Regioselective one pot synthesis of 1,2,3-triazole derivatives bearing phthalazine moiety and their pharmacological activity

Article abstract of DOI:10.1007/s00044-016-1629-4

A new series of phthalazine-based 1,2,3-triazole derivatives (5a–h, 6a–f and 7a–d) were synthesized from the corresponding 2-(4-methyl/chloro benzyloxy) benzoic acid by multi-step reactions. Synthesized compounds were characterized by spectral studies and

Full text of DOI:10.1007/s00044-016-1629-4

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-016-1629-4
ORIGINAL RESEARCH
Regioselective one pot synthesis of 1,2,3-triazole derivatives bearing
phthalazine moiety and their pharmacological activity
P. C. Shyma1,2 Balakrishna Kalluraya1 S. K. Peethambar3 A. M. Vijesh4
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Received: 29 January 2015 / Accepted: 27 June 2016
© Springer Science+Business Media New York 2016
Abstract A new series of phthalazine-based 1,2,3-triazole
derivatives (5a–h, 6a–f and 7a–d) were synthesized from
the corresponding 2-(4-methyl/chloro benzyloxy) benzoic
acid by multi-step reactions. Synthesized compounds were
characterized by spectral studies and C, H, N analysis. The
final compounds were screened for their antimicrobial,
antifungal and antioxidant activity. Among them com-
pounds 5c, 5g, 5h, 6b and 6e showed good antibacterial
activity as compared to the standard drug streptomycin,
whereas compounds 5g and 6d showed good antifungal
activity comparable to the standard drug Fluconazole.
Compounds 5a, 5f and 7c showed significant antioxidant
property when compared with the standard butylated
hydroxytoluene.
Introduction
Synthesis of new heterocyclic derivatives and screening
their pharmacological activities are the major target in the
present day research senario. Now a days microbial stains
are getting more resistant towards the existing drugs and it
is a challenge to the synthetic chemists to replace the less-
active drugs with newer molecules that are more effective
with different mode of action. Phthalazines are an important
class of nitrogen heterocycles that possess various
biological activities. Phthalazines have been reported to
possess antimicrobial activitiy as shown in literature
(Joshi et al., 2000, Chung-Kyu et al., 2007, Khalil et al.,
2009, Sridhara et al., 2010, Maher et al., 2012, Ibrahim
et al., 2014.
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Keywords Phthalazine 1,2,3, Triazole Click chemistry
Antimicrobial activity Antioxidant activity
In recent years, regioselective click chemistry has
become popular in the synthetic organic and biomedicinal
chemistry. Synthesis of 1,2,3-triazoles by the reaction of
azides and terminal alkynes is well known and in presence
of Copper(I) catalyst, the reaction is highly regiospecific
and exclusively gives 1,4-disubstituted 1,2,3-triazoles
(Vsevolod et al., 2002). Literature reveals that 1,2,3-tria-
zoles are highly privileged structure and the derivatives of
which exhibit excellent biological activities such as anti-
microbial (Ashok et al., 2014; Zhao et al., 2012; Thomas
et al., 2010), antitubercular (Rama et al., 2010), anticancer
(Hichem et al., 2013), antiviral (Aurelien et al., 2011),
antiepileptic (Ulloora et al., 2013) etc.
●
Electronic supplementary material The online version of this article
(doi:10.1007/s00044-016-1629-4) contains supplementary material,
which is available to authorized users.
* Balakrishna Kalluraya
bkalluraya@gmail.com
1
Department of Studies in Chemistry, Mangalore University,
Prompted by these observations and in continuation of
our search on biologically active heterocycles, we hereby
report the synthesis of some new 1,2,3-triazole derivatives
bearing phthalazine moiety via click chemistry approach.
The new compounds so synthesized were screened for
its antimicrobial activity and antioxidant activity
(Schemes 1, 2).
Mangalagangothri 574 199 Karnataka, India
2
SeQuent Scientific Limited, No:120 A&B, Industrial Area,
Baikampady, New Mangalore 575 011 Karnataka, India
3
Department of Bio-Chemistry, Jnanasahyadri, Kuvempu
University, Shankaraghatta 577 451 Karnataka, India
4
Department of Chemistry, Payyanur College, Payyanur 670 327
Kerala, India

Med Chem Res
Scheme 1 Synthetic route for 4-
(4-chloro/methylphenyl)
phthalazin-1-ol (3a, b)
R
O
COOC 2H5
N2H4 H2O
O
COOH
H+, C2H5OH
N
N
C H OH,
Δ
2
5
Δ
R
2a,b
R
1a,b
3a,b
OH
Where R= CH3, Cl
Scheme 2 Synthetic route for1-
[(1-substituted-1H-1,2,3-triazol-
4-yl)methoxy]-4-(4-chloro/
methylphenyl) phthalazine
(5a–h, 6a–f and 7a–d)
H
N
N
O
R
R
R
3a,b
i
CH
N
N
ii
R
O
N
N
iv
N
N
O
N
O
4a,b
N
O
N
N
iii
N
N
R lll
N
RI
R ll
5a-h
7a-d
N
N
N
N
R
O
6a-f
Where R= CH3
, Cl
R
I= 3-methylphenyl, 4-nitrophenyl, 2,4-dichlorophenyl, phenyl
RII= 4-methylphenyl, 4-hydroxyphenyl, 2,4-dichlorophenyl
RIII = Isopropyl, allyl
(i) Propargyl bromide, K2CO3, DMF, 65 °C, 2 h. (ii, iii and iv) benzyl, phenacyl
and alkyl bromide, NaN3, aqueous PEG 400 (10 mL, 1:1, v/v), sodium ascorbate,
10 mol % of CuSO4 5H2O, RT, 10-16hrs.
Experimental
recorded on a JASCO FT/IR-4100 spectrophotometer.
1H-NMR and 13C NMR spectra were recorded (dimethyl-
sulphoxide (DMSO)-d6, CDCl3) on a Bruker (400, 100
MHz) instrument using TMS as internal standard. Chemical
Analysis and instruments
Melting points were determined by open capillary method
and were uncorrected. The IR spectra (in KBr pellets) were
shift values are given in δ (ppm) scales. The mass spectra
were recorded on a JEOL JMS-D 300 mass spectrometer

Med Chem Res
operating at 70 eV. Elemental analyses were performed on a
Flash EA 1112 series CHNS-O Analyzer. The completion
of the reaction was checked by thin layer chromatography
(TLC) on silica gel coated aluminium sheets (silica gel 60
F254) obtained from Merck. Commercial grade solvents
were used and reagents were purchased from S. D. Fine
chemicals-India. 2,2-diphenyl-1-picrylhydrazyl (DPPH)
scavenging assay was performed on a Shimadzu UV-1800,
UV-visible spectrophotometer.
(C-6 of phthalazine), 138.79 (C-4 of 4-methylbenzene),
146.73 (C-4 of phthalazine), 157.48(CO, C-1 of phthala-
zine); . LC–MS (m/z): 275 (M + 1, 100 % ); Anal. calcd. For
C18H14N2O; Calcd: C, 78.81; H, 5.14; N, 10.21; found: C,
78.83; H, 5.14; N, 10.20.
4-(4-chlorophenyl)-2-prop-2-yn-1-ylphthalazin-1(2H)-one (4b)
Yield: 65 %; Yellowish microcrystals; mp: 146–148 °C. IR
(KBr νmax/cm−1): 2948 (C–H–str), 2220 (C≡C),1650
(C=O), 1111 (C-O); 1H NMR (400 MHz, CDCl3): δ 3.30 (s,
1H, C≡CH), 4.95 (s, 1H, N–CH2 ), 7.57 (d, 2H, ArH), 7.65
(d, 2H, ArH), 7.70 (1H, ArH), 7.91 (2H, ArH ), 8.36 (1H,
ArH ); 13C NMR (100 MHz, CDCl3): 40.33 (N–CH2),
74.91 (acetylenic C), 78.91(acetylenic C), 126.51 (C-5 of
phthalazine), 126.95 (C-8 of phthalazine), 127.95 (C-9 of
phthalazine), 128.98 (C-3 of 4-chlorobenzene), 129.12 (C-1
of 4-chlorobenzene), 131.76 (C-10 of phthalazine), 132.51
(C-2 of 4-chlorobenzene), 133.79 (C-7 of phthalazine),
134.29 (C-6 of phthalazine), 134.53 (C-4 of 4-chlor-
obenzene), 146.71 (C-4 of phthalazine), 157.48 (CO);
LC–MS (m/z): 295 (M + 1, 100 %); Anal. calcd. For
C17H11ClN2O; Calcd: C, 69.28; H, 3.76; N, 12.03; found:
C, 69.29; H, 3.78; N, 12.01.
Synthesis of 4-(4-chloro/methylphenyl)phthalazin-1-ol (3a, b)
2-(4-chloro/methylbenzoyl)benzoic acid (1) (0.1 mol) is
refluxed in ethanol (25 mL) for 5 h in presence of catalytic
amount of sulphuric acid. After the completion of reaction
ethanol is distilled out, the ester is dissolved in ethyl acetate
and washed with 5 % sodium bicarbonate solution followed
by water wash. Ethyl acetate layer is concentrated to get the
crude ethyl 2-(4-chloro/methylbenzoyl)benzoate 2a, b. The
ethyl 2-(4-chloro/methylbenzoyl)benzoate 2a, b was further
refluxed with hydrazine hydrate (5 mL, 98 %) in absolute
ethanol (50 mL) with one or two drops of sulphuric acid for
2 h. Solid separated on cooling was filtered off, washed with
little chilled ethanol and dried to give 3a, b (Desai and
Desai, 1980). The product was taken as such for next stage
reaction without further purification.
General procedure for the syntheses of 2-{[1-(alkyl/4-
substitutedbenyl/benzoyl)-1H-1,2,3-triazol-4-yl]methyl}-4-
(4-chloro/methylphenyl)phthalazin-1(2H)-one (5a–h, 6a–f
and 7a–d)
Syntheses of 4-(4-chloro/methylphenyl)-2-prop-2-yn-1-
ylphthalazin-1(2H)-one (4a, b)
A mixture of 4-(4-chloro/methylphenyl)phthalazin-1-ol (3a,
b) (0.015 mol), anhydrous potassium carbonate (3.04 g
0.022 mol) and propargylbromide (1.78 g, 0.015 mol) in
DMF (25 mL) was stirred at 65 °C for 2 h. The completion
of reaction was monitored by TLC. The reaction mixture
was poured into ice-cold water. The solid product obtained
was purified by column chromatography using n-hexane
and ethyl acetate mixture as eluent to get pure compound.
To a stirred solution of alkyl bromide (benzyl, phenacyl or
alkyl/alkenyl) (0.50 g, 0.0015 mol) and sodium azide (0.12
g, 0.0018 mol) in aqueous PEG 400 (polyethylene glycol)
(10 mL, 1:1, v/v), 4-(4-chloro/methylphenyl)-2-prop-2-yn-
1-ylphthalazin-1(2H)-one (4a, b) (0.0015 mol), sodium
ascorbate (0.356 g, 0.0015 mol) and 10 mol % of copper
sulphate were added. The heterogeneous mixture was stir-
red vigorously overnight (12 h). Completion of the reaction
was monitored by TLC. The product was then extracted
with ethyl acetate and concentrated. The crude product was
recrystallized from ethyl acetate to get the pure compound.
4-(4-methylphenyl)-2-prop-2-yn-1-ylphthalazin-1(2H)-one (4a)
Yield: 73 %; white microcrystals; mp: 168–170 °C. IR (KBr
ν
max/cm−1): 2951 (C–H–str), 2215 (C≡C), 1657 (C=O),
2-{[1-(3-Methylbenzyl)-1H-1,2,3-triazol-4-yl]methyl}-4-(4-
methylphenyl)phthalazin-1(2H)-one (5a)
1
1117 (C–O); H NMR ( 400 MHz, CDCl3 ): δ 2.40 (s, 3H,
CH3), 3.32 (s, 1H, C≡CH), 4.97 (s, 2H, N–CH2 ), 7.37 (d,
2H, ArH, J =8 Hz ), 7.48 (d, 2H, ArH, J =8 Hz), 7.71 (1H,
ArH), 7.91 (2H, ArH), 8.36 (1H, ArH); 13C NMR (100
MHz, CDCl3): 20.89 (CH3), 40.30(N–CH2), 74.95 (acet-
ylenic C), 79.01(acetylenic C), 126.51(C-5 of phthalazine),
126.85(C-8 of phthalazine), 127.30(C-2 of 4-methylben-
zene), 128.68(C-9 of phthalazine), 129.12, (C-1 of 4-
methylbenzene), 129.28 (C-10 of phthalazine), 131.56 (C-3
of 4-methylbenzene), 132.11 (C-7 of phthalazine), 133.79
White microcrystals; Yield: 82 % ; mp: 198–200 °C; IR
1
(KBr) νmax: 2976, 1660, 1320 cm−1; H NMR (400 MHz,
DMSO-d6 ): δ 2.24 (s, 3H, CH3 ), 2.40 (s, 3H, CH3 ), 5.41
(s, 2H, CH2), 5.49 (s, 2H, CH2), 7.09 (m, 3H, ArH), 7.22
(m, 1H, ArH), 7.34 (d, 2H, ArH, J = 8 Hz), 7.44 (d, 2H,
ArH, J = 8 Hz), 7.69–7.71 (m, 1H, ArH), 7.89–7.91 (m, 2H,
ArH), 8.35 (s, 1H, 1,2,3-triazole H), 8.37 (m,1H, ArH); 13
C
NMR (100 MHz, DMSO-d6): 20.88 (CH3), 46.16 (N–CH2),

Med Chem Res
52.72 (N–CH2), 123.86 (C-5 of triazole), 125.05 (C-5 of
phthalazine), 126.51 (C-8 of phthalazine), 126.70 (C-4 of 3-
methylbenzene), 127.47 (C-6 of 3-methylbenzene), 128.51
(C-2 of 4-methylbenzene, C-2 of 3-methylbenzene), 128.60
(C-9 of phthalazine), 128.71 (C-5 of 3-methylbenzene),
129.07 (C-1 of 4-methylbenzene), 129.28 (C-10 of phtha-
lazine), 131.72 (C-3 of 4-methylbenzene), 131.93 (C-7 of
phthalazine), 133.61 (C-6 of phthalazine), 135.92 (C-3 of 3-
methylbenzene), 137.91 (C-1 of 3-methylbenzene),138.68
(C-4 of 4-methylbenzene), 143.00 (C-4 of triazole), 146.36
(C-4 of phthalazine),157.82 (CO, C-1 of phthalazine);
LC–MS (m/z): 422 (M + 1, 100 %); Anal. calcd. For
C26H23N5O ; Calcd: C, 74.09; H, 5.50; N, 16.62; found: C,
74.07; H, 5.51; N, 16.63.
129.58 (C-1 of methylbenzene),129.77 (C-10 of phthala-
zine), 132.21 (C-3 of 2,4-dichlorobenzene), 132.26 (C-3 of
methylbenzene), 132.44 (C-6 of 2,4-dichlorobenzene),
132.95 (C-7 of phthalazine), 134.12 (C-2 of 2,4-dichlor-
obenzene), 134.37 (C-6 of phthalazine), 139.20 (C-4 of 2,4-
dichlorobenzene), 143.43 (C-5 of triazole), 144.22 (C-1 of
2,4-dichlorobenzene), 144.89 (C-4 of methylbenzene),
146.87 (C-4 of phthalazine), 158.33 (CO, C-1 of phthala-
zine); LC–MS (m/z): 477 (M + 1, 100 %); Anal. calcd. For
C25H19Cl2N5O; Calcd: C, 63.03; H, 4.02; N, 14.70; found:
C, 63.03; H, 4.01; N, 14.72.
2-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]-4-(4-
methylphenyl)phthalazin-1(2H)-one (5d)
2-{[1-(4-nitrobenzyl)-1H-1,2,3-triazol-4-yl]methyl}-4-(4-
methylphenyl)phthalazin-1(2H)-one (5b)
White microcrystals; Yield: 85 %; mp: 174–176 °C; IR
(KBr νmax/cm−1): 2963 (C–H–str), 1662 (C=O), 1206
(N=N); H NMR (400 MHz, DMSO-d6): δ 2.42 (s, 3H,
1
Pale yellow microcrystals; Yield: 77 %; mp: 140–142 °C;
IR (KBr νmax/cm−1): 2960 (C–H–str), 1661 (C=O), 1304
(N=N); 1H NMR (400 MHz, DMSO-d6): δ 3.1 (s, 3H,
CH3), 5.52 (s, 2H, CH2 ), 5.81(s, 2H, CH2), 7.27 (d,2H,
ArH), 7.34 (d, 2H, ArH), 7.69–7.78 ( m, 4H, ArH), 7.95 (m,
2H, ArH), 8.27–8.31 (m, 2H, ArH), 8.38 (1H, 1,2,3-triazole
H); 13C NMR (100 MHz, DMSO-d6): 21.52 (CH3), 46.70
(N–CH2 ), 52.25 (N–CH2 ), 124.40 (C-3 of 4-nitrobenzene),
125.01(C-5 of triazole), 126.12 (C-5 of phthalazine), 127.03
(C-8 of phthalazine), 127.25 (C-2 of 4-nitrobenzene),
127.98 (C-2 of 4-methylbenzene), 129.12 (C-9 of phthala-
zine), 129.55 (C-1 of 4-methylbenzene), 129.90 (C-10 of
phthalazine), 132.30 (C-3 of 4-methylbenzene), 132.51 (C-
7 of phthalazine), 134.14 (C-6 of phthalazine), 136.25 (C-1
of 4-nitrobenzene), 138.88 (C-4 of 4-methylbenzene),
143.12 (C-4 of triazole), 145.25 (C-1 of 4-nitrobenzene),
147.69 (C-4 of phthalazine), 158.30 (CO, C-1 of phthala-
zine); LC–MS (m/z): 453 (M + 1, 100 % ); Anal. calcd. For
C25H20N6O3; Calcd: C, 66.36; H, 4.46; N, 18.57; found: C,
66.34; H, 4.47; N, 18.58.
CH3), 5.44 (s, 2H, CH2), 5.56 (s, 2H, CH2), 7.29–7.37 (m,
7H, ArH), 7.45 (d, 2H, ArH), 7.72 (1H, ArH), 7.91 (d, 2H,
ArH), 8.16 (s, 1H, 1,2,3-triazole H), 8.38 (m, 1H, ArH); 13
C
NMR (100 MHz, DMSO-d6): 21.38 (CH3), 46.65 (N–CH2),
53.23 (N–CH2), 124.41 (C-5 of triazole), 127.02 (C-5 of
phthalazine), 127.20 (C-8 of phthalazine), 127.96 (C-2 of
methylbenzene), 128.42 (C-9 of phthalazine), 128.58 (C-1
of methylbenzene), 129.12 (C-3 of phenyl ring), 129.19 (C-
10 of phthalazine), 129.58 (C-2 of phenyl ring), 129.78 (C-
3 of chlorobenzene), 132.21 (C-7 of phthalazine), 132.43
(C-1 of phenyl ring), 134.11 (C-6 of phthalazine), 136.53
(C-4 of methylbenzene),139.19 (C-4 of phenyl ring), 143.53
(C-4 of triazole), 146.87 (C-4 of phthalazine), 158.32 (CO,
C-1 of phthalazine); LC–MS (m/z): 408 (M + 1, 100 % );
Anal. calcd. For C25H21N5O; Calcd: C, 73.69; H, 5.19; N,
17.19; found: C, 73.71; H, 5.18; N, 17.17.
2-{[1-(3-methylbenzyl)-1H-1,2,3-triazol-4-yl]methyl}-4-(4-
chlorophenyl) phthalazin-1(2H)-one (5e)
White microcrystals; Yield: 72 %; mp: 210–212 °C; IR (KBr
1
2-{[1-(2,4-dichlorobenzyl)-1H-1,2,3-triazol-4-yl]methyl}-4-
ν
max/cm−1): 2978 (C–H–str), 1704 (C=O), 1222 (N=N); H
(4-methylphenyl)phthalazin-1(2H)-one (5c)
NMR (400 MHz, DMSO-d6): δ 2.32 (s, 3H, CH3), 5.41 (s,
2H, CH2), 5.51 (s, 2H, CH2), 7.11 (m, 3H, ArH), 7.25 (s, 1H,
ArH), 7.61–7.69 (m, 4H, ArH), 7.74 (m, 1H, ArH),
7.90–7.92 (m, 2H, ArH), 8.29 (s, 1H, 1,2,3-triazole H), 8.38
(1H, ArH); 13C NMR (100 MHz, DMSO-d6): 20.91 (CH3),
46.22 (N–CH2), 52.75 (N–CH2), 124.01 (C-5 of triazole),
125.06 (C-5 of phthalazine), 126.56 (C-8 of phthalazine),
127.07 (C-4 of 3-methylbenzene), 127.15 (C-6 of 3-
methylbenzene), 128.05 (C-2 of 3-methylbenzene), 128.65
(C-9 of phthalazine), 128.78 (C-3 of chlorobenzene), 128.99
(C-5 of 3-methylbenzene), 129.18 (C-1 of chlorobenzene),
131.77 (C-10 of phthalazine), 132.59 (C-2 of chlor-
obenzene), 133.95 (C-7 of phthalazine), 134.25 (C-6 of
Yellow microcrystals; Yield: 79 %; mp: 176–178 °C; IR
(KBr νmax/cm−1): 2968 (C–H–str), 1664 (C=O), 1206
1
(N=N); H NMR (400 MHz, DMSO-d6): δ 2.42 (s, 3H,
CH3), 5.45 (s, 2H, CH2), 5.67 (s, 2H, CH2), 7.23 (d, 1H,
ArH ), 7.36 (d, 2H, ArH, J =8 Hz), 7.44 (m, 3H, ArH), 7.71
(2H, ArH), 7.91 (2H, ArH), 8.15 (s, 1H, 1,2,3-triazole H),
8.38 (1H, ArH); 13C NMR (100 MHz, DMSO-d6): 21.38
(CH3), 46.45 (N–CH2), 50.45 (N–CH2), 124.92 (C-5 of
triazole), 127.03 (C-5 of phthalazine), 127.19 (C-8 of
phthalazine), 127.95 (C-5 of 2,4-dichlorobenzene), 128.34
(C-2 of methylbenzene), 129.08 (C-9 of phthalazine),

Med Chem Res
phthalazine), 134.55 (C-4 of chlorobenzene), 138.02 (C-4 of
triazole), 139.05 (C-3 of 3-methylbenzene), 139.75 (C-1 of
3-methylbenzene), 149.40 (C-4 of phthalazine), 157.98 (CO);
LC–MS (m/z): 443 (M + 1, 100 % ); Anal. calcd. For
C25H20ClN5O; Calcd: C, 67.95; H, 4.56; N, 15.85; found: C,
67.97; H, 5.51; N, 15.87.
2-[(1-Benzyl-1H-1,2,3-triazol-4-yl)methyl]-4-(4-
chlorophenyl)phthalazin-1(2H)-one (5h)
White microcrystals; Yield: 89 %; mp: 194–196 °C; IR
(KBr νmax/cm−1): 2963 (C–H–str), 1662 (C=O), 1206
1
(N=N); H NMR (400 MHz, DMSO-d6): δ 5.52 (s, 2H,
CH2), 5.81 (s, 2H, CH2), 7.57 (2H, ArH), 7.69–7.78 (m,
6H, ArH), 7.95 (2H, ArH), 8.27–8.31 (m, 2H, ArH and
1,2,3-triazole H), 8.44 (m, 1H, ArH ); 13C NMR (100 MHz,
DMSO-d6): 46.76 (N–CH2), 52.35 (N–CH2), 123.98 (C-5
of triazole), 126.99 (C-5 of phthalazine), 127.08 (C-8 of
phthalazine), 127.97 (C-9 of phthalazine), 128.39 (C-3 of
chlorobenzene), 128.55 (C-3 of phenyl ring), 128.75 (C-1
of chlorobenzene), 129.15 (C-10 of phthalazine), 129.99
(C-2 of phenyl ring), 131.78 (C-7 of phthalazine), 132.55
(C-1 of phenyl ring), 133.94 (C-6 of phthalazine), 134.22
(C-4 of chlorobenzene), 142.50 (C-5 of triazole), 145.70 (C-4
of phthalazine), 158.32 (CO, C-1 of phthalazine); LC–MS
(m/z): 429 (M + 1, 100 % ); Anal. calcd. For C24H18ClN5O;
Calcd: C, 67.37; H, 4.24; N, 16.37; found: C, 67.39; H,
4.23; N, 16.35.
2-{[1-(4-Nitrobenzyl)-1H-1,2,3-triazol-4-yl]methyl}-4-(4-
chlorophenyl)phthalazin-1(2H)-one (5f)
Yellow microcrystals; Yield: 75 %; mp: 180–182 °C; IR
(KBr νmax/cm−1): 2965 (C–H–str), 1660 (C=O), 1208
(N=N), 801 (C–H bond); 1H NMR (400 MHz, DMSO-d6): δ
5.52 (s, 2H, CH2), 5.80 (s, 2H, CH2), 7.57 (d, 2H, ArH ),
7.67 (m, 4H, ArH), 7.76 (m, 1H, ArH ), 7.98 (m, 2H, ArH),
8.27 (d, 2H, ArH ), 8.31 (s, 1H, 1,2,3-triazole H), 8.44 (m,
1H, ArH); 13C NMR (100 MHz, DMSO-d6): 46.73
(N–CH2), 52.33 (N–CH2), 124.35 (C-3 of 4-nitrobenzene),
124.92 (C-5 of triazole), 127.02 (C-5 of phthalazine), 127.07
(C-8 of phthalazine), 127.92 (C-2 of 4-nitrobenzene), 128.86
(C-3 of 4-chlorobenzene), 129.13 (C-9 of phthalazine),
129.51 (C-10 of phthalazine), 131.75, 132.61 (C-7 of
phthalazine), 133.88 (C-6 of phthalazine), 134.26 (C-3 of 4-
chlorobenzene) 4, 134.54 (C-1 of 4-nitrobenzene), 143.60
(C-1 of 4-nitrobenzene), 143.91(C-4 of triazole), 145.80 (C-1
of 4-nitrobenzene), 147.67(C-4 of phthalazine), 158.34
(CO, C-1 of phthalazine); LC–MS (m/z): 474 (M + 1, 100 % );
Anal. calcd. For C24H17ClN6O3; Calcd: C, 60.96; H, 3.62;
N, 17.77; found: C, 60.99; H, 3.60; N, 17.76.
2-{[1-(4-hydroxybenzoyl)-1H-1,2,3-triazol-4-yl]methyl}-4-
(4-methylphenyl)phthalazin-1(2H)-one (6a)
Off-white microcrystals; Yield: 56 %; mp: 220 °C (decom-
poses); IR (KBr νmax/cm−1): 3273 (O–H str), 2961
(C–H–str), 1684 (C=O), 1648 (C=O), 1206 (N=N); 1H
NMR (400 MHz, DMSO-d6): δ 3.1 (s, 3H, CH3), 5.52 (s,
2H, N–CH2), 5.81 (s, 2H, COCH2), 6.89 (m, 2H, ArH),
7.32 (d, 2H, ArH ), 7.41 (d, 2H, ArH ), 7.69 (m, 1H, ArH),
7.71–7.76 (m, 4H, ArH), 8.1 (s, 1H, 1,2,3-triazole H), 8.46
(m,1H, ArH); 13C NMR (100 MHz, DMSO-d6): 21.40
(CH3), 46.83 (N–CH2), 54.18 (N–CH2), 115.05 (C-3 of 4-
hydroxybenzene), 126.28 (C-5 of triazole), 127.04 (C-5 of
phthalazine), 127.28 (C-8 of phthalazine), 127.97 (C-2 of
methylbenzene), 128.11 (C-9 of phthalazine), 128.50 (C-1
of methylbenzene), 129.15 (C-10 of phthalazine), 129.63
(C-2 of 4-hydroxybenzene), 129.85 (C-3 of methylben-
zene), 132.16 (C-7 of phthalazine), 132.48 (C-1 of 4-
hydroxybenzene), 134.16 (C-6 of phthalazine), 137.24 (C-4
of triazole), 142.45 (C-4 of methylbenzene), 146.98 (C-4 of
phthalazine), 156.05 (C-4,C-OH) 158.42 (CO, C-1 of
phthalazine), 188.92 (CO); LC–MS (m/z): 452 (M + 1, 100
%); Anal. calcd. For C26H21N5O3; Calcd: C, 69.17; H, 4.69;
N, 15.51; found: C, 69.19; H, 4.70; N, 15.49.
2-{[1-(2,4-Dichlorobenzyl)-1H-1,2,3-triazol-4-yl]methyl}-
4-(4-chlorophenyl)phthalazin-1(2H)-one (5g)
Off-white microcrystals; Yield: 76 %; mp: 188–190 °C; IR
(KBr νmax/cm−1): 2963 (C–H–str), 1662 (C=O), 1206
1
(N=N); H NMR (400 MHz, DMSO-d6): δ 5.52 (s, 2H,
CH2), 5.81 (s, 2H, CH2), 7.57 (m, 3H, ArH ), 7.69–7.78 (m,
5H, ArH), 7.95 (m, 2H, ArH), 8.12 (s, 1H, 1,2,3-triazole H),
8.44 (m, 1H, ArH ); 13C NMR (100 MHz, DMSO-d6):
46.70 (N–CH2), 52.35 (N–CH2), 124.96 (C-5 of triazole),
126.98 (C-5 of phthalazine), 127.07 (C-8 of phthalazine),
127.95(C-5 of 2,4-dichlorobenzene), 128.92 (C-9 of
phthalazine), 129.15 (C-3 of 4-chlorobenzene), 129.76 (C-1
of 4-chlorobenzene), 130.25 (C-10 of phthalazine), 130.55
(C-2 of 4-chlorobenzene), 130.79 (C-3 of 2,4-dichlor-
obenzene), 130.98 (C-6 of 2,4-dichlorobenzene), 132.76
(C-7 of phthalazine), 134.40 (C-2 of 2,4-dichlorobenzene),
134.55 (C-6 of phthalazine), 135.00 (C-6 of 2,4-dichlor-
obenzene), 141.20 (C-4 of 2,4-dichlorobenzene), 142.70
(C-4 of triazole), 147.98 (C-4 of phthalazine), 158.32 (CO,
C-1 of phthalazine); LC–MS (m/z): 497 (M + 1, 100 % );
Anal. calcd. For C24H16Cl3N5O; Calcd: C, 58.03; H, 3.25;
N, 14.10; found: C, 58.05; H, 3.24; N, 14.09.
2-{[1-(2,4-dichlorobenzoyl)-1H-1,2,3-triazol-4-yl]methyl}-
4-(4-methylphenyl)phthalazin-1(2H)-one (6b)
Yellow microcrystals; Yield: 61 %; mp: 213 °C (decom-
poses); IR (KBr νmax/cm−1): 2976 (C–H–str), 1705 (C=O),
1
1652 (C=O), 1220 (N=N); H NMR (400 MHz, DMSO-

Med Chem Res
d6): δ 2.51 (s, 3H, CH3), 5.49 (s, 2H, NCH2), 6.02 (s, 2H,
COCH2), 7.38 (d, 2H, ArH, J = 7.6 Hz), 7.51 (d, 2H, ArH,
J = 7.6 Hz), 7.64 (dd, 1H, ArH), 7.75 (m, 1H, ArH ), 7.82
(d,1H, ArH), 7.93–7.99 (m, 3H, ArH), 8.11 (s, 1H, 1,2,3-
triazole H), 8.40 (d,1H, ArH); 13C NMR (100 MHz,
DMSO-d6): 21.47 (CH3), 46.40 (N–CH2), 50.42 (N–CH2),
124.93 (C-5 of triazole), 127.05 (C-5 of phthalazine),
127.21 (C-8 of phthalazine), 127.95 (C-5 of 2,4-dichlor-
obenzene), 128.10 (C-2 of methylbenzene), 128.34 (C-9 of
phthalazine), 128.82 (C-1 of methylbenzene), 129.15 (C-10
of phthalazine), 129.62 (C-6 of 2,4-dichlorobenzene),
129.78 (C-3 of methylbenzene), 132.30 (C-3 of 2,4-
dichlorobenzene), 132.51 (C-7 of phthalazine), 133.00 (C-2
of 2,4-dichlorobenzene), 134.08 (C-6 of phthalazine),
134.40 (C-1 of 2,4-dichlorobenzene), 137.20 (C-4 of tria-
zole), 139.25 (C-4 of 2,4-dichlorobenzene), 142.45 (C-2 of
methylbenzene), 147.00 (C-4 of phthalazine), 158.50 (CO,
C-1 of phthalazine), 189.09 (CO); LC–MS (m/z): 505 (M +
1, 100 %); Anal. calcd. For C26H19Cl2N5O2; Calcd: C,
61.91; H, 3.80; N, 14.06; found: C, 61.90; H, 3.81; N,
14.06.
NMR (400 MHz, DMSO-d6): δ 5.50 (s, 2H, NCH2), 6.02 (s,
2H, COCH2), 6.91 (d, 2H, ArH, J = 8Hz), 7.63–7.68 (m,
4H, ArH), 7.73 (m, 1H, ArH), 7.93 (m, 4H, ArH), 8.07 (s,
1H, 1,2,3-triazole H), 8.41 (m, 1H, ArH), 10.59 (s, 1H,
OH); 13C NMR (100 MHz, DMSO-d6): 46.70 (N–CH2),
52.38 (N–CH2), 115.03 (C-3 of 4-hydroxybenzene), 125.02
(C-5 of triazole), 127.01 (C-5 of phthalazine), 127.11 (C-8
of phthalazine), 127.99 (C-9 of phthalazine), 128.50 (C-3 of
chlorobenzene), 128.95 (C-1 of chlorobenzene), 129.16 (C-
10 of phthalazine), 129.30 (C-2 of 4-hydroxybenzene),
131.77 (C-2 of chlorobenzene), 132.02 (C-7 of phthala-
zine), 132.61 (C-1 of 4-hydroxybenzene), 133.95 (C-6 of
phthalazine), 134.23 (C-4 of chlorobenzene), 134.50 (C-4
of triazole), 145.79 (C-4 of phthalazine), 156.09 (C-4,C-
OH), 158.20 (CO, C-1 of phthalazine), 189.15 (CO);
LC–MS (m/z): 473 (M + 1, 100 % ); Anal. calcd. For
C25H18ClN5O3; Calcd: C, 63.63; H, 3.84; N, 14.84; found:
C, 63.64; H, 3.85; N, 14.82.
2-{[1-(2,4-dichlorobenzoyl)-1H-1,2,3-triazol-4-yl]methyl}-
4-(4-chlorophenyl) phthalazin-1(2H)-one (6e)
2-{[1-(4-methylbenzoyl)-1H-1,2,3-triazol-4-yl]methyl}-4-
(4-methylphenyl)phthalazin-1(2H)-one (6c)
Pale yellow microcrystals; Yield: 49 %; mp: 225 °C
(decomposes); IR (KBr νmax/cm−1): 2980 (C–H–str), 1700
1
(C=O), 1648 (C=O), 1225 (N=N); H NMR (400 MHz,
Yellow microcrystals; Yield: 58 %; mp: 200 °C (decom-
DMSO-d6): δ 5.53 (s, 2H, NCH2), 6.05 (s, 2H, COCH2),
7.09 (d, 2H, ArH ), 7.67 (d, 2H, ArH), 7.71–7.91 (m, 6H,
poses); IR (KBr νmax/cm−1): 2963 (C–H–str), 1682 (C=O),
1
1642 (C=O), 1206 (N=N); H NMR (400 MHz, DMSO-
ArH), 8.11 (s, 1H, 1,2,3-triazole H), 8.37 (d, 1H, ArH); 13
C
d6): δ 2.40 (s, 6H, CH3), 5.48 (s, 2H, NCH2), 6.09 (s, 2H,
COCH2), 7.37 (4H, ArH), 7.50 (d, 2H, ArH), 7.72 (m, 1H,
ArH), 7.91 (m, 3H, ArH), 8.06 (s, 1H, 1,2,3-triazole H),
8.38 (m, 1H, ArH); 13C NMR (100 MHz, DMSO-d6): 21.39
(CH3), 21.73 (CH3), 46.81 (N–CH2), 56.15 (N–CH2),
126.00 (C-5 of triazole), 127.03 (C-5 of phthalazine),
127.23 (C-8 of phthalazine), 127.99 (C-2 of methylben-
zene), 128.70 (C-9 of phthalazine), 129.13 (C-1 of
methylbenzene), 129.61 (C-2 of methylbenzene), 129.85
(C-10 of phthalazine), 129.96 (C-3 of methylbenzene),
132.12 (C-3 of methylbenzene), 132.23 (C-7 of phthala-
zine), 132.46 (C’-1 of methylbenzene), 134.14 (C-6 of
phthalazine), 139.21 (C-4 of triazole), 143.12 (C-4 of
methylbenzene), 145.25 (C-3 of methylbenzene), 146.89
(C-4 of phthalazine), 158.32 (CO, C-1 of phthalazine),
188.90 (CO); LC–MS (m/z): 450 (M + 1, 100 %); Anal.
calcd. For C27H23N5O2; Calcd: C, 72.14; H, 5.16; N, 15.58;
found: C, 72.12; H, 5.14; N, 15.61.
NMR (100 MHz, DMSO-d6): 46.72 (N–CH2), 52.40
(N–CH2), 124.99 (C-5 of triazole), 127.01 (C-5 of phtha-
lazine), 127.10 (C-8 of phthalazine), 127.89 (C-5 of 2,4-
dichlorobenzene),128.09 (C-9 of phthalazine), 128.90 (C-3
of chlorobenzene), 129.05 (C-1 of chlorobenzene), 129.20
(C-10 of phthalazine),129.62 (C-2 of chlorobenzene),
130.78 (C-6 of 2,4-dichlorobenzene), 131.50 (C-3 of 2,4-
dichlorobenzene), 132.25 (C-7 of phthalazine), 133.35 (C-2
of 2,4-dichlorobenzene), 133.71 (C-6 of phthalazine),
134.33 (C-4 of chlorobenzene), 134.80 (C-1 of 2,4-
dichlorobenzene), 134.98 (C-4 of triazole), 139.98 (C-4 of
2,4-dichlorobenzene), 146.90 (C-4 of phthalazine), 159.20
(CO, C-1 of phthalazine), 192.15 (CO); LC–MS (m/z): 525
(M + 1, 100 %); Anal. calcd. For C25H16Cl3N5O2; Calcd: C,
57.22; H, 3.07; N, 13.35; found: C, 57.25; H, 3.09; N,
13.30.
2-{[1-(4-methylbenzoyl)-1H-1,2,3-triazol-4-yl]methyl}-4-
(4-chlorophenyl) phthalazin-1(2H)-one (6f)
2-{[1-(4-hydroxybenzoyl)-1H-1,2,3-triazol-4-yl]methyl}-4-
(4-chlorophenyl)phthalazin-1(2H)-one (6d)
White microcrystals; Yield: 62 %; mp: 192 °C (decom-
poses); IR (KBr νmax/cm−1): 2963 (C–H–str), 1688 (C=O),
1
Yellow microcrystals; Yield: 52 %; mp: 216 °C (decom-
poses); IR (KBr νmax/cm−1): 3390 (O–H str), 2979
(C–H–str), 1680 (C=O), 1644 (C=O), 1208 (N=N); 1H
1638 (C=O), 1206 (N=N); H NMR (400 MHz, DMSO-
d6): δ 2.50 (s, 3H, CH3), 5.52 (s, 2H, NCH2), 5.81 (s, 2H,
COCH2), 7.37 (d, 2H, ArH), 7.42 (d, 2H, ArH), 7.69–7.81

Med Chem Res
(m, 5H, ArH), 7.95 (d, 2H, ArH), 8.09 (s, 1H, 1,2,3-triazole
H), 8.43 (d, 1H, ArH); 13C NMR (100 MHz, DMSO-d6):
21.73 (CH3), 46.88 (N–CH2), 54.19 (N–CH2), 124.99 (C-5
of triazole), 126.05 (C-5 of phthalazine), 126.99 (C-8 of
phthalazine), 127.99 (C-9 of phthalazine), 128.56 (C-3 of
chlorobenzene), 128.70 (C-1 of chlorobenzene), 128.92 (C-
10 of phthalazine), 129.15 (C-2 of methylbenzene), 129.49
(C-2 of chlorobenzene), 130 (C-3 of methylbenzene),
131.80 (C-7 of phthalazine), 132.15 (C-1 of methylben-
zene), 133.94 (C-6 of phthalazine), 134.22 (C-4 of chlor-
obenzene), 134.53 (C-4 of triazole), 142.98 (C-4 of
methylbenzene), 145.73 (C-4 of phthalazine), 158.32 (CO,
C-1 of phthalazine), 192.10 (CO); LC–MS (m/z): 471(M +
1, 100 %); Anal. calcd. For C26H20ClN5O2; Calcd: C,
66.45; H, 4.29; N, 14.90; found: C, 66.43; H, 4.31; N,
14.91.
methylbenzene), 129.14 (C-3 of methylbenzene), 129.60
(C-5 of phthalazine), 129.82 (C-10 of phthalazine), 132.23
(C-7 of phthalazine), 132.43 (C-6 of phthalazine), 133.28
(CH of propelene), 134.12 (C-9 of phthalazine), 139.20 (C-
4 of methylbenzene), 143.36 (C-5 of triazole), 146.87 (C-4
of phthalazine), 158.33 (CO, C-1 of phthalazine); LC–MS
(m/z): (M + 1, 100 %); Anal. calcd. For C21H19N5O; Calcd:
C, 70.57; H, 5.36; N, 19.59; found: C, 70.55; H, 5.35; N,
19.61.
2-[(1-Isopropyl-1H-1,2,3-triazol-4-ylm)ethyl]-4-(4-
chlorophenyl)phthalazin-1(2H)-one (7c)
White microcrystals; Yield: 78 %; mp: 162–164 °C; IR
(KBr νmax/cm−1): 2965(C–H–str), 1708 (C=O), 1225
1
(N=N); H NMR (400 MHz, DMSO-d6): δ 1.45 (d, 6H,
CH3), 4.78 (m, 1H, CH), 5.44 (s, 2H, NCH2), 7.64 (m, 4H,
ArH), 7.72 (m, 1H, ArH), 7.93 (m, 2H, ArH), 8.13 (s, 1H,
1,2,3-triazole H), 8.39 (1H, ArH); 13C NMR (100 MHz,
DMSO-d6): 23.15 (CH3), 46.96 (N–CH), 52.77 (N–CH2),
121.97 (C-4 of triazole), 126.99 (C-8 of phthalazine),
127.09 (C-3 of chlorobenzene), 127.98 (C-1 of chlor-
obenzene), 128.91 (C-5 of phthalazine), 129.15 (C-10 of
phthalazine), 131.79 (C-2 of chlorobenzene), 132.57 (C-7
of phthalazine), 133.94 ( C-6 of phthalazine), 134.22 ( C-9
of phthalazine), 134.53 (C-4 of chlorobenzene), 142.98 (C-
5 of triazole), 145.73 (C-4 of phthalazine), 158.33 (CO, C-1
of phthalazine); LC–MS (m/z): 381 (M + 1, 100 %); Anal.
calcd. For C20H18ClN5O; Calcd: C, 63.24; H, 4.78; N,
18.44; found: C, 63.23; H, 4.76; N, 18.46.
2-{[1-isopropyl-1H-1,2,3-triazol-4-yl]methyl}-4-(4-
methylphenyl)phthalazin-1(2H)-one (7a)
White microcrystals; Yield: 76 %; mp: 150–152 °C; IR
(KBr νmax/cm−1): 2975 (C–H–str), 1672 (C=O), 1206
1
(N=N); H NMR (400 MHz, DMSO-d6): δ 1.49 (d, 6H,
CH3), 4.80 (m, 1H, CH), 5.48 (s, 2H, NCH2), 7.40 (d, 2H,
ArH, J = 8 Hz), 7.49 (d, 2H, ArH, J = 8 Hz), 7.75–7.96 (m,
3H, ArH), 8.11 (s, 1H, 1,2,3-triazole H), 8.38 (d, 1H, ArH);
13C NMR (100 MHz, DMSO-d6): 21.40 (CH3), 23.15
(isopropyl CH3), 46.89 (N–CH), 52.15 (N–CH2), 123.11
(C-4 of triazole), 127.00 (C-8 of phthalazine), 127.20 (C-1
of methylbenzene), 127.97 (C-2 of methylbenzene), 129.12
(C-3 of methylbenzene), 129.59 (C-5 of phthalazine),
129.80 (C-10 of phthalazine), 132.21 (C-7 of phthalazine),
132.44 (C-6 of phthalazine), 134.12 (C-9 of phthalazine),
139.20 (C-4 of methylbenzene), 143.10 (C-5 of triazole),
146.90 (C-4 of phthalazine), 158.30 (CO, C-1 of phthala-
zine); LC–MS (m/z): (M + 1, 100 %); Anal. calcd. For
C21H21N5O; Calcd: C, 70.17; H, 5.89; N, 19.48; found: C,
70.15; H, 5.87; N, 19.51.
2-{[1-(2-Propenyl)-1H-1,2,3-triazol-4-yl]methyl}-4-(4-
chlorophenyl)phthalazin-1(2H)-one (7d)
Cream coloured microcrystals; Yield: 69 %; mp: 120–122 °
C; IR (KBr νmax/cm−1): 2979 (C–H–str), 1698 (C=O), 1221
1
(N=N); H NMR (400 MHz, DMSO-d6): δ 4.92 (d, 2H,
CH2), 5.11–5.23 (dd, 2H, allylic CH2), 5.43 (s, 2H, NCH2),
5.96–6.07 (m, 1H, allylic CH), 7.63 (d, 2H, ArH, J = 8Hz),
7.71 (d, 2H, ArH, J = 8 Hz), 7.78 (d, 1H, ArH), 7.92 (m,
2H, ArH), 8.11 (s, 1H, 1,2,3-triazole H), 8.41 (d, 1H, ArH);
13C NMR (100 MHz, DMSO-d6): 46.88 (N–CH2), 52.17
(N–CH2), 119.21 (CH2), 122.95 (C-4 of triazole), 126.98
(C-8 of phthalazine), 127.08 (C-3 of chlorobenzene),
127.92 (C-1 of chlorobenzene), 126.88 (C-5 of phthala-
zine), 129.13 (C-3 of chlorobenzene), 131.77 (C-2 of
chlorobenzene), 132.55 (C-7 of phthalazine), 133.44 (CH of
propelene), 133.92 ( C-6 of phthalazine), 134.20 ( C-9 of
phthalazine), 134.51 (C-4 of chlorobenzene), 142.95 (C-5
of triazole), 145.70 (C-4 of phthalazine), 158.28 (CO, C-1
of phthalazine); LC–MS (m/z): 379 (M+1, 100 %); Anal.
calcd. For C20H16ClN5O; Calcd: C, 63.58; H, 4.27; N,
18.54; found: C, 63.55; H, 4.25; N, 18.57.
2-{[1-(2-propenyl)-1H-1,2,3-triazol-4-yl]methyl}-4-(4-
methylphenyl)phthalazin-1(2H)-one (7b)
Off-white microcrystals; Yield: 62 %; mp: 108–110 °C; IR
(KBr νmax/cm−1): 2979 (C–H–str), 1698 (C=O), 1221
1
(N=N); H NMR (400 MHz, DMSO-d6): δ 2.42 (s, 3H,
CH3), 4.98 (d, 2H, CH2), 5.15–5.25 (dd, 2H, allylic CH2),
5.45 (s, 2H, NCH2), 5.98–6.08 (m, 1H, allylic CH), 7.38 (d,
2H, ArH, J = 8Hz), 7.47 (d, 2H, ArH, J = 8 Hz), 7.73 (m,
1H, ArH), 7.92 (m, 2H, ArH), 8.05 (s, 1H, 1,2,3-triazole H),
8.39 (1H, ArH); 13C NMR (100 MHz, DMSO-d6): 21.38
(CH3), 46.82 (N–CH2), 52.11 (N–CH2), 119.24 (CH2),
124.20 (C-4 of triazole), 127.02 (C-8 of phthalazine),
127.21 (C-1 of methylbenzene), 127.99 (C-2 of

Med Chem Res
Results and discussion
Chemistry
microbial strains compared to the standard drug. Among
them, compounds 5c, 5g, 5h, 6b and 6e showed excellent
antibacterial activity. The data further reveals that 2,4-
dichlorophenyl substituted compounds are showing
enhanced antibacterial activity. Similarly compound 5h
with a phenyl substitution is also showing very good anti-
bacterial activity comparable with the standard drug Strep-
tomycin. All other compounds are showing moderate
activity against all the tested bacterial strains compared to
the standard drug.
The results of in vitro antifungal activities of new deri-
vatives 5a–h, 6a–f and 7a–d indicate that, among the tested
compounds 5g and 6d are active against all tested fungal
strains. Compound 5g bearing 2,4-dichlorophenyl sub-
stituent in 1,2,3-triazole ring and 4-chlorophenyl substituent
in phthalazine moiety and compound 6d possessing 4-
hydroxyphenyl substituent in 1,2,3-triazole ring, and 4-
chlorophenyl substituent in phthalazine are the leads among
the tested compounds. All other compounds are showing
moderate to feeble activity against all the tested fungal
strains compared to the standard drug fluconazole.
Phthalazine derivatives were synthesized from 2-(4-methyl/
chloro benzyloxy) benzoic acid by esterification followed
by
hydrazinolysis.
The
4-(4-methyl/chlorophenyl)
phthalazine-1-ol is then condensed with propargyl bromide
to get 4-(4-chloro/methylphenyl)-2-prop-2-yn-1-ylphthala-
zin-1(2H)-one (4a, b). The targeted regioselective 1,4-dis-
ubstituted 1,2,3-triazole derivatives (5a–h, 6a–f and 7a–d)
were synthesized by multicomponent one pot click chem-
istry approach, by reacting 4-(4-chloro/methylphenyl)-2-
prop-2-yn-1-ylphthalazin-1(2H)-one (4a, b) with various
benzyl/phenacyl/alkyl bromides. Newly synthesized com-
pounds were characterized by IR, NMR, mass spectral and
C, H, N elemental analyses.
In the IR spectrum of 4a, the carbonyl absorption band was
observed at 1657/cm−1. The acetylenic absorption band was
seen at 2215/cm−1. Further in the 1H NMR spectrum of 4-(4-
methylphenyl)-2-prop-2-yn-1-ylphthalazin-1(2H)-one 4a, the
methyl group attached to the phenyl ring came into resonance
as a singlet at δ 2.40 integrating for three protons. The acet-
ylenic proton gave a distinct peak at δ 3.32. The –NCH2
protons appeared as a singlet at δ 4.97. The signals due to
aromatic protons of phenyl ring appeared as two doublets
centred at 7.37 and 7.48 integrating for two protons each. The
peak due to aromatic protons of phthalazine ring appeared at
7.71, 7.91 and 8.36 corresponding to four protons.
The free radical-scavenging activity of the final com-
pounds was measured by DPPH. Antioxidant activity result
shows that 1,2,3-triazole derivatives 5a, 5f and 7c showed
significant antioxidant property when compared with the
standard butylhydroxytoluene (BHT). Compounds 5a, 5f
and 7c contains 3-methyl phenyl, 4-nitrophenyl and iso-
propyl substituents, respectively, in 1,2,3-triazole ring,
which may be accounted for the enhanced activity.
In the IR spectrum of 5a, the acetylinic triple bond
1
stretching at 2215/cm−1 gets disappeared. In the H NMR
Biological activity
spectrum the methyl groups attached to the phenyl ring came
into resonance as singlet at δ 2.24 and 2.40, respectively,
integrating for three protons each. The CH2 protons attached
to phthalazine nitrogen came into resonance at δ 5.41 while
the CH2 proton attached to the triazole appeared at δ 5.49
each integrating for two protons. The signals due to aromatic
protons appeared as a multiplet at δ 7.09 corresponding to
three protons, δ 7.22 corresponds to one proton, doublets at δ
7.34 and δ 7.44 corresponds to two protons each, a multiplet
centred at δ 7.7 corresponds to one proton, a multiplet centred
at δ 7.9 corresponds to two protons and a multiplet centred at
δ 8.37 corresponds to one proton. The lone triazole proton
appeared as a singlet at δ 8.35. Further the mass spectrum of
this compound showed the molecular ion peak at m/z 422 (M
+ 1 peak, 100 %) consistent with the molecular formula
C26H23N5O. The characterization data of the newly synthe-
sized compounds are given in the experimental section.
Antimicrobial studies: antibacterial studies
The newly synthesized compounds (5a–h, 6a–f and 7a–d)
were screened for their in vitro antibacterial activity against
Escherichia coli (ATCC 25922), Pseudomonas aeruginosa
(ATCC 27853) and Bacillus subtilis (MTCC- 441) by well-
plate method (zone of inhibition) in Muller Hinton agar
(Leandro et al., 1995; Beth et al., 2000). The test com-
pounds were dissolved in DMSO at concentrations of 0.5
and 1.0 mg/mL.
All bacterial strains were maintained on nutrient agar
medium at 37 °C. The cultures were inoculated in fresh 10
mL Nutrient Broth to yield an initial suspension of
approximately 10–100 CFU/mL. All broths were then
incubated statically at 37 °C for 18–24 h. The bacterial
suspensions were diluted 10 fold in distilled water and 0.1
mL of the bacterial suspension was spread on nutrient agar
in order to give a population of approximately 106 CFU/
plate. The wells were dug in each petri plate by sterilized
cork borer. The compounds were dissolved in DMSO and
appropriate dilutions were made (1 and 0.5 mg/mL). Each
Pharmacology
The antibacterial screening revealed that, all the tested
compounds showed good inhibition against various

Med Chem Res
Table 1 Antibacterial activity
of title compounds 5a–h, 6a–f
and 7a–d
Compound no.
Escherichia coli
Pseudomonas
aeruginosa
Bacillus subtilis
Concentration in mg/mL
Control
1
0.5
1
0.5
1
0.5
00
00
00
Standard Streptomycin
21.3 0.17 18.4 0.43 19.6 0 .26 17.2 0.58 20.3 0.14 18.2 0.44
12.2 0.27 9.6 0.21 14.3 0.36 10.1 0.71 11.8 0.31 9.3 0.29
13.4 0.45 10.1 0.18 11.1 0.62 7.6 0.44 13.6 0.32 10.2 0.51
16.3 0.27 13.1 0.16 14.6 0.67 12.2 0.30 15.4 0.38 12.5 0.25
14.5 0.52 12.3 0.43 11.5 0.27 9.8 0.15 10.1 0.40 8.8 0.68
14.7 0.39 12.3 0.28 10.3 0.54 5.3 0.63 14.3 0.27 10.6 0.31
12.4 0.83 07.8 0.92 12.1 0.27 9.8 0.57 12.3 0.31 10.9 0.54
19.4 0.22 17.8 0.17 16.3 0.25 14.2 0.79 18.5 0.25 13.2 0.18
17.8 0.21 14.5 0.27 15.5 0.38 12.4 0.74 17.3 0.64 13.6 0.71
10.4 0.35 06.3 0.31 08.7 0.12 6.2 0.28 05.2 0.14 03.7 0.57
15.8 0.92 12.7 0.15 13.6 0.53 11.5 0.18 12.1 0.41 10.4 0.83
10.5 0.57 06.6 0.23 12.6 0.38 8.3 0.24 10.5 0.17 10.8 0.49
12.5 0.36 08.2 0.17 07.5 0.27 4.2 0.44 9.2 0.62 5.7 0.23
17.9 0.33 15.2 0.29 13.6 0.65 10.9 0.17 12.8 0.27 10.2 0.44
12.8 0.34 10.9 0.54 09.3 0.25 6.2 0.78 04.9 0.24 03.7 0.54
8.6 0.52 5.3 0.26 8.4 0.44 4.7 0.32 6.2 0.65 3.6 0.38
5a
5b
5c
5d
5e
5f
5g
5h
6a
6b
6c
6d
6e
6f
7a
7b
7c
7d
00
10.6 0.38 8.3 0.24 7.5 0.17 5.8 0.49
00 00 00 00
00
00
00
00
00
00
00
00
00
experiment was carried out in triplicate. After the inocula-
tion of the organism and compound, the petri plates were
incubated for 18 h at 37 oC. The diameter of zone of inhi-
bition was measured. Streptomycin was taken as the stan-
dard drug for antibacterial screening. The result of
antimicrobial activity determined for 5a–h, 6a–f and 7a–d
are summerised in Table 1.
positive control at a concentration of 1 mg/mL. The zone of
inhibition was determined for 5a–h, 6a–f and 7a–d and the
results are summerised in Table 2.
Antioxidant studies: DPPH radical-scavenging assay
Free radical-scavenging capacities of the final compounds
5a–h, 6a–f and 7a–d were determined using the stable
DPPH (Brand-Williams et al., 1995) . The stock solution of
test compounds (1 mg/mL) and DPPH (0.004 %) were
prepared using 95 % methanol. Freshly prepared DPPH
solution were taken in test tubes and organic compounds
were then added (100 μg) to every test tube. The absorbance
was measured after 10 min at 517 nm using a UV-visible
spectrophotometer (Shimadzu UV-1800, Japan). BHT was
used as a reference standard. Control sample was prepared
without any test compounds or BHT. 95 % Methanol was
used as blank.
Antifungal studies
The newly synthesized compounds were also screened for
their antifungal activity against Aspergillus flavus (MTCC
3306), Chrysosporium keratinophilum (MTCC 2827) and
Candida albicans (MTCC 227). The compounds were
dissolved in DMSO and antimicrobial activity was deter-
mined by well-plate method (MacLowry et al., 1970; Por-
tillo et al., 2001) at concentration of 1 and 0.5 mg/mL. The
required amounts of each fungal strain were taken from the
stock and suspended in 5 mL of distilled water with two
drops of Tween 80. This suspension was uniformly spread
on petri plates containing Potato dextrose agar media using
sterile swabs. After applying the samples into the wells
formed by using the same technique for tests on bacteria,
the plates were incubated at 25 °C for 3 days. The plates
were then examined for the presence of zones of inhibition
and the results were recorded. Fluconazole was used as a
DPPH radical scavenging activityð%Þ
¼ Abs Control ꢀ Abs Sample=Abs Control ´ 100;
where ‘Abs Control’ is the absorbance of DPPH radical
+ methanol; ‘Abs Sample’ is the absorbance of DPPH
radical + test sample/standard BHT.

Med Chem Res
Table 2 Antifungal activity of
title compounds 5a–h, 6a–f and
7a–d
Compound no.
Aspergillus flavus
Chrysosporium
keratinophilum
Candida albicans
Concentration in mg/mL
Control
1
0.5
1
0.5
1
0.5
00
00
00
Standard Fluconazole
13 0.2
03 0.1
00
10 0.1
01 0.1
00
17 0.2
03 0.2
00
15 0.2
01 0.1
00
22 0.2
04 0.1
00
20 0.2
02 0.2
00
5a
5b
5c
5d
5e
5f
00
00
00
00
00
00
00
00
00
00
00
00
07 0.1
05 0.2
10 0.1
09 0.2
04 0.1
06 0.2
09 0.2
10 0.1
00
05 0.2
03 0.1
08 0.2
07 0.2
02 0.2
04 0.1
07 0.2
07 0.1
00
06 0.1
04 0.1
13 0.2
08 0.1
05 0.2
05 0.2
08 0.1
12 0.2
00
04 0.2
03 0.2
10 0.2
07 0.1
02 0.2
04 0.1
07 0.1
10 0.1
00
04 0.1
05 0.2
15 0.1
06 0.2
05 0.2
04 0.2
06 0.2
16 0.2
00
03 0.2
02 0.2
11 0.1
04 0.1
03 0.1
03 0.2
04 0.1
13 0.1
00
5g
5h
6a
6b
6c
6d
6e
6f
03 0.2
7.3 0.3
00
01 0.1
5.7 0.3
00
04 0.1
4.5 0.3
00
02 0.2
3.2 0.6
00
03 0.1
7.1 0.8
00
02 0.2
4.4 0.5
00
7a
7b
7c
7d
00
00
00
00
00
00
00
00
00
00
00
00
Results were presented in Table 3 and Fig. 1 shows the
graphical representation of antioxidant activity.
Table 3 DPPH scavenging activity of title compounds 5a–h, 6a–f
and 7a–d
Compounds
DPPH assay in
per cent
5a
5b
5c
74.3
50.5
40.4
34.8
37.2
70.4
52.3
39.5
60.5
57.3
14.3
59.4
32.3
39.3
38.3
34.4
65.8
39.4
90.42
Conclusion
Three series of phthalazine-based 1,2,3-triazoles derivatives
(5a–h, 6a–f and 7a–d) were synthesized by multi-step
reactions in reasonably good yields and were characterized
by spectral studies and elemental analyses. All the final
derivatives were screened for their antimicrobial and anti-
oxidant activitiy. From the biological screening results we
can conclude that, a combination of two heterocyclic sys-
tems namely phthalazine and 1,2,3-triazoles has enhanced
the biological effect and hence they are suitable for further
modifications to get more effective antimicrobial/anti-
oxidant compounds.
5d
5e
5f
5g
5h
6a
6b
6c
6d
6e
6f
7a
7b
7c
Acknowledgments The authors are grateful to the Management,
SEQUENT SCIENTIFIC LTD, New Mangalore, India, for their
invaluable support and allocation of resources for this work. The
authors are also thankful to the Chairman, Department of Chemistry,
Mangalore University. SPC thanks to MIT, Manipal for recording
spectra.
7d
BHT

Med Chem Res
Fig. 1 DPPH scavenging
activity of the compounds 5a–h,
6a–f and 7a–d. “The experiment
was performed in triplicate and
the values expressed are as
Mean SD”
100
90
80
70
60
50
40
30
20
10
0
5a 5b 5c 5d 5e 5f 5g 5h 6a 6b 6c 6d 6e 6f 7a 7b 7c 7d BHT
Organic compounds
Compliance with ethical standards
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bacterial activity of some new heterocycles incorporating phtha-
lazine. Eur J Med Chem 44:4448–4454
Conflict of interest The authors declare that they have no conflict of
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