Synthesis and antifungal activities of N3-substituted quinazolin-4-one catalyzed by 3-Methylimidazole ionic liquids

Article abstract of DOI:10.14233/ajchem.2013.15509

N³-Substituted quinazolin-4-one was synthesized by alkyl bromide and quinazolin-4-one was synthesized by anthranilic acid and formamide, catalyzing in various 3-methylimidazole ionic liquids and TBAB. The results showed that the yield of N³-substituted quinazolin-4-one increased appreciably and the reaction time shorted under ionic liquids and TBAB. Using 1-methyl-3-(2-hydroxyl-3- acetoxylpropyl)imidazolium fluoroborate or 1-propyl-3-methylimidazole fluoroborate as catalyst, the yield of N3-benzylquinazolin-4-one reached 85.1 and 82.0 %, increased 27 % more than the yield of traditional conditions. The compounds were evaluated for their in vitro antifungal activity against Fusarium graminearum, Fusarium oxysporum and Cytospora mandshurica. Compound 3f inhibited Fusarium graminearum with EC ₅₀ 28.85 μg/mL, Fusarium oxysporum with EC₅₀ 24.68 μg/mL and Cytospora mandshurica with EC₅₀ 37.67 μg/mL.

Full text of DOI:10.14233/ajchem.2013.15509

Asian Journal of Chemistry; Vol. 25, No. 17 (2013), 9853-9856
http://dx.doi.org/10.14233/ajchem.2013.15509
Synthesis and Antifungal Activities of N3-Substituted
Quinazolin-4-one Catalyzed by 3-Methylimidazole Ionic Liquids
*
G. LIU , C.P. LIU, C.N. JI, L. SUN, X.G. LIU, Q.W. WEN and S.G. XU
School of Chemistry and Materials Science, Ludong University, Yantai 264025, P.R. China
*Corresponding author: Fax: +86 535 6696281; Tel: +86 535 6673048; E-mail: shdliugang@163.com
(Received: 20 March 2013; Accepted: 25 October 2013)
AJC-14289
N3-Substituted quinazolin-4-one was synthesized by alkyl bromide and quinazolin-4-one was synthesized by anthranilic acid and formamide,
catalyzing in various 3-methylimidazole ionic liquids and TBAB. The results showed that the yield of N3-substituted quinazolin-4-one
increased appreciably and the reaction time shorted under ionic liquids and TBAB. Using 1-methyl–3-(2-hydroxyl-3-
acetoxylpropyl)imidazolium fluoroborate or 1-propyl-3-methylimidazole fluoroborate as catalyst, the yield of N3-benzylquinazolin-4-one
reached 85.1 and 82.0 %, increased 27 % more than the yield of traditional conditions. The compounds were evaluated for their in vitro
antifungal activity against Fusarium graminearum, Fusarium oxysporum and Cytospora mandshurica. Compound 3f inhibited Fusarium
graminearum with EC50 28.85 µg/mL, Fusarium oxysporum with EC50 24.68 µg/mL and Cytospora mandshurica with EC50 37.67 µg/mL.
Key Words: Quinazolin-4-one, Ionic liquids, Synthesis, Antifungal activity.
([HAPmim] BF4) or 1-propyl-3-methylimidazole fluoroborate
([Pmim] BF4) as catalyst, the yield of N3-benzylquinazolin-
4-one reached 85.1 and 82.0 % (Scheme-I). To the best of our
knowledge, this is the first report on the synthesis of N3-substi-
tuted quinazolin-4-one catalyzing by [HAPmim]BF4. The
structures of the title compounds were characterized by IR,
1H NMR and MS spectroscopy. The preliminary biological
tests showed that some of them exhibit good antifungal
activities.
INTRODUCTION
Ionic liquids (IL) provide a useful extension to the range
of solvents and catalysts that are available for synthetic chemistry.
Some more papers showing an overview of the potential of
ionic liquids as solvents for synthesis and catalysis are avail-
able1. The number of papers and patents being published
reflects both academic and industrial interest in using ionic
liquids in diverse areas ranging from synthetic and catalytic
chemistry to biotechnology, electrochemistry and material
science2.
O
O
CO OH
R
R-Br
Over the past decade, the synthesis of heterocycles has
become one of the important aspects of medicinal chemistry3.
Among the nitrogen-containing heterocycles, substituted
quinazolinones represent the medicinally and pharmaceutically
important class of compounds because of their wide range of
biological activities such as anticancer, diuretic, antiinflam-
matory, anticonvulsant and antihypertensive activities4,5. N3-
Substituted quinazolin-4-one is a key intermediate for the
production of the medicines. However, the yield of N3-substituted
quinazolin-4-one compounds was low in traditional method.
In view of these facts and in order to study the influence of
different ionic liquids, we had prepared six N3-substituted
quinazolin-4-one catalyzing in various 3-methylimidazole
ionic liquids. The results showed that every ionic liquid can
increase the yield of N3-benzylquinazolin-4-one. Using 1-methyl-
3-(2-hydroxyl-3-acetoxyl propyl)imidazolium fluoroborate
HCO NH2
NH
N
+
PhCH3 / NaOH,H2
TBAB / Ionic liquids
O
NH2
N
N
1
2
3a-f
Scheme-I: Synthesis route of N3-substituted quinazolin-4-one
EXPERIMENTAL
Unless otherwise indicated, all common reagents and
solvents were used as obtained from commercial supplies with-
out further purification. All melting points of the products were
determined on a XT-4 binocular microscope (Beijing Tech
Instrument Co., China) and are not corrected. The infrared
spectra were recorded on a Bruker VECTOR22 spectrometer
in KBr disks. 1H NMR (solvent DMSO-d6) were recorded on
a Bruker AVANCE/AV400 (400 MHz) spectrometer at room
temperature using TMS as internal standard. The mass spectra
were taken on a GCMS-QP2010 spectrometer. Quinazolin-4-

9854 Liu et al.
Asian J. Chem.
one (2) was prepared according to literature procedure6.
3-Methylimidazole ionic liquids were prepared according to
literature procedures7-9.
method10. The compounds 3a-f were dissolved in acetone
before mixing with 90 mL potato dextrose agar (PDA). The
final concentration of 3a-f in the medium was 50 µg/mL. All
kinds of fungi were incubated in PDA at 27 1 ºC for 4 days
to get new mycelium for antifungal assay. Then mycelia dishes
of ca. 4 mm diameter were cut from culture medium and one
of them was picked up with a sterilized inoculation needle
and inoculated in the center of PDA plate aseptically. The
inoculated plates were incubated at 27 1 ºC for 5 days.
Acetone in sterile distilled water served as control, while
hymexazole served as positive control. For each treatment,
three replicates were conducted. The radial growth of the
fungal colonies was measured and the data were statistically
analyzed. The inhibition effects of the tested compound in
vitro on these fungi were calculated by the formula:
General procedure
General procedure for preparation of compounds (3a-f):
1.5g (10 mmol) quinazolin-4-one, (10 mmol) alkyl bromide,
0.26 g (0.8 mmol) TBAB and (0.5 mmol) 3-methylimidazole
ionic liquids were added in the mixture of 30 mL toluene and
30 mL 35 % KOH. The mixture was refluxed for 1 h and then
cooled to room temperature. The organic layer was separated
and washed with distilled water (10 mL × 2). The organic
phases were dried (anhyd MgSO4), filtered, evaporated under
reduced pressure and recrystallized from ethanol to give 3a-f
(Scheme-I).
N3-Benzylquinazolin-4-one (3a): White crystal; yield
85.1 %, m.p. 116-117 ºC. FT-IR (KBr, νmax, cm-1): 3035 (Ar-
H), 1679.2 (C=O), 1595.7-1456.9 (Ph and quinazoline skeleton
I (%) = [(C - T)/(C - 0.4)] × 100
where C represents the diameter of fungi growth on untreated
PDA and T represents the diameter of fungi on treated PDA
while I means inhibition rate. The EC50 values were estimated
statistically by Probit analysis with Probit package of SPSS
11.5 software using a personal computer11. The average EC50
(µg/mL) was taken (effective dose for 50 % inhibition) from
at least three separate analyses for inhibition of growth using
the Basic LD50 program version 1.1. The inhibition effect of
3a-f in Table-4. The toxicity of 3a-f in Table-5.
1
vibration), 779.2, 689.2 (δPh-H). H NMR (400 MHz, DMSO-
d6) δ: 2.88 (s, 2H, CH2),7.55-8.23 (m, 10H, Ph-H + quinazoline-
H). EIMS: m/z 236 (M+·, 16.4).
N3-n-Propylquinazolin-4-one (3b): White crystal; yield
67.7 %, m.p. 93-94 ºC. FT-IR (KBr, νmax, cm-1): 3035.3 (Ar-
H), 2961.9 (CH3), 2935.6 (CH2), 1664.3 (C=O), 1608.3-1474.0
(quinazoline skeleton vibration). 1H NMR (400 MHz, DMSO-
d6) δ: 1.05 (t, 3H, J=7.0 Hz, CH3), 1.56-2.16 (m, 2H, CH2),
3.96 (t, 2H, J=7.2 Hz, NCH2), 7.31-7.77 (m, 5H,
quinazolinone-H). EIMS: m/z 188 (M+·, 13.5).
RESULTS AND DISCUSSION
N3-i-Propylquinazolin-4-one (3c): White crystal; yield
55.9 %, m.p. 92-93 ºC. FT-IR (KBr, νmax, cm-1): 3036.4 (Ar-
H), 2980.2 (CH3), 1664.4 (C=O), 1604.2-1474.8 (quinazoline
skeleton vibration), 1383.2, 1365.8 (CH(CH3)2). 1H NMR (400
MHz, DMSO-d6) δ: 1.43, 1.55 (2s, 6H, 2CH3), 5.10-5.31 (m,
1H, CH), 7.47-8.39 (m, 5H, quinazolinone-H). EIMS: m/z 188
(M+·, 17.2).
N3-(2-Bromoethyl)quinazolin-4-one (3d):White crystal;
yield 48.2 %, m.p. 137-138 ºC. FT-IR (KBr, νmax, cm-1): 3032.1
(Ar-H), 2976.9 (CH2), 1669.9 (C=O), 1608.9-1474.0
(quinazoline skeleton vibration). 1H NMR (400 MHz, DMSO-
d6) δ: 1.62 (t, 2H, J = 7.4 Hz, CH2), 1.75 (t, 2H, J = 7.4 Hz,
CH2), 7.42-8.14 (m, 5H, quinazolinone-H). EIMS: m/z 252
(M+·, 13.9).
The reaction results in traditional method or in ionic liquids
catalytic method are shown in Table-1. It can be seen that the
presence of 3-methylimidazole ionic liquid [HAPmim]BF4
both accelerated the reactions and gave higher yields. The
reaction time for synthesis of compounds 3a-f was shortened
from 2-4 h to 1 h only with added 5 % mol [HAPmim]BF4.
TABLE-1
YIELDS AND REACTION CONDITIONS USED FOR
IONIC LIQUIDS CATALYTIC SYNTHESIS OF 3a-f
Method Aa
Method Bb
Product
R
Reaction Yield Reaction Yield
time (h)
(%)
57.6
38.9
27.3
16.9
24.8
52.1
time (h)
(%)
85.1
67.7
55.9
48.2
52.6
88.2
CH2Ph
2
4
4
4
4
4
1
1
1
1
1
1
3a
3b
3c
3d
3e
3f
CH2CH2CH3
CH(CH3)2
N3-n-Butylquinazolin-4-one (3e): White crystal; yield
52.6 %, m.p. 79-80 ºC. FT-IR (KBr, νmax, cm-1): 3062.0 (Ar-
H), 2955.6 (CH3), 2930.6 (CH2), 1667.7 (C=O), 1613.2-1472.7
CH2CH2Br
CH2CH2CH2CH3
CH2CH=CH2
1
(quinazoline skeleton vibration). H NMR (400 MHz,
Note: a. Reaction conditions of traditional method: 2 (10mmol), alkyl
bromide (10 mmol), TBAB (0.8 mmol), 30 mL toluene +30 mL 35 %
KOH, reflux 2-4 h; b. Reaction conditions of ionic liquids catalytic
method: 2 (10 mmol), alkyl bromide (10 mmol), TBAB (0.8 mmol)
and [HAPmim]BF4 (0.5 mmol), 30 mL toluene +30 mL 35 % KOH,
reflux 1 h.
DMSO-d6): 0.97 (t, 3H, J = 7.0 Hz, CH3), 1.22-1.92 (m, 4H,
CH2CH2), 4.02 (t, 2H, J = 7.2 Hz, NCH2), 7.30-8.37(m, 5H,
quinazolinone-H). EIMS: m/z 202 (M+·, 12.1).
N3-Allylquinazolin-4-one (3f): White crystal; yield
88.2 %, m.p. 64-65 ºC. FT-IR (KBr, νmax, cm-1): 3078.4 (=CH2),
3035.8 (Ar-H), 2926.3 (CH2), 1675.2 (C=O), 1615.7 (C=C),
1610.8-1467.2 (quinazoline skeleton vibration). 1H NMR (400
MHz, DMSO-d6) δ: 4.52-4.58 (m, 2H, CH2), 5.12-5.24 (m,
2H, =CH2), 5.82-5.95 (m, 1H, =CH), 7.20-8.11 (m, 5H,
quinazolinone-H). EIMS: m/z 186 (M+·, 22.7).
Twelve ionic liquids were used as catalyst to synthesize
N3-benzylquinazolin-4-one with TBAB.The reaction results
with various 3-methylimidazole ionic liquids are shown in
Table-2. It can be seen that the presence of 3-methylimidazole
ionic liquids both accelerated the reactions and gave higher
yields. The reaction time for synthesis of compound 3a was
shortened from 2 h to 1 h with 5 mol % ionic liquids. Using
[HAPmim]BF4 or [Pmim]BF4 as catalyst, the yield of compound
Antifungal assay: The antifungal activities of 3a-f were
tested against Fusarium graminearum, Fusarium oxysporum
and Cytospora mandshurica by mycelia growth inhibition

Vol. 25, No. 17 (2013)
Synthesis and Antifungal Activities of N3-Substituted Quinazolin-4-one 9855
TABLE-2
DIFFERENT CONDITIONS USED FOR IONIC
LIQUIDS CATALYZED SYNTHESIS OF 3a
ment was observed under [Bmim]PF6 when the dosage of ionic
liquids varied from 5-8 and 10 mol % and the yield even
decreased a little (Table-2, entries 4 and 10-11), a fact we
Dosage of ionic
liquids (mol %)
Reaction Yield
time (h)
Entry
Ionic liquids
[Bmim]Bra
attribute to the formation of the solubility of ionic liquids.
(%)
In order to study catalyical function in different separated
3-methylimidazole ionic liquids, we selected different ionic
liquids single handed as catalyst. These results are shown
in Table-3. The yield of N3-benzylquinazolin-4-one was
contrasted catalyzing 3-methylimidazole ionic liquids or
TBAB.
1
2
5
5
5
5
5
5
5
5
2
8
10
5
5
5
5
5
5
5
5
0
1
1
70.1
65.0
75.1
75.9
40.7
58.4
76.5
76.9
60.9
72.8
68.6
82.0
73.0
72.8
71.8
70.5
73.9
63.9
85.1
57.6
[Bmim]Bph4b
[Bmim]BF4c
[Bmim]PF6d
[Bmim]PF6d
[Bmim]PF6d
[Bmim]PF6d
[Bmim]PF6d
3
1
4
1
5
0.25
0.5
1.5
2
6
7
8
d
TABLE-3
INFLUENCE OF DIFFERENT SEPARATED CATALYST
9
[Bmim]PF6
1
10
11
12
13
14
15
16
17
18
19
20
[Bmim]PF6d
[Bmim]PF6d
[Pmim]BF4e
[Pmim]Br f
1
Dosage of
catalyst (mol %)
Reaction
time (h)
Yield
(%)
1
Entry
Catalyst
1
1
2
[Bmim]Br
5
5
5
5
5
5
5
5
5
5
5
5
8
2
2
2
2
2
2
2
2
2
2
2
2
2
59.7
50.0
62.7
62.5
58.6
61.7
62.2
59.5
60.8
63.7
57.9
58.7
57.6
1
[Bzmim]Brg
[Bzmim]BF4h
[HAPmim]Br i
[HAPmim]NO3j
[HAPmim]H2PO4k
[HAPmim]BF4l
NILm
1
[Bmim]Bph4
[Bmim]BF4
[Bmim]PF6
[Pmim]BF4
[Pmim]Br
3
1
4
1
5
1
6
1
7
[Bzmim]Br
[Bzmim]BF4
[HAPmim]Br
[HAPmim]NO3
[HAPmim]H2PO4
[HAPmim]BF4
TBAB
1
8
9
2
Note: Reaction conditions: 2 (10 mmol), benzyl bromide (10 mmol),
TBAB (0.8 mmol) and ionic liquids, 30 mL toluene +30 mL 35 %
KOH, reflux 1-2 h; TBAB: Tetrabutyl ammonium bromide; a.
[Bmim]Br: 1-Butyl-3-methyl imidazolium bromide; b. [Bmim]Bph4:1-
Butyl-3-methylimidazolium tetraphenylborate; c. [Bmim]BF4:1-Butyl-
3-methylimidazolium tetrafluoroborate; d. [Bmim]PF6: 1-Butyl-3-
methylimidazolium hexafluorophosphate; e. [Pmim]Br: 1-Propyl-3-
10
11
12
13
Note: Reaction conditions: 2 (10 mmol), benzyl bromide (10 mmol),
TBAB (0.8 mmol) or ionic liquids (0.5 mmol), 30 mL toluene +30 mL
35 % KOH, reflux 2 h.
methylimidazolium
bromide;
f.
[Pmim]BF4:
1-Propyl-3-
methylimidazolium tetrafluoroborate; g. [Bzmim]Br: 1-Benzyl-3-
methylimidazolium bromide; h. [Bzmim]BF4: 1-Benzyl-3-methyl
imidazolium tetrafluoroborate; i. [HAPmim]Br: 1-Methyl–3-(2-
hydroxyl-3-acetoxylpropyl) imidazolium Bromide; j. [HAPmim]NO3:
1-Methyl–3-(2-hydroxyl-3-acetoxylpropyl)imidazolium nitrate; k.
The antifungal activities in vitro of these compounds were
evaluated against Fusarium graminearum, Fusarium
oxysporum and Cytospora mandshurica. The results for title
compounds 3a-f are summarized in Table-4. Toxic regression
equation and EC50 of 3f inhibited Fusarium graminearum with
EC50 28.85 µg/mL, Fusarium oxysporum with EC50 24.68 µg/mL
and Cytospora mandshurica with EC50 37.67 µg/mL are summa-
rized in Table-5.
[HAPmim]H2PO4:
1-Methyl-3-
(2-hydroxyl-3-acetoxylpropyl)
imidazolium dihydric phosphate; l. [HAPmim]BF4: 1-Methyl-3-(2-
hydroxyl-3-acetoxylpropyl)imidazolium tetrafluoroborate, m. NIL: no
ionic liquids.
3a reached 85.1 and 82.0 %, increased ca. 27 % more than the
yield of traditional conditions (Table-2, entries 12 and 19-20).
In order to optimize the reaction parameters, we selected
N3-benzylquinazolin-4-one catalyzing by [Bmim]PF6 for
further study under different conditions. These results are
shown in entryies 4-11 of Table-2. Without ionic liquids, N3-
benzylquinazolin-4-one catalyzing by TBAB could be obtained
in 57.6 % after 2 h (Table-2, entry 20). When the reaction was
carried out under [Bmim]PF6 and TBAB for 15 min, the yield
of N3-benzylquinazolin-4-one was reduced to 40.7 % and
contrasted to 58.7 % when the reaction time was extended to
0.5 h and increased to 75.9 % when the reaction time was
extend to 1 h. (Table-2, entries 4-6). However, no further
improvement of the yield was noted when the reaction time was
prolonged to 1.5 h and 2 h. (Table-2, entries 7-8). Consequently,
we chose 1 h as the optimum reaction time (Table-2, entry 4).
As for the effect of the dosage of ionic liquids, it could be
seen that when it was increased from 2 to 5, 8 and 10 mol %,
the yields of N3-benzylquinazolin-4-one were 60.9, 75.9, 72.8
and 68.6 %, respectively (Table-2, entries 4 and 9-11). Hence,
it’s better for the reaction to be carried out at 2 mol % or higher
dosage settings than only catalyzing by TBAB. No improve-
TABLE-4
INHIBITION RATE OF ANTIFUNGAL ACTIVITY OF 3a-f
Inhibition (%)a
Comp.
Conc.
(µg
F.
F.
C.
graminearum oxysporum mandshurica
mL-1)
3a
3b
50
50
50
50
50
50
50
21.2
24.1
14.6
29.4
24.2
63.6
69.5
22.1
22.3
22.7
39.4
12.1
51.9
61.5
16.8
32.5
13.2
34.1
8.1
3c
3d
3e
60.8
65.8
3f
Hymexazoleb
aAverage of three replicates. bStandard drug.
TABLE-5
TOXIC REGRESSION EQUATION AND
EC50 OF 3f AGAINST THREE FUNGI
Toxic regression
EC50a (µg mL-1)
Fungi
r
equationa
F. graminearum
F. oxysporum
C. mandshurica
28.85 3.37
24.68 4.26
37.67 3.74
y = 2.59x + 2.17
y = 2.03x + 3.24
y = 2.93x + 2.73
0.996
0.988
0.994
aAverage of three replicates.

9856 Liu et al.
Asian J. Chem.
Conclusion
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