Synthesis, characterization, and application of cobalt hydrogen sulfate as a new heterogeneous, reusable and efficient catalyst in one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes and 1,8-dioxooctahydroxanthenes

Article abstract of DOI:10.1134/S0023158414040041

Cobalt hydrogen sulfate is synthesized and characterized by XRD, FTIR and TEM measurements. The efficiency of this readily available, cheap, non-toxic, heterogeneous and reusable catalyst is shown in the one-pot preparation of aryl- and alkyl-14H-dibenzox

Full text of DOI:10.1134/S0023158414040041

ISSN 0023ꢀ1584, Kinetics and Catalysis, 2014, Vol. 55, No. 4, pp. 428–433. © Pleiades Publishing, Ltd., 2014.
Synthesis, Characterization, and Application
of Cobalt Hydrogen Sulfate as a New Heterogeneous, Reusable
and Efficient Catalyst in OneꢀPot Synthesis
of 14ꢀarylꢀ14Hꢀdibenzo[a,j]xanthenes
and 1,8ꢀdioxooctahydroxanthenes1
H. Eshghi*, M. Rahimizadeh, M. Eftekhar, and M. Bakavoli
Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, 91775ꢀ1436 Iran
*eꢀmail: heshghi@um.ac.ir
Received August 14, 2013
Abstract—Cobalt hydrogen sulfate is synthesized and characterized by XRD, FTIR and TEM measurements.
The efficiency of this readily available, cheap, nonꢀtoxic, heterogeneous and reusable catalyst is shown in the
oneꢀpot preparation of arylꢀ and alkylꢀ14Hꢀdibenzoxanthenes and 1,8ꢀdioxooctahydroxanthene derivatives
by cyclocondensation of substituted benzaldehydes and ꢀnaphthol or 5,5ꢀdimethylꢀ1,3ꢀcyclohexanedione
β
respectively. Among advantages of these methods are high yields, a clean reaction strategy, simple methodolꢀ
ogy, green conditions and easy workup.
DOI: 10.1134/S0023158414040041
1
Metal hydrogen sulfates are widely used as efficient Among these are acetic acid and sulfuric acid [15], silꢀ
reagents in synthetic organic chemistry. A broad range ica and sulfuric acid [16],
pꢀtoluene sulfonic acid [17],
amberlyst
ꢀ15 [18], ferric hydrogen sulfate [19], and
of reactions including protection, deprotection, oxiꢀ
dation, C–C, C–N, and C–O bond formation and
cleavage took place in the presence of these reagents.
In addition, stability, cheapness, and efficiency and in
many cases heterogeneity and reusability are other
important advantages of these reagents [1–5].
heteropolyacids (HPAs) [20]. On the other hand, the
an increased application both in the field of medicinal
chemistry and material science produced a renewed
interest in the synthesis of 1,8ꢀdioxooctahydroxanꢀ
thene compounds. In recent years, synthesis of 1,8ꢀ
dioxooctahydroxanthenes was focused on the condenꢀ
sation of dimedone (5,5ꢀdimethylꢀ1,3ꢀcyclohexꢀ
anedione) with various aromatic aldehydes, by using
different catalysts such as silica sulfuric acid [21],
Dowexꢀ50W [22], HClO4–SiO2 and PPA–SiO2 [23],
The synthesis of xanthene derivatives, especially
benzoxanthenes, has attracted attention of organic
chemists due to their wide range of biological and
therapeutic properties such as antibacterial [6] and
antiviral efficiency [7] and also because they can be
used for photodynamic treatments (PDT) [8]. Benꢀ
zoxanthenes are used in production of dyes [9], in laser
technologies [10], and in manufacturing of fluorescent
materials for visualization of biomolecules [11]. Many
procedures are disclosed to synthesize xanthenes and
benzoxanthenes like trapping of benzynes by phenols
[12], cyclocondensation between 2ꢀhydroxy aromatic
aldehydes and 2ꢀtetralone [13], interamolecular pheꢀ
nylꢀcarbonyl coupling reaction of benzaldehydes and
acetophenones [14]. In addition, 14Hꢀdibenzoxanꢀ
thenes and related products are prepared by dehydraꢀ
NaHSO4–SiO2 and silica chloride [24], p–dodecylꢀ
benzenesulfonic acid [25], Fe3+–montmorillonite
[26], amberlystꢀ15 [27], diammonium hydrogen
phosphate [28], TMSCl [29], tetrabutylammonium
hydrogen sulphate [30], and hydrochloric acid [31].
In spite of potential utility of aforementioned
routes for the synthesis of xanthenes derivatives, many
of these methods have serious shortcomings. They use
expensive reagents, strong acidic conditions, and long
reaction times but afford low yields. Moreover, excess
of reagents/catalysts and toxic organic solvents are
involved in the synthesis. A possible approach to corꢀ
rect these problems is a search for new active, efficient
and recyclable catalysts and simple workꢀup for the
preparation of xanthenes under neutral, mild and
practical conditions. In the present paper, we report a
tion reaction of
ꢀnaphthol with aldehyde. In this
β
context some methods and catalysts suitable for the
synthesis of benzoxanthenes have been reported.
1
The article is published in the original.
428

SYNTHESIS, CHARACTERIZATION, AND APPLICATION
429
R
OH
Co(HSO )
4 2
DCE, reflux
2
+
RCHO
O
1
2
3a–l
3a R = C6H5
3f R = 4ꢀBrC6H4
3b R = 4ꢀO2NC6H4 3g R = 4ꢀClC6H4
3c R = 4ꢀMeC6H4
3d R = 4ꢀHOC6H4
3h R = 3ꢀO2NC6H4
3i R = 2ꢀClC6H4
3e R = 4ꢀMeOC6H4 3j R = 2ꢀOMe
3k R = C2H5 3l R = C5H11
Scheme 1. Synthesis of 14ꢀarylꢀ14Hꢀdibenzo[a,j]xanthenes.
oneꢀpot synthesis of arylꢀ14Hꢀdibenzoxanthene and in 1,2ꢀdichloroethane (DCE, 10 ml) was allowed to
stir at reflux condition for appropriate time according
to Table 1. TLC monitored the progress of the reacꢀ
tion. After reaction, the reaction mixture was filtered
and the organic solvent was cooled and concentrated.
The crystalline solid that was precipitated was recrysꢀ
tallized from ethanol to give a pure product. All prodꢀ
ucts are known compounds, which were characterized
by IR and 1H NMR spectroscopic data and their meltꢀ
ing points were compared with reported values.
1,8ꢀdioxooctahydroxanthene derivatives by the reacꢀ
tion of various aromatic aldehydes with ꢀnaphthol or
dimedone, respectively in the presence of Co(HSO4)2
β
as an heterogeneous catalyst (Scheme 1).
EXPERIMENTAL
All materials and solvents were procured from
“Merck” and “Fluka” chemical companies. Melting
points were determined in open capillary tubes using
an IA 9000 melting point apparatus (“Electrotherꢀ
mal”). IR spectra were recorded using Avatar 370 FTꢀ
IR spectrometer (“Therma Nicolet”). 1H NMR specꢀ
tra were recorded with a Brukerꢀ100 MHz instrument
(“Bruker”) using tetramethylsilane (TMS) as an interꢀ
nal standard. The mass spectra were scanned on a
Varian Mat CHꢀ7 instrument (“Varian”) at 70 eV. Eleꢀ
mental analyses were obtained on a Flash EA
microanalyzer (“Thermo Finnigan”).
14ꢀ(4ꢀHydroxyphenyl)ꢀ14Hꢀdibenzo[a,j]xanꢀ
thene 3d (Table 1, entry 4): pink solid. Yield: 90%.
M.p.: 140–141°
C, 1H NMR (CDCl3, 100 MHz): 4.97
(br s, 1H, OH), 6.42 (s, 1H, CH), 6.56–8.36 (m, 16H,
Ar–H). FTIR (KBr, cm–1): 1592, 1511, 1401, 1250,
1242, 816.
General Procedure for the Preparation
of 9ꢀArylꢀ1,8ꢀDioxooctahydroxanthene 5a–l
A mixture of dimedone (2 mmol), aldehyde
(1 mmol) and Co(HSO4)2 (0.1 mmol) was refluxed in
dichloroethane. After the end of the reaction moniꢀ
tored by TLC, the reaction mixture was cooled to
Preparation of Co(HSO4)2
A 50 ml suction flask was equipped with a dropping
funnel. The gas outlet was connected to a vacuum sysꢀ
tem through an alkaline solution trap. Cobalt chloride
(10 mmol) was charged into the flask and concenꢀ
trated sulfuric acid 98% (30 mmol) was added drop
wise over a period of 30 min at room temperature.
Gaseous HCl was evolved immediately. After adding
sulfuric acid, the mixture was shaken for 30 min at
100°C, while the residual HCl was removed by sucꢀ
tion. Finally, Co(HSO4)2 was obtained in 95% yield.
room temprature, extracted with EtOAc (
3
×
15 mL),
filtered to isolate the catalyst and the filtrate was conꢀ
centrated to obtain crude product. The residue was
crystallized in ethanol to obtain pure 9ꢀarylꢀ1,8ꢀ
dioxooctahydroxanthene 5a–l as a crystalline solid.
All the products obtained were fully characterized by
1
spectroscopic methods such as IR, H NMR, 13C
NMR and mass spectroscopy and also by comparison
of the spectral data with those reported in literature.
General Procedure for the Preparation of 14ꢀArylꢀ
3,3,6,6ꢀTetramethylꢀ9ꢀphenylꢀ3,4,6,7ꢀtetrahyꢀ
droꢀ2Hꢀxantheneꢀ1,8(5H, 9H)dione 5a (Table 2,
entry 1): white solid. Yield: 90%. M.p.: 203–
or Alkylꢀ14HꢀDibenzo[a,j]xanthenes 3a–l
A mixture of 2ꢀnaphthol (0.145 g, 1 mmol), aldeꢀ
hyde (0.5 mmol), and Co(HSO4)2 (0.025 g, 0.1 mmol) 205°
C,1H NMR (CDCl3, 100 MHz): 7.24–7.19 (m,
KINETICS AND CATALYSIS Vol. 55
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430
ESHGHI et al.
a
Table 1. Synthesis of 14ꢀarylꢀ14Hꢀdibenzo[a,j]xanthenes in the presence of Co(HSO4)2
Melting point, °C
observed reported
Yieldb, %
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
Entry
Aldehyde
C6H4
Product
Time, h
Reference
1
2
3
4
5
6
7
8
9
3a
3b
3c
3d
3e
3f
4
80
95
90
95
80
85
95
80
75
70
80
70
182–183
183–184
311–12
238–240
140–141
203–205
297–298
287–288
211–212
215
[19]
[19]
[19]
[16]
[19]
[19]
[16]
[17]
[17]
[17]
[19]
[19]
4ꢀO2NC6H4
4ꢀMeC6H4
4ꢀHOC6H4
4ꢀMeOC6H4
4ꢀBrC6H4
1
308–310
239–240
140–141
204–205
298–300
288–290
210–212
214–216
260–261
151–152
99–101
4
3
4
3
4ꢀClC6H4
3g
3h
3i
2
3ꢀO2NC6H4
2ꢀClC6H4
2.5
3
10 2ꢀMeOC6H4
11 C2H5
3j
5
258–260
150–151
98–100
3k
31
7
12 C5H11
6
a
b
Reaction conditions:
Yields of the isolated product.
β
ꢀnaphthol (2.0 mmol), aromatic aldehyde (1 mmol), Co(HSO ) (0.1 mmol), DCE (10 mL) reflux.
4 2
a
Table 2. Synthesis of 9ꢀarylꢀ1,8ꢀdioxooctahydroxanthenes in the presence of Co(HSO4)2
Melting point, °C
observed reported
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
Entry
Aldehyde
Product
Time, h
4
Yieldb, %
Reference
1
2
C6H4
5a
5b
5c
5d
5e
5f
85
90
95
87
85
85
95
80
75
75
80
70
203–205
204–205
225–227
217–218
247–248
244–246
234–236
229–230
170–172
228–230
258–260
177–180
190–191
[26]
[23]
[25]
[26]
[26]
[26]
[26]
[26]
[26]
[25]
[25]
[25]
4ꢀO2NC6H4
4ꢀMeC6H4
4ꢀHOC6H4
4ꢀMeOC6H4
4ꢀBrC6H4
3
226–228
218–220
246–248
242–244
233–235
228–230
168–170
229–231
258–260
178–180
187–189
3
4
4
3.5
3
5
6
4
7
4ꢀClC6H4
5g
5h
5i
3
8
3ꢀO2NC6H4
2ꢀClC6H4
4
9
5
10
11
12
2ꢀNO2C6H4
3ꢀOMeC6H4
2ꢀOMeC6H4
5j
6
5k
51
4
6
a
b
Reaction conditions: dimedone (2.0 mmol), aromatic aldehyde (1 mmol), Co(HSO ) (0.1 mmol), DCE (10 mL) reflux.
Yields of the isolated product.
4 2
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SYNTHESIS, CHARACTERIZATION, AND APPLICATION
431
15
20
30
40
50
60
2θ, deg
Fig. 1. XRD pattern of Co(HSO ) nanoparticles.
4 2
2H, ArH), 7.14–7.09 (m, 1H, ArH), 7.04–7.01 (d, was recorded using the KBr disk technique. The specꢀ
= 7.93 Hz, 2H, ArH), 5.47 (s, 1H, CH), 2.47–2.25
J
trum shows a broad OH stretching absorption around
3374 cm–1 for hydrogen sulfate anions in Co(HSO4)2
(m, 8H, 4CH2), 1.25 (s, 6H, 2CH3), 1.11 (s, 6H, 2
2CH3). FT–IR (KBr, cm–1): 2962, 2928, 1592, 1372,
1159, 1041, 842, 774, 692.
,
the FTꢀIR absorption of the O=S=O stretching
modes lies at 1120 cm–1, and that of the S–O stretchꢀ
ing mode lies in the range 600–700 cm–1. These charꢀ
acteristic bands are comparable with bands reported
for sodium hydrogen sulfate and ferric hydrogen sulfate
[32–35]. Also Fig. 4 compares the UVꢀVis spectra of
Co(HSO4)2 and Co(NO3)2. The characteristic peaks
of Co2+ at λmax = 511 nm can be readily recognized.
9ꢀ(4ꢀChlorophenyl)ꢀ3,3,6,6ꢀtetramethylꢀ3,4,6,7ꢀtetꢀ
rahydroꢀ2Hꢀxantheneꢀ1,8(5H, 9H)ꢀdione 5g (Table 2,
entry 7): white solid. Yield: 95%. M.p.: 228–230
1H NMR (100 MHz, CDCl3): 7.25–7.18 (m, 2H,
ArH), 6.97–6.95 (d, = 8.12 Hz, 2H, ArH), 5.40 (s,
1H, CH), 2.46–2.25 (m, 8H, 4CH2), 1.22 (s, 6H,
2CH3), 1.11 (s, 6H, 2CH3). FTꢀIR (KBr, cm–1): 2960,
2929, 1589, 1305, 1093, 887, 833, 720, 658.
°C,
J
Catalyst Characterization
Powder Xꢀray diffraction (XRD). Figure 1 shows the
Xꢀray diffraction patterns of the Co(HSO4)2 sample
obtained by using Cu
K radiation. The XRD patterns
α
show characteristic peaks corresponding to
Co(HSO4)2 crystallites as evidenced by the references
of the ICDD database. The data of XRD shows that
Co(HSO4)2 crystallizes in a monoclinic phase with
6.9630 = 7.5800 = 7.4700 Å and space group
C2/c ( = 4).
a =
Å
,
b
Å, c
Z
Based on the signal of the (311) peak, Co(HSO4)2
crystallites have an average size of 40 nm calculated
using Xꢀray line broadening via the Scherrer equation.
Transmission electron microscopy (TEM) analysis.
Figure 2 shows the TEM images of the Co(HSO4)2
nanoparticles taken with different magnifications.
TEM images imply a homogeneous morphology of
nanoparticles. The nanoparticles consist of uniform
quasiꢀspherical crystallites with an average size of 40 nm.
It can be seen that the obtained value is in agreement
with the result indicated by XRD measurements.
64 nm
Fourier transform infrared (FTꢀIR) and UVꢀVisible
spectra of Co(HSO4)2. The FTꢀIR spectrum of the
catalyst is shown in Fig. 3. The solid state IR spectrum
Fig. 2. TEM image of Co(HSO ) nanocatalyst.
4 2
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432
ESHGHI et al.
1
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
2
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber, cm–1
Fig. 3. FTꢀIR spectrum of Fe(HSO ) (1) and Co(HSO ) (2).
4 3 4 2
RESULTS AND DISCUSSION
In order to optimize the reaction conditions
DMF, CH3CN and 1,2ꢀdichloroethane (DCE)
were tested in the condensation of 4ꢀnitrobenzaleꢀ
hyde and ꢀnaphthol, and the reaction of 4ꢀmethꢀ
β
and evaluate the catalytic efficiency of
Co(HSO4)2, initially two model reactions were
carried out to synthesize 3b (Scheme 1) and 5b
ylbenzalehyde and dimedone in the presence of
10 mol % of catalyst. DCE was superior to other solꢀ
vents since it gave better yields in shorter reaction times.
(Scheme 2). Solvents such as
n
ꢀhexane, CHCl3,
O
Ar
O
O
O
Co(HSO )
4 2
DCE, reflux
2
+
ArCHO
O
2
4
5a–l
5a Ar = C6H5
5b Ar = 4ꢀO2NC6H4 5h Ar = 3ꢀO2NC6H4
5c Ar = 4ꢀMeC6H4 5i Ar = 2ꢀClC6H4
5g Ar = 4ꢀClC6H4
5d Ar = 4ꢀHOC6H4 5j Ar =2ꢀO2NC6H4
5e Ar = 4ꢀMeOC6H4 5k Ar = 2ꢀMeOC6H4
5f Ar = 4ꢀBrC6H4
5l Ar = 3ꢀMeOC6H4
Scheme 2. Synthesis of 9ꢀarylꢀ1,8ꢀdioxooctahydroxanthenes.
Under the optimal reaction conditions in the presꢀ the recovered catalyst was reused in subsequent reacꢀ
ence of 10 mol % of Co(HSO4)2 initial reactants were
completely converted to give the products in the highꢀ
est yields. One of the special advantages of cobalt
hydrogen sulfate is its insolubility in organic solvents
that makes its recovery very convenient. After the reacꢀ
tion was complete, the catalyst was separated by simꢀ
tions without significant decreases in activity even
after five runs.
After optimizing the reaction conditions we preꢀ
pared a range of 1,8ꢀdioxooctahydroxanthenes and
arylꢀ14Hꢀdibenzoxanthene derivatives. The results
ple filtration, dried at 100°C under vacuum for 2 h and are shown in Tables 1 and 2. One important feature is
KINETICS AND CATALYSIS Vol. 55
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SYNTHESIS, CHARACTERIZATION, AND APPLICATION
433
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0.25
0.20
0.15
0.10
0.05
0
,
1
2
9. Banerjee, A. and Mukherjee, A.K., Stain Technol.
,
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400 420 440 460 480 500 520 540 560
Wavelength, nm
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Fig. 4. UVꢀVis absorbance of Co(HSO )
Co(NO ) (2).
3 2
(1) and
4 2
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that aryl aldehydes, both possessing electronꢀwithꢀ
drawing and electronꢀdonating groups, afforded the
corresponding products in good yields. In particular,
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aryl aldehydes with substrates at the paraꢀ and metaꢀ
positions of the benzene ring gave products in high
yield, whereas those with substrates at the orthoꢀposiꢀ
tion gave products in somewhat lower yields, probably
due to steric hindrance. Work up procedures is very
simple and include filtration of reaction mixture to
separate the heterogeneous catalyst. The filtrate was
concentrated to give a crude product which was then
recrystallized from ethanol to give pure 14ꢀarylꢀ14Hꢀ
dibenzoxanthene (3a–l) and 9ꢀarylꢀ1,8ꢀdioxooctahyꢀ
droxanthene (5a–l) in excellent yields. Absence of OH
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1
absorptions in the H NMR and IR spectra confirms
the structure of 14ꢀarylꢀ14Hꢀdibenzoxanthene. In all
1
the H NMR spectra (CDCl3), the characteristic peak
of 14ꢀHꢀdibenzoxanthene appeared as a singlet in the
range 5.5–7.0 ppm. On the other hand, in all the
1H NMR spectra of 9ꢀarylꢀ1,8ꢀdioxooctahydroxanꢀ
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thene
(CDCl3), the characteristic peak of
9Hꢀdioxooctahydroxanthene appeared as a singlet in
the 4.6–5.5 ppm region.
In conclusion, cobalt hydrogen sulfate is prepared
for the first time by treatment of cobalt chloride with
concentrated sulfuric acid. This catalyst was characꢀ
terized by FTꢀIR, TEM and XRD. The efficiently of
this new catalyst was demonstrated in the synthesis of
14ꢀarylꢀ14Hꢀdibenzoxanthenes and synthesis of 1,8ꢀ
dioxooctahydroxanthenes by using Co(HSO4)2 as a
heterogeneous acid catalyst. The simplicity, together
with the use of inexpensive, nonꢀtoxic, recyclable and
environmentally friendly catalyst belongs to other
remarkable features of the procedure.
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