Efficient and clean synthesis of 1,8-dioxooctahydroxanthenes in aqueous medium

Article abstract of DOI:10.14233/ajchem.2018.21452

In this work, an efficient synthesis of 1,8-dioxooctahydroxanthenes in aqueous medium is reported. The reaction was catalyzed by aqueous extract of plant material (pericarp of Sapindus trifoliatus fruit), which makes this protocol 'green' and eco-friendly

Full text of DOI:10.14233/ajchem.2018.21452

Asian Journal of Chemistry; Vol. 30, No. 12 (2018), 2621-2624
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2018.21452
Efficient and Clean Synthesis of 1,8-Dioxooctahydroxanthenes in Aqueous Medium
SANTOSH B. PORE
Organic Research Laboratory, Post-Graduate Department of Chemistry, Balwant College, Vita-415 311, India
Corresponding author: Tel.: +91 2347 272096; E-mail: santoshbpore@gmail.com
Received: 17 May 2018;
Accepted: 14 August 2018;
Published online: 31 October 2018;
AJC-19121
In this work, an efficient synthesis of 1,8-dioxooctahydroxanthenes in aqueous medium is reported. The reaction was catalyzed by
aqueous extract of plant material (pericarp of Sapindus trifoliatus fruit), which makes this protocol 'green' and eco-friendly. Differently
substituted aromatic aldehydes underwent condensation with dimedone resulting in the formation of only the desired product in good to
excellent yield. This reaction provides an alternative route to useful organic substances, employing simple reaction conditions, without
organic solvents and hazardous chemical catalysts.
Keywords: 1,8-Dioxooctahydroxanthenes, Sapindus trifoliatus, Aqueous medium, Green catalyst.
[16]. Cervinomycin A1 possesses antibiotic activity against
anaerobic bacteria such as Clostridium perfringens, Peptoco-
ccus prevotii and Bacteroides fragilis [17].
INTRODUCTION
Xanthenes have attracted a number of research efforts in
synthetic organic chemistry due to their wide range of biolo-
gical and pharmacological properties like antiviral [1], anti-
bacterial [2] and anti-inflammatory activities [3], as well as in
photodynamic therapy [4] and as antagonists of the paralyzing
action of zoxazolamine [5]. Xanthenes are also available from
many natural sources. The prominent among them are dibenzo-
xanthenes, hexahydroxanthene and octahydroxanthene.
Xanthenes are frequently occurring motifs in a number
of natural products [6] and have been used as versatile synthons
due to the inherent reactivity of inbuilt pyran ring [7]. Octahydro-
xanthene derivatives containing a structural unit of benzopyrans
can be used as antispasm agents [8] and fluorescent fuel [9].
Furthermore, due to their useful spectroscopic properties, they
are used as dyes and pigments [10,11], in laser technologies
[12] and in fluorescent materials for visualization of biomole-
cules [13].
1,8-Dioxooctahydroxanthene is an important member of
xanthene family. Tetramethyl derivative of this synthetically
useful precursor is generally obtained by condensation of 5,5-
dimethyl-1,3-cyclohexanedione (dimedone) with an aromatic
aldehyde. Literature survey shows a number of routes to obtain
1,8-dioxooctahydroxanthene and its variants, employing either
different starting materials or catalysts. Literature methods
include catalysts like molecular iodine [18], zirconyl triflate
[19], nano-TiO2 [20], nanoparticles of iron(II, III) oxide [21],
iron(III) complex [22], nano-SPA [23] and barium perchlorate
[24] among others. However, contemporary research in organic
chemistry desires protocols to be in conformity with green chem-
istry principles.An attempt to achieve 'green synthesis' of 1,8-
dioxooctahydroxanthene using plant-derived catalyst with
excellent results is decribed in this work.
Xanthenes are also known to possess many pharmacological
properties. Allanxanthone C, a xanthene derivative obtained
from Allanblackia monticola exhibits excellent biological
properties [14]. Ehretianone, a quinonoid xanthene obtained
from Ehretia buxifolia is reported to possess anti-snake venom
activity [15]. A spiro-compound of xanthene, xanthene spiro-
piperidine, is well-known as a sedative and antihistaminic agent
EXPERIMENTAL
Melting points were determined in open capillaries and
are uncorrected. Reagent grade chemicals were purchased from
s.d. Fine Chem., Spectrochem Co. and others and used as received
without further purification. IR spectra were recorded on a Perkin-
Elmer 1310 FT-IR spectrometer using KBr pellets. 1H NMR
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2622 Pore
Asian J. Chem.
(300 MHz) and 13C NMR (75 MHz) spectra were recorded on
Varian instrument using CDCl3 as solvent and TMS as internal
reference. The progress of reaction was monitored by TLC run on
silica gel G (Merck). Mass spectra were recorded on a Shimadzu
QP 2010 GCMS with an ion source temperature of 200 ºC.
General procedure for the synthesis of 3,3,6,6-tetra-
methyl-9-(substituted)-1,8-dioxooctahydroxanthene: The
mixture of 5,5-dimethyl-1,3-cyclohexanedione (10 mmol) and
benzaldehyde (5 mmol) was mixed with aqueous extract of
pericarp of Sapindus trifoliatus fruit (10 mL) and stirred magneti-
cally at 80 ºC for appropriate time. The progress of the reaction
was monitored at an interval of 60 minutes with the help of
TLC (ethyl acetate/n-hexane in 2:8). The reaction mixture was
washed by cold water to remove traces of bio-catalyst and then
filtered (Scheme-I). The remaining solid material was washed
with cold water. The solid product was recrystallized by using
ethanol to yield pure product.
3,3,6,6-Tetramethyl-9-phenyl-1,8-dioxooctahydro-
xanthene (Table-1, entry 1): 1H NMR (300 MHz, CDCl3) δ
ppm: 0.90 (s, 6H), 1.04 (s, 6H), 2.11 (d, J = 9 Hz, 2H), 2.27
(d, J = 9.1 Hz, 2H), 2.54 (d, J = 10.2 Hz, 2H), 2.60 (d, J = 10.3
Hz, 2H), 4.57 (s, 1H), 7.10 (t, J = 4.2 Hz, 1H), 7.16 (d, J = 4.1
Hz, 2H), 7.23 (t, J = 4.2 Hz, 2H). 13C NMR (75 MHz, CDCl3)
δ ppm: 27.3, 29.3, 31.8, 32.2, 40.9, 50.7, 115.6, 126.4, 128.4,
128.9, 143.6, 161.7, 197.3.Anal. calcd. found (%) for C23H26O3:
C 78.83 (78.64), H 7.48 (7.53).
28.9, 31.7, 32.6, 41.5, 51.4, 116.7, 127.9, 129.6, 135.8, 141.3,
161.4, 195.3. Anal. calcd. found (%) for C24H28O3: C 79.09
(78.73), H 7.74 (7.69).
3,3,6,6-Tetramethyl-9-(3-nitrophenyl)-1,8-dioxoocta-
hydroxanthene (Table-1, entry 3): 1H NMR (300 MHz, CDCl3)
δ (ppm): 1.07 (s, 6H), 1.12 (s, 6H), 2.16 (d, J = 9.2 Hz, 2H), 2.27
(d, J = 9.2 Hz, 2H), 2.54 (t, J = 10.9 Hz, 4H), 4.87 (s, 1H),
7.42 (t, J = 5.3 Hz, 1H), 7.78 (d, J = 4.5 Hz, 1H), 7.96 (d, J = 4.9
Hz, 1H), 8.12 (s, 1H). 13C NMR (75 MHz, CDCl3) δ ppm:
26.9, 29.8, 31.8, 32.6, 41.5, 49.8, 112.9, 122.8, 123.5, 129.2,
135.3, 145.7, 148.7, 164.2, 196.3. Anal. calcd. found (%) for
C23H25NO5: C 69.86 (69.78), H 6.37 (6.52), N 3.54 (3.49).
3,3,6,6-Tetramethyl-9-(4-nitrophenyl)-1,8-dioxoocta-
hydroxanthene (Table-1, entry 4): 1H NMR (300 MHz, CDCl3)
δ ppm: 1.05 (s, 6H), 1.14 (s, 6H), 2.14 (d, J = 9.8 Hz, 2H), 2.25
(d, J = 9.9 Hz, 2H), 2.48 (t, J = 11.2 Hz, 4H), 4.85 (s, 1H), 7.46
(d, J = 4.8 Hz, 2H), 8.11 (2H, J = 4.8 Hz, 2H). 13C NMR (75
MHz, CDCl3) δ ppm: 27.3, 29.8, 32.1, 33.4, 41.5, 51.0, 115.3,
123.2, 130.4, 145.9, 151.6, 163.5, 195.8. Anal. calcd. found
(%) for C23H25NO5: C 69.86 (69.89), H 6.37 (6.23), N 3.54 (3.58).
3,3,6,6-Tetramethyl-9-(4-chlorophenyl)-1,8-dioxo-
octahydroxanthene (Table-1, entry 5): 1H NMR (300 MHz,
CDCl3) δ ppm: 0.96 (s, 6H), 1.08 (s, 6H), 2.13 (d, J = 9.6 Hz,
2H), 2.26 (d, J = 9.7 Hz, 2H), 2.53 (d, 2H), 2.61 (d, J = 10.5 Hz,
2H), 4.54 (s, 1H), 7.21 (d, J = 4.9 Hz, 2H), 7.26 (d, J = 4.8 Hz,
2H). 13C NMR (75 MHz, CDCl3) δ ppm: 27.5, 28.8, 31.4, 32.6,
40.3, 51.2, 114.9, 127.5, 129.2, 132.4, 143.6, 162.5, 196.4.Anal.
calcd. found (%) for C23H25O3Cl: C 71.77 (71.68), H 6.55 (6.68).
3,3,6,6-Tetramethyl-9-(4-methoxyphenyl)-1,8-dioxo-
octahydroxanthene (Table-1, entry 6): 1H NMR (300 MHz,
CDCl3) δ ppm: 1.01 (s, 6H), 1.12 (s, 6H), 2.18 (d, J = 12.1 Hz,
3,3,6,6-Tetramethyl-9-(4-methylphenyl)-1,8-dioxo-
octahydroxanthene (Table-1, entry 2): 1H NMR (300 MHz,
CDCl3) δ ppm: 0.98 (s, 6H), 1.18 (s, 6H), 2.18-2.29 (m, 7H),
2.45 (s, 4H), 4.79 (s, 1H), 7.06 (d , J = 4.5 Hz, 2H), 7.18 (d, J =
4.2 Hz, 2H); 13C NMR (75 MHz, CDCl3): ? (ppm) 20.9, 27.3,
O
Ar
O
O
Aqueous extract of pericarp of
Sapindus trif oliatus fruits
Ar–CHO
2
+
H3C
H3C
CH3
CH3
CH3
CH3
80 °C
O
O
3a-m
Scheme-I
TABLE-1
SYNTHESIS OF SUBSTITUTED 1,8-DIOXOOCTAHYDROXANTHENES
m.p. (°C)
Entry
Ar-
Product
Time (h)
Yield (%)b
Observed
Literature
[19]
205-206 [19]
[19]
216-217 [19]
[19]
167-168 [19]
[19]
221-223 [19]
1
2
3
4
5
6
7
8
9
10
11
12
13
C6H5-
3a
3b
3c
3d
3e
3f
3g
3h
3i
2.0
2.5
1.5
1.5
1.5
3.0
2.5
3.0
3.0
2.5
1.5
1.5
2.0
92
90
93
93
90
85
88
85
80
85
90
92
90
205-207
214-216
165-166
218-220
226-228
240-242
242-245
226-228
211-214
221-224
177-180
214-216
224-227
4-CH3C6H4-
3-NO2C6H4-
4-NO2C6H4-
4-ClC6H4-
4-MeOC6H4-
4-OHC6H4-
4-OH(3-MeO)C6H3-
3,4-MeOC6H4-
4-(N,N-CH3)C6H4-
3-ClC6H4-
[28]
229-230 [28]
[19]
241-243 [19]
246-248 [199]]
225-227 [199]]
209-212 [299]]
218-220 [288]]
179-181 [288]]
216-217 [255]]
226-229 [255]]
3j
3k
3l
4-CNC6H4-
4-BrC6H4-
3m
aReaction conditions: 1:2 moles of aldehyde:dimedone, room temperature, 10 mL biocatalyst; bIsolated yield after purification.

Vol. 30, No. 12 (2018)
Efficient and Clean Synthesis of 1,8-Dioxooctahydroxanthenes in Aqueous Medium 2623
2H), 2.25 (d, J = 12.1 Hz, 2H), 2.48 (s, 4H), 3.75 (s, 3H), 4.72
(s, 1H), 6.77 (d, J= 6.6 Hz, 2H), 7.22 (d, J= 6.5 Hz, 2H). 13C NMR
(75 MHz, CDCl3) δ ppm: 27.3, 29.3, 30.9, 32.2, 40.9, 50.8,
55.1, 113.5, 115.8, 129.3, 136.5, 157.9, 162.1, 196.5. Anal.
calcd. found (%) for C24H28O4: C 75.76 (75.94), H 7.42 (7.31).
3,3,6,6-Tetramethyl-9-(4-hydroxyphenyl)-1,8-dioxo-
octahydroxanthene (Table-1, entry 7): 1H NMR (300 MHz,
CDCl3) δ ppm: 0.96 (s, 6H), 1.08 (s, 6H), 2.11-2.24 (m, 4H),
2.47 (s, 4H), 4.62 (s, 1H), 6.55 (d, J = 7.4 Hz, 2H), 7.11 (d, J
= 7.4 Hz, 2H), 7.19 (s, 1H). 13CNMR (75 MHz, CDCl3) δ ppm:
29.1, 29.8, 31.3, 32.6, 41.2, 50.5, 114.7, 117.2, 129.8, 135.9,
155.6, 163.5, 196.9. Anal. calcd. found (%) for C23H26O4: C
75.38 (75.57), H 7.15 (7.31).
CDCl3) δ ppm: 0.98 (s, 6H), 1.08 (s, 6H), 2.08 (d, J = 9.6 Hz,
2H), 2.28 (d, J = 9.7 Hz, 2H), 2.52 (s, 4H), 4.51 (s, 1H), 7.14
(d, J = 4.9 Hz, 2H), 7.43 (d, J = 4.9 Hz, 2H).13CNMR(75 MHz,
CDCl3) δ ppm: 27.5, 29.7, 31.8, 32.5, 41.3, 51.2, 114.8, 121.2,
129.7, 131.4, 143.8, 163.5, 196.7. Anal. calcd. found (%) for
C23H25O3Br: C 64.34 (64.47), H 5.87 (5.82).
RESULTS AND DISCUSSION
Most of the catalysts employed for the synthesis of 1,8-
dioxooctahydroxanthenes fall under the category of acidic
substances (organic, mineral or Lewis acids). Some of them
are easily available, cost-effective and conform well to 'Green
Chemistry' parameters [25], while there are many which require
special methods of preparation [26]. We have demonstrated
earlier [27] that aqueous extract of pericarp of Sapindus
trifoliatus fruits serves as an excellent catalyst to bring about
a variety of organic transformations. Different substrates have
been successfully made to react by this catalyst in aqueous
medium. Reactions were carried out at room temperature with
maximum atom efficiency, thereby producing minimum organic
waste. In this context, it is also apparent that substrates with
carbonyl function have inherent tendency to react, although
reaction conditions may differ.
Temperature optimization: It is evident that the reaction
takes place at a very slow rate when carried out at room temper-
ature. Even after 5 h, only 30 % reactants were converted into
products. The alternative was to carry out the reaction at elevated
temperatures.An oil bath with temperature-control facility was
used to provide necessary heat to attain required temperature
in sustained manner. The results summarized in Table-2 indi-
cated that the maximum yield of product was obtained when
the reaction was carried out at 80 ºC and time duration 2 h.
3,3,6,6-Tetramethyl-9-(4-hydroxy-3-methoxyphenyl)-
1
1,8-dioxooctahydroxanthene (Table-1, entry 8): H NMR
(300 MHz, CDCl3) δ ppm: 0.96 (s, 6H), 1.08 (s, 6H), 2.11-2.24
(m, 4H), 2.47 (s, 4H), 3.75 (s, 3H), 4.62 (s, 1H), 6.69 (dd, J =
8.3 Hz, 1H), 6.78 (d, J = 4.9 Hz, 1H), 6.83 (d, J = 4.9 Hz, 1H).
13CNMR(75 MHz, CDCl3) δ ppm: 29.1, 29.8, 31.3, 32.6, 41.2,
50.5, 114.7, 117.2, 129.8, 135.9, 155.6, 163.5, 196.9. Anal.
calcd. found (%) for C24H28O5: C 75.82 (75.76), H 7.45 (7.52).
3,3,6,6-Tetramethyl-9-(3,4-dimethoxyphenyl)-1,8-
dioxooctahydroxanthene (Table-1, entry 9): 1H NMR (300
MHz, CDCl3) δ ppm: 0.98 (s, 6H), 1.08 (s, 6H), 2.12 (d, J = 9.6
Hz, 2H), 2.29 (d, J = 9.6 Hz, 2H), 2.52 (d, J = 10.5 Hz, 2H),
2.59 (d, J = 10.4 Hz, 2H), 3.71 (s, 6H), 4.47 (s, 1H), 6.68 (dd,
J = 8.3, 1.3 Hz, 1H), 6.75 (d, J = 4.9 Hz, 1H), 6.81 (d, J = 4.9
Hz, 1H). 13C NMR (75 MHz, CDCl3) δ ppm: 27.3, 29.7, 31.5,
33.1, 51.4, 56.7, 57.3, 114.1, 115.2, 115.9, 121.3, 138.6, 147.5,
148.9, 164.3, 197.3. Anal. calcd. found (%) for C25H30O5: C
73.15 (72.84), H 7.37 (7.45).
3,3,6,6-Tetramethyl-9-(4-N,N-dimethylphenyl)-1,8-
dioxooctahydroxanthene (Table-1, entry 10): 1H NMR (300
MHz, CDCl3) δppm: 0.98 (s, 6H), 1.08 (s, 6H), 2.08 (d, J = 9.6
Hz, 2H), 2.28 (d, J = 9.6 Hz, 2H), 2.52 (s, 4H), 2.89 (s, 6H),
4.51 (s, 1H), 7.13 (d, J = 4.9 Hz, 2H), 7.25 (d, J = 4.9 Hz, 2H).
13CNMR(75 MHz, CDCl3) δ ppm: 27.5, 29.7, 31.8, 32.5, 41.3,
51.2, 114.8, 121.2, 129.7, 131.4, 143.8, 163.5, 196.7.Anal. calcd.
found (%) for C23H31NO3: C 76.30 (76.28), H 7.94 (7.89), N
3.58 (3.68).
TABLE-2
EFFECT OF TEMPERATURE ON REACTION
TIME AND YIELD OF THE REACTION
Reaction
temperature (°C)
Entry
Time (h)
Yield (%)
1
2
3
4
5
50
60
70
80
90
5
4
3
2
2
80
85
85
92
92
3,3,6,6-Tetramethyl-9-(3-chlorophenyl)-1,8-dioxo-
octahydroxanthene (Table-1, entry 11): 1H NMR (300 MHz,
CDCl3) δ ppm: 1.01 (s, 6H), 1.13 (s, 6H), 2.21 (s, 4H), 2.53 (t,
J = 8.6 Hz, 4H), 4.76 (s, 1H), 7.11 (d, J = 4.5 Hz, 1H), 7.17 (t,
Different substituted benzaldehydes were made to react
with dimedone at 80 ºC in presence of aqueous extract of pericarp
of Soap nut fruit. Results are in agreement with general behaviour
of differently substituted benzaldehydes. Benzaldehydes with
electron-donating substituents required more time to react
(Table-1, entries 2, 6, 8, 9) which is expected as electron-donating
substituents render carbonyl carbon less reactive. Reverse tend-
ency is recorded with benzaldehydes containing electron-
attracting substituents.
13
J = 4.6 Hz, 2H), 7.27 (s, 1H). C NMR (75 MHz, CDCl3) δ
ppm: 27.6, 29.7, 31.8, 32.9, 41.3, 50.8, 115.7, 126.4, 127.7,
129.8, 130.5, 134.9, 147.3, 164.2, 196.7. Anal. calcd. found
(%) for C23H25O3Cl: C 71.77 (71.63), H 6.55 (6.48).
3,3,6,6-Tetramethyl-9-(4-cyanophenyl)-1,8-dioxo-
octahydroxanthene (Table 3, entry 12): 1H NMR (300 MHz,
CDCl3) δ ppm: 1.03 (s, 6H), 1.14 (s, 6H), 2.18 (d, J = 9.8 Hz,
2H), 2.28 (d, J = 9.8 Hz, 2H), 2.53 (t, J = 9.1 Hz, 4H), 4.81 (s,
1H), 7.45 (d, J = 8.4 Hz, 2H), 7.54 (2H, J= 4.8 Hz, 2H). 13CNMR
(75 MHz, CDCl3) δ ppm: 27.5, 29.3, 32.5, 32.7, 41.3, 51.3,
111.3, 115.6, 118.7, 128.9, 132.6, 150.3, 163.2, 197.2. Anal.
calcd. found (%) for C24H25NO3: C 76.77 (76.83), H 6.71 (6.68),
N 3.73 (3.69).
Conclusion
It is demonstrated that 1,8-dioxooctahydroxanthenes can
be synthesized in aqueous medium in good to excellent yield.
The reaction could be efficiently catalyzed by aqueous extract
of pericarp of Sapindus trifoliatus fruit.
3,3,6,6-Tetramethyl-9-(4-bromophenyl)-1,8-dioxo-
octahydroxanthene (Table-1, entry 13): 1H NMR (300 MHz,

2624 Pore
Asian J. Chem.
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CONFLICT OF INTEREST
The authors declare that there is no conflict of interests
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