Ionic liquid promoted and mediated green preparation of arylbispyranylmethane and pyran derivatives and their hybrid with a pyrimidine nucleoside

Article abstract of DOI:10.3184/030823409X465321

The utilisation of an ionic liquid-[bmim][BF₄] as both reaction medium and promoter for the reaction between aldehyde and 4-hydroxy-6- methylpyran-2-one is described. Without any added catalyst, this reaction was realised efficiently to give arylbispyranylmethane derivatives in high yields. Alternatively, when this reaction was carried out in the presence of acetic anhydride, fused pyran derivatives were obtained. These two novel procedures have advantages such as an environmentally benign nature, high efficiency, simple operation process and mild reaction conditions. As an application, these procedures were used in the preparation of novel 5-substituted pyrimidine nucleoside derivatives with potential antiviral activities.

Full text of DOI:10.3184/030823409X465321

JOURNAL OF CHEMICAL RESEARCH 2009
AUGUST, 473–477
RESEARCH PAPER 473
Ionic liquid promoted and mediated green preparation of
arylbispyranylmethane and pyran derivatives and their hybrid
with a pyrimidine nucleoside
Xinying Zhang*, Yingying Qu, Xuesen Fan*, Xia Wang and Jianji Wang
School of Chemistry and Environmental Sciences, Henan Key Laboratory for Environmental Pollution Control,
Henan Normal University, Xinxiang, Henan 453007, P. R. China
The utilisation of an ionic liquid–[bmim][BF4] as both reaction medium and promoter for the reaction between
aldehyde and 4-hydroxy-6-methylpyran-2-one is described. Without any added catalyst, this reaction was realised
efficiently to give arylbispyranylmethane derivatives in high yields. Alternatively, when this reaction was carried
out in the presence of acetic anhydride, fused pyran derivatives were obtained. These two novel procedures have
advantages such as an environmentally benign nature, high efficiency, simple operation process and mild reaction
conditions. As an application, these procedures were used in the preparation of novel 5-substituted pyrimidine
nucleoside derivatives with potential antiviral activities.
Keywords: ionic liquid, arylbispyranylmethane, pyran derivatives, 5-substituted pyrimidine nucleoside, green chemistry
Room temperature ionic liquids (RTILs) have gained wide
popularity for their increasing use as greener reaction media
due to their unique properties such as non-volatility, non-
flammability, excellent chemical and thermal stability,
and recyclability.1,2 Their high polarity and their ability to
solubilise both inorganic and organic compounds can result in
enhanced rates of chemical processes and can provide higher
selectivities compared to conventional solvents.3,4 Moreover,
ionic liquids are simple and inexpensive to prepare and easy to
recycle and their properties can be fine-tuned by changing the
anion or the alkyl group attached to cation. Recently, how to
use ILs to promote the selectivity of various organic reactions
and to dramatically influence the outcome of chemical
reactions has attracted much attention.5
Substituted pyrans are biologically interesting compounds
due to their antibacterial,6 antitubercular,7 antiproliferation
and antitumor activities.11 Particularly, pyrano ring fused
to a polycyclic system such as acridone12,13 and xanthone11
exhibits interesting cytotoxic and antitumor properties.
Among them, dipyrano[4,3-b:3,4-e]pyran system has created
lots of interest and several preparative procedures have been
reported. Classically, they were prepared through a two-step
procedure from aldehyde and 4-hydroxy-6-methylpyran-
2-one using toxic reagents such as triphenylphosphine,
diethyl azodicarboxylate, and benzene.12 Recently, Tu, Gao
and coauthors reported two improved procedures either by
employing KF/Al2O3 as catalyst under traditional heating
conditions;13 or by employing microwave irradiation with
glycol as energy-transferring agent without catalyst.14 It was
also reported by Gao et al.15 that dipyrano[4,3-b:3,4-e]pyran
could be obtained by reacting aldehyde and 4-hydroxyl-6-
methylpyran-2-one in acetic anhydride for 10–12 hours. On
the other hand, arylbispyranylmethane derivatives have been
showntoexhibitanticoagulantactivity,16 beingalsostructurally
related to the well known anticoagulant 3,3'-methylenebis
(4-hydroxycoumarin). For their preparation, they were usually
obtained from the reaction of 4-hydroxy-6-methylpyran-2-one
with corresponding aldehyde under the catalysis of organic
bases.17,18 In view of the increasingly important role played
by greener chemistry in the field of organic chemistry, we find
it is of interest to develop more efficient and environmentally
benign methods for the preparation of both dipyrano[4,3-
b:3,4-e]pyran and arylbispyranylmethane derivatives.
liquids as novel reaction medium and promoter,19-22 we now
report our preliminary results on the novel preparation of
arylbispyranylmethane (3) and dipyrano[4,3-b:3,4-e]pyran (4)
from aldehyde (1) and 4-hydroxy-6-methylpyran-2-one (2) in
anionicliquid–1-butyl-3-methylimidazoliumtetrafluoroborate
([bmim][BF4]) acting as a recyclable solvent and promoter.
Results and discussion
Firstly, 4-nitrobenzaldehyde (1a) was used as model substrate
to test if our envisioned method works. Thus, 1a (0.5 mmol)
and 4-hydroxy-6-methylpyran-2-one (2, 1 mmol) were treated
with [bmim][BF4] (Scheme 1) and the mixture was stirred at
ambient temperature. The reaction took place slowly at room
temperture to give a solid product, which was collected by
suction and then submitted to identification. NMR and MS
spectra showed that the product was 3a, bis(4-hydroxy-6-
methyl-2-oxo-2H-pyran-3yl)(4-nitrophenyl)methane, not 4a
(Scheme 1). Firstly, ESI MS showed a molecular weight of
385 for 3a instead of 367 for 4a. Secondly, 1H NMR spectrum
showed two broad singlet at 10.81 and 10.94 ppm with one
proton each corresponding to the two OH groups. Finally,
the structure was further confirmed by comparison with the
authentic product prepared with known method.
Efforts were made to improve the reaction in terms of yield
and reaction period. By varying the reaction temperature,
it was found that when it was run at 80°C, all the starting
materials were consumed in 2 h and 3a was obtained in a yield
of 95%. Considering its simple procedure, high efficiency and
its being free of added basic catalyst, this method is expected
NO2
O
O
O
O
O
O
O
CHO
O
OH OH
3a
NO2
O
[bmim]BF4
OH
2
+
NO2
1a
2
O
As
a continuation of our research interest in the
development of novel methods for the preparation of various
biologically important heterocyclic compounds by using ionic
O
4a
* Correspondent. E-mail: xuesen.fan@yahoo.com
Scheme 1

474 JOURNAL OF CHEMICAL RESEARCH 2009
of 1a (1 mmol) and 2 (2 mmol) at 100°C gave 4a in a yield
of 72% in 3 h. This result is in remarkable contrast to that
with FeCl3·6H2O as a promoter or without any additives at
all. Moreover, studies with more acetic anhydride than 0.2 mL
gave no remarkable improvements. To study the generality
of the above procedure, other aldehyde substrates were also
tried (Scheme 4). It turned out that in the presence of acetic
anhydride all aldehydes studied reacted with 2 efficiently
to give compound 4 in moderate to good yields. The results
were listed in Table 2. Note that compared with the literature
method,12 this procedure needs much less amount of acetic
anhydride and much shorter reaction period to obtain
comparable results, thus remarkably alleviated its impact to
the environment.
Recently we have pursued a chemistry-driven strategy for
the discovery of lead nucleoside molecules with antiviral
activity.25-27 Our approach to new antivirals has been guided
by the following considerations: (a) since the privileged
structure of nucleosides has led to a variety of efficacious
antiviral agents, the nucleosides scaffold is an excellent point
of departure in the search for new antiviral drugs; (b) other
privileged molecular scaffolds exist, like fused pyran and
arylbis-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)methane
derivatives, have spawned a significant number of drugs and
other biologically active agents, and can be used to discover
molecular “masterkeys”. As a part of our ongoing program,
we are interested in the preparation of novel pyrimidine
nucleoside-fused pyran (4i, Scheme 5) and pyrimidine
nucleoside-bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)
methane hybrid (3i, Scheme 5) with the aim of getting new
chemical entities with synergic effects on its biological
activities.
R
O
O
O
[bmim]BF4
O
O
O
2
+
R-CHO
OH
OH OH
3
1
2
Scheme 2
to be developed as a novel alternative for the preparation of
arylbis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)methane
derivatives. Thus, several aldehyde substrates were treated
with 2 in [bmim][BF4] to explore its scope and generality
(Scheme 2). It turned out that all the aldehydes studied, with
either electron-donating group or electron-withdrawing group,
reacted with 2 smoothly and efficiently to give compound 3 in
good yields. The results are listed in Table 1.
It should be noted that dipyrano[4,3-b:3,4-e]pyran (4) were
not formed from 1 and 2 in [bmim][BF4] without catalysts.
Bearing in mind that FeCl3·6H2O could efficiently promote
similarcondensationcyclisationprocessesin[bmim][BF4],23-24
we then made further efforts by employing catalytic amount
of FeCl3·6H2O as an additional promoter to get compound
4. However, it turned out that in the presence of 20 mol%
FeCl3·6H2O, the reaction between 1a and 2 at 80°C gave a
mixture of 3a and 4a. With a higher temperature and an
increased amount of FeCl3·6H2O, the reaction did not improve
significantly in terms of selectivity for 4a.
As a further resort, acetic anhydride were used since, as
mentioned previously, Gao et al.15 reported that compounds
like 4a could be obtained by reacting 1a and 2 in refluxing
acetic anhydride. Thus, the reaction was run again in
[bmim][BF4] in the presence of acetic anhydride. It turned
out that in the presence of 0.2 mL acetic anhydride, reaction
Thus, a mixture of 5-formyl-2'-deoxyuridine (1, Scheme 5)
and 2 was stirred in [bmim]BF4 with or without acetic
R
R
O
O
O
O
O
FeCl3·6H2O
[bmim]BF4
O
O
O
O
O
+
2
+
R CHO
O
OH
OH OH
3
4
1
2
Scheme 3
Table 1 Preparation of 3 in [bmim][BF4]
Entry
R
Product
Reaction time/h
Temperature/°C
Yield/%a, b
1
2
3
4
5
6
7
8
4-NO2C6H4
C6H5
3a
3b
3c
3d
3e
3f
2
3
2
2
3
4
2
2
80
80
80
80
80
80
80
80
95
88
90
91
85
83
95
96
4-FC6H4
4-ClC6H4
4-CH3C6H4
4-CH3OC6H4
4-NCC6H4
4-F3CC6H4
3g
3h
aIsolated yield; b1: 1 mmol, 2: 2 mmol.
Table 2 Preparation of 4 in [bmim][BF4] with acetic anhydride
Entry
R
Product
Reaction time/h
Temperature/°C
Yield/%a,b
1
2
3
4
5
6
7
8
4-NO2C6H4
C6H5
4a
4b
4c
4d
4e
4f
3 (10~12)15
4 (10~12)15
3
100
100
100
100
100
100
100
100
72 (58)15
63 (60)15
66
4-FC6H4
4-BrC6H4
4-CH3C6H4
2-ClC6H4
4-NCC6H4
2-F3CC6H4
3 (10~12)15
4 (10~12)15
4 (10~12)15
3
62 (66)15
60 (56)15
58 (61)15
73
4g
4h
3
80
aIsolated yield; b1: 1 mmol, 2: 2 mmol, acetic anhydride: 0.2 mL.

JOURNAL OF CHEMICAL RESEARCH 2009 475
O
R
O
O
[bmim]BF4
(CH3CO)2O
O
O
O
2
+
R-CHO
OH
O
4
1
2
Scheme 4
anhydride at 80°C. It turned out that just as other aldehyde
substrates, the reaction of 1 with 2 underwent smoothly and
afforded the desired products in good yields. The structure
of 3i and 4i was fully characterised by their spectra data of
NMR, MS and HRMS. The screen of their antiviral activities
against various virus members is underway.
or pyran derivatives respectively by using [bmim][BF4] as
both reaction medium and promoter with or without acetic
anhydride. These two novel procedures have advantages
of being environmentally benign, highly efficient, a simple
operation process with mild reaction conditions.
On the other hand, one of the goals in ionic liquids study is to
identify the additional advantages they have over conventional
organic solvent besides a greener nature. In this regard, it has
been documented that compared with classical organic solvents,
reactions carried out in ionic liquids possess the advantages of
offering simpler operational process and/or enhanced reactivity
and better yields. This was indeed demonstrated by comparing
[bmim]BF4 with several conventional volatile organic solvents
including ethanol, methanol, toluene and THF. The following
is the results (shown in Table 3) of investigations using 1a and
2 as model substrates for the preparation of 3a.
The results listed in Table 3 clearly showed that of the five
solvents studied, [bmim][BF4] gave the best result. Moreover,
using [bmim][BF4] as a reaction medium made the separation
process much easier since in [bmim][BF4] 3a is in solid state
and can be obtained with high purity through suction. On the
other hand, with ethanol, methanol, toluene or THF as the
reaction medium, it usually resulted in a complicated mixture
and 3a could only be obtained through tedious column
chromatography.
Experimental
Melting points were measured by a Kofler micromelting point
apparatus and were uncorrected. H NMR spectra were determined
1
on a Bruker AC 400 spectrometer as CDCl3 or DMSO-d6 solutions.
Chemical shifts (d) were expressed in ppm downfield from the
internal standard tetramethylsilane and coupling constants J were
given in Hz. Mass spectra were obtained in ESI mode using a
Bruker Esquire 3000 mass spectrometer. The HRMS (high resolution
mass spectra) were performed on a JEOL HX 110A spectrometer.
Elemental analyses were performed on an EA-1110 instrument.
General procedure for the preparation of arylbis(4-hydroxy-6-methyl-
2-oxo-2H-pyran-3-yl)methane derivatives (3)
To 1 mL of [bmim][BF4] was added aldehyde (1, 1 mmol) and
4-hydroxy- 6-methylpyran-2-one (2, 2 mmol). The reaction mixture
was stirred at 80°C until a complete reaction (monitored by TLC).
Then, the mixture was cooled to room temperature and 1 mL of 50%
ethanol in water was added. The solids were collected by suction
and rinsed with ethanol, and then dried to give 3 with high purity.
The ionic liquid layer was dried at 100°C under reduced pressure to
recover the ionic liquid.
Bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)(4-nitrophenyl)
methane (3a): M.p. 215–217°C (lit.17 214–217°C); 1H NMR (CDCl3)
d: 2.32 (s, 6H, 2 ¥ CH3), 5.78 (s, 1H, CH), 6.11 (s, 2H, 2 ¥ CH), 7.33
In conclusion, two efficient and selective procedures have
been developed for the preparation of arylbispyranylmethane
O
OAc
HN
N
O
O
O
O
OAc
O
O
O
CHO
O
HN
OH OH
[bmim]BF4
OH
O
2
3i
O
N
+
AcO
O
O
2
OAc
HN
N
O
(CH3CO)2O
OAc
1
O
O
O
OAc
O
O
O
4i
Scheme 5
Table 3 Preparation of 3a in different solvents
Entry
Solvent
Temperature/°C
Product
Reaction time/h
Yield/%
1
2
3
4
5
[bmim][BF4]
Ethanol
Methanol
Toluene
THF
80
3a
3a
3a
3a
3a
2
3
3
3
3
95
45
35
30
35
Reflux
Reflux
80
Reflux

476 JOURNAL OF CHEMICAL RESEARCH 2009
(d, 2H, J = 8.8 Hz, ArH), 8.17 (d, 2H, J = 8.8 Hz, ArH), 10.81 (br s,
1H, OH), 10.94 (br s, 1H, OH); MS: m/z 408 [M + Na] +.
Bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)phenylmethane
(3b): M.p. 214–215°C (lit.17 214–215°C); 1H NMR (CDCl3) d: 2.31
(s, 6H, 2 ¥ CH3), 5.78 (s, 1H, CH), 6.05 (s, 1H, CH), 6.12 (s, 1H,
CH), 7.17–7.35 (m, 5H, ArH), 10.75 (br s, 1H, OH), 11.00 (br s, 1H,
OH); MS: m/z 363 [M + Na] +.
10-(4-Bromophenyl)-3,7-dimethyl-1H,9H,10H-dipyrano[4,3-b:
3,4-e]pyran-1,9-dione (4d): M.p. 294–295°C (lit.13 293–295°C);
1H NMR (DMSO-d6) d: 2.25 (s, 6H, 2 ¥ CH3), 4.68 (s, 1H, CH), 6.39
(s, 2H, 2 ¥ CH), 7.16 (d, 2H, J = 8.0 Hz, ArH), 7.38 (d, 2H, J = 8.0 Hz,
ArH); MS: m/z 423 [M + Na] +.
3,7-Dimethyl-10-(4-methylphenyl)-1H,9H,10H-dipyrano[4,3-b:
3,4-e]pyran-1,9-dione (4e): M.p. 282–283°C (lit.13 282–284°C);
1H NMR (DMSO-d6) d: 2.23 (s, 9H, 3 ¥ CH3), 4.51 (s, 1H, CH),
6.46 (s, 2H, 2 ¥ CH), 7.06 (d, 2H, J = 8.0 Hz, ArH), 7.11 (d, 2H,
J = 8.0 Hz, ArH); MS: m/z 359 [M + Na] +.
(4-Fluorophenyl)bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)
1
methane (3c): M.p. 202–204°C; H NMR (CDCl3) d: 2.31 (s, 6H,
2 ¥ CH3), 5.74 (s, 1H, CH), 6.09 (s, 2H, 2 ¥ CH), 6.98–7.15 (m, 4H,
ArH), 10.81 (br s, 1H, OH), 10.97 (br s, 1H, OH); 13C NMR (CDCl3)
d: 19.64, 34.20, 103.32, 115.19, 115.41, 127.99, 128.07, 130.96,
131.00, 160.37, 162.81; MS: m/z 381 [M + Na] +. Anal. Calcd for
C19H15FO6: C, 63.69; H, 4.22. Found: C, 63.80; H, 4.12%.
10-(2-Chlorophenyl)-3,7-dimethyl-1H,9H,10H-dipyrano[4,3-
b:3,4-e]pyran-1,9-dione (4f): M.p. 268–270°C (lit.13 271–273°C);
1H NMR (DMSO-d6) d: 2.26 (s, 6H, 2 ¥ CH3), 4.82 (s, 1H, CH), 6.16
(s, 2H, 2 ¥ CH), 7.16–7.59 (m, 4H, ArH); MS: m/z 379 [M + Na] +.
10-(4-Cyanophenyl)-3,7-dimethyl-1H,9H,10H-dipyrano[4,3-
(4-Chlorophenyl)bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)
methane (3d): M.p. 201–203°C (lit.17 202–205°C); 1H NMR (CDCl3)
d: 2.30 (s, 6H, 2 ¥ CH3), 5.76 (s, 1H, CH), 6.10 (s, 2H, 2 ¥ CH),
7.03 (d, 2H, J = 8.8 Hz, ArH), 7.23 (d, 2H, J = 8.8 Hz, ArH), 11.2
(br s, 2H, 2 ¥ OH); MS: m/z 397 [M + Na] +.
Bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)(4-methylphenyl)
methane (3e): M.p. 186–187°C; 1H NMR (CDCl3) d: 2.20 (s, 6H,
2 ¥ CH3), 2.24 (s, 3H, CH3), 5.93 (s, 1H, CH), 6.08 (s, 2H, 2 ¥ CH),
6.86 (d, 2H, J = 8.0 Hz, ArH), 7.03 (d, 2H, J = 8.0 Hz, ArH), 11.70
(br s, 2H, 2 ¥ OH); 13C NMR (CDCl3) d: 19.52, 20.93, 33.91, 101.80,
102.17, 126.81, 129.12, 135.00, 136.75, 161.61, 166.77, 168.53; MS:
m/z 377 [M + Na] +. Anal. Calcd for C20H18O6: C, 67.79; H, 5.12.
Found: C, 67.90; H, 5.06%.
1
b:3,4-e]pyran-1,9-dione (4g): M.p. 270–273°C; H NMR (DMSO-
d6) d: 2.24 (s, 6H, 2 ¥ CH3), 4.64 (s, 1H, CH), 6.50 (s, 2H, 2 ¥ CH),
7.47 (d, 2H, J = 8.0 Hz, ArH), 7.74 (d, 2H, J = 8.0 Hz, ArH); 13C
NMR (DMSO-d6) d: 19.78, 34.26, 98.61, 101.37, 110.24, 119.11,
130.21, 132.44, 147.89, 158.89, 162.84, 163.83; MS: m/z 370 [M +
Na] +. Anal. Calcd for C20H13NO5: C, 69.16; H, 3.77; N, 4.03. Found:
C, 69.02; H, 3.88; N, 3.92%.
3,7-Dimethyl-10-(4-trifluoromethylophenyl)-1H,9H,10H-dipyrano[4,3-
b:3,4-e]pyran-1,9-dione (4h): M.p. 241–242°C; 1H NMR (DMSO-d6)
d: 2.22 (s, 6H, 2 ¥ CH3), 5.54 (s, 1H, CH), 6.35 (s, 2H, 2 ¥ CH), 7.33 (d,
2H, J = 8.0 Hz, ArH), 7.63 (d, 2H, J = 8.0 Hz, ArH); 13C NMR (DMSO-
d6) d: 19.74, 33.99, 103.26, 112.76, 125.45, 128.97, 144.27, 160.63,
161.29, 163.52, 163.73, 167.21; MS: m/z 413 [M + Na]+. Anal. Calcd for
C20H13F3O5: C, 61.54; H, 3.36. Found: C, 61.62; H, 3.51%.
3,7-Dimethyl-10-[4-(3,5-di-O-acetyl-2-deoxy-b-D-ribosyl)-
1,2,3,4-tetrahydropyrimidin-5-yl]-1H,9H,10H-dipyrano[4,3-b:3,4-
e]pyran-1,9-dione (4i): M.p. 152–154°C; 1H NMR (DMSO-d6) d:
2.08 (s, 3H, CH3), 2.13 (s, 3H, CH3), 2.17 (s, 6H, 2 ¥ CH3), 2.30–
2.40 (m, 2H, 2'-H), 4.20–4.32 (m, 4H, 5'-H, 4'-H, CH), 5.23–5.25 (m,
1H, 3'-H), 6.15–6.17 (m, 1H, 1'-H), 6.40 (s, 2H, 2 ¥ CH), 7.75 (s, 1H,
CH), 11.36 (br s, 1H, NH); 13C NMR (DMSO-d6) d: 19.77, 21.06,
21.20, 29.08, 36.76, 64.27, 74.66, 81.98, 85.19, 98.64, 99.03, 111.04,
139.82, 150.34, 159.95, 160.03, 161.98, 162.05, 163.24, 163.35,
170.60, 170.70; MS: m/z 579 [M + Na] +. HRMS (FAB) Calcd for
C26H24N2O12: 557.1407 (MH)+. Found: 557.1413.
Bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)(4-methoxyphenyl)
methane (3f): M.p. 173–175°C (lit. 17 174–176°C); 1H NMR (CDCl3)
d: 2.27 (s, 6H, 2 ¥ CH3), 3.72 (s, 3H, OCH3), 5.78 (s, 1H, CH), 6.05
(s, 2H, 2 ¥ CH), 6.78 (d, 2H, J = 7.2 Hz), 7.13 (d, 2H, J = 7.2 Hz,
ArH), 10.99 (br s, 2H, 2 ¥ OH); MS: m/z 393 [M + Na]+.
(4-Cyanophenyl)bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)
1
methane (3g): M.p. 201–203°C; H NMR (DMSO-d6) d: 2.18 (s, 6H,
2 ¥ CH3), 5.82 (s, 1H, CH), 6.03 (s, 2H, 2 ¥ CH), 7.20 (d, 2H, J = 8.0 Hz,
ArH), 7.67 (d, 2H, J = 8.0 Hz, ArH); 13C NMR (DMSO-d6) d: 19.59,
35.70, 101.10, 101.38, 108.71, 119.53, 128.46, 132.23, 147.47, 161.72,
165.78, 168.09; MS: m/z 388 [M + Na] +. Anal. Calcd for C20H15NO6:
C, 65.75; H, 4.14; N, 3.83. Found: C, 65.88; H, 4.02; N, 3.70%.
Bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)(4-trifluoromethyl-
phenyl)methane (3h): M.p. 184–186°C; 1H NMR (DMSO-d6) d:
2.19 (s, 6H, 2 ¥ CH3), 5.87 (s, 1H, CH), 6.05 (s, 2H, 2 ¥ CH), 7.23
(d, 2H, J = 8.0 Hz, ArH), 7.58 (d, 2H, J = 8.0 Hz, ArH); 13C NMR
(DMSO-d6) d: 19.58, 35.29, 101.36, 101.53, 125.21, 128.07, 146.12,
161.64, 165.95, 168.23; MS: m/z 431 [M + Na] +. Anal. Calcd for
C20H15F3O6: C, 58.83; H, 3.70. Found: C, 58.72; H, 3.80%.
We are grateful to the National Natural Science Foundation
of China (No. 20772025), the Program for Science &
Technology Innovation Talents in Universities of Henan
Province (No. 2008HASTIT006) and the Natural Science
Foundation of Department of Education of Henan Province
(No. 2008A150013).
Bis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)[4-(3,5-di-O-acetyl-
2-deoxy-b-D-ribosyl)-1,2,3,4-tetrahydropyrimidin-5-yl]methane
1
(3I): M.p. 208–209°C; H NMR (DMSO-d6) d: 1.99 (s, 3H, CH3),
2.06 (s, 3H, CH3), 2.12 (s, 6H, 2 ¥ CH3), 2.15–2.18 (m, 1H, 2'-H1),
2.32–2.35 (m, 1H, 2'-H2), 4.02–4.05 (m, 2H, 5'-H), 4.15–4.17 (m,
1H, 4'-H), 5.11–5.13 (m, 1H, 3'-H), 5.23 (s, 1H, CH), 5.90 (s, 1H,
CH), 5.91 (s, 1H, CH), 6.05–6.08 (m, 1H, 1'-H), 6.93 (s, 1H, CH),
11.26 (br s, 3H, NH, 2 ¥ OH); MS: m/z 597 [M + Na]+. HRMS (FAB)
Calcd for C26H26N2O13: 575.1513 (MH)+. Found: 575.1520.
Received 17 March 2009; accepted 27 May 2009
Paper 09/0500 doi: 10.3184/030823409X465321
Published online: 10 August 2009
General procedure for the preparation of 3,6,9-trioxanthracene (4)
To 1 mL of [bmim][BF4] were added aldehyde (1, 1 mmol), 4-hydroxy-
6-methylpyran-2-one (2, 2 mmol) and 0.2 mL acetic anhydride.
The reaction mixture was stirred at 100°C till a complete reaction
(monitored by TLC). Acetic anhydride was removed under reduced
pressure and the mixture was cooled to room temperature. Then, 1
mL of 50% ethanol in water was added. The solids thus formed were
collected and recrystallised from ethanol to give 4 with high purity.
3,7-Dimethyl-10-(4-nitrophenyl)-1H,9H,10H-dipyrano[4,3-b:3,4-e]
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