An improved iron-mediated synthesis of N-2-aryl substituted 1,2,3-triazoles

Article abstract of DOI:10.1039/c3ra22485f

Treatment of various chalcones and sodium azide in the presence of catalytic amounts of commercially available iron oxide nanoparticles, followed by the addition of aryl halides afforded N-2-arylated 1,2,3-triazoles in very good yields. This tandem three-

Full text of DOI:10.1039/c3ra22485f

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An improved iron-mediated synthesis of N-2-aryl
substituted 1,2,3-triazoles3
Cite this: RSC Advances, 2013, 3,
7419
Ahmed Kamal* and Ponnampalli Swapna
Treatment of various chalcones and sodium azide in the presence of catalytic amounts of commercially
available iron oxide nanoparticles, followed by the addition of aryl halides afforded N-2-arylated 1,2,3-
triazoles in very good yields. This tandem three-component reaction involves an oxidative 1,3-dipolar
cycloaddition of the chalcone and azide and subsequent regioselective N-2-arylation. The nano-catalyst is
easily recoverable and can be reused without any significant loss in catalytic activity.
Received 11th October 2012,
Accepted 28th February 2013
DOI: 10.1039/c3ra22485f
www.rsc.org/advances
Catalysis of organic transformations by nanoparticles is an
emerging area that has received significant attention in recent
Introduction
Ever since the advent of click chemistry (Scheme 1),1 the
synthesis of 1,2,3-triazoles and their applications in various
areas2,3 such as medicinal chemistry, chemical biology and
material science have become popular and fruitful realms of
research. The 1,2,3-triazole moiety is an important heterocyclic
pharmacophore that function as integral structural fragment
of a number of biologically active compounds such as kinase
inhibitors,4 anti-HIV agents,5 antimicrobials6 and anticancer
agents.7 Although click chemistry and functionalization of
triazoles and its derivatives deliver a variety of N-1-substituted
1,2,3-triazoles8 in a very efficient manner, methods for the
synthesis of N-2-substituted-1,2,3-triazoles are rare.9
years.12 Low catalyst loading resulting from the enhanced
surface area per unit mass, ease of separation of products from
the catalyst, recyclability and affordability are certain advan-
tages that nanoparticle catalysts offer over bulk materials.13
Therefore, we were intrigued by the possibility of developing a
synthesis of N-2-aryl-1,2,3-triazoles by employing a readily
available, affordable, non-toxic and environmentally friendly
metal oxide nanoparticle as catalyst. Iron oxides and a few iron
salts were selected as potential catalysts for the process as they
satisfy the above-described criteria.14,15
Yamamoto and coworkers reported a Pd(0)–Cu(I) catalyzed
three component coupling reaction of allyl carbonate, alkynes
and TMSN3 to afford 2,4-disubstituted 1,2,3-triazoles.9a Chen
and coworkers reported a metal and base free regioselective
three-component reaction involving ynones, sodium azide and
alkyl halides to generate 2,4,5-trisubstituted 1,2,3-triazoles
(Scheme 2, eqn (1)).10 Recently, the same group also reported a
CuO-promoted one-pot synthesis of N-2-aryl substituted 1,2,3-
triazoles via an azide–chalcone oxidative cycloaddition and
post-triazole N-arylation (Scheme 2, eqn (2)).11 It may be noted
that the protocol requires the use of stoichiometric quantities
of CuO. In view of the above-mentioned importance of 1,2,3-
triazoles, a catalytic method for accessing N-2-arylated-1,2,3-
triazoles assumes importance.
Results and discussion
We initiated our studies by using (E)-1,3-bis(4-fluorophenyl)
prop-2-en-1-one (1a) as
a representative substrate with
different Fe sources and solvents at variant temperatures
(Table 1). Pleasingly, the treatment of a 1 : 1 mixture of 1a,
sodium azide with 10.0 mol%, commercially available Fe3O4
nanoparticles in DMSO (2 mL) at 70 uC and subsequent
addition of 2-NO2-C6H4F (2a) afforded N-2 arylated product 3a
in 65% yield (Table 1, entry 1; the reaction was conducted in
an open flask). Inspired by this observation, different sources
of iron, such as Fe2O3 nanoparticles, FeSO4?7H2O, FeCl3,
FeBr2, Fe(acac)2 and bulk-Fe2O3 were screened for their
catalytic activity (Table 1, entries 2–6 and 16). Among them,
Division of Organic Chemistry, CSIR-Indian Institute of Chemical Technology,
Hyderabad, 500007, India. E-mail: ahmedkamal@iict.res.in; Fax: +91-40-27193189;
Tel: +91-40-27193157
Electronic supplementary information (ESI) available: Experimental
3
procedures, powder XRD spectra, 1H NMR and 13C NMR spectroscopic data of all
the compounds. CCDC reference number of the compound 3m, 900346. For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
c3ra22485f
Scheme 1 Click chemistry approach to 1,2,3-triazoles.
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and it was observed that desired product was not formed at
room temperature whereas enhancing the temperature to 100
uC did not improve the yield of the product (Table 1, entries
14–15). Finally, a blank reaction was conducted excluding
catalyst to know the role of the catalyst (Table 1, entry 16); no
product was formed in this experiment and the starting
materials remained as such. Therefore, catalyst plays an
important role in this oxidative dehydrogenative coupling
reaction.
Under the optimized conditions, the scope of the metho-
dology was investigated with various chalcones and the results
are described in Table 2. Chalcones with electron-withdrawing
groups on R1 and/or R2 gave higher yields (3a–e, 3r and 3s;
Table 2, entries 1–5 and 18, 19) consistent with the observation
made by Chen.11 On the other hand, chalcones with electron-
donating groups produced comparatively lower yields of the
products (Table 2, entries 6–17). In addition, replacing the
carbonyl attached aromatic ring of the chalcone R2 of 1a with
the five membered heterocycles such as thiophene and pyrrole
(Table 2, entries 20–21) did not afford the desired products
and decomposition of starting materials were observed.
Chalcones derived from a,b-unsaturated carbonyl compounds
such as trans-cinnamaldehyde, ethyl acrylate and methyl
cinnamate, did not react under these optimized conditions
and the starting materials were recovered from the reaction
mass. The a,b-unsaturated aldehydes and esters also failed to
participate in this reaction.
The aryl halide component (2a–f) of the reaction can also be
varied to include electron-deficient aryl halides, such as,
2-NO2-C6H4F (2a), 3,4-difluoro-C6H3NO2 (2b) and 2,4-dinitro-
C6H3Cl (2c) to furnish the corresponding 2,4,5-trisubstituted
1,2,3-triazoles. However, this reaction using 2-NO2-C6H4Cl (2d)
and 2-Cl, 4-NO2-C5H3N (2e) and electron rich aryl chloride
2-CH3-C6H4Cl (2f) did not yield the desired products (Table 2,
entries 22–24). Finally, confirmation of the structure and the
site of N-arylation of the product were obtained by the single
crystal X-ray analysis of 3m (Fig. 1).
Scheme 2 Chen’s synthesis of N-2-aryl-1,2,3-triazoles.
commercially available nano-Fe2O3 (,50 nm) was found
perform best affording the desired product in 89% yield
(Table 1, entry 2).
Interestingly, on decreasing the loading of Fe2O3 nanopar-
ticles to 5 mol% enhanced the yield of the product to 92%
(Table 1, entry 7). However, upon further decreasing the
loading of Fe2O3 nanoparticles to 2 mol% reduced the yield to
69% (Table 1, entry 8). 5 mol% of the catalyst was found to be
optimal for this conversion. Additionally, the role of the
solvent was also investigated; it was observed that DMSO is the
most suitable solvent for this reaction whereas solvents such
as DMF and CH3CN afforded the product in lower yields
(Table 1, entries 9, 10). Solvents like EtOH, 1,4-dioxane and
H2O failed to produce the desired product (Table 1, entries 11–
13). Meanwhile, the effect of temperature was also examined
Table 1 Optimization of various Fe sourcesa
It is evident that the triazoles are formed via an oxidative
cycloaddition and in order to gain insight into the mechanism
of this conversion, the reaction between 1a and 2a was
conducted under a nitrogen atmosphere using 5.0 mol% of
Fe2O3 nanoparticles. A lower yield of the product 3a (40%) was
obtained even after the best efforts were made to exclude
oxygen. Additionally, no product was formed in the absence of
the catalyst under aerobic conditions (Table 1, entry 17).
Therefore, it is clear that atmospheric oxygen acts as the
sacrificial oxidant only in the presence of the catalyst. It is
presumable that the Fe(III) species in the catalyst is respon-
sible for the oxidation and atmospheric oxygen regenerates the
catalytically active species by re-oxidation of the low-valent
iron intermediates. Further investigations are required to
unravel the details of the catalytic cycle and mechanism of this
intriguing transformation.
Entry Fe
Solvent
T (uC) Mol (%) Yieldb (%)
1
2
Nano-Fe3O4
Nano-Fe2O3
DMSO
DMSO
70
70
70
70
70
70
70
70
70
70
10.0
10.0
10.0
10.0
10.0
10.0
5.0
2.0
10.0
5.0
5.0
5.0
5.0
5.0
65
89
45
30
None
40
92
69
68
3
4
FeSO4?7H2O DMSO
FeCl3
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
5
6
FeBr2
Fe(acac)2
7
8
9
Nano-Fe2O3
Nano-Fe2O3
Nano-Fe2O3
Nano-Fe2O3
Nano-Fe2O3
Nano-Fe2O3
Nano-Fe2O3
Nano-Fe2O3
Nano-Fe2O3
Bulk-Fe2O3
None
10
11
12
13
14
15
16
17
CH3CN
1,4-Dioxane 70
51
None
Trace
None
None
75
49
None
EtOH
H2O
DMSO
DMSO
DMSO
DMSO
70
70
Rt
100
70
70
5.0
5.0
None
a
Reaction conditions: all of the reactions were carried out with
substrate 1a (0.3 mmol), NaN3 (0.3 mmol), and 5.0 mol% of Fe2O3
nanoparticles in the solvent DMSO (2 mL) at 70 uC under air for 18
h followed by the addition of 2-NO2-C6H4F (2a) (0.3 mmol) to the
Another advantage of the present method is the reusability
of the nano-Fe2O3. The catalyst gets adhered to the magnetic
stirring bar once the latter is stationary and thus can be easily
b
reaction mixture and continued for 4 h. Isolated yields.
7420 | RSC Adv., 2013, 3, 7419–7426
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Table 2 Iron-promoted tandem reactions of chalcones with arylhalides for the
synthesis of N-2-aryl-1,2,3-triazolesa
Table 2 (Continued)
Entry
10
1
2
3 (Yieldb)
Entry
1
1
2
3 (Yieldb)
2a
2
3
2a
2a
11
12
1i
1h
2b
4
2a
13
14
1i
5
6
7
2a
2a
2a
1h
2c
2a
15
16
17
2a
2b
8
9
2a
2a
1l
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Table 2 (Continued)
Entry
18
1
2
3 (Yieldb)
1c
2b
19
1a
2c
Fig. 1 Single crystal X-ray structure of 3m.
20
21
2a
2a
catalytic activity was observed over three cycles of use for the
catalyst (Table 3). It was evident from the Powder-XRD spectral
studies and SEM-analysis that there was no change in the
nature of the catalyst even after the third cycle.16
Conclusions
In summary, we have developed a new Fe2O3 nanoparticle
catalyzed three-component reaction for the construction of
2,4,5-trisubstituted-1,2,3-triazole from chalcones, sodium
azide and aryl halides. The reaction has good substrate scope
and furnishes the products in very good yields. Importantly,
the catalyst is easily recoverable and may be reused without
any significant loss in catalytic activity. Control experiments
suggest that atmospheric oxygen acts as the sacrificial oxidant
in the reaction. The biological evaluation of the synthesized
N-2-aryl-substituted-1,2,3-triazoles (3a–s) is ongoing in our
laboratory and will be communicated in due course.
22
23
1l
3p (None)
1a
24
1l
Experimental section
General methods
Reactions were monitored by TLC, performed on silica gel
glass plates containing 60 F-254 and visualization on TLC was
achieved by UV light or iodine indicator. Column chromato-
a
All of the reactions were carried out with substrate 1a (0.3 mmol),
NaN3 (0.3 mmol), and 5.0 mol% of Fe2O3 nanoparticles in the
solvent DMSO (2 mL) at 70 uC under air for 18 h followed by the
addition of 2-NO2-C6H4F (2a) (0.3 mmol) to the reaction mixture,
b
and continued for 4 h. Isolated yields in %.
Table 3 Recycling of Fe2O3 nanoparticles
Recycles
Catalyst recovery (wt%)
Yield of 3a (%)
recovered. The recovered catalyst was reused after sequential
washing with ethyl acetate and acetone followed by drying in a
hot air oven at 80 uC. Remarkably, no significant loss in
1
2
3
90
88
85
92
89
86
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graphy was performed with Merck (Navi Mumbai, India) 60–
120 mesh silica gel. Spectral patterns were designated as s,
singlet; d, doublet; dd, double doublet; t, triplet; td, triplet
doublet; m, multiplet. 1H NMR and 13C NMR were spectra
were recorded on Avance 300 MHz and 75 MHz (Bruker,
Fallanden, Switzerland) instruments. Chemical shifts (d) were
reported in ppm, downfield from internal TMS standard. ESI
spectra were recorded on Micro mass, Quattro LC using ESI
software with capillary voltage of 3.98 kV and ESI mode
positive ion trap detector. High-resolution mass spectra
(HRMS) were recorded on QSTAR XL Hybrid MS/MS mass
spectrometer. IR spectra were recorded on a FT-IR spectro-
meter and only major peaks are reported in cm21. Melting
points were determined on a microscopic apparatus and were
uncorrected. Starting materials and reagents were purchased
from Lancaster (Alfa Aesar, Johnson Matthey Co, Ward Hill,
MA, USA), Sigma-Aldrich (St Louis, MO, USA) and Spectrochem
Pvt Ltd (Mumbai, India).
1H), 7.22–7.12 (m, 4H). 13C NMR (75 MHz, CDCl3): d 185.4,
167.8, 164.4, 150.5, 143.4, 133.3, 131.9, 129.8, 125.5, 124.9,
115.7, 115.6, 115.4, 115.3. IR (KBr): nmax 3077, 1651, 1539
cm21. ESI HRMS: calcd. for C21H12O3N4F2Na [M + Na]+:
429.07697, found: 429.07798.
(5-(4-Fluorophenyl)-2-(2-nitrophenyl)-2H-1,2,3-triazol-4-yl)(4-
(trifluoromethyl)phenyl)-methanone (3b)
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (90%,
122 mg), mp: 95–96 uC. 1H NMR (300 MHz, CDCl3): d 8.20 (d, J
= 8.3 Hz, 2 H, Ar), 8.02 (dd, J = 6.7 Hz, 1.5 Hz, 1 H, Ar), 7.99–
7.93 (m, 3 H, Ar), 7.81–7.76 (m, 3 H, Ar), 7.68–7.63 (td, J = 6.0
Hz, 1.5 Hz, 1 H, Ar), 7.17 (t, J = 6.0 Hz, 2 H, Ar) ppm. 13C NMR
(75 MHz, CDCl3): d 186.0, 165.4, 139.5, 133.1, 131.6, 131.2,
131.1, 130.0, 126.1, 125.6, 125.4, 125.0, 124.6, 118.6, 116.9,
115.7, 115.4 ppm. IR (KBr): nmax 2995, 2358, 1666, 1546 cm21
.
ESI HRMS: calcd. for C22H13O3N4F4 [M + H]+: 457.09183,
found: 457.09271.
(2-(2-Nitrophenyl)-5-(4-nitrophenyl)-2H-1,2,3-triazol-4-
yl)(phenyl)methanone11 (3c)
General procedure for synthesis of chalcones 1a–n
The following procedure is representative synthesis of all
chalcones. The substituted acetophenone (0.5 mmol) and
NaOH (0.1 mmol) were dissolved in 20 mL ethanol, and taken
in a round bottom of flask equipped with stirrer. The reaction
was stirred at 0–5 uC; then the aldehyde was dissolved in 10 mL
ethanol and added dropwise for 30 min, then the reaction was
allowed to continue for 5 h at room temperature. The residual
mass was quenched in the ice–water mixture and neutralized
with 10% HCl solution. Then chromatography separation was
followed by recrystallization from 95% ethanol in increasing
order of polarity.
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (109 mg,
yield: 89%). 1H NMR (300 MHz, CDCl3): d 8.29 (d, J = 8.7 Hz, 2
H, Ar), 8.12 (t, J = 8.7 Hz, 4 H, Ar), 8.02 (d, J = 8.7 Hz, 1 H, Ar),
7.97 (d, J = 7.8 Hz, 1 H, Ar), 7.80 (t, J = 7.8 Hz, 1 H, Ar), 7.69 (d, J
= 7.8 Hz, 1 H, Ar), 7.65 (d, J = 6.8 Hz, 1 H, Ar), 7.53 (t, J = 7.8 Hz,
2 H, Ar) ppm. 13C NMR (75 MHz, CDCl3): d 186.9, 149.2, 148.3,
144.4, 143.8, 136.3, 135.0, 134.1, 133.2, 131.7, 130.5, 130.2,
129.8, 128.5, 125.8, 125.2, 123.6 ppm.
(5-(4-Chloro-3-fluorophenyl)-2-(2-nitrophenyl)-2H-1,2,3-tria-
zol-4-yl)(4-fluorophenyl)methanone (3d)
The general procedure for the synthesis of compounds 3a–s
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (108 mg,
yield: 80%), mp: 91–92 uC. 1H NMR (300 MHz, CDCl3): d 8.17–
8.12 (m, 2H), 8.01 (d, J = 8.3 Hz, 1H), 7.96 (d, J = 8.3, 1H), 7.84–
7.77 (m, 2H), 7.72–7.64 (m, 2H), 7.48 (t, J = 7.5 Hz, 1H), 7.20 (t,
J = 9.0 Hz, 2H). 13C NMR (75 MHz, CDCl3): d 185.1, 165.5,
164.7, 149.7, 144.0, 139.9, 133.4, 132.6, 130.7, 128.6, 127.5,
125.3, 117.3, 117.0, 116.8, 115.9, 115.6, 113.5, 113.1. IR (KBr):
All reactions were performed on a 0.30 mmol scale relative to
chalcones. The a,b-unsaturated carbonyl compound (1) (0.30
mmol), sodium azide (0.20 mmol) 5 mol% Fe2O3 and 2 mL
DMSO were taken in a round bottom flask equipped with
stirrer. The reaction mixture was stirred at 70 uC for 18 h, then
arylnitrohalides (2) (0.30 mmol) were added to the mixture and
the reaction continued at 70 uC for 4 h. To the reaction
mixture, water (5 mL) was added and extracted with ester (3 6
10 mL). The combined organic phases were washed with brine
(2 6 5 mL), dried over anhydrous Na2SO4 and concentrated in
vacuo. The reaction mass was subjected to flash column
chromatography with hexanes/EtOAc (5 : 1) as eluent to obtain
the desired product 3. All of the substituted triazoles were
prepared in the similar manner and their characterization
data are as follows:
nmax 3080, 1655, 1540 cm21
21H12O3N4ClF2 [M + H]+: 441.05644, found: 441.05605.
. ESI HRMS: calcd. for
C
(4-Fluorophenyl)(2-(2-nitrophenyl)-5-(4-
(trifluoromethyl)phenyl)-2H-1,2,3-triazol-4-yl)methanone (3e)
Eluent: hexane–ethylacetate (5 : 1). Yellow solid (80%, 108
mg), mp: 91–92 uC. 1H NMR (300 MHz, CDCl3): d 8.19–8.13 (m,
2H), 8.05 (d, J = 8.0 Hz, 3H), 7.96 (dd, J = 6.7, 1.5 Hz, 1H), 7.80
(td, J = 6.7, 1.5 Hz, 1H), 7.71 (d, J = 8.3 Hz, 2H), 7.67 (td, J = 6.7,
1.5 Hz, 1H), 7.23–7.14 (m, 2H). 13C NMR (75 MHz, CDCl3): d
185.3, 168.0, 150.1, 143.7, 133.3, 133.2, 133.1, 132.5, 132.1,
131.6, 130.1, 129.3, 125.7, 125.3, 125.1, 118.9, 115.9, 115.6. IR
(KBr): nmax 3080, 1655, 1540 cm21. ESI HRMS: calcd. for
Spectral data of the compounds
C
22H13O3N4F4 [M + H]+: 457.09183, found: 457.09275.
(4-Fluorophenyl)(5-(4-fluorophenyl)-2-(2-nitrophenyl)-2H-1,2,3-
triazol-4-yl)methanone (3a)
(2-(2-Nitrophenyl)-5-p-tolyl-2H-1,2,3-triazol-4-
yl)(phenyl)methanone11 (3f)
Eluent: hexane–ethylacetate (5 : 1). Orange yellow solid (92%,
1
111 mg), mp: 130–131 uC. H NMR (300 MHz, CDCl3): d 8.17–
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (85 mg,
yield: 75%), mp: 152–153 uC. 1H NMR (300 MHz, CDCl3): d 8.04
(d, J = 8.0 Hz, 2H), 7.96 (d, J = 8.0 Hz, 1H), 7.84 (d, J = 8.0 Hz,
8.12 (m, 2H), 8.02 (dd, J = 6.7 Hz, 1.5 Hz, 1H), 7.95–7.90 (m,
3H), 7.78 (td, J = 6.0 Hz, 1.5 Hz, 1H), 7.65 (td, J = 6.7 Hz, 1.5 Hz,
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1H), 7.68 (t, J = 8.0 Hz, 1H), 7.56–7.51 (m, 2H), 7.41 (t, J = 8.0
Hz, 2H), 7.33 (d, J = 8.0 Hz, 1H), 7.28–7.16 (m, 4H), 2.21 (s, 3H).
13C NMR (75 MHz, CDCl3): d 186.6, 152.1, 145.5, 142.2, 137.6,
136.8, 133.9, 133.3, 132.3, 130.7, 130.1, 129.7, 129.0, 128.7,
126.0, 125.9, 125.3, 20.4.
9.0 Hz, 1H), 7.61 (d, J = 8.3 Hz, 1H), 7.24 (s, 1H), 7.22–7.14 (m,
2H), 7.00–6.92 (m, 2H), 3.86 (s, 3H). 13C NMR (75 MHz, CDCl3):
d 185.5, 161.7, 160.9, 144.8, 133.3, 130.9, 130.3, 130.2, 127.4,
124.7, 120.6, 119.9, 119.2, 115.8, 115.4, 144.4, 113.9, 55.39. IR
(KBr): nmax 3089, 2364, 1659, 1601, 1534 cm21. ESI HRMS:
calcd. for C22H14O4N4F2Na [M + Na]+: 459.08753, found:
459.08847.
(4-Methoxyphenyl)(2-(2-nitrophenyl)-5-phenyl-2H-1,2,3-triazol-
4-yl)m-ethanone11 (3g)
(3-Chlorophenyl)(2-(2-fluoro-4-nitrophenyl)-5-(4-
methoxyphenyl)-2H-1,2,3-triazol-4-yl)methanone (3l)
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (77 mg,
yield: 65%), mp: 139–140 uC. 1H NMR (300 MHz, CDCl3): 8.09–
8.04 (m, 2H), 7.97 (d, J = 8.8 Hz, 1H), 7.86–7.79 (m, 3H), 7.70 (t,
J = 8.0 Hz, 1H), 7.55 (t, J = 8.0 Hz, 1H), 7.19–7.09 (m, 3H), 6.91
(d, J = 8.8 Hz, 2H), 3.79 (s, 3H). 13C NMR (75 MHz, CDCl3): d
185.8, 164.5, 151.3, 143.4, 133.3, 133.2, 133.2, 133.0, 130.4,
129.6, 125.5, 125.0, 115.8, 115.5, 113.9, 55.3.
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (81 mg,
yield: 59%), mp: 183–184 uC. 1H NMR (300 MHz, CDCl3): d
8.27–8.17 (m, 4 H, Ar), 8.06 (d, J = 7.5 Hz, 1H), 7.88 (d, J = 8.3
Hz, 2H), 7.62 (d, J = 7.5 Hz, 1H), 7.47 (d, J = 8.3 Hz, 1H), 7.00 (d,
J = 9.0 Hz, 2H), 3.87 (s, 3H). 13C NMR (75 MHz, CDCl3): d 197.3,
161.0, 151.8, 150.1, 143.6, 138.5, 138.2, 134.7, 133.6, 130.5,
130.4, 129.7, 128.6, 124.8, 120.5, 114.3, 114.0, 55.3. IR (KBr):
(3-Chlorophenyl)(5-(4-methoxyphenyl)-2-(2-nitrophenyl)-
2H-1,2,3-tria-zol-4-yl)methanone (3h)
nmax 3083, 1670, 1535 cm21
22H14O4N4ClFNa [M + Na]+: 475.05798, found: 475.05808.
. ESI HRMS: calcd. for
Eluent: hexane–ethylacetate (5 : 1). Yellow solid (90 mg, yield:
C
1
70%), mp: 101–102 uC. H NMR (300 MHz, CDCl3) d 8.08 (s,
(2-(2,4-Dinitrophenyl)-5-(4-methoxyphenyl)-2H-1,2,3-triazol-4-
yl)(4-fluorophenyl)methanone (3m)
1H), 8.03 (d, J = 7.9 Hz, 1.2 Hz 1H), 7.97–7.86 (m, 4H), 7.76 (t, J
= 7.7 Hz, 1H), 7.64–7.57 (m, 2H), 7.45 (t, J = 8.0 Hz, 1H), 6.97 (d,
J = 8.8 Hz, 2H), 3.86 (s, 3H). 13C NMR (75 MHz, CDCl3): d 185.9,
160.8, 151.4, 143.6, 143.1, 138.4, 134.6, 133.6, 132.9, 131.7,
130.41, 130.1, 129.6, 128.7, 125.5, 124.9, 120.8, 113.8, 55.2. IR
(KBr): nmax 2954, 1669, 1544 cm21. ESI HRMS: calcd. for
C22H15O4N4ClNa: 457.06740, found: 457.06727.
Eluent: hexane–ethylacetate (5 : 1). light yellow solid (95 mg,
yield: 70%), mp: 169–170 uC. 1H NMR (300 MHz, CDCl3): d 8.69
(d, J = 2.2 Hz, 1H), 8.58 (dd, J = 6.5, 2.2 Hz, 1H), 8.37 (d, J = 9.0
Hz, 1H), 8.14–8.09 (m, 2H), 7.85 (d, J = 8.3 Hz, 2H), 7.21 (d, J =
9.0 Hz, 2H), 6.98 (d, J = 9.0 Hz, 2H), 3.86 (s, 3H). 13C NMR (75
MHz, CDCl3): d 185.3, 161.2, 152.2, 146.3, 144.6, 134.8, 133.3,
133.1, 130.4, 127.1, 125.1, 120.7, 120.1, 116.0, 115.7, 114.1,
55.3. IR (KBr): nmax 3087, 2359, 1660, 1536 cm21. ESI HRMS:
calcd. for C22H15O6N5F [M + H]+: 464.10009, found: 464.10051.
(4-Fluorophenyl)(5-(4-methoxyphenyl)-2-(2-nitrophenyl)-
2H-1,2,3-tria-zol-4-yl)methanone (3i)
Eluent: hexane–ethylacetate (5 : 1). Light yellow semi-solid (93
1
mg, yield: 75%). H NMR (300 MHz, CDCl3): d 8.16–8.11 (m,
2H), 8.03 (dd, J = 6.9 Hz, 1.2 Hz, 1H), 7.92 (dd, J = 6.9 Hz, 1.2
Hz, 1H), 7.88 (d, J = 8.6 Hz, 2H), 7.77 (td, J = 6.4 Hz, 1.2 Hz,
1H), 7.62 (td, J = 6.4 Hz, 1.2 Hz, 1H), 7.19 (t, J = 8.4 Hz, 2H),
6.98 (d, J = 8.6 Hz, 2H), 3.86 (s, 3H). 13C NMR (75 MHz, CDCl3):
d 185.7, 167.8, 164.4, 160.7, 151.2, 134.6, 133.2, 133.1, 132.9,
131.7, 130.3, 129.5, 125.4, 124.9, 120.9, 115.7, 115.4, 113.8,
55.2. IR (KBr): nmax 2954, 1669, 1544 cm21. ESI HRMS: calcd.
for C22H16O4N4F [M + H]+: 419.11501, found: 419.11525.
(3-Chlorophenyl)(2-(2,4-dinitrophenyl)-5-(4-methoxyphenyl)-
2H-1,2,3-triazol-4-yl)methanone (3n)
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (96 mg,
yield: 68%), mp: 136–137 uC. 1H NMR (300 MHz, CDCl3): d 8.67
(d, J = 2.1 Hz, 1H), 8.57 (dd, J = 6.5, 2.1 Hz, 1H), 8.36 (d, J = 8.7
Hz, 1H), 8.06 (s, 1H), 7.94 (d, J = 7.6 Hz, 1H), 7.85 (d, J = 8.7 Hz,
2H), 7.62 (d, J = 6.5 Hz, 1H), 7.47 (t, J = 7.6 Hz, 1H), 6.98 (d, J =
8.7 Hz, 2H), 3.87 (s, 3 H). 13C NMR (75 MHz, CDCl3): d 185.4,
161.2, 152.2, 146.3, 144.2, 142.3, 137.8, 134.8, 134.7, 133.8,
130.3, 130.0, 129.8, 128.6, 127.1, 125.1, 120.6, 119.9, 114.0,
55.3. IR (KBr): nmax 3083, 1670, 1535 cm21. ESI HRMS: calcd.
for C22H15O6N5Cl [M + H]+: 480.07054, found: 480.07095.
(5-(4-Fluoro-3-methoxyphenyl)-2-(2-nitrophenyl)-2H-1,2,3-
triazol-4-yl)(4-fluorophenyl)methanone (3j)
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (120 mg,
yield: 72%), mp: 101–102 uC. 1H NMR (300 MHz, CDCl3): d 8.19
(d, J = 8.3 Hz, 2H), 8.01 (dd, J = 6.7 Hz, 1.5 Hz, 1H), 7.92 (dd, J =
6.7 Hz, 1.5 Hz, 1H), 7.81–7.74 (m, 5H), 7.64 (td, J = 6.7 Hz, 1.5
Hz, 1H), 7.03 (t, J = 8.3 Hz, 1H), 3.92 (s, 3H). 13C NMR (75 MHz,
CDCl3): d 186.0, 153.5, 150.6, 150.2, 149.1, 143.6, 143.0, 139.6,
133.0, 131.5, 130.7, 130.0, 125.5, 125.4, 125.3, 125.0, 16.9,
112.8, 56.1. IR (KBr): nmax 3080, 1669, 1544 cm21. ESI HRMS:
calcd. for C22H14O4N4F2Na [M + Na]+: 459.08753, found:
459.08841.
(5-(4-Isopropylphenyl)-2-(2-nitrophenyl)-2H-1,2,3-triazol-4-
yl)(phenyl)methanone (3o)
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (76 mg,
1
yield: 62%), mp: 132–133 uC. H NMR (300 MHz, CDCl3): 8.08
(dd, J = 7.5, 1.5 Hz, 2H), 8.03 (dd, J = 8.3, 1.5 Hz, 1H), 7.92 (dd, J
= 8.3, 1.5 Hz, 1H), 7.83 (d, J = 8.3 Hz, 2H), 7.77 (td, J = 8.3, 1.5
Hz, 1H), 7.65–7.59 (m, 2H), 7.52 (t, J = 7.5 Hz, 2H), 7.30 (d, J =
8.3 Hz, 2H), 3.00–2.90 (m, 1H), 1.27 (dd, J = 6.7 Hz, 6H). 13C
NMR (75 MHz, CDCl3): d 187.5, 151.4, 150.6, 7, 133.7, 132.9,
131.9, 130.4, 130.3, 129.5, 128.8, 128.7, 128.4, 126.5, 126.0,
(2-(2-Fluoro-4-nitrophenyl)-5-(4-methoxyphenyl)-2H-1,2,3-
triazol-4-yl)(4-fluorophenyl)methanone (3k)
125.6, 124.9, 34.0, 23.8. IR (KBr): nmax 3065, 1655, 1561 cm21
.
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (79 mg,
yield: 62%), mp: 121–122 uC. 1H NMR (300 MHz, CDCl3): d
8.30–8.20 (m, 3H), 8.04 (dd, J = 8.3 Hz, 3.0 Hz, 1H), 7.86 (d, J =
ESI HRMS: calcd. for C24H21O3N4 [M + H]+: 413.1613, found
413.1625.
7424 | RSC Adv., 2013, 3, 7419–7426
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(2-(2-Nitrophenyl)-5-o-tolyl-2H-1,2,3-triazol-4-
yl)(phenyl)methanone (3p)
Notes and references
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Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (78 mg,
yield: 69%), mp: 142–143 uC. 1H NMR (300 MHz, CDCl3): d 8.12
(d, J = 7.9 Hz, 2H), 8.04 (d, J = 7.9 Hz, 1H), 7.92 (d, J = 7.9 Hz,
1H), 7.76 (t, J = 7.9 Hz, 1H), 7.62 (d, J = 8.9 Hz, 1H), 7.59 (d, J =
7.9 Hz, 1H), 7.49 (t, J = 7.9 Hz, 2H), 7.40 (d, J = 7.9 Hz, 1H), 7.34
(t, J = 6.9 Hz, 1H), 7.30–7.23 (m, 2 H), 2.29 (s, 3H). 13C NMR (75
MHz, CDCl3): d 186.2, 151.7, 145.0, 143.8, 137.1, 136.4, 133.5,
132.9, 131.9, 130.3, 130.3, 129.7, 129.3, 128.6, 128.3, 128.3,
125.7, 125.5, 124.9, 20.1. ESI HRMS: calcd. for C22H17O3N4 [M
+ H]+: 385.1295, found: 385.1310.
(2-(2-Fluoro-4-nitrophenyl)-5-o-tolyl-2H-1,2,3-triazol-4-
yl)(phenyl)methanone (3q)
´
B. Voit, J. Pyun, J. M. J. Frechet, K. B. Sharpless and V.
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (77 mg,
yield: 65%), mp: 150–151 uC. 1H NMR (300 MHz, CDCl3): d 8.28
(t, J = 9.0 Hz, 1H), 8.25–8.20 (m, 4H), 7.62 (t, J = 7.0 Hz, 1H),
7.50 (t, J = 8.0 Hz, 2H), 7.39 (d, J = 7.0 Hz, 1H), 7.36 (d, J = 8.0
Hz, 1H), 7.31 (t, J = 7.0 Hz, 1H), 7.27 (d, J = 7.0 Hz, 1H), 2.30 (s,
3H). 13C NMR (75 MHz, CDCl3): d 185.9, 155.1, 152.0, 147.4,
145.6, 137.0, 136.3, 133.7, 132.3, 130.4, 130.4, 130.1, 129.6,
128.4, 125.7, 124.8, 120.0, 114.3, 113.9, 20.2. IR (KBr): nmax
cm21. ESI HRMS: calcd. for C22H16O3N4F [M + H]+: 403.1201,
found: 403.1212.
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4-yl)(phenyl)methanone (3r)
Eluent: hexane–ethylacetate (5 : 1). Light yellow solid (110 mg,
1
yield: 86%), mp: uC. H NMR (300 MHz, CDCl3): d 8.32 (d, J =
8.9 Hz, 2H), 8.28–8.26 (m, 3H), 8.19 (d, J = 6.9 Hz, 2H), 8.13 (d,
J = 7.9 Hz, 2H), 7.69 (t, J = 6.9 Hz, 1H), 7.55 (t, J = 6.9 Hz, 2H).
13C NMR (75 MHz, CDCl3): d 185.9, 156.7, 155.2, 151.7, 143.9,
143.6, 134.3, 130.6, 129.8, 128.6, 125.0, 123.7, 10.0, 114.4,
114.0. IR (KBr): nmax 3094, 2925, 1662, 1515 cm21. ESI HRMS:
calcd. for C21H13O5N5F [M + H]+: 434.09006, found: 434.09121.
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Eluent: hexane–ethylacetate (5 : 1). Light white solid (125 mg,
yield: 93%), mp: 166–167 uC. 1H NMR (300 MHz, CDCl3): d 8.71
(d, J = 2.2 Hz, 1H), 8.60 (dd, J = 6.0, 2.2 Hz, 1H), 8.37 (d, J = 9.0
Hz, 1H), 8.15–8.10 (m, 2H), 7.93–7.89 (m, 2H), 7.25–7.14 (m,
4H). 13C NMR (75 MHz, CDCl3): d 185.0, 165.6, 164.7, 146.5,
144.7, 134.8, 133.3, 133.2, 131.1, 131.0, 127.3, 125.3, 120.8,
116.0, 115.9, 115.7, 115.6. IR (KBr): nmax 3096, 1663, 1545
cm21. ESI HRMS: calcd. for C21H13O5N5F [M + H]+: 452.08066,
found: 452.08071.
Acknowledgements
One of the authors (PS) is thankful to the Council of Scientific
and Industrial Research (CSIR), New Delhi, for the award of a
research fellowship.
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16 Powder X-ray diffraction spectra’s and the SEM-analysis
images of the Fe O nanoparticles can be found in the ESI .
3
2
3
7426 | RSC Adv., 2013, 3, 7419–7426
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