Full text of DOI:10.1002/jhet.5570400422

Jul-Aug 2003
A Simple Synthesis of 5-Ethoxycarbonyl-6-phenyl-1,3-dioxin-4-ones
and Ethyl 3-Benzoyl-4-oxo-2,6-diphenylpyran-5-carboxylate
Ahmet S¸ener, Hasan Genç and M. Kasım S¸ener
697
Yüzüncü Yıl Üniversity, Art and Science Faculty, Chemistry Department, 65080-VAN-Turkey
Received February 19, 2003
4-Ethoxycarbonyl-5-phenyl-2,3-dihydrofuran-2,3-dione 1 reacts with aldehydes via the acylketene inter-
mediate 2 giving the 1,3-dioxin-4-ones 3a-e and the 1,4-bis(5-ethoxycarbonyl-4-oxo-6-phenyl-4H-1,3-
dioxin-2-yl)benzene 4, and a one step reaction between dibenzoylmethane and oxalylchloride gave 3,5-
dibenzoyl-2,6-diphenyl-4-pyrone 7. The reaction of 1 with dibenzoylmethane, a dicarbonyl compound, pro-
vided ethyl 3-benzoyl-4-oxo-2,6-diphenylpyran-5-carboxylate derivative 9. Compound 9 was converted into
the corresponding ethyl 3-benzoyl-4-hydroxy-2,6-diphenylpyridine-5-carboxylate derivative 10 via its reac-
tion with ammonium hydroxyde solution in 1-butanol.
J. Heterocyclic Chem., 40, 697(2003).
a -Oxoketenes (acyl ketenes) are highly reactive mole-
cules which usually cannot be isolated under ordinary
reaction conditions, although several examples have been
detected by low-temperature ir spectroscopy technique [1],
and some sterically or electronically-hindered a -
oxoketenes have been stabilized by preparative flash vac-
uum pyrolysis method in recent years [2]. These ketenes
are currently of considerable interest, not only because of
mechanistic and theoretical considerations [3], but also
because of their use as synthetic building blocks in organic
synthesis [2,4].
4-Ethoxycarbonyl-5-phenyl-2,3-dihydrofuran-2,3-dione
1 reacts easily with aldehydes via the ethoxycarbonylben-
zoylketene intermediate 2 yielding the 1,3-dioxin-4-one
derivatives 3 in moderate yields.
A simple useful procedure of the generation of
a -oxoketenes II is the thermal decomposition of 2,3-
dihydrofuran-2,3-diones I in solution [4,5]. Elevated tem-
perature leads to the thermal decomposition of furandiones
I with the loss of CO to give the corresponding
a -oxoketenes intermediates II [7]. Typically, reactive
ketene II is generated in situ from furandione at approxi-
mately 80-130 °C, and is trapped immediately with
nucleophiles [5], or in [2+4] cycloaddition reactions with
heterodienophiles having double or triple polar bonds [6].
If there is not any heterodienophile or nucleophile in reac-
tion medium, it is well known that all acyl and diacyl
ketenes (a -oxoketenes) undergo dimerization which pro-
ceeds via [2+4] cycloaddition of one a -oxoketene mole-
cule to the C=C bond of another to give 2,4-pyrandiones
III [8]. In the case of the presence of a carbonyl compound
or another heterodienophile such as a Schiff base, a nitrile,
or isocyanate, the [2+4] cycloaddition reaction now
involves one molecule of a -oxoketene as a component
with four electrons being added to the one of C=O, C=N,
Cº N or N=C=O groups of heterodienophiles, to give vari-
ous dioxinone, oxazinone, and oxazindione derivatives
[6,7,9], respectively (Scheme 1).
The reaction between 1 and aldehydes was realized in
boiling benzene (80 °C). During this type of reactions,
due to reason mentioned above, side reactions, such as
dimerization of a -oxoketenes may accur, which can also
explain moderate yields of cycloadduct obtained in this
work. Consequently, a -oxoketene 2 generated in sıtu
from 1 in boiling benzene showed a pronounced ten-
dency to form [2+4] Diels-Alder adduct when trapped by
aldehydes that behave as a heterodienophyle in these
reactions. The structures of 1,3-dioxinone derivatives 3
and 4 obtained in this way were confirmed by analytical
and spectral data (see experimental). In the ir spectra, the
presence of C=O absorbtion bands at approximately
In this study we envisioned that we could generate
a -oxoketene from 4-ethoxycarbonyl-5-phenyl-2,3-dihy-
drofuran-2,3-dione 1 which was obtained by the cyclocon-
densation reaction between ethylbenzoylacetate and oxa-
lylchloride [6], and trap it in [2+4] cycloaddition reactions
with some carbonyl compounds.

698
A. S¸ ener, H. Genç and M. K. S¸ener
Vol. 40
-1
1750-1720 cm besides the absence of OH vibration
addition, compound 9 could be easily converted via its
reactions with ammoniumhydroxyde solution in 1-butanol
into the corresponding pyridine derivative 10, structure of
which was also elucidated by elemental analysis and spec-
troscopic data (Scheme 4).
The formation of 9 (or 7) is probably occurring via
[2+4] cycloaddition of a -oxoketene intermediates 2 (or 6)
to C=C bond of cyclic enol form of dibenzoylmethane and
elimination of water in the final step affording pyrane
nucleus similar to the cycloaddition of a -oxoketenes to
vinyl ethers [2b]. Nucleophilic attack of OH group in enol
form of dibenzoylmethane and cycloaddition of carbonyl
group of dibenzoylmethane to ketene group of
1
bands is characteristic for 1,3-dioxin-4-ones [10]. H-
nmr spectrum exhibits a singlet at d=6.05-7.46 ppm for
aldehyde adducts (Scheme 2).
In our previous research, we demonstrated that diben-
zoylketene 6 generated in situ from 4-benzoyl-5-phenyl-
2,3-dihydrofuran-2,3-dione 5 in refluxing xylene, has
reacted easily with dibenzoylmethane to give 3,5-diben-
zoyl-2,6-diphenyl-4-pyrone derivative 7 [11] in higher
yield than that reported in the literature [12]. In this study,
the same pyrone compound has been obtained again in one
step reaction between dibenzoylmethane and oxalylchlo-
ride (Scheme 3).
a -
oxoketene intermediates 2 (or 6) would lead to the for-
On the other hand, the reaction of 1 with dibenzoyl-
methane, which is a 1,3-dicarbonyl compound instead of
aldehyde did not lead to the corresponding 1,3-dioxinone
derivative. When dibenzoylmethane was added to 2 gener-
ated from 1, a new g-pyrone derivative 9 was obtained. In
mation of compounds different than the g-pyrone deriva-
tives 9 (or 7) (Scheme 3 and 4). Additionally, nucleophilic
attacks of OH group at the furan ring carbon atoms in 5
could convert furandione 5 into starting materials; these

Jul-Aug 2003
A Simple Synthesis of 5-Ethoxycarbonyl-6-phenyl-1,3-dioxin-4-ones
699
130.73, 130.97, 132.61, 132.69, 134.73, 135.00, 161.47 (C-6),
165.68, (C=O, ester),172.61 ppm (C=O, C-4).
Anal. Calcd. for C19H16O5: C, 70.36; H, 4.97. Found: C,
70.51; H, 4.96.
materials are dibenzoylmethane and oxalic acid deriva-
tives [13]. From these reactions in Scheme 3 and 4, it may
be deduced that dibenzoylmethane is found in the cyclic
enol form having a strong intramolecular hydrogen bond
in boiling xylene, therefore its OH group cannot react with
furandiones of type 1 or 5.
Ethyl 2-Naphth-1-yl-4-oxo-6-phenyl-4H-1,3-dioxine-5-carboxy-
late (3d).
The structures of compounds 3a-e, 4-10 and 7 were con-
firmed by analytical and spectral data (see experimental).
Compound 3d was prepared according to the general proce-
dure above with a reflux time of 5 hours (1-naphthaldehyde)
resulting in 65 % yield (0.243 g); mp 164 °C (anhydrous aceti-
cacid); ir: 3097-3008 cm-1 (Ar-H), 2938-2850 cm-1 (R-H), 1745,
1697 cm-1 (C=O); 1H-nmr (200 MHz, deuteriochloroform): d
1.05 (t, 3H, CH3), 4.15 (m, 2H, O-CH2), 7.37 (s, 1H, H-2), 7.51-
8.42 ppm (m, 12H, Ar-H).
EXPERIMENTAL
Solvents were dried by refluxing with the appropriate drying
agents and distilled before use. Melting points were determined
on an Electrothermal Gallenkamp apparatus and are uncorrected.
Microanalyses were performed on a Carlo Erba Elemental
Analyser Model 1108. The ir spectra were obtained as potassium
bromide pellets using a Mattson 1000 FTIR spectrometer. The 1H
and 13C-nmr spectra were recorded on Varian (200 MHz) and
Varian (50 MHz) spectrometers, respectively, using TMS as an
internal standard. All experiments were followed by the using
DC Alufolien Kieselgel 60 F 254 Merc and Camag tlc lamp
(254/366 nm).
Anal. Calcd. for C23H18O5: C, 73.79; H, 4.85. Found: C,
73.54; H, 4.84.
Ethyl 4-Oxo-6-phenyl-2-pyridin-3-yl-4H-1,3-dioxine-5-car-
boxylate (3e).
Compound 3e was prepared according to the general proce-
dure above with a reflux time of 6 hours (3-pyridine carbalde-
hyde) resulting in 60 % yield (0.195 g); mp 165 °C (ethanol); ir:
3150-3075 cm-1 (Ar-H), 2975-2890 cm-1 (R-H), 1735 cm-1, 1723
1
cm-1 (C=O); H-nmr (200 MHz, deuteriochloroform): d 1.13 (t,
3H, CH3), 4.21 (m, 2H, O-CH2), 6.73 (s, 1H, H-2), 7.27-8.9 ppm
(m, 9H, Ar-H); 13C-nmr (50 MHz, deuteriochloroform): d 15.67
(CH3), 63.91 (O-CH2), 100.35 (C-2), 106.51 (C-5), 125.57,
125.59, 130.70, 131.00, 132.21, 135.04, 136.41, 150.18 (C-2’ or
C-6’, pyr), 153.92 (C-2’ or C-6’, pyr), 160.91 (C-6), 165.44
(C=O, ester), 172.95 ppm (C=O).
Ethyl 4-Oxo-6-phenyl-2-propenyl-4H-1,3-dioxine-5-carboxylate
(3a).
General Procedure.
A milliequimolar mixture of 1 (0.246 g, 1 mmol) and croton-
aldehyde (0.07 g, 1 mmol) was refluxed in benzene (20 ml) for 6
h. After the solvent was removed by evaporation, the oily residue
was treated with ether for 4 h., with stirring. The formed crude
product was crystallized from ethanol to give 0.153 g (53%) of
3a; mp 120 °C; ir: 3076 cm-1 (Ar-H), 2987-2906 cm-1 (R-H),
1757, 1715 cm-1 (C=O); 1H-nmr (200 MHz, deuteriochloro-
form): d 1.09 (t, 3H, CH3, ethyl), 1.87 (d, 3H, CH3, propenyl),
4.16 (m, 2H, O-CH2), 5.83 (d.d, 1H, H-1’), 6.05 (d, 1H, H-2),
6.25 (m,1H, H-2’), 7.26-7.63 ppm (m, 5H, Ar-H).
Anal. Calcd. for C18H15NO5: C, 66.46; H, 4.65; N, 4.31.
Found: C, 66.68; H, 4.64; N, 4.30.
1,4-Bis(5-ethoxycarbonyl-4-oxo-6-phenyl-4H-1,3-dioxin-2-yl)-
benzene (4).
This compound was obtained from 1 and terephthaldicarbox-
aldehyde (molar ratio 2:1), according to the general procedure
above with a reflux time of 7 hours resulting in 55 % yield (0.314
g); m.p 178 °C (anhydrous acetic acid); ir: 3085 cm-1 (Ar-H),
Anal. Calcd. for C16H16O5: C, 66.66; H, 5.59. Found: C,
66.48; H, 5.58.
1
2981, 2900 cm-1 (R-H), 1761, 1708 cm-1 (C=O); H-nmr (200
MHz, deuteriochloroform): d 1.03 (t, 6H, CH3), 4.12 (m, 4H,
OCH2), 7.46 (s, 2H, H-2), 7.50-7.98 ppm (m, 14H, Ar-H).
Anal. Calcd. for C32H26O10: C, 67.36; H, 4.59. Found: C,
67.20; H, 4.58.
Ethyl 4-Oxo-6-phenyl-2-p-tolyl-4H-1,3-dioxine-5-carboxylate (3b).
Compound 3b was prepared according to the general proce-
dure above with a reflux time of 5 hours (4-methylbenzaldehyde)
resulting in 55 % yield (0.186 g); mp 138 °C (Ethanol); ir: 3000-
3050 cm-1 (Ar-H), 2960- 2875 cm-1 (R-H); 1746, 1705 cm-1
3,5-Dibenzoyl-2,6-diphenyl-4-pyrone (7).
1
A milliequimolar solution of dibenzoylmethane (0.224 g, 1
mmol) and oxalylchloride (0.122 ml, 1 mmol) in xylene (20 ml)
was refluxed for about 15 minutes until the solution became yel-
low color. After the addition of the remaining dibenzoylmethane
(0.224 g, 1 mmol) to the reaction mixture, the solution was
refluxed again for 2.5 hours until the appearance of white precip-
itates. Subsequent to cooling at room temperature, the formed
precipitate was collected by filtration and recrystallized from 1-
butanol to give 0.296 g (65 %) of 7. m.p 280 °C (Lit. mp 280 °C);
ir: 3106-3000 cm-1 (Ar-H), 1702,1651 cm-1 (C=O), 1625 cm-1
(C=C, pyrone); 1H-nmr (200 MHz, deuteriochloroform): d 8.10-
7.42 ppm (Ar-H); 13C-nmr (50 MHz, deuteriochloroform): d
127.05, 130.07, 130.68, 130.79, 131.00, 132.73, 133.34, 136.06,
138.06, 163.72 (C-2 and C-6), 177.56 (C=O, C-4), 194.28 ppm
(C=O, benzoyl).
(C=O), H-nmr (200 MHz, deuteriochloroform): d 1.12 (t, 3H,
CH3, ethyl), 2.41 (s, 3H, CH3), 4.17 (m, 2H, O-CH2), 6.61 (s, 1H,
H-2), 7.26- 7.67 ppm (m, 9H, Ar- H).
Anal. Calcd. for C20H18O5: C, 70.99; H, 5.36. Found: C,
70.81; H, 5.34.
Ethyl 4-Oxo-2,6-diphenyl-4H-1,3-dioxine-5-carboxylate (3c).
Compound 3c was prepared according to the general proce-
dure above with a reflux time of 7 hours (benzaldehyde) resulting
in 64 % yield (0.207 g); mp 145 °C (1-propanol); ir: 3073-3043
cm-1 (Ar- H), 2979-2874 cm-1 (R-H), 1757,1704 cm-1 (C=O);
1H-nmr (200 MHz, deuteriochloroform): d 1.10 (t. 3H, CH3),
4.18 (m, 2H, O-CH2), 6.63 (s, 1H, H-2), 7.38-7.66 ppm (m, 10H,
Ar-H); 13C-nmr (50 MHz, deuteriochloroform): d 15.66 (CH3),
63.68 (O-CH2), 102.14 (C-2), 106.29 (C-5), 128.71,130.57,

700
A. S¸ ener, H. Genç and M. K. S¸ener
Vol. 40
Anal. Calcd. for C31H20O4: C, 81.56; H, 4.42. Found: C,
Anal. Calcd. for C27H21NO4: C, 76.58; H, 5.00; N, 3.31.
81.38; H, 4.41.
Found: C, 76.87; H, 4.98; N, 3.32.
Ethyl 3-Benzoyl-2,6-diphenyl-4-pyrone-5-carboxylate (9).
Acknowledgement.
A miliequimolar mixture of 1 (0.246 g, 1 mmol) and diben-
zoylmethane (0.224 g, 1 mmol) was refluxed in xylene (20 ml)
for about 2 hours until the appearance of white crystals. After
cooling at room temperature, the formed crystals were collected
by filtration and recrystallized from 1-butanol to give 0.326 g
(77 %) of 5 mp 197 .°C; ir: 3080-3060 cm-1 (Ar-H), 2950-2850
cm-1 (R-H), 1736, 1677, 1641 cm-1 (C=O), 1620 cm-1 (C=C,
The authors thank the research fund of Yuzuncu Yil University
for financial support
REFERENCES AND NOTES
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1
pyrone); H-nmr (200 MHz, deuteriochloroform): d 1.17 (t, 3H,
CH3), 4.26 (q, 2H, O-CH2), 7.29-7.95 ppm (m, 15H, Ar-H);
13C-nmr (50 MHz, deuteriochloroform): d 15.80 (CH3), 64.00
(O-CH2), 123.75 (C-3 or C-5), 128.03(C-3 or C-5), 129.92,
130.22, 130,77, 130.86, 130.93, 131.32, 132.77, 133.02,
133.56, 133.81, 135.86, 138.72, 163.79 (C-2 or C-6), 164.51
(C-2 or C-6),166.06 (C=O, ester),176.40 (C=O,C-4), 194.21
ppm (C=O. benzoyl)
Anal. Calcd. for C27H20O5: C, 76.40; H, 4.75. Found: C,
76.65; H, 4.74.
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Ethyl 3-Benzoyl-2,6-diphenyl-4-hydroxypyridine-5-carboxylate
(10).
To the solution of 9 (0.456 g, 1 mmol) in 1-butanol (25 ml)
was added a slight excess of saturated aqueous solution of
ammoniumhydroxyde with stirring. Then the reaction mixture
was refluxed for 4 hours. After the solvents were removed by
evaporation, the oily residue was treated with ether and the
formed crude product was crystallized from methanol to give
0.220 g (52 %) of 10 m.p 297 °C; ir: 3100-3015 cm-1 (Ar-H),
2985-2875 cm-1 (R-H), 1745 cm-1, 1695 cm-1, 1655 cm-1
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1
(C=O); H-nmr (200 MHz, deuteriochloroform): d 0.92 (t, 3H,
CH3), 4.13 (q, 2H, OCH2), 7.22-7.85 ppm (m, 15H, Ar-H); 13C-
nmr (50 MHz, deuteriochloroform): d 15.18 (CH3), 63.89
(OCH2), 114.63, 129.89, 130.00, 130.27, 130.53, 130.66,
130.79, 131.17, 131.31, 131.43, 135.49, 139.32, 140.20, 154.23
(C-2 or C-6), 157.91 (C-2 or C-6), 168.28 (ester), 171.75 (C=O,
C-4), 197.23 ppm (C=O, benzoyl).