Facile expeditious one-pot synthesis and antifungal evaluation of disubstituted 1,2,3-triazole with two amide linkages

Article abstract of DOI:10.1080/00397911.2017.1369124

A library of twenty five amide linked 1,4-disubstituted 1,2,3-triazoles have been prepared through a facile expeditious synthetic protocol involving Cu(I) mediated cyclization of N-(2-methylbut-3-yn-2-yl)aromatic amides and in situ generated 2-azido-N-substituted propanamides. Structures of newly synthesized compounds (5a–5y) were confirmed by analytical techniques, such as FTIR, ¹H NMR, ¹³C NMR, and HRMS. In vitro antifungal activity was also examined against two fungal strains Candida albicans and Aspergillus niger by serial dilution method. The compounds 5 m and 5w exhibited appreciable potent activity.

Full text of DOI:10.1080/00397911.2017.1369124

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
A facile expeditious one pot synthesis and
antifungal evaluation of disubstituted 1,2,3-
triazole with two amide linkages
C. P. Kaushik & Raj Luxmi
To cite this article: C. P. Kaushik & Raj Luxmi (2017): A facile expeditious one pot synthesis
and antifungal evaluation of disubstituted 1,2,3-triazole with two amide linkages, Synthetic
Communications, DOI: 10.1080/00397911.2017.1369124
To link to this article: http://dx.doi.org/10.1080/00397911.2017.1369124
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Date: 29 August 2017, At: 05:37

A facile expeditious one pot synthesis and antifungal
evaluation of disubstituted 1,2,3-triazole with two amide
linkages
C. P. Kaushik
Department of Chemistry, Guru Jambheshwar University of Science & Technology, Hisar,
Haryana, India
Raj Luxmi
Department of Chemistry, Guru Jambheshwar University of Science & Technology, Hisar,
Haryana, India
Address correspondence to C. P. Kaushik. Tele.: + 91 1662 263152. Fax: + 91 1662 276240. E-
mail: kaushikcp@gmail.com
Abstract
A library of twenty five amide linked 1,4-disubstituted 1,2,3-triazoles have been prepared
through a facile expeditious synthetic protocol involving Cu(I) mediated cyclization of N-(2-
methylbut-3-yn-2-yl)aromatic amides and in situ generated 2-azido-N-substituted propanamides.
Structures of newly synthesized compounds (5a–5y) were confirmed by analytical techniques
1
13
like FTIR, H NMR, C NMR, and HRMS. In vitro antifungal activity was also examined
1

against two fungal strains Candida albicans and Aspergillus niger by serial dilution method. The
compounds 5m and 5w exhibited appreciable potent activity.
Graphical Abstract
KEYWORDS: 1,3-dipolar cycloaddition, 1,4-disubstitued 1,2,3-triazoles, antifungal activity,
synthesis
Introduction
The triazoles constitute a class of heterocyclic compounds, which attracted the attention
of medicinal chemists due to broad spectrum pharmaceutical applications. Molecules with 1,2,3-
triazole entity possess anti-HIV,[1,2] anticancer,[3–5] anti-oxidant,[6,7] antibacterial,[8–10]
antifungal,[11–13] antimalarial,[14–16] antitubercular,[17,18] anti-phytopathogenic[19] and anti-
inflammatory[20] activities. Further, the triazole also shows several applications in material
science,[21,22] bioconjugation,[23] polymer chemistry[24] and as high performance organic
coatings.[25] The most remarkable features of 1,2,3-triazoles are its stability towards metabolic
degradation and capablity of hydrogen bonding in living system which favors effective binding
to biomolecule targets leading to appreciable biological activity.[26]
2

The usual method for the synthesis of disubstituted 1,2,3-triazoles through 1,3-dipolar
cycloaddition of organic azides and terminal alkynes resulting to 1,4- and 1,5- isomers was
initially induced by Huisgen.[27] The major limitations of this non-catalyzed pathway are high
temperature condition and poor regioselectivity in products. To overcome these drawbacks
Sharpless[28] and Meldal[29] introduced the Cu (I) catalyst for synthesis of substituted 1,2,3-
triazoles which yields only single isomer i.e. 1,4-disubstituted 1,2,3-triazole under milder
reaction conditions. Some other synthetic protocols for triazoles using nominal reaction
conditions have also been reported.[30–32]
Though, in continuation of our previous work on synthesis of substituted 1,2,3-
triazoles[33] we synthesized twenty five new amide linked compounds from N-(2-methylbut-3-yn-
2-yl)aromatic amides, 2-bromo-N-substituted propanamides and sodium azide using copper
sulphate pentahydrate as a catalyst and characterized by analytical techniques.
Further, fungal infections constitute a worldwide health problem and the number of
diseases caused by pathogenic fungi is observed in humans and plants.[34,35] These infections are
difficult to treat and have remarkable impacts on the crops, and often lead to significant yield
reduction and economic losses in agriculture. The search for newer antifungal agents continues
due to the rapid development of the resistance among fungi to the existing antimicrobial agents.
In continue to this antifungal evaluation of synthesized compounds was carried out against two
fungal strains viz. C. albicans and A. Niger.
Result and discussion
Chemistry
3

Herein we reported three component Cu (I) catalyzed one-pot synthesis of 1,4-
disubstituted 1,2,3-triazoles with two amide linkages from the reaction of 2-bromo-N-substituted
propanamide, N-(2-methylbut-3-yn-2-yl) aromatic amide and sodium azide in dimethylforamide-
water. N-(2-methylbut-3-yn-2-yl)aromatic amides (2) were synthesized from reaction of aromatic
acid chloride (1) and 2-methylbut-3-yn-2-amine in the presence of 4-dimethylaminopyridine
(DMAP). 2-Bromo-N-substituted propanamides (4) were synthesized from reaction of 2-
bromopropanoyl bromide and aromatic amines (3) in the presence of potassium carbonate. The
targeted disubstitited triazoles (5a–5y) were synthesized by reaction of 2-azido-N-substituted
propanamide (generated in situ from reaction between 2-bromo-N-substituted propanamide (4)
and sodium azide) with N-(2-methylbut-3-yn-2-yl)aromatic amide (2) in the presence of copper
sulphate pentahydrate and sodium ascorbate using DMF:water as solvent.
1
13
The structures of synthesized triazoles (5a–5y) were confirmed by FTIR, H NMR, C
NMR spectroscopy and HRMS. In IR spectra of all the compounds characteristic absorption
band observed at 3199–3132 cm-1 due to C–H stretching of triazole ring, 3394–3315 cm-1 and
3284–3207 cm-1 due to N-H stretching of amide linkages, 1716–1674 cm-1 and 1647–1618 cm-1
were due to C = O stretching of amide bonds.
1H NMR spectra of compounds displayed two characteristic singlets in the range of δ
11.28–10.34, δ 8.72–8.14 were due to N-H protons and singlet at δ 8.16–8.01 was due to
triazolyl proton. Aromatic protons appeared in the range of δ 8.30–6.90 and a single proton
attached to N1 of triazole ring appeared as quartet in range of δ 5.79–5.47. In 13C NMR spectra a
characteristic signal of C = O appeared in range of δ 168.8–167.2 and δ 166.5–164.9. C–4 and
C–5 of triazoles ring appeared at δ 153.5–153.2 and δ 121.0–120.7 respectively. HRMS spectral
4

analysis of synthesized compounds was found in accordance with the theoretically predicted
molecular masses.
Antifungal activity
The synthesized 1,4-disubstituted 1,2,3-triazoles (5a-5y) were examined for in vitro
antifungal activity against two fungal strains – Candida albicans (MTCC 227) and Aspergillus
niger (MTCC 282) using serial dilution method.[36] Fluconazole was used as a standard drug. The
minimum inhibitory concentration (MIC) values were presented in µmol/mL (Table 1).
Results indicated that some of the synthesized compounds possess appreciable activity.
The Compounds 5h, 5j, 5l, 5m, 5o, 5w showed better activity in case of C. albicans with MIC,
0.0552, 0.0546, 0.0552, 0.0536, 0.0530 and 0.0302 µmol/mL respectively. In case of A. niger the
compounds 5h, 5l, 5m, 5o, 5w, 5y showed moderate to good activity as evident the MIC, 0.0276,
0.0276, 0.0134, 0.0265, 0.0151 and 0.0288 µmol/mL respectively.
The activity results revealed that presence of electron withdrawing group, i.e. nitro
displayed good antifungal efficiency while naphthyl group on nitrogen atom of amide linkage
showed potent antifungal activity. Triazoles having thienyl moiety exhibited good activity in
case of A. niger in comparison to furyl moiety, where as triazoles having thienyl and nitro group
exhibited remarkable antifungal efficiency in comparison with the reference.
Conclusion
In summary, we have reported the one pot facile synthesis of a library of amide linked
1,4-disubstituted 1,2,3-triazoles from the click reaction of N-(2-methylbut-3-yn-2-yl)aromatic
amide and 2-azido-N-substituted propanamides (synthesized in situ from reaction of 2-bromo-N-
5

substituted propanamides and sodium azide). The synthesized compounds were characterized by
1
13
various analytical techniques viz. FT-IR, H NMR, C NMR, HRMS. Antifungal evaluation of
compounds was carried out by two fungal strains C. albicans and A. niger. The compound 5m
and 5w exhibited persuasive activity.
Experimental
Material and methods
All chemicals used in the synthesis were purchased from Alfa-Aesar, Sigma-Aldrich, Hi-
media, Qualigens and used without purification. The progress of the reactions was monitored by
thin layer chromatography. Melting points were determined by open capillary method and are
uncorrected. IR spectra were recorded on a SHIMADZU IR AFFINITY-I FT-IR
spectrophotometer using KBr powder and the values are expressed in cm-1. The 1H and 13C NMR
spectra of the synthesized molecules were recorded at 400 MHz and 100 MHz, respectively,
using Bruker Avance II 400 MHz NMR spectrometer in DMSO-d6 solvent, and the chemical
shifts were expressed in δ and coupling constants (J) in Hz. Splitting patterns were indicated as s:
singlet, d: doublet, dd: doublet of doublet, t: triplet, q: quartet, m: multiplet. HRMS were
obtained on Waters Micromass Q-Tof Micro (ESI) spectrophotometer and values were quoted in
m/z.
Typical procedure for the synthesis of N-(2-(1-(1-oxo-1-(phenylamino)propan-2-
yl)-1H-1,2,3-triazol-4-yl)propan-2-yl)benzamide
The starting reactant N-(2-methylbut-3-yn-2-yl)benzamide (2a) was synthesized from
reaction of benzoyl chloride (1.0 mmol) and 2-methylbut-3-yn-2-amine in the presence of 4-
6

dimethylaminopyridine (DMAP) in dry dichloromethane with continuous stirring at 0–10 ºC for
3–4 h. 2-Bromo-N-phenyl propanamide (4a) was synthesized by drop wise addition of 2-
bromopropanoyl bromide (1.2 mmol) to aniline (1.0 mmol) using dichloromethane as solvent in
the presence of potassium carbonate at 0–5 ºC for 15–20 minutes. Further for synthesis of N-(2-
(1-(1-oxo-1-(phenylamino)propan-2-yl)-1H-1,2,3-triazol-4-yl)propan-2-yl)benzamide (5a), 2-
bromo-N-phenyl propanamide (1.0 mmol) was dissolved in dimethylformamide in a round
bottom flask, aqueous sodium azide (3.0 mmol) was added and stirred for 30 min at 40–50 ºC.
To the above mixture N-(2-methylbut-3-yn-2-yl)benzamide (1.0 mmol), aqueous copper sulphate
pentahydrate (0.1 mmol) and sodium ascorbate (0.4 mmol) were added and stirring was
continued for 12 h at same temperature. After completion of reaction, ice cold water was added
to reaction mixture. Precipitated product was filtered and washed with ammonia solution and
then with water. Crude product was washed with ethyl acetate and dried under vacuum to get
desired product (5a) in good yield.
N-(2-(1-(1-oxo-1-(phenylamino)propan-2-yl)-1H-1,2,3-triazol-4-yl)propan-2-
yl)benzamide
Yield 83% as white solid; m.p.164–168 ºC; IR (KBr), ν (cm−1): 3394, 3253 (N-H amide
str.), 3124(C-H str. triazole), 3041(C-H str. aromatic ring), 2983(C-H str., aliphatic), 1681, 1635
(C = O str. amide); 1H NMR (400 MHz, DMSO): δ 10.48 (s, 1H, N-H amide), 8.32 (s, 1H, N-H
amide), 8.06 (s, 1H, C-H triazole), 7.83 (d, 2H, ArH, J = 8.0 Hz), 7.60 (d, 2H, ArH, J = 8.0 Hz),
7.51 (t, 1H, ArH, J = 8.0 Hz), 7.44 (t, 2H, ArH, J = 8.0 Hz), 7.33 (t, 2H, ArH, J = 8.0 Hz), 7.10
13
(t, 1H, ArH, J = 8.0 Hz), 5.52 (q, 1H, J = 8.0 Hz), 1.77 (d, 3H, J = 8.0 Hz), 1.74 (s, 6H); C
NMR (100 MHz, DMSO): δ 167.7, 166.4, 153.4, 138.8, 135.8, 131.4, 129.1, 128.5, 127.9, 124.4,
7

120.7, 119.9, 59.2, 51.5, 28.9, 18.3. HRMS [M + H] + for C21H23N5O2 calc: 378.1852, found:.
378.1925.
General procedure for in vitro Antifungal activity
The newly synthesized 1,4-disubstituted 1,2,3-triazoles (5a–5y) were studied for
antifungal activity against Candida albicans (MTCC 227) and Aspergillus niger (MTCC 282) by
serial dilution method using a stock solution of 100 µg/mL concentration. Sabouraud dextrose
was employed as culture media. Dimethylsulfoxide was used as solvent control. Fluconazole was
used as standard drug for fungal activity assay. The stock solutions of the test compounds and
standard drug were serially diluted to get the concentration of 50–3.12 µg/mL and then
inoculated with suspension of respective microorganism in sterile saline. The inoculated test
tubes were incubated at 25 ºC in case of C. albicans for 48 h and at 25 ºC for 120 h in case of A.
niger. Antifungal potential of synthesized triazoles was assessed in terms of minimum inhibitory
concentration of microbial growth.
References
8

Table 1. Antifungal activity of 1,4-disubstituted 1,2,3-triazoles (5a–5y) (MIC in μmol/mL)
Compound
C. albicans (MTCC 227)
0.1324
A. niger (MTCC 282)
0.0662
5a
5b
5c
5d
5e
5f
0.0613
0.0613
0.0591
0.0591
0.0632
0.0632
0.0584
0.0584
0.0613
0.0613
5g
5h
5i
0.0571
0.0571
0.0552
0.0276
0.0587
0.0587
5j
0.0546
0.0546
5k
5l
0.0591
0.0591
0.0552
0.0276
5m
5n
5o
5p
0.0536
0.0134
0.0566
0.0283
0.0530
0.0265
0.0680
0.0340
9

5q
0.0628
0.0606
0.0648
0.0598
0.0650
0.0582
0.0302
0.0622
0.0576
0.0408
0.0314
0.0303
0.0324
0.0299
0.0325
0.0291
0.0151
0.0311
0.0288
0.0102
5r
5s
5t
5u
5v
5w
5x
5y
Fluconazole
10

Scheme 1. Synthesis of 1,4-disubstituted 1,2,3-triazoles (5a–5y).
Compound No.
R1
R2
Reaction
Time (h)
Yield %
5a
5b
5c
5d
5e
5f
C6H5
C6H5
C6H5
4-CH3OC6H4
4-NO2C6H4
4-FC6H4
12
14
12
16
16
12
15
16
12
14
83
91
87
82
78
84
92
84
87
81
C6H5
C6H5
C6H5
α-C10H7
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
C6H5
5g
5h
5i
4-CH3OC6H4
4-NO2C6H4
4-FC6H4
5j
α-C10H7
11

5k
5l
4-NO2C6H4
4-NO2C6H4
4-NO2C6H4
4-NO2C6H4
4-NO2C6H4
C4H3O
C6H5
4-CH3OC6H4
4-NO2C6H4
4-FC6H4
13
12
14
15
15
14
16
13
12
15
14
14
13
14
16
88
86
92
89
84
86
83
88
84
91
90
88
92
94
86
5m
5n
5o
5p
5q
5r
α-C10H7
C6H5
C4H3O
4-CH3OC6H4
4-NO2C6H4
4-FC6H4
C4H3O
5s
C4H3O
5t
C4H3O
α-C10H7
5u
5v
5w
5x
5y
C4H3S
C6H5
C4H3S
4-CH3OC6H4
4-NO2C6H4
4-FC6H4
C4H3S
C4H3S
C4H3S
α-C10H7
12