Envirocat EPZ-10: A solid acid catalyst for the synthesis of 1,8-dioxo-octahydroxanthenes in aqueous medium

Article abstract of DOI:10.1080/00397910903221027

An efficient method for synthesis of 1,8-dioxo-octahydroxanthenes using EPZ-10 as a heterogeneous catalyst is developed. In this method, aldehydes and dimedone/cyclohexane-1,3-dione are heated at 70C in the presence of a catalytic amount of EPZ-10 in wate

Full text of DOI:10.1080/00397910903221027

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Envirocat EPZ-10: A Solid Acid Catalyst
for the Synthesis of 1,8-Dioxo-
octahydroxanthenes in Aqueous Medium
D. M. Pore a , T. S. Shaikh a , N. G. Patil a , S. B. Dongare a & U. V.
Desai a
a Department of Chemistry, Shivaji University, Kolhapur, India
Version of record first published: 07 Jul 2010
To cite this article: D. M. Pore, T. S. Shaikh, N. G. Patil, S. B. Dongare & U. V. Desai (2010): Envirocat
EPZ-10: A Solid Acid Catalyst for the Synthesis of 1,8-Dioxo-octahydroxanthenes in Aqueous Medium,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 40:15, 2215-2219
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Synthetic Communications1, 40: 2215–2219, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903221027
ENVIROCAT EPZ-10: A SOLID ACID CATALYST FOR THE
SYNTHESIS OF 1,8-DIOXO-OCTAHYDROXANTHENES
IN AQUEOUS MEDIUM
D. M. Pore, T. S. Shaikh, N. G. Patil, S. B. Dongare,
and U. V. Desai
Department of Chemistry, Shivaji University, Kolhapur, India
An efficient method for synthesis of 1,8-dioxo-octahydroxanthenes using EPZ-10 as a
heterogeneous catalyst is developed. In this method, aldehydes and dimedone / cyclohexane-
1,3-dione are heated at 70 ꢀC in the presence of a catalytic amount of EPZ-10 in water as a
universal solvent, affording the corresponding 1,8-dioxo-octahydroxanthenes in moderate to
excellent yields. Also, domino Knoevenagel / hetero-Michael-addition reaction is described
in water without any catalyst with excellent yields. The major advantages of this method
are excellent yields, short reaction time, and ease of operation. This green protocol works
well with dimedone as well as cyclohexane-1,3-dione.
Keywords: 1,8-Dioxo-octahydroxanthenes; domino reaction; Envirocat EPZ-10; heterogeneous catalyst;
xanthenedione derivatives
Xanthene derivatives such as octahydroxanthenes have attracted the attention of
synthetic organic chemists and are becoming increasingly popular because they are
frequently occurring motifs in a number of natural products[1] and have been used
as versatile synthons because of the inherent reactivity of the pyran ring.[2] The syn-
thesis of 1,8-dioxo-octahydroxanthenes (Scheme 1) is an useful reaction that involves
the condensation between an aldehyde and dimedone or cyclohexane-1,3-dione in the
presence of Lewis acids.[3] However, most of these reported procedures have disad-
vantages including poor yields, prolonged reaction times, use of an excess of reagents
and catalysts, and use of toxic organic solvents. Therefore, an environmentally benign
protocol for synthesis of 1,8-dioxo-octahydroxanthenes is highly desirable.
An intriguing line in the development of ecofriendly methodologies is being
fueled by basic paradigm shift from use of traditional catalysts to clay as catalysts
because they fulfill the principles of green chemistry. Envirocat EPZ-10, a clay
catalyst, has received considerable attention as a versatile catalyst because of its high
reactivity, stability, ease of handling, easy preparation, and low toxicity. [Envirocats
catalysts are available from Contract Chemicals, England (www.contract-chemicals.
com).] EPZ-10, which is prepared by supporting ZnCl2 on clay, is known to contain
Received March 19, 2009.
Address correspondence to Dattaprasad Marutrao Pore, Department of Chemistry, Shivaji
University, Kolhapur 416 004, India. E-mail: p_dattaprasad@rediffmail.com
2215

2216
D. M. PORE ET AL.
Scheme 1. Synthesis of 1,8-dioxo-octahydroxanthenes.
Table 1. Synthesis of product 3 in water at 100 ꢀC without any catalyst
Entry
Product (3)
Time (h)
Yield (%)a
0
=
R
a
b
c
R ¼ H
3
86
96
90
84
86
90
95
89
88
96
92
93
93
95
95
84
R ¼ H; R0 ¼ 4-OMe
3
R ¼ H; R0 ¼ 4-Me
3.5
3.5
3
d
e
R ¼ H; R0 ¼ 4-Cl
R ¼ H; R0 ¼ 3-OMe, 4-OH
f
R ¼ H; R0 ¼ 4-CN
2.5
2.5
3.0
2.5
3.0
2.5
2.5
2.5
3.0
3.0
3.0
g
h
i
R ¼ CH3; R0 ¼ H
R ¼ CH3; R0 ¼ 4-OMe
R ¼ CH3; R0 ¼ 4-CH3
R ¼ CH3; R0 ¼ 4-Cl
j
k
l
R ¼ CH3; R0 ¼ 4-NO2
R ¼ CH3; R0 ¼ 4-CN
R ¼ CH3; R0 ¼ 3,4-(OMe)2
R ¼ CH3; R0 ¼ 4-N,N-(CH3)2
R ¼ CH3; R0 ¼ 2-NO2
R ¼ CH3; R0 ¼ 3,4-O2CH2
m
n
o
p
aYields refer to pure isolated products.

SYNTHESIS OF 1,8-DIOXO-OCTAHYDROXANTHENES
2217
Table 2. EPZ-10-catalyzed synthesis of 1,8-dioxo-octahydroxanthenes
Entry
Product (4)
Time (h)
Yield (%)a,b
a
b
c
d
e
f
R ¼ R0 ¼ H
2
82
84
91
87
80
95
86
92
89
84
88
86
92
91
82
83
85
87
86
94
R ¼ H; R0 ¼ 4-Cl
2.5
2.5
3
R ¼ H; R0 ¼ 4-OMe
R ¼ H; R0 ¼ 4-Me
R ¼ H; R0 ¼ 4-NO2
3.0
2
R ¼ H; R0 ¼ 4-N,N-(CH3)2
R ¼ H; R0 ¼ 3-OMe, 4-OH
R ¼ CH3; R0 ¼ H
g
h
i
2
2.5
2.5
2.5
2.5
3.0
2.5
2.0
3
R ¼ CH3; R0 ¼ 4-OMe
R ¼ CH3; R0 ¼ 4-Me
R ¼ CH3; R0 ¼ 4-Cl
j
k
l
R ¼ CH3; R0 ¼ 4-NO2
R ¼ CH3; R0 ¼ 4-N,N-(CH3)2
R ¼ CH3; R0 ¼ 3-OMe, 4-OH
R ¼ CH3; R0 ¼ 2-NO2
R ¼ CH3; R0 ¼ 3-NO2
R ¼ CH3; R0 ¼ CN
m
n
o
p
q
r
3
2.5
2
R ¼ CH3; R0 ¼ Ph-CH ¼ CHꢁ
R ¼ CH3; R0 ¼ 3,4-(OMe)2
R ¼ CH3; R0 ¼ thienyl
s
2.5
2
t
aYields refer to pure isolated products.
bAll products gave satisfactory spectroscopic (IR, 1H NMR, MS) analysis.
predominantly strong Lewis acid sites as well as weak Brønsted acid sites.[4] It has
been used as a catalyst for several transformations such as the Friedel–Crafts
alkylation, aromatic bromination and benzylation, Biginelli reaction,[5a] synthesis
of 3-carboxycoumarins,[5b] and synthesis of geminal diacetates.[5c] As a part of our
program aimed at developing selective and environmental friendly methodologies,[6]
we report herein the synthesis of 1,8-dioxo-octahydroxanthene derivatives using a
catalytic amount of EPZ-10 at 70 ꢀC in water as a solvent (Scheme 1).
Initially, the reaction of dimedone and p-chlorobenzaldehyde was carried out
without any catalyst in an aqueous medium at 100 ꢀC and, as expected, product 3
was formed. No traces of cyclized product 4 was observed, to allude that the acid
is essential for cyclodehydration of 3 to 4.
A series of aldehydes were then studied for undergoing domino Knoevenagel=
hetero-Michael-addition reaction in water without any catalyst at 100 ꢀC. We
observed that product 3 is formed in moderate to excellent yields as shown in Table 1.
After these initial scrutinizes, we then extended our attention to the synthesis of
1,8-dioxo-octahydroxanthenes. We studied the condensation of dimedone and

2218
D. M. PORE ET AL.
p-chlorobenzaldehyde in water using EPZ-10 as a catalyst under elevated tempera-
ture to obtain the product 4. The versatility of this reaction to other aldehydes is
reported in Table 2.
CONCLUSION
In this report, we have described an elegant protocol for the synthesis of
1,8-dioxo-octahydroxanthenes via domino Knoevenagel=hetero-Michael-addition
reaction followed by dehydration in water using a catalytic amount of EPZ-10.
EXPERIMENTAL
General Procedure
Domino Knoevenagel / hetero-Michael-addition reaction. 1,3-Diketone
(10 mmol) was added to a solution of an aldehyde (5 mmol) in water (10 mL) and
heated at reflux until completion of the reaction. Progress of the reaction was mon-
itored by testing with thin-layer chromatography (TLC). On completion of the reac-
tion, the formed solid product was filtered and dried.
EPZ-10-Catalyzed synthesis of 1,8-dioxo-octahydroxanthenes. A
mixture of an aldehyde (2.5 mmol), 1,3-diketone (5 mmol) in water (15 mL), and
EPZ-10 (10 mol%) was stirred at 70 ꢀC, and the progress of the reaction was
monitored by TLC. After completion of the reaction, the reaction mixture was
extracted with ether (30 mL) and dried over anhydrous sodium sulfate. The ether
was evaporated to obtain the desired 1,8-dioxo-octahydroxanthenes. These products
were characterized by the usual elemental analysis and spectral techniques [i.e.,
1
infrared (IR), H NMR, mass spectrometry (MS)].
Spectral Data of Unknown Compounds
Compound 3m: 2,20-(3,4-dimethoxyphenyl)methylene-bis (3-hydroxy-
5,5-dimethyl-2-cyclohexene-1-one). Mp 180 ꢀC; IR (KBr): 3009, 2963, 1588,
1
1463, 1375, 1239, 1147, 1027, 868 cmꢁ1; H NMR (200 MHz, CDC13): d 12 (s,
1H), 6.61–6.85 (3H, m), 5.51 (1H, s), 3.85 (3H, s), 3.78 (3H, s), 2.40 (4H, s), 2.27
(4H, s), 1.06 (6H, s), 1.02 (6H, s); EIMS: m=z 428 (Mþ), 288, 273, 257, 201, 176,
140, 91, 76, 65, 55, 40. CHN analysis calcd. for C25H32O6: C, 70.07; H, 7.53. Found:
C, 69.80; H, 7.68.
Compound 4s: 3,3,6,6-tetramethyl-9-(3,4-dimethoxy phenyl)-1,8-dioxo-
octahydroxanthene. Mp 170 ꢀC; IR (KBr): 2960, 1596, 1514, 1375, 1252, 1238,
1
1146, 1027, 871 cmꢁ1; H NMR (200 MHz, CDC13): d 6.90 (1H, s), 6.71 (2H, s),
4.67 (1H, s), 3.86 (3H, s), 3.80 (3H, s), 2.45 (4H, s), 2.21 (4H, s), 1.11 (6H, s), 1.01
(6H, s); EIMS: m=z 410 (Mþ), 379, 273, 217, 161, 105, 91, 77, 55, 41. CHN analysis
calcd. for C25H30O5: C, 73.15; H, 7.37. Found: C, 73.01; H, 7.49.
Compound 4t: 3,3,6,6,-tetramethyl-9-(2-thienyl)-1,8-dioxo-octahydro
xanthene. Mp 145 ꢀC; IR (KBr): 2960, 2928, 2870, 1594, 1375, 1311, 1260, 1166,
1
868, 702 cmꢁ1; H NMR (200 MHz, CDC13): d 6.92 (1H, dt), 6.77 (1H, t), 6.64

SYNTHESIS OF 1,8-DIOXO-OCTAHYDROXANTHENES
2219
(1H, m), 5.08 (1H, s), 2.39 (4H, s), 2.20 (4H, s), 1.04 (6H, s), 0.99 (6H, s); EIMS: m=z
356 (Mþ), 339, 323, 272, 217, 188, 161, 83, 55. CHN analysis calcd. for C21H24O3S:
C, 70.76; H, 6.79; S, 8.99. Found: C, 70.48; H, 6.95; S, 8.89.
ACKNOWLEDGMENTS
D. M. P. and K. A. U. thank the University Grants Commission, New Delhi, for
financial assistance [F.2-3=2007(Policy=SR)] and for a research project fellowship,
respectively.
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