Synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione derivatives using wet cyanuric chloride under solvent-free condition

Article abstract of DOI:10.1002/jccs.201000198

A simple and facile synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)- trione derivatives has been accomplished by a three-component condensation reaction of dimedone, aromatic aldehydes and phthalhydrazide under solvent-free conditions in the presen

Full text of DOI:10.1002/jccs.201000198

Journal of the Chinese Chemical Society, 2010, 57, 1341-1345
1341
Synthesis of 2H-Indazolo[2,1-b]phthalazine-1,6,11(13H)-trione Derivatives
Using Wet Cyanuric Chloride under Solvent-Free Condition
Xiao Wang (
Li-Qiang Wu* (
), Wei-Wei Ma (
) and Fu-Lin Yan (
),
)
School of Pharmacy, Xinxiang Medical University, Xinxiang, Henan 453003, P. R. China
A simple and facile synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione derivatives has
been accomplished by a three-component condensation reaction of dimedone, aromatic aldehydes and
phthalhydrazide under solvent-free conditions in the presence of wet cyanuric chloride as a catalyst.
Keywords: 2H-Indazolo[2,1-b]phthalazine-1,6,11(13H)-trione; Dimedone; Phthalhydrazide;
Cyanuric chloride; Solvent-free; Multicomponent reation.
INTRODUCTION
Scheme I
Phthalazine are important heterocycles that are
known to possess multiple biological activities such as
antimicrobial,1 anticonvulsant,2 antifungal,3 anticancer,4
and anti-inflammatory activities.5 Therefore, a number of
methods have been reported for the synthesis of phth-
alazine derivatives.6 Nevertheless the development of new
synthetic methods for the efficient preparation of hetero-
cycles containing phthalazine ring fragment is an interest-
ing challenge. Recently, synthesis of 2H-indazolo[2,1-b]-
phthalazine-1,6,11(13H)-trione derivatives have been re-
ported using p-TSA,7 Me3SiCl,8 silica sulfuric acid,9
H2SO4,10 Mg(HSO4)2,11 and silica supported poly phospho-
ric acid12 as catalysts. However, many of these methodolo-
gies are associated with one or more disadvantages such as
use of expensive catalyst or toxic organic solvents (8, 11),
strong acidic conditions (7, 10), and harsh reaction condi-
tions (7-12).
examined the amount of catalyst and the reaction tempera-
ture, the reaction of dimedone, benzaldehyde and phth-
alhydrazide to the corresponding 3,4-dihydro-3,3-dimeth-
yl-13-phenyl-2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-
trione was studied under solvent-free conditions in the
presence of wet-cyanuric chloride at different tempera-
tures. The results are summarized in Table 1. As shown in
Table 1, the reaction using 3 mol % cyanuric chloride at
100 °C proceeded in highest yield.
Based on the optimized reaction conditions, a range
of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione de-
rivatives was synthesized by the reaction of dimedone, al-
dehyde and phthalhydrazide. The reaction proceeded at
100 °C within 25 min in excellent yields after the addition
of 3 mol % cyanuric chloride (Table 2). The structures of
the products were established from their spectral properties
(1H NMR, 13C NMR and elemental analysis) and also by
comparison with available literature data.
Recently, 2,4,6-trichloro-1,3,5-triazine (cyanuric chlo-
ride, TCT) has emerged as an inexpensive and easily avail-
able reagent in organic synthesis.13 In this paper, we wish to
report, a simple and facile synthesis of 2H-indazolo[2,1-
b]phthalazine-1,6,11(13H)-trione derivatives by a three-
component condensation reaction of dimedone, aromatic
aldehydes and phthalhydrazide under solvent-free condi-
tions in the presence of wet cyanuric chloride as a catalyst.
HCl generated in situ, from cyanuric chloride, effi-
ciently catalyzes these reactions, a plausible mechanism is
shown in Scheme II. Accordingly, cyanuric chloride reacts
with ‘incipient’ moisture and releases 3 equvient of HCl
RESULTS AND DISCUSSION
In order to optimize the reaction conditions, we first
* Corresponding author. E-mail: wliq870@163.com

1342 J. Chin. Chem. Soc., Vol. 57, No. 6, 2010
Wang et al.
Table 1. The amounts of catalyst and temperature optimization
for the synthesis of 3,4-dihydro-3,3-dimethyl-13-
phenyl-2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-
trionea
Scheme II
Entry TCT/mol% Temperature/°C Time/min Yield/%b
1
0
1
2
3
3
3
3
3
3
3
4
4
5
6
7
8
100
100
100
025
050
080
090
100
110
120
090
100
100
100
100
100
60
45
45
1200
60
45
30
15
15
15
20
20
20
20
15
15
00
68
80
00
46
57
78
96
95
96
88
94
89
90
92
94
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
To recognize the capability of the present method in
comparison with reported methods for the preparation of
2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione deriv-
atives from dimedone, aromatic aldehydes and phthalhy-
drazide, the model reaction of dimedone, benzaldehyde
and phthalhydrazide was described. While in most of these
cases comparative yields of the desired product were ob-
tained following the TCT-catalyzed procedure, the re-
ported procedures required expensive catalyst or toxic or-
ganic solvents (entry 3, 4, 6), strong acidic conditions (en-
try 1, 4), high catalyst loading (entry 1-6), and long reac-
tion time (4, 5). These results clearly demonstrate that TCT
is an equally or more efficient catalyst for this three-com-
ponent reaction.
a Reaction conditions: dimedone (1 mmol); benzaldehyde (1.2
mmol); phthalhydrazide (1 mmol); H2O (3 drops); neat.
b Isolated yield.
and cyanuric acid (removable by washing with water) as
by-product. The formation of products 4a-4i can be ratio-
nalized by initial formation of heterodiene 5 by standard
Knoevenagel condensation of dimedone and aromatic al-
dehyde in the presence of a catalytic amount of HCl. Subse-
quent Michael-type addition of phthalhydrazide to the
heterodienes followed by cyclization and dehydration af-
ford the corresponding products 4a-4i.
Table 2. Synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione derivativesa
Entry Time/min m.p./°C (Lit. m.p.)
Yield/%b
15 96
205-207 (204-206) 10
R
a
C6H5
b
c
d
e
f
4-Cl-C6H4
15
10
10
15
20
15
15
10
10
25
97
95
96
91
91
94
91
95
90
89
262-264 (258-260) 10
220-221 (218-220) 9
228-230 (226-231) 10
220-222 (216-218) 10
270-270 (269-271) 10
220-220-2 (221-223) 10
262-264 (266-269) 10
222-224 (218-220) 10
262-264
4-MeO-C6H4
4-Me-C6H4
4-NO2-C6H4
3-NO2-C6H4
4-F-C6H4
g
h
i
2-Cl-C6H4
2,4-Cl2-C6H3
3,4-Cl2-C6H3
3,4,5-MeO-C6H2
j
k
233-235 (232-234) 10
a Reaction conditions: dimedone (1 mmol); aldehyde (1.2 mmol); phthalhydrazide (1
mmol); TCT (0.03 mmol); H2O (3 drops); neat; 100 °C.
b Isolated yield.

Synthesis of 2H-Indazolo[2,1-b]phthalazines
J. Chin. Chem. Soc., Vol. 57, No. 6, 2010 1343
Table 3. Effect of catalyst on the reaction of dimedone, benzaldehyde and phthalhydrazide
Entry
Reagent and Conditions
Time/min Yield/%
Ref.
1
2
3
4
5
6
7
p-Toluenesulfonic acid, solvent-free, 80 °C, 30 mol%
Poly phosphoric acid-SiO2, solvent-free, 100 °C, 5 mol%
Mg(HSO4)2, solvent-free, 100 °C, 10 mol%
H2SO4, [bmim][BF4], 80 °C, 15 mol%
10
06
04
30
07
30
15
93
93
88
94
91
90
96
07
12
11
10
Silica sulfuric acid, solvent-free, 100 °C, 6.5 mol%
TMSCl, CH3CN/DMF (8:2), 80 °C,
09
08
TCT, solvent-free, 100 °C, 3 mol%
This work
In summary, a novel and highly efficient methodol-
ogy for the synthesis of 2H-indazolo[2,1-b]phthalazine-
1,6,11(13H)-trione by a three-component condensation re-
action of dimedone, aromatic aldehydes and phthalhydra-
zide under solvent-free conditions in the presence of wet-
cyanuric chloride as a catalyst is reported. In addition, this
protocol describes a very fast, user friendly, ‘green’ and
low cost procedure for the synthesis of these products. Fur-
thermore, cyanuric chloride is a catalyst with cyanuric acid
as byproduct that is removable by washing with water. This
easy removal of the catalyst makes this method a better
choice for chemical industries.
3.25 (dd, 1H, J = 2.4, 18.8 Hz), 2.35 (s, 2H), 1.22 (s, 6H);
13C NMR (CDCl3, 100 MHz) d: 192.1, 156.0, 154.3, 150.8,
136.4, 134.5, 133.5, 129.1, 129.0, 128.7, 128.0, 127.7,
127.1, 118.6, 65.0, 50.9, 38.0, 34.6. 28.7, 28.5; Anal. calcd
for C23H20N2O3: C 74.18, H 5.41, N 7.52; found: C 74.25,
H 5.36, N 7.48.
3,4-Dihydro-3,3-dimethyl-13-(4-chlorophenyl)-2H-in-
dazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4b)
1H NMR (CDCl3, 400 MHz) d: 8.38-8.26 (m, 2H),
7.88-7.85 (m, 2H), 7.37 (d, 2H, J = 8.4 Hz), 7.31 (d, 2H, J =
8.4 Hz), 6.42 (s, 1H), 3.41 (d, 1H, J = 18.8 Hz), 3.25 (dd,
1H, J = 2.0, 18.8 Hz), 2.35 (s, 2H), 1.27-1.21 (m, 6H); 13
C
NMR (CDCl3, 100 MHz) d: 192.1, 156.0, 154.4, 151.1,
134.9, 134.6, 134.5, 133.7, 129.0, 128.9, 128.5, 128.0,
127.7, 118.0, 64.3, 50.9, 38.0, 34.7, 28.7, 28.4; Anal. calcd
for C23H19ClN2O3: C 67.90, H 4.71, N 6.89; found: C
67.95, H 4.82, N 6.79.
EXPERIMENTAL
NMR spectra were determined on Bruker AV-400
spectrometer at room temperature using TMS as internal
standard, coupling constants (J) were measured in Hz; Ele-
mental analysis were performed by a Vario-III elemental
analyzer; Melting points were determined on a XT-4 binoc-
ular microscope and were uncorrected; Commercially
available reagents were used throughout without further
purification unless otherwise stated.
3,4-Dihydro-3,3-dimethyl-13-(4-methoxylphenyl)-2H-
indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4c)
1H NMR (CDCl3, 400 MHz) d: 8.36-8.26 (m, 2H),
7.86-7.83 (m, 2H), 7.35 (d, 2H, J = 8.8 Hz), 6.86 (d, 2H, J =
8.4 Hz), 6.43 (s, 1H), 3.77 (s, 3H), 3.43 (d, 1H, J = 18.8
Hz), 3.24 (dd, 1H, J = 2.0, 18.8 Hz), 2.35 (s, 2H), 1.29-1.22
(m, 6H); 13C NMR (CDCl3, 100 MHz) d: 192.2, 159.7,
156.0, 154.2, 150.7, 134.4, 133.4, 129.1, 128.9, 128.5,
128.3, 127.9, 127.7, 118.5, 114.1, 64.6, 55.2, 51.0, 38.0,
34.6, 28.7, 28.5; Anal. calcd for C24H22N2O4: C 71.63, H
5.51, N 6.96; found: C 71.59, H 5.62, N 7.02.
General Procedure for synthesis of 4
A mixture of dimeone (1 mmol), aldehydes (1.2
mmol), phthalhydrazide (1 mmol), cyanuric chloride (0.03
mmol) and H2O (3 drops) was heated at 100 °C for the ap-
propriate time (Table 2). The reaction was monitored by
TLC. After completion of the reaction, the mixture was
cooled to room temperature and washed with water. The
solid products were purified by recrystallization from
aqueous EtOH (25%).
3,4-Dihydro-3,3-dimethyl-13-(4-methylphenyl)-2H-
indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4d)
1H NMR (CDCl3, 400 MHz) d: 8.37-8.27 (m, 2H),
7.87-7.83 (m, 2H), 7.31 (d, 2H, J = 8.0 Hz), 7.15 (d, 2H, J =
7.6 Hz), 6.43 (s, 1H), 3.43 (d, 1H, J = 18.8 Hz), 3.25 (dd,
1H, J = 2.0, 18.8 Hz), 2.34 (s, 2H), 2.31 (s, 3H), 1.22 (s,
6H); 13C NMR (CDCl3, 100 MHz) d: 192.2, 156.0, 154.2,
150.7, 138.5, 134.4, 133.4, 133.3, 129.4, 129.1, 127.9,
3,4-Dihydro-3,3-dimethyl-13-phenyl-2H-indazolo[2,1-
b]phthalazine-1,6,11(13H)-trione (4a)
1H NMR (CDCl3, 400 MHz) d: 8.37-8.27 (m, 2H),
7.86 (dd, 2H, J = 3.2, 7.6 Hz), 7.42 (d, 2H, J = 7.2 Hz),
7.37-7.29 (m, 3H), 6.46 (s, 1H), 3.43 (d, 1H, J = 18.8 Hz),

1344 J. Chin. Chem. Soc., Vol. 57, No. 6, 2010
Wang et al.
127.7, 118.7, 64.8, 51.0, 38.0, 34.6, 28.7, 28.4, 21.2; Anal.
calcd for C24H22N2O3: C 74.59, H 5.74, N 7.25; found: C
74.62, H 5.69, N 7.37.
3,4-Dihydro-3,3-dimethyl-13-(2,4-dichlorophenyl)-2H-
indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4i)
1H NMR (CDCl3, 400 MHz) d: 8.38-8.24 (m, 2H),
7.90-7.86 (m, 2H), 7.43 (d, 1H, J = 8.0Hz), 7.35-7.27 (m,
2H), 6.64 (s, 1H), 3.40 (d, 1H, J = 18.8 Hz), 3.25 (dd, 1H, J
3,4-Dihydro-3,3-dimethyl-13-(4-nitrophenyl)-2H-inda-
zolo[2,1-b]phthalazine-1,6,11(13H)-trione (4e)
1H NMR (CDCl3, 400 MHz) d: 8.40-8.24 (m, 2H),
8.21 (d, 2H, J = 8.8 Hz), 7.90 (dd, 2H, J = 1.6, 5.6 Hz), 7.62
(d, 2H, J = 8.8 Hz), 6.52 (s, 1H), 3.42 (d, 1H, J = 19.2 Hz),
3.27 (dd, 1H, J = 2.0, 19.2 Hz), 2.34 (s, 2H), 1.29-1.20 (s,
6H); 13C NMR (CDCl3, 100 MHz) d: 192.0, 155.9, 154.5,
151.6, 147.9, 143.4, 134.8, 133.9, 128.9, 128.6, 128.2,
128.0, 127.8, 124.0, 117.3, 64.1, 50.8, 38.0, 34.7, 28.7,
28.4; Anal. calcd for C23H19N3O5: C 66.18, H 4.59, N
10.07; found: C 66.21, H 4.50, N 10.01.
= 2.4, 18.8 Hz), 2.38-2.29 (m 2H), 1.23-1.21 (m, 6H); 13
C
NMR (CDCl3, 100 MHz) d: 192.1, 156.1, 154.3, 152.1,
135.1, 134.6, 133.7, 131.7, 130.4, 129.0, 128.5, 128.1,
127.7, 127.6, 116.1, 64.2, 50.8, 38.0, 34.6, 28.8, 28.4;
Anal. calcd for C23H18Cl2N2O3: C 62.60, H 4.11, N 6.35;
found: C 62.76, H 4.02, N 6.48.
3,4-Dihydro-3,3-dimethyl-13-(3,4-dichlorophenyl)-2H-
indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4j)
1H NMR (CDCl3, 400 MHz) d: 8.39-8.27 (m, 2H),
7.90-7.87 (m, 2H), 7.46-7.42 (m, 2H), 7.32 (dd, 1H, J =
2.0, 7.6 Hz), 6.39 (s, 1H), 3.41 (d, 1H, J = 19.2 Hz), 3.25
(dd, 1H, J = 1.6, 19.2 Hz), 2.35 (s, 2H), 1.27-1.22 (s, 6H);
13C NMR (CDCl3, 100 MHz) d: 192.0, 155.9, 154.5, 151.4,
136.6, 134.7, 133.8, 133.0, 132.8, 130.7, 128.9, 128.8,
128.7, 128.1, 127.7, 126.8, 117.5, 63.8, 50.8, 38.0, 34.7,
28.6, 28.5; Anal. calcd for C23H18Cl2N2O3: C 62.60, H
4.11, N 6.35; found: C 62.65, H 4.23, N 6.30.
3,4-Dihydro-3,3-dimethyl-13-(3-nitrophenyl)-2H-inda-
zolo[2,1-b]phthalazine-1,6,11(13H)-trione (4f)
1H NMR (CDCl3, 400 MHz) d: 8.41-8.25 (m, 2H),
8.18 (d, 2H, J = 7.2 Hz), 7.92-7.89 (m, 3H), 7.57 (t, 1H, J =
7.2 Hz), 6.54 (s, 1H), 3.45 (d, 1H, J = 19.6 Hz), 3.29 (dd,
1H, J = 2.0, 19.6 Hz), 2.36 (s, 2H), 1.27-1.19 (s, 6H); 13
C
NMR (CDCl3, 100 MHz) d: 192.1, 156.0, 154.6, 151.8,
148.5, 138.6, 134.8, 134.2, 133.9, 129.7, 129.0, 128.6,
128.2, 127.7, 123.7, 121.5, 117.1, 64.1, 50.8, 38.0, 34.7,
28.7, 28.4; Anal. calcd for C23H19N3O5: C 66.18, H 4.59, N
10.07; found: C 66.18, H 4.65, N 10.05.
3,4-Dihydro-3,3-dimethyl-13-(3,4,5-trimethoxyl)-2H-
indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4k)
1H NMR (CDCl3, 400 MHz) d: 8.38-8.30 (m, 2H),
7.89-7.87 (m, 2H), 6.64 (s, 2H), 6.40 (s, 1H), 3.83-3.81 (m,
9H), 3.46 (d, 1H, J = 18.8 Hz), 3.24 (dd, 1H, J = 2.0, 18.8
Hz), 2.37 (s, 2H), 1.26-1.24 (s, 6H); 13C NMR (CDCl3, 100
MHz) d: 192.2, 156.1, 154.5, 153.3, 150.8, 138.2, 134.6,
133.6, 131.8, 129.0, 128.9, 128.0, 127.7, 118.3, 104.6,
65.0, 60.7, 56.2, 50.9, 38.1, 34.6, 29.7, 28.9, 28.1; Anal.
calcd for C26H26N2O6: C 67.52, H 5.67, N 6.06; found: C
67.62, H 5.74, N 6.01.
3,4-Dihydro-3,3-dimethyl-13-(4-fluorophenyl)-2H-in-
dazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4g)
1H NMR (CDCl3, 400 MHz) d: 8.37-8.26 (m, 2H),
7.88-7.85 (m, 2H), 7.43-7.39 (m, 2H), 7.03 (t, 2H, J = 8.8
Hz), 6.44 (s, 1H), 3.42 (d, 1H, J = 18.8 Hz), 3.25 (dd, 1H, J
= 2.4, 18.8 Hz), 2.35 (s, 2H), 1.27-1.22 (s, 6H); 13C NMR
(CDCl3, 100 MHz) d: 192.1, 163.9, 161.5, 156.0, 154.4,
151.0, 134.6, 133.6, 132.2, 129.0, 128.9, 128.0, 127.7,
118.2, 115.8, 115.6, 64.3, 50.9, 38.0, 34.6, 28.7, 28.4;
Anal. calcd for C23H19FN2O3: C 70.76, H 4.91, N 7.18;
found: C 70.82, H 4.88, N 7.26.
ACKNOWLEDGMENT
We are pleased to acknowledge the financial support
from Xinxiang Medical University.
3,4-Dihydro-3,3-dimethyl-13-(2-chlorophenyl)-2H-in-
dazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4h)
1H NMR (CDCl3, 400 MHz) d: 8.39-8.25 (m, 2H),
7.89-7.84 (m, 2H), 7.49 (d, 1H, J = 6.8Hz), 7.34-7.22 (m,
3H), 6.69 (s, 1H), 3.42 (d, 1H, J = 18.8 Hz), 3.25 (dd, 1H, J
= 2.0, 18.8 Hz), 2.33 (s, 2H), 1.27-1.22 (m, 6H); 13C NMR
(CDCl3, 100 MHz) d: 192.1, 156.2, 154.2, 151.8, 134.5,
133.6, 133.0, 132.5, 130.5, 129.9, 129.0, 128.7, 128.0,
127.7, 127.2, 64.1, 50.8, 38.0, 34.6, 28.8, 28.4; Anal. calcd
for C23H19ClN2O3: C 67.90, H 4.71, N 6.89; found: C
70.02, H 4.69, N 6.95.
Received May 11, 2010.
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