Superacid catalysed the one-pot synthesis of spiro[indole-3,9'-tetrazolo[5, 1-b]quinazoline]-2,8'(1H, 5'H)-dione in aqueous medium

Article abstract of DOI:10.3184/174751913X13815671990200

An efficient, one-pot synthesis of spiro[indole-3,9'-tetrazolo[5,1-b] quinazoline]-2,8'(1H,5'H)-dione derivatives by the reaction of isatin, 5-amino-1H-tetrazole, and 5,5-dimethylcyclohexane-1,3-dione catalysed by a superacid ([MeC(OH)2]+ClO4 -) in aqueous medium is described. This protocol provides a simple one-step procedure with the advantages of easy work-up, high yield, mild reaction conditions and is environmental friendly.

Full text of DOI:10.3184/174751913X13815671990200

JOURNAL OF CHEMICAL RESEARCH 2013
NOVEMBER, 705–708
RESEARCH PAPER 705
Superacid catalysed the one-pot synthesis of spiro[indole-3,9’-
tetrazolo[5,1-b]quinazoline]-2,8’(1H, 5’H)-dione in aqueous medium
Yong Dai*a,b, Gang Qia,b and Xiao-rong Qiana,b
aSchool of Chemical and Biological Engineering, Yancheng Institute of Technology, Yancheng 224051, P.R. China
bKey Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology, 224051, P.R. China
An efficient, one-pot synthesis of spiro[indole-3,9’-tetrazolo[5,1-b]quinazoline]-2,8’(1H,5’H)-dione derivatives by the reaction of
–
isatin, 5-amino-1H-tetrazole, and 5,5-dimethylcyclohexane-1,3-dione catalysed by a superacid ([MeC(OH)2]+ClO ) in aqueous
medium is described. This protocol provides a simple one-step procedure with the advantages of easy work-up, h4igh yield, mild
reaction conditions and is environmental friendly.
Keywords: spirooxindole, 5-amino-1H-tetrazole, multicomponent reactions, superacid
The heterocyclic spirooxindole skeleton is an important
structure in organic and medicinal chemistry due to its
potency and variety of applications such as antifungal,1 anti-
mycobacterial,2 anti-tumour,3 anti-oxidant,4 antimicrobial,5 and
other biological activities6 and can also serve as synthons for
naturally occurring alkaloids and pharmaceutically important
drug molecules.7
Initially, the reaction of isatin, 5-amino-1H-tetrazole and
dimedone was carried out to optimise the reaction conditions
(Table 1). First, several solvents such as DCM, toluene, MeOH,
EtOH and water were tested. Table 1 reveals that the solvent
played an important role. Generally, polar solvents were more
effective than the non-polar ones. However, when the reaction
proceeded in pure water, only moderate yield (65%, entry 7)
was obtained, possibly due to the lesser homogeneity of the
reaction mixture. Results clearly showed that EtOH/H2O (1:1,
v/v) was the best choice, affording the corresponding product
4a in 90% yield within 3 hours (entry 8). Similarly, the acid
catalysts also showed a large influence on the reaction. It was
observed that the model reaction was very sluggish in the
absence of any catalyst. Some strong Brønsted acids including
conc. H2SO4, HClO4, and toluene-p-sulfonic acid could promote
the reaction, however, the reaction time was long and the yields
were moderate. The most optimal quantity of catalyst seemed
Multicomponent reactions (MCRs) have attracted much
attention for the construction of bioactive heterocyclic
compounds by virtue of their convergence, productivity, facile
execution, and generally high yields of products.8 A series
of efficient methods have been reported for the synthesis
of compounds bearing heterocyclic spirooxindole skeletons
via multicomponent condensation reactions in good to
excellent yields.9–13 A recent development in this field is the
incorporation of different functional groups or moieties such
as 5-aminopyrazoles,9 trifluoromethyl,10 and thiazolidinone13
into the heterocyclic spirooxindole ring system to achieve good
bioactivity. On the other hand, the tetrazole ring system also
exhibits a wide range of bioactivities,14,15 and has been used
as an activator16 and in anticonvulsants17. Thus, heterocyclic
systems resulting from the annulations of the tetrazole ring on
a biologically versatile oxindole moiety in a single molecular
framework may increase their biological activities or produce
new medicinal properties.
to be 10 mol% of [MeC(OH)2]+ClO4 .
–
With the optimised reaction conditions obtained, the
generality and functional group tolerance of this protocol were
investigated for this MCR. As shown in Table 2, it was obvious
that this method showed good substrate compatibility for isatin.
Different electron-withdrawing groups as well as methyl in the
5-, 6-, and 7- positions showed negligible influences, providing
the products in good to excellent yields. Moreover, we found
that different N-substituted isatins were also compatible with
this protocol, giving product 4i and 4j in 89% and 86% yield,
respectively.
The plausible reaction mechanism was outlined in Scheme 2.
In the first step, condensation of isatin and dimedone was
proposed to give intermediate A, which was further attacked
by 5-amino-1H-tetrazole to provide intermediate B. Finally, the
intermediate B underwent intramolecular cyclisation to form
the target product 4a.
As part of our on-going research programs directed at the
development of efficient methodologies for the preparation of
heterocyclic compounds and our interest in the environmentally
friendly synthetic methodologies, we now report a fast and
efficient protocol for the synthesis of spiroheterocycles
containing both tetrazole ring and oxindole ring in the presence
of catalytic amount of superacid ([MeC(OH)2]+ClO4 ), which is
–
simply prepared by mixing acetic acid and perchloric acid at
room temperature.18,19 (Scheme 1) To the best of our knowledge,
this is the first report of the synthesis of spiroheterocycles
containing both tetrazole ring and oxindole rings.
R2
R1
N
O
O
+ClO4
solvent
-
[
]
O
N
N
MeC(OH)2
NH
O
R1
O
+
N
+
NH2
N
N
N
N
O
R2
N
N
H
Scheme 1 Superacid catalysed the one-pot synthesis of spiroheterocycles.
* Correspondent. E-mail: daiyong_88@126.com
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706 JOURNAL OF CHEMICAL RESEARCH 2013
Table 1 Optimisation of reaction conditionsa
HN
N
O
O
O
N
N
NH
catalyst
O
+
+
O
N
NH2
N
N
solvent, Temperature
H
N
O
N
N
H
1
2
3
a
4
Entry
Solvent
Catalyst/mol%
Temperature/°C
Time/h
Yield/%b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
CH2Cl2
Toluene
THF
EtOAc
MeOH
EtOH
[MeC(OH)2]+ClO4– (10)
[MeC(OH)2]+ClO4– (10)
[MeC(OH)2]+ClO4– (10)
[MeC(OH)2]+ClO4– (10)
[MeC(OH)2]+ClO4– (10)
[MeC(OH)2]+ClO4– (10)
[MeC(OH)2]+ClO4– (10)
[MeC(OH)2]+ClO4– (10)
[MeC(OH)2]+ClO4– (10)
–
[MeC(OH)2]+ClO4– (5)
[MeC(OH)2]+ClO4– (20)
Conc. H2SO4 (50)
HClO4 (50)
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
80
80
80
80
80
12
12
12
12
12
6
12
3
3
24
12
3
12
12
12
12
15
40
42
38
71
82
65
90
83
trace
41
H2O
EtOH/H2O (1:1)
EtOH/H2O (1:2)
EtOH/H2O (1:1)
EtOH/H2O (1:1)
EtOH/H2O (1:1)
EtOH/H2O (1:1)
EtOH/H2O (1:1)
EtOH/H2O (1:1)
EtOH/H2O (1:1)
91
35
60
21
80
80
80
80
CH3COOH (50)
p-TSA (50)
53
aReaction conditions: isatin (1 mmol), 5 amino-1H-tetrazole (1 mmol), dimedone (1 mmol), solvent (4 mL), heating.
bIsolated yield.
Table 2 Synthesis of spiroheterocycles 4a–ja
F
HN
N
HN
N
HN
N
F
l
C
O
N
O
N
O
N
O
O
O
N
N
N
N
N
N
N
N
N
H
H
H
4b: 92%b
4c: 88%b
4d: 85%b
l
C
F
3C
HN
N
HN
N
HN
O
O
O
N
O
O
O
N
N
N
N
N
N
N
N
N
N
N
N
H
H
H
4e: 82%b
4f: 80%b
4g: 87%b
F
Ph
HN
N
N
F
O
N
O
O
O
O
O
N
N
N
N
N
N
N
N
N
N
N
N
N
H
N
H
H
4h: 81%b
4i: 89%b
4j: 86%b
aReaction conditions: substituted isatin (1 mmol), 5-amino-1H-tetrazole (1 mmol), dimedone (1 mmol), EtOH/H2O (1:1, 4 mL), 80 °C, 3 h.
bIsolated yield.
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JOURNAL OF CHEMICAL RESEARCH 2013 707
N
N
O
H2N
O
N
HN
O
N
H+
H
O
O
H
+
O
N
-
H
2O
O
H
O
A
HN
N
HN
O
N
O
H+
O
O
H
O
NH
-
H2O
N
N
N
N
N
N
N
H
H
4a
B
Scheme 2 Plausible mechanism.
δ 193.33, 173.44, 153.62, 148.70, 142.05, 131.84, 130.59, 126.62, 124.63,
111.94, 104.46, 65.39, 50.17, 32.95, 27.84; HRMS (ESI+): calcd for
C17H16ClN6O2: 371.1024, found [M+H]+: 371.1021.
Experimental
Caution: Acetic acid–perchloric acid mixture is a super acid
(pH=4.4). The mixture can cause severe skin and eye burns. The
vapour is irritating to the eyes and respiratory tract. Harmful if
swallowed. Goggles and gloves must be worn.
7-Fluoro-6’,6’-dimethyl-6’,7’-dihydro-4’H-spiro[indole-3,9’-
tetrazolo[5,1-b]quinazoline]-2,8’(1H,5’H)-dione (4d): Yield 83%;
1
white solid, m.p. 297–299 °C; H NMR (400 MHz, DMSO-d6) δ 12.14
(s, 1H), 11.47 (s, 1H), 7.51–7.11 (m, 1H), 7.02 (d, J=7.1 Hz, 1H), 6.98–
6.66 (m, 1H), 2.72 (d, J=16.0 Hz, 1H), 2.62 (d, J=16.0 Hz, 1H), 2.23 (d,
J=16.0 Hz, 1H), 2.13 (d, J=16.0 Hz, 1H), 1.05 (d, J=11.1 Hz, 6H); 13C
NMR (100 MHz, DMSO-d6) δ 193.34, 173.38, 153.46, 148.65, 145.67,
132.63, 130.18, 123.67, 120.25, 117.93, 104.66, 65.40, 50.10, 32.94,
28.18, 27.38; HRMS (ESI+): calcd for C17H16FN6O2: 355.1320, found
[M+H]+:355.1315.
All reagents were obtained from local commercial suppliers and used
without further purification. Melting points were determined with a
MPA100 apparatus (USA) and are uncorrected. 1H and 13C NMR
spectra were recorded on a Bruker Avance III 400 analyser in
DMSO-d6 with TMS as internal standard. Mass spectra were taken on
an Agilent 6540 UHD Accurate-Mass LC-MS instrument in the
electrospray ionisation (positive ESI) mode.
7-Chloro-6’,6’-dimethyl-6’,7’-dihydro-4’H-spiro[indole-3,9’-
tetrazolo[5,1-b]quinazoline]-2,8’(1H,5’H)-dione (4e): Yield 79%; white
solid, m.p. 296–298 °C; 1H NMR (400 MHz, DMSO-d6) δ 12.15 (s, 1H),
11.38 (s, 1H), 7.37 (dd, J=8.2, 1.0 Hz, 1H), 7.15 (d, J=7.2 Hz, 1H), 7.03–
6.84 (m, 1H), 2.72 (d, J=16.0 Hz, 1H), 2.63 (d, J=16.0 Hz, 1H), 2.24 (d,
J=16.0 Hz, 1H), 2.14 (d, J=16.0 Hz, 1H), 1.05 (d, J=11.3 Hz, 6H); 13C
NMR (100 MHz, DMSO-d6) δ 193.35, 173.59, 153.51, 148.64, 140.82,
131.68, 130.80, 124.04, 122.86, 114.80, 104.65, 65.88, 50.09, 32.95, 28.18,
27.39; HRMS (ESI+): calcd for C17H16ClN6O2: 371.1024, found [M+H]+:
371.1021.
Synthesis of the title compounds; typical procedure
A
mixture of 5-amimotetrazole (1 mmol, 0.085 g), appropriate
isatin (1 mmol), dimedone (1 mmol, 0.14 g) and [MeC(OH)2]+ClO4
(10 mol%) was stirred in EtOH/H2O (1:1, 4 mL) at 80 °C. After the
indicated time, the reaction was quenched into water (50 mL) and
cooled. The precipitated product was separated by centrifugation and
purified by silica gel chromatography to afford the desired product. All
the products were characterised by melting point, 1H NMR, 13C NMR
and LC-MS.
–
6’,6’-Dimethyl-6’,7’-dihydro-4’H-spiro[indole-3,9’-tetrazolo[5,1-b]
quinazoline]-2,8’(1H,5’H)-dione (4a): Yield 90%; white solid, m.p.
6’,6’-Dimethyl-7-(trifluoromethyl)-6’,7’-dihydro-4’H-spiro[indole-
3,9’-tetrazolo[5,1-b]quinazoline]-2,8’(1H,5’H)-dione
(4f):
Yield
1
1
312–316 °C; H NMR (400 MHz, DMSO-d6) δ 12.03 (s, 1H), 10.88 (s,
89%; white solid, m.p. 302–304 °C; H NMR (400 MHz, DMSO-d6)
δ 12.01 (s, 1H), 10.78 (s, 1H), 7.07 (dd, J=7.9, 0.9 Hz, 1H), 6.91 (s, 1H),
6.81 (d, J=7.9 Hz, 1H), 2.66 (d, J=3.6 Hz, 2H), 2.36–2.02 (m, 5H), 1.05
(d, J=4.0 Hz, 6H); 13C NMR (100 MHz, DMSO-d6) δ 193.36, 174.12,
153.81, 148.76, 140.51, 131.73, 128.27, 127.25, 125.29, 122.96, 112.68,
111.37, 104.50, 64.27, 50.04, 32.96, 28.13, 27.44; HRMS (ESI+): calcd for
C18H16F3N6O2: 405.1288, found [M+H]+: 405.1283.
1H), 7.28 (t, J=7.6 Hz, 1H), 7.10 (d, J=7.3 Hz, 1H), 6.91 (dd, J= 15.0,
7.6 Hz, 2H), 2.70 (d, J=16.0 Hz, 1H), 2.62 (d, J=16.0 Hz, 1H), 2.18 (d,
J=16.0 Hz, 1H), 2.12 (d, J=16.0 Hz, 1H), 1.05 (d, J=10.0 Hz, 6H); 13C
NMR (100 MHz, DMSO-d6) δ 193.14, 173.55, 153.15, 148.74, 143.02,
130.75, 130.16, 123.99, 122.66, 110.55, 104.92, 65.51, 50.23, 32.90, 28.23,
27.37; HRMS (ESI+): calcd for C17H17N6O2: 337.1414, found [M+H]+:
337.1411.
5,6’,6’-Trimethyl-6’,7’-dihydro-4’H-spiro[indole-3,9’-tetrazolo[5,1-b]
quinazoline]-2,8’(1H,5’H)-dione (4g): Yield 77%; white solid, m.p. 280–
5-Fluoro-6’,6’-dimethyl-6’,7’-dihydro-4’H-spiro[indole-3,9’-
tetrazolo[5,1-b]quinazoline]-2,8’(1H,5’H)-dione (4b): Yield 90%;
1
284 °C; H NMR (400 MHz, DMSO-d6) δ 12.01 (s, 1H), 10.78 (s, 1H),
1
white solid, m.p. 306–310 °C; H NMR (400 MHz, DMSO-d6) δ 12.08
7.07 (dd, J=7.9, 0.9 Hz, 1H), 6.91 (s, 1H), 6.81 (d, J=7.9 Hz, 1H), 2.66
(d, J=3.6 Hz, 2H), 2.36–2.02 (m, 5H), 1.05 (d, J=4.0 Hz, 6H); 13C NMR
(100 MHz, DMSO-d6) δ 193.15, 173.52, 153.01, 148.69, 140.56, 131.70,
130.96, 130.24, 124.46, 110.30, 104.97, 65.63, 50.25, 32.93, 28.07, 27.60,
20.93; HRMS (ESI+): calcd for C18H19N6O2: 351.1570, found [M+H]+:
351.1570.
5,6-Difluoro-6’,6’-dimethyl-6’,7’-dihydro-4’H-spiro[indole-3,9’-
tetrazolo[5,1-b]quinazoline]-2,8’(1H,5’H)-dione (4h): Yield 75%; white
solid, m.p. 330–332 °C; 1H NMR (400 MHz, DMSO-d6) δ 12.09 (s, 1H),
11.05 (s, 1H), 7.51 (dd, J=9.7, 8.0 Hz, 1H), 7.00 (dd, J=10.4, 6.6 Hz,
1H), 2.69 (d, J=16.0 Hz, 1H), 2.61 (d, J=16.0 Hz, 1H), 2.32–2.07 (m,
2H), 1.05 (s, 6H); 13C NMR (100 MHz, DMSO-d6) δ 193.32, 173.80,
153.65, 148.70, 139.99, 125.81, 114.60, 114.39, 104.38, 100.46, 100.19,
(s, 1H), 10.92 (s, 1H), 7.21 (dd, J=7.9, 2.2 Hz, 1H), 7.12 (s, 1H), 6.93 (d,
J=4.2 Hz, 1H), 2.69 (d, J=16.0 Hz, 1H), 2.61 (d, J=16.0 Hz, 1H), 2.18
(d, J=10.9 Hz, 2H), 1.05 (s, 6H); 13C NMR (100 MHz, DMSO-d6) δ
193.25, 173.68, 159.85, 157.49, 153.47, 148.69, 139.36, 131.44, 117.02,
112.45, 111.36, 104.57, 65.63, 50.19, 32.91, 27.84; HRMS (ESI+): calcd for
C17H16FN6O2: 355.1320, found [M+H]+: 355.1318.
5-Chloro-6’,6’-dimethyl-6’,7’-dihydro-4’H-spiro[indole-3,9’-
tetrazolo[5,1-b]quinazoline]-2,8’(1H,5’H)-dione (4c): Yield 87%;
1
white solid, m.p. 306–308 °C; H NMR (400 MHz, DMSO-d6) δ 12.08
(s, 1H), 11.03 (s, 1H), 7.63–7.15 (m, 2H), 6.94 (d, J=8.3 Hz, 1H), 2.68
(d, J=16.0 Hz, 1H), 2.60 (d, J=16.0 Hz, 1H), 2.23 (d, J=16.0 Hz, 1H),
2.13 (d, J=16.0 Hz, 1H), 1.05 (s, 6H); 13C NMR (100 MHz, DMSO-d6)
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65.22, 50.16, 32.91, 28.06, 27.63; HRMS (ESI+): calcd for C17H15F2N6O2:
373.1225, found [M+H]+: 373.1223.
Received 22 July 2013; accepted 27 August 2013
Paper 1302077 doi: 10.3184/174751913X13815671990200
Published online: 11 November 2013
1,6’,6’-Trimethyl-6’,7’-dihydro-4’H-spiro[indole-3,9’-tetrazolo[5,1-b]
quinazoline]-2,8’(1H,5’H)-dione (4i): Yield 88%; white solid, m.p. 332–
334 °C; 1H NMR (400 MHz, DMSO-d6) δ 12.10 (s, 1H), 7.39 (td, J= 7.7,
1.2 Hz, 1H), 7.27–7.09 (m, 2H), 6.99 (t, J=7.5 Hz, 1H), 3.25 (s, 3H), 2.75
(d, J=16.0 Hz, 1H), 2.67 (d, J=16.0 Hz, 1H), 2.19 (d, J=16.0 Hz, 1H),
2.11 (d, J=16.0 Hz, 1H), 1.05 (d, J=10.2 Hz, 6H); 13C NMR (100 MHz,
DMSO-d6) δ 193.16, 172.23, 153.26, 148.80, 144.39, 130.93, 129.37,
123.73, 123.40, 109.47, 104.89, 65.03, 50.18, 32.93, 28.15, 27.43, 27.14;
HRMS (ESI+): calcd for C18H19N6O2: 351.1570, found [M+H]+: 351.1567.
6’,6’-Dimethyl-1-phenyl-6’,7’-dihydro-4’H-spiro[indole-3,9’-
tetrazolo[5,1-b]quinazoline]-2,8’(1H,5’H)-dione (4j): Yield 87%; white
solid, m.p. 325–327 °C; 1H NMR (400 MHz, DMSO-d6) δ 12.22 (s, 1H),
7.65 (t, J=7.7 Hz, 2H), 7.53 (t, J=7.5 Hz, 3H), 7.32 (dd, J=14.2, 7.4 Hz,
2H), 7.05 (t, J=7.5 Hz, 1H), 6.81 (d, J=7.9 Hz, 1H), 2.75 (d, J=16.0 Hz,
1H), 2.67 (d, J=16.0 Hz, 1H), 2.28 (d, J=16.0 Hz, 1H), 2.18 (d,
J=16.0 Hz, 1H), 1.07 (d, J=6.1 Hz, 6H); 13C NMR (100 MHz, DMSO-d6)
δ 193.60, 171.85, 153.49, 148.88, 144.22, 134.61, 131.08, 130.34, 129.01,
127.04, 124.45, 124.07, 109.87, 105.23, 65.25, 50.07, 33.01, 28.25, 27.40;
HRMS (ESI+): calcd for C23H21N6O2: 413.1727, found [M+H]+: 413.1724.
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Conclusions
We have described a superacid catalysed highly efficient, one-
potprotocolforthesynthesisofspiro[indole-3,9’-tetrazolo[5,1-b]
quinazoline]-2,8’(1H,5’H)-diones in good to excellent yields
in aqueous medium. Easy work up, the ready availability of
the catalyst, mild conditions and an environmentally friendly
reaction medium make the procedure attractive and acceptable.
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The project was supported by the research fund of the Key
Laboratory for Advanced Technology in Environmental
Protection of Jiangsu Province (AE201118).
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