanuric acid and triphenylphosphine
oxide were produced as side products during the course of
reaction, which were easily removed from the target prod-
uct N-acylbenzotriazole during column chromatography
step. Further, the HCl formed in the reaction does not create
any problem and the reaction is base-free as evidenced
from experimental procedure. The resulting benzotriazole
derivatives were found to be sufficiently stable during the
course of reaction. Finally, we optimized the reaction sol-
vent and found that dichloromethane and chloroform go
equally well for the above reaction (Table 1).
benzene
toluene
CHCl3
DMSO
a Benzoic acid: 1.0 mmol.
b Anhydrous solvents.
c Yields reported after purification by column chromatography (SiO2).
After optimization, the reaction was generalized for var-
ious carboxylic acids by varying the length of aliphatic ac-
ids, taking different substitutions on aromatic ring of aro-
matic acids, and changing heterocyclic acids, amino acids,
or sugar acids. In all the cases, the yields were found not to
fluctuate much. This shows that TClCA/PPh3 reagent prefers
to attack at the carboxylic acid group irrespective of the
moiety attached to it. The crude reaction mass was purified
by 240–400 mesh column chromatography with gradient
mixture (5–15%) of ethyl acetate/n-hexane and the corre-
sponding N-acylbenzotriazoles 227–36 (Scheme 3) were
characterized by 1H and 13C NMR spectroscopic studies.
Figure 1 31P NMR monitoring of the progress of the reaction between
benzoic acid and BtH in CDCl3
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

C
M. Singh et al.
Paper
Synthesis
For the quantitative generalization of this reaction, the
above optimized reaction conditions were applied for a re-
action of 5.0 g of benzoic acid. Reaction went well and the
final product N-benzoylbenzotriazole (2a) was produced in
80% yield (Scheme 4).
A possible mechanism for the reaction has been depict-
ed in Scheme 5 in which, first of all, triphenylphosphine re-
acts with trichloroisocyanuric acid to give the intermediate
A. Further, intermediate A reacts with carboxylic acid 1 to
give the corresponding acyloxyphosphonium ion B20 with
O
O
TClCA (0.35 equiv), PPh3 (1.2 equiv)
BtH (1.0 equiv), anhyd DCM, r.t.
N
N
OH
1a–ae
N
2a–ae
O
O
Cl
O
O
Cl
N
N
N
N
N
N
N
N
N
N
N
N
Cl
F
2a (92%)
2b (73%)
2c (82%)
2d (75%)
O
O
F
O
O
N
N
N
N
N
N
N
N
N
N
N
N
F
F
2f (80%)
2e (85%)
2g (70%)
2h (84%)
O
O
O
O
N
N
N
N
N
N
N
10
N
N
N
N
N
Br
CF3
Br
I
2j (75%)
2l (84%)
2k(70%)
2i (61%)
O
O
O
N
O
O
N
N
N
N
N
N
N
N
N
N
N
HO
2o (81%)
O
2n (69%)
2p (85%)
2m (70%)
O
O
CN
O
Cl
O
O
NO2
O
N
Cl
N
N
N
N
N
N
N
N
N
N
N
2t (64%)
2s (60%)
2r (74%)
2q (82%)
O
N
O
O
O
N
N
N
N
N
N
N
N
N
N
N
O
2v (78%)
Ph
2u (80%)
2w (81%)
2x(78%)
O
O
O
O
N
O
N
O
N
O
N
N
7
7
N
N
N
N
N
N
N
2ab (81%)
2z(79%)
2aa (83%)
2y (76%)
O
O
O
O
O
N
O
O
O
O
O
O
N
N
N
N
N
N
N
O
N
O
O
O
O
2ad (78%)
2ae (75%)
2ac (69%)
Scheme 3 Synthesis of N-acylbenzotriazoles 2a–ae from acids using TCICA/PPh3. Reagents and conditions: carboxylic acids 1a–ae (1.0 equiv), TClCA
(0.35 equiv), PPh3 (1.2 equiv), benzotriazole (1.0 equiv). Yields shown are after flash column chromatography (SiO2).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

D
M. Singh et al.
Paper
Synthesis
the loss of 1,3,5-triazinane-2,4,6-trione. The intermediate B
reacts with benzotriazole to give the final product 2.
N-acylbenzotriazoles and their derivatives are valuable in-
termediates useful in the synthesis of diverse range of bio-
logically relevant molecules.37–41
O
O
TClCA (3.327 g), PPh3 (12.884 g)
BtH (4.876 g), anhyd DCM
OH
N
N
All solvents and reagents used were of pure analytical grade. TLC was
performed on precoated aluminum plates and displayed either with
ultraviolet lamp (λmax = 254 nm) or I2 vapor as color reagent. Column
chromatography was carried out on silica gel (230–400 mesh, Merck)
by using distilled n-hexane and EtOAc, and solvents were evaporated
at <50 °C under vacuum. NMR (1H and 13C) spectra were recorded at
500 MHz (13C) and 125 MHz (1H), respectively. Chemical shifts given
in ppm downfield from internal TMS; J values in hertz (Hz).
N
1a (5.0 g)
2a (7.31 g, 80%)
Scheme 4 Reaction executed in gram-scale
For determining the mechanism and intermediate, a 31
P
NMR study was carried out. At first, a blank PPh3 sample
was taken in CDCl3 and a peak was obtained at δ = –4.76,
which corresponds to the presence of PPh3 (t = 0). After
adding TClCA and stirring the reaction mixture for five min-
utes, new peaks appeared at δ = 65.08 and 29.73 and a trip-
let at δ = 25.24 in the 31P NMR spectrum, which corre-
sponds to P–Cl, P–O, and P–N bond, respectively; while
complete disappearance of PPh3 peak at δ = –4.76 indicates
the formation of intermediate A (Figure 1). In the same re-
action mixture, when benzoic acid was added and the stir-
ring was allowed for further 10 minutes a single peak ap-
peared at δ = 29.81 (corresponding to O=PPh3). After 30
minutes stirring of the same reaction mixture with ben-
zotriazole, the 31P NMR spectrum showed no change in
peaks. Thus, by 31P NMR study it was justified that the reac-
tion may go through formation of intermediate A as shown
in Scheme 5.
(1H-1,2,3-Benzo[d][1,2,3]triazol-1-yl)(phenyl)methanone (2a);27
Typical Procedure
Trichloroisocyanuric acid (0.640 g, 2.76 mmol, 0.35 equiv) and PPh3
(0.640 g, 2.76 mmol, 1.2 equiv) were taken in anhyd DCM in a round-
bottomed flask. After stirring for 10 min, benzoic acid (1a; 0.962 g,
7.89 mmol, 1.0 equiv) was added and the reaction mixture was
stirred for an additional 30 min. Then, benzoic acid (0.939 g, 7.89
mmol, 1.0 equiv) was added and the resulting mixture was allowed to
stir for 4–5 h. After completion of the reaction (monitored by TLC),
the reaction mass was concentrated under reduced pressure until dry.
Purification using flash column chromatography (SiO2) using gradient
mixtures of EtOAc and n-hexane gave 2a in pure form; white solid;
yield: 1.62 g (92%, 7.29 mmol) mp 111–114 °C; Rf = 0.6 (5% EtOAc/n-
hexane).
1H NMR (500 MHz, CDCl3): δ = 8.29 (d, J = 8.5 Hz, 1 H), 8.12–8.06 (m, 3
H), 7.60–7.59 (m, 2 H), 7.50–7.43 (m, 3 H).
13C NMR (125 MHz, CDCl3): δ = 166.6, 145.7, 133.6, 132.2, 131.6,
131.4, 130.3, 128.3, 126.2, 120.1, 114.7.
O
O
O
OH
Cl
Cl
O
(1H-Benzo[d][1,2,3]triazol-1-yl)(2-chlorophenyl)methanone
1
N
N
3 PPh3
(2b)27
+
3
N
N
PPh3
Cl
O
N
H
White solid; yield: 0.120 g (73%); mp 80–82 °C; Rf = 0.5 (5% EtOAc/n-
hexane).
1H NMR (500 MHz, CDCl3): δ = 8.32 (d, J = 7.5 Hz, 1 H), 8.07 (d, J = 8.0
Hz, 1 H), 7.65 (t, J = 7.5 Hz, 1 H), 7.57 (d, J = 7.5 Hz, 1 H), 7.49–7.45 (m,
3 H), 7.38–7.35 (m, 1 H).
O
N
O
O
O
N
Cl
HN
NH
A
O
13C NMR (125 MHz, CDCl3): δ = 165.8, 146.2, 132.8, 132.5, 132.3,
131.2, 130.6, 130.1, 130.0, 126.7, 126.6, 120.3, 114.4.
H
N
O
N
O
N
N
PPh3
N
N
O
(1H-Benzo[d][1,2,3]triazol-1-yl)(3-chlorophenyl)methanone
(2c)29
Cl
Ph3P=O
B
White solid; yield: 0.134 g (82%); mp 120–123 °C; Rf = 0.5 (5%
EtOAc/n-hexane).
2
1H NMR (500 MHz, CDCl3): δ = 8.39 (d, J = 7.5 Hz, 1 H), 8.22–8.18 (m, 2
H), 8.13 (d, J = 7.5 Hz, 1 H), 7.73 (t, J = 7.0 Hz, 1 H), 7.67 (d, J = 8.5 Hz, 1
H), 7.59–7.51 (m, 2 H).
Scheme 5 Proposed mechanism for the synthesis of N-acylbenzotri-
azoles 2
13C NMR (125 MHz, CDCl3): δ = 165.3, 145.7, 134.6, 133.6, 133.0,
132.1, 131.5, 130.6, 129.8, 129.7, 126.5, 120.3, 114.4.
In brief, we have established an effective methodology
for the synthesis of N-acylbenzotriazoles by using less toxic
environment and under mild reaction conditions. The de-
veloped method works well in gram scale and furnishes
good yields of N-acylbenzotriazoles up to 92% at room tem-
perature. Reaction shows compatibility with a broad range
of acids including aliphatic, aromatic, and sugar acids. The
(1H-Benzo[d][1,2,3]triazol-1-yl)(4-chlorophenyl)methanone
(2d)27
White solid; yield: 0.123 g (75%); mp 136–138 °C; Rf = 0.5 (10%
EtOAc/n-hexane)
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M. Singh et al.
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Synthesis
1H NMR (500 MHz, CDCl3): δ = 8.39 (d, J = 8.5 Hz, 1 H), 8.22–8.17 (m, 3
H), 7.72 (t, J = 7.5 Hz, 1 H), 7.58–7.55 (m, 3 H).
13C NMR (125 MHz, CDCl3): δ = 165.7, 145.8, 140.5, 133.2, 132.3,
(1H-Benzo[d][1,2,3]triazol-1-yl)(3-bromophenyl)methanone (2j)30
White solid; yield: 0.113 g (75%); mp 157–160 °C; Rf = 0.6 (5%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.36–8.33 (m, 2 H), 8.17–8.14 (m, 2 H),
7.79 (d, J = 7.5 Hz, 1 H), 7.70 (t, J = 7.5 Hz, 1 H), 7.54 (t, J = 8.0 Hz, 1 H),
7.44 (d, J = 7.5 Hz, 1 H).
130.6, 129.8, 128.9, 126.5, 120.3, 114.8.
(1H-Benzo[d][1,2,3]triazol-1-yl)(o-tolyl)methanone (2e)27
13C NMR (125 MHz, CDCl3): δ = 165.3, 145.8, 136.6, 134.4, 133.3,
White solid; yield: 0.148 g (85%); mp 87–89 °C; Rf = 0.5 (5% EtOAc/n-
hexane).
132.2, 130.7, 130.3, 130.0, 126.6, 122.5, 120.3, 114.8.
1H NMR (500 MHz, CDCl3): δ = 8.38 (d, J = 8.5 Hz, 1 H), 8.14 (d, J = 8.5
Hz, 1 H), 7.69 (t, J = 7.5 Hz, 1 H), 7.62 (d, J = 7.5 Hz, 1 H), 7.54–7.47 (m,
2 H), 7.36–7.32 (m, 2 H), 2.43 (s, 3 H).
(1H-Benzo[d][1,2,3]triazol-1-yl)(4-bromophenyl)methanone
(2k)31
13C NMR (125 MHz, CDCl3): δ = 168.3, 146.2, 138.0, 132.3, 131.9,
131.8, 131.1, 130.5, 126.5, 125.5, 120.3, 114.6, 20.1.
Light yellow solid; yield: 0.105 g (70%); mp 134–137 °C; Rf = 0.5 (5%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.36 (d, J = 8.0 Hz, 1 H), 8.16 (d, J = 8.5
Hz, 1 H), 8.11 (d, J = 8.5 Hz, 2 H), 7.72–7.69 (m, 3 H), 7.55 (t, J = 7.5 Hz,
1 H).
(1H-Benzo[d][1,2,3]triazol-1-yl)(p-tolyl)methanone (2f)27
White crystalline solid; yield: 0.139 g (80%); mp 121–124 °C; Rf = 0.4
(5% EtOAc/n-hexane).
13C NMR (125 MHz, CDCl3): δ = 165.8, 145.8, 133.2, 132.3, 131.9,
1H NMR (500 MHz, CDCl3): δ = 8.39 (d, J = 7.5 Hz, 1 H), 8.18–8.14 (m, 3
H), 7.70 (t, J = 7.5 Hz, 1 H), 7.55 (t, J = 7.5 Hz, 1 H), 7.39 (d, J = 7.5 Hz, 2
H), 2.49 (s, 3 H).
130.6, 130.2, 129.2, 126.5, 120.3, 114.8.
1-(1H-Benzo[d][1,2,3]triazol-1-yl)dodecan-1-one (2l)27
13C NMR (125 MHz, CDCl3): δ = 166.5, 145.7, 144.8, 132.4, 131.9,
White solid; yield: 0.126 g (84%); mp 45–46 °C; Rf = 0.5 (5% EtOAc/n-
hexane).
130.2, 129.2, 128.6, 126.2, 120.1, 114.8, 21.8.
1H NMR (500 MHz, CDCl3): δ = 8.21 (d, J = 8.5 Hz, 1 H), 8.04 (d, J = 9.0
Hz, 1 H), 7.56 (t, J = 7.5 Hz, 1 H), 7.43–7.40 (m, 1 H), 3.35–3.32 (m, 2
H), 1.85–1.79 (m, 2 H), 1.41–1.36 (m, 2 H), 1.31–1.18 (m, 14 H), 0.79
(t, J = 6.5 Hz, 3 H).
(1H-Benzo[d][1,2,3]triazol-1-yl)(2,6-difluorophenyl)methanone
(2g)29
White solid; yield: 0.114 g (70%); mp 121–123 °C; Rf = 0.6 (10%
EtOAc/n-hexane).
13C NMR (125 MHz, CDCl3): δ = 172.6, 146.1, 131.0, 130.2, 126.0,
1H NMR (500 MHz, CDCl3): δ = 8.32 (d, J = 9.0 Hz, 1 H), 8.07 (d, J = 9.0
120.0, 114.4, 35.4, 31.8, 29.5, 29.4, 29.2, 29.0, 24.4, 22.6, 14.0.
Hz, 1 H), 7.67–7.64 (m, 1 H), 7.52–7.46 (m, 2 H), 7.00 (t, J = 8.0 Hz, 2
H).
(1H-Benzo[d][1,2,3]triazol-1-yl)(4-hydroxyphenyl)methanone
(2m)32
13C NMR (125 MHz, CDCl3): δ = 161.0, 160.9, 159.9, 159.0, 158.9,
146.3, 133.8, 133.7, 133.6, 130.9, 130.7, 126.8, 120.4, 114.3, 112.1,
112.0, 111.9, 111.8.
Pale yellow solid; yield: 0.121 g (70%); mp 114–117 °C; Rf = 0.7 (20%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3, DMSO-d6): δ = 10.01 (s, 1 H), 8.35–8.33 (m,
1 H), 8.20–8.14 (m, 3 H), 7.68–7.67 (m, 1 H), 7.55–7.52 (m, 1 H), 7.02–
7.00 (m, 2 H).
(1H-Benzo[d][1,2,3]triazol-1-yl)(3,5-difluorophenyl)methanone
(2h)29
13C NMR (125 MHz, CDCl3): δ = 165.7, 163.1, 145.5, 134.6, 132.6,
130.0, 126.0, 121.7, 119.9, 115.6, 114.7.
White solid; yield: 0.138 g (84%); mp 115–118 °C; Rf = 0.5 (10%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.38 (d, J = 7.5 Hz, 1 H), 8.20 (d, J = 8.5
Hz, 1 H), 7.82 (d, J = 8.5 Hz, 2 H), 7.75 (t, J = 7.5 Hz, 1 H), 7.59 (t, J = 7.5
Hz, 1 H), 7.17–7.14 (m, 1 H).
(1H-Benzo[d][1,2,3]triazol-1-yl)(2-iodophenyl)methanone (2n)29
White solid; yield: 0.097 g (69%); mp 80–82 °C; Rf = 0.6 (10% EtOAc/n-
13C NMR (125 MHz, CDCl3): δ = 163.6, 163.5, 161.6, 145.8, 134.2,
132.2, 130.9, 126.8, 126.2 120.5, 115.1, 115.0, 114.9, 114.8, 109.4,
109.2, 109.0.
hexane).
1H NMR (500 MHz, CDCl3): δ = 8.39 (d, J = 7.5 Hz, 1 H), 8.14 (d, J = 8.5
Hz, 1 H), 7.95 (d, J = 8.0 Hz, 1 H), 7.71 (t, J = 7.5 Hz, 1 H), 7.57–7.49 (m,
3 H), 7.28–7.24 (m, 1 H).
(1H-Benzo[d][1,2,3]triazol-1-yl)[3-(trifluoromethyl)phe-
13C NMR (125 MHz, CDCl3): δ = 167.7, 146.3, 139.8, 139.0, 132.5,
131.5, 130.8, 130.0, 127.9, 126.8, 120.4, 114.5, 93.3.
nyl]methanone (2i)27
White solid; yield: 0.093 g (61%); mp 52–56 °C; Rf = 0.7 (10% EtOAc/n-
hexane).
(1H-Benzo[d][1,2,3]triazol-1-yl)(2-methoxyphenyl)methanone
1H NMR (500 MHz, CDCl3): δ = 8.49 (s, 1 H), 8.44 (d, J = 7.5 Hz, 1 H),
8.38 (d, J = 9.0 Hz, 1 H), 8.17 (d, J = 7.5 Hz, 1 H), 7.95 (d, J = 7.5 Hz, 1 H),
7.74–7.71 (m, 2 H), 7.58–7.55 (m, 1 H).
13C NMR (125 MHz, CDCl3): δ = 165.4, 145.8, 134.9, 132.3, 132.2
130.8, 130.1, 129.1, 128.7, 128.6, 126.7, 120.4, 114.8.
(2o)33
Colorless solid; yield: 0.134 g (81%); mp 94–96 °C; Rf = 0.4 (5%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.38 (d, J = 9.0 Hz, 1 H), 8.12 (d, J = 7.5
Hz, 1 H), 7.67 (t, J = 8.0 Hz, 1 H), 7.61 (d, J = 8.5 Hz, 1 H), 7.56 (t, J = 7.5
Hz, 1 H), 7.51 (t, J = 8.0 Hz, 1 H), 7.10 (t, J = 8.0 Hz, 1 H), 7.05 (d, J = 9.0
Hz, 1 H), 3.76 (s, 3 H).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

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M. Singh et al.
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Synthesis
13C NMR (125 MHz, CDCl3): δ = 166.9, 157.7, 145.9, 133.4, 131.3,
(1H-Benzo[d][1,2,3]triazol-1-yl)(m-tolyl)methanone (2u)27
130.2, 130.1, 126.0, 122.6, 120.4, 119.9, 114.3, 111.6, 55.7.
White crystalline solid; yield: 0.139 g (80%); mp 64–66 °C; Rf = 0.6 (5%
EtOAc/n-hexane).
(1H-Benzo[d][1,2,3]triazol-1-yl)(3-methoxyphenyl)methanone
1H NMR (500 MHz, CDCl3): δ = 8.37 (d, J = 7.5 Hz, 1 H), 8.16 (d, J = 9.0
Hz, 1 H), 8.00–7.99 (m, 2 H), 7.68 (t, J = 8.5 Hz, 1 H), 7.53 (t, J = 7.0 Hz,
1 H), 7.49–7.45 (m, 1 H), 7. 32–7.30 (m, 1 H), 2.46 (s, 3 H).
(2p)27
White solid; yield: 0.141 g (85%); mp 82–84 °C; Rf = 0.4 (5% EtOAc/n-
hexane).
13C NMR (125 MHz, CDCl3): δ = 167.0, 145.8, 138.4, 134.5, 132.4,
132.1, 131.5, 130.4, 129.0, 128.4, 126.3, 120.2, 114.8, 21.4.
1H NMR (500 MHz, CDCl3): δ = 8.36 (d, J = 8.5 Hz, 1 H), 8.15 (d, J = 8.0
Hz, 1 H), 7.79 (d, J = 7.5 Hz, 1 H), 7.70–7.66 (m, 2 H), 7.53 (t, J = 7.5 Hz,
1 H), 7.46 (t, J = 7.5 Hz, 1 H), 7.22–7.20 (m, 1 H), 3.87 (s, 3 H).
(1H-Benzo[d][1,2,3]triazol-1-yl)(naphthalen-2-yl)methanone
13C NMR (125 MHz, CDCl3): δ = 166.6, 159.3, 145.7, 132.5, 132.3,
(2v)27
130.3, 129.4, 126.2, 124.2, 120.2, 120.1, 116.1, 114.7, 55.5.
White solid; yield: 0.124 g (78%); mp 117–119 °C; Rf = 0.6 (5%
EtOAc/n-hexane).
(1H-Benzo[d][1,2,3]triazol-1-yl)(3,5-dimethoxyphenyl)metha-
1H NMR (500 MHz, CDCl3): δ = 8.81 (s, 1 H), 8.38 (d, J = 8.0 Hz, 1 H),
8.19–8.14 (m, 2 H), 7.96 (t, J = 10.5 Hz, 2 H), 7.88 (d, J = 7.5 Hz, 1 H),
7.66 (t, J = 7.5 Hz, 1 H), 7.62–7.59 (m, 1 H), 7.56–7.49 (m, 2 H).
13C NMR (75 MHz, CDCl3): δ = 166.7, 145.8, 135.7, 134.3, 132.5, 132.2,
130.4, 129.9, 129.1, 128.5, 128.3, 127.8, 127.1, 126.6, 126.4, 120.2,
114.9.
none (2q)34
White solid; yield: 0.127 g (82%); mp 114–117 °C; Rf = 0.6 (10%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.36 (d, J = 8.0 Hz, 1 H), 8.16 (d, J = 7.5
Hz, 1 H), 7.69 (t, J = 7.5 Hz, 1 H), 7.54 (t, J = 7.5 Hz, 1 H), 7.34 (d, J = 2.0
Hz, 2 H), 6.76 (s, 1 H), 3.86 (s, 6 H).
13C NMR (125 MHz, CDCl3): δ = 166.5, 160.6, 145.8, 133.1, 132.4,
130.4, 126.4, 120.2, 114.8, 109.5, 106.3, 55.7.
(3r,5r,7r)-Adamantan-1-yl(1H-benzo[d][1,2,3]triazol-1-yl)metha-
none (2w)29
White solid; yield: 0.126 g (81%); mp 118–120 °C; Rf = 0.8 (10%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.27 (d, J = 8.5 Hz, 1 H), 8.10 (d, J = 8.5
Hz, 1 H), 7.61 (t, J = 8.0 Hz, 1 H), 7.47 (t, J = 8.0 Hz, 1 H), 2.42–2.41 (m,
6 H), 2.15 (br s, 3 H), 1.88–1.80 (m, 6 H).
(1H-Benzo[d][1,2,3]triazol-1-yl)(2,3-dichlorophenyl)methanone
(2r)30
White solid; yield: 0.113 g (74%); mp 134–136 °C; Rf = 0.6 (15%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.41 (d, J = 8.5 Hz, 1 H), 8.17 (d, J = 8.5
Hz, 1 H), 7.75 (t, J = 7.5 Hz, 1 H ), 7.71–7.69 (m, 1 H), 7.60–7.57 (m, 1
H), 7.54 (d, J = 8.5 Hz, 1 H ), 7.41 (t, J = 8.0 Hz 1 H).
13C NMR (125 MHz, CDCl3): δ = 176.7, 144.8, 132.3, 130.2, 125.9,
119.9, 115.2, 45.1, 38.7, 36.5, 36.2, 28.2.
13C NMR (125 MHz, CDCl3): δ = 165.1, 146.3, 135.1, 134.2, 133.1,
131.2, 130.9, 130.7, 127.9, 127.7, 126.9, 120.5, 114.4.
(1H-Benzo[d][1,2,3]triazol-1-yl)(3-phenoxyphenyl)methanone
(2x)30
White solid; yield: 0.115 g (78%); mp 51–53 °C; Rf = 0.6 (5% EtOAc/n-
2-(1H-Benzo[d][1,2,3]triazole-1-carbonyl)benzonitrile (2s)
hexane).
1H NMR (500 MHz, CDCl3): δ = 8.35 (d, J = 8.5 Hz, 1 H), 8.14 (d, J = 8.5
Hz, 1 H), 7.92 (d, J = 7.5 Hz, 1 H), 7.81 (s, 1 H), 7.68 (t, J = 7.5 Hz, 1 H),
7.54–7.50 (m, 2 H), 7.38–7.30 (m, 2 H), 7.14 (t, J = 7.0 Hz, 1 H), 7.08 (d,
J = 8.0 Hz, 2 H).
13C NMR (125 MHz, CDCl3): δ = 166.2, 157.5, 156.4, 145.8, 133.1,
132.3, 130.5, 130.1, 129.9, 126.5, 126.3, 124.1, 123.8, 121.4, 120.3,
119.4, 114.8.
White solid; yield: 0.101 g (60%); mp 178–180 °C; Rf = 0.8 (10%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.44 (s, 1 H), 8.39 (d, J = 7.5 Hz, 1 H),
8.29 (d, J = 8.5 Hz, 1 H), 8.04 (d, J = 8.0 Hz, 1 H), 7.89 (d, J = 7.5 Hz, 1 H),
7.67–7.64 (m, 1 H).
13C NMR (125 MHz, CDCl3): δ = 164.6, 145.8, 136.5, 135.2, 131.0,
129.3, 126.9, 120.4, 117.6, 114.7, 113.1.
MS: m/z = 249 (M + H)+.
(1H-Benzo[d][1,2,3]triazol-1-yl)(naphthalen-1-yl)methanone
Anal. Calcd for C14H8N4O: C, 67.74; H, 3.25; N, 22.57. Found: C, 67.88;
H, 3.19; N, 22.06.
(2y)36
White solid; yield: 0.121 g (76%); mp 139–142 °C; Rf = 0.7 (5%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.47 (d, J = 8.5 Hz, 1 H), 8.15–8.07 (m, 3
H), 8.19–8.14 (m, 2 H), 7.92 (d, J = 6.5 Hz, 2 H), 7.71 (t, J = 7.5 Hz, 1 H),
7.59–7.52 (m, 1 H).
13C NMR (125 MHz, CDCl3): δ = 167.7, 146.2, 133.6, 133.1, 132.1,
132.2, 131.1, 130.6, 130.3, 129.4, 128.4, 128.0, 126.8, 126.5, 124.8,
124.4, 120.4, 114.8.
(1H-Benzo[d][1,2,3]triazol-1-yl)(2-nitrophenyl)methanone (2t)35
White solid; yield: 0.103 g (64%); mp 128–130 °C; Rf = 0.8 (10%
EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.37–8.29 (m, 2 H), 8.09 (d, J = 8.5 Hz, 1
H), 7.99–7.73 (m, 4 H), 7.57–7.54 (m, 1 H).
13C NMR (125 MHz, CDCl3): δ = 164.0, 145.5, 145.0, 133.9, 131.4,
130.1, 130.8, 129.0, 128.4, 126.0, 123.5, 119.3, 113.2.
MS: m/z = 269 (M + H)+.
(E)-1-(1H-Benzo[d][1,2,3]triazol-1-yl)octadec-9-en-1-one (2z)29
Yellow oil; yield: 0.107 g (79%); Rf = 0.7 (5% EtOAc/n-hexane).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

G
M. Singh et al.
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Synthesis
1H NMR (500 MHz, CDCl3): δ = 8.26 (d, J = 8.5 Hz, 1 H), 8.09 (d, J = 8.5
Hz, 1 H), 7.61 (t, J = 8.0 Hz, 1 H), 7.47 (t, J = 7.0 Hz, 1 H), 5.36–5.33 (m,
2 H), 3.41 (t, J = 7.5 Hz, 2 H), 2.05–1.94 (m, 4 H), 1.93–1.87 (m, 2 H),
1.50–1.46 (m, 2 H), 1.42–1.25 (m, 18 H), 0.88–0.85 (m, 3 H).
1H NMR (500 MHz, CDCl3): δ = 8.28 (d, J = 8.5 Hz, 1 H), 8.09 (d, J = 8.5
Hz, 1 H), 7.64 (t, J = 7.5 Hz, 1 H), 7.51–7.48 (m, 1 H), 6.18 (d, J = 4.0 Hz,
1 H), 6.00 (d, J = 4.5 Hz, 1 H), 4.67–4.62 (m, 2 H), 3.12 (s, 3 H), 1.52 (s,
3 H), 1.34 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 172.6, 146.1, 131.1, 130.2, 130.0,
129.7, 126.0, 120.1, 114.4, 35.5, 31.9, 29.8, 29.7, 29.3, 29.2, 29.1, 27.3,
27.2, 24.4, 22.7, 14.1.
13C NMR (125 MHz, CDCl3): δ = 165.4, 145.1, 130.5, 130.2, 126.0,
119.6, 113.8, 112.3, 105.3, 85.6, 81.1, 80.8, 57.5, 26.7, 25.9.
(1H-Benzo[d][1,2,3]triazol-1-yl)(furan-2-yl)methanone (2aa)29
Funding Information
White crystalline solid; yield: 0.157 g (83%); mp 169–171 °C; Rf = 0.8
(10% EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.40 (d, J = 8.5 Hz, 1 H), 8.17–8.14 (m, 2
H), 7.87 (s, 1 H), 7.69 (t, J = 7.5 Hz, 1 H), 7.53 (t, J = 8.0 Hz, 1 H), 6.74–
6.73 (m, 1 H).
13C NMR (125 MHz, CDCl3): δ = 155.1, 149.0, 145.6, 144.6, 132.2,
130.6, 126.4, 124.8, 120.2, 114.8, 113.0.
Science and Engineering Research Board (SERB), New Delhi (Grant No.
EMR/2016/001123).
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Acknowledgment
CISC-BHU is thanked for providing spectroscopic studies of the devel-
oped molecules. AKA acknowledge to CSIR for JRF fellowship.
(1H-Benzo[d][1,2,3]triazol-1-yl)[3,5-bis(prop-2-yn-1-yloxy)phe-
nyl]methanone (2ab)29
Supporting Information
White solid; yield: 0.116 g (81%); mp 117–119 °C; Rf = 0.6 (10% EtO-
Ac/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.38 (d, J = 8.5 Hz, 1 H), 8.18 (d, J = 8.5
Hz, 1 H), 7.72 (t, J = 7.5 Hz, 1 H), 7.56 (t, J = 7.5 Hz, 1 H), 7.48 (d, J = 2.0
Hz, 2 H), 6.95 (s, 1 H), 4.77 (d, J = 1.5 Hz, 4 H), 2.58 (br s, 2 H).
Supporting information for this article is available online at
https://doi.org/10.1055/s-0037-1611724. Included are copies of 1H
and 13C NMR spectra for all the developed N-acylbenzotriazoles for
this article.
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13C NMR (125 MHz, CDCl3): δ = 166.1, 158.4, 145.8, 133.2, 132.4,
130.6, 126.5, 120.3, 114.9, 111.2, 108.2, 77.8, 76.3, 56.3.
References
1,2:3,4-Di-O-isopropylidene-α-D-galactopyranuronosylbenzotri-
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azole (2ac)28
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White solid; yield: 0.094 g (69%); mp 174–176 °C; Rf = 0.4 (15% EtO-
Ac/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.35 (d, J = 8.5 Hz, 1 H), 8.14 (d, J = 8.5
Hz, 1 H), 7.69 (t, J = 6.5 Hz, 1 H), 7.53 (t, J = 7.5 Hz, 1 H), 5.83 (d, J = 5.0
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13C NMR (125 MHz, CDCl3): δ = 165.8, 145.9, 131.2, 130.8, 126.5,
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(1H-Benzo[d][1,2,3]triazol-1-yl)[6-(isopentyloxy)-2,2-dimethyl-
tetrahydrofuro[2,3-d][1,3]dioxol-5-yl]methanone (2ad)28
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Colorless oil; yield: 0.107 g (78%); Rf = 0.6 (10% EtOAc/n-hexane).
1H NMR (500 MHz, CDCl3): δ = 8.27 (d, J = 8.5 Hz, 1 H), 8.09 (d, J = 9.0
Hz, 1 H), 7.64 (t, J = 7.5 Hz, 1 H), 7.49 (t, J = 7.5 Hz, 1 H), 6.19 (d, J = 4.0
Hz, 1 H), 6.05 (d, J = 4.0 Hz, 1 H), 4.67–4.62 (m, 2 H), 3.49–3.45 (m, 1
H), 3.04–2.99 (m, 1 H), 1.53 (s, 3 H), 1.34 (s, 3 H), 1.06–0.82 (m, 3 H),
0.45 (d, J = 7.0 Hz, 3 H), 0.14 (d, J = 7.0 Hz, 3 H).
13C NMR (125 MHz, CDCl3): δ = 166.0, 145.7, 131.0, 130.7, 126.4,
120.1, 114.2, 112.8, 106.0, 84.6, 82.8, 81.5, 68.6, 37.7, 27.2, 26.5, 24.0,
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(1H-Benzo[d][1,2,3]triazol-1-yl)(6-methoxy-2,2-dimethyltetra-
hydrofuro[2,3-d][1,3]dioxol-5-yl)methanone (2ae)28
Colorless oil; yield: 0.110 g (75%); Rf = 0.5 (20% EtOAc/n-hexane).
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