Chemistry of 1,5-diketones: IV. New aspects of the chemistry of 1,5-Dioxo compounds of the 2H-pyran-2-one series

Article abstract of DOI:10.1134/S1070428015010108

Reactions of 3,3′-(phenylmethanediyl)bis(4-hydroxy-6-methyl-2H-pyran-2-one) with electrophilic (PCl₅, CF₃COOH, BF₃ · Et₂O) and nucleophilic reagents (P₂S₅) in different solvents were studie

Full text of DOI:10.1134/S1070428015010108

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 1, pp. 65–68. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © O.V. Fedotova, A.A. Shkel’, O.A. Mazhukina, N.V. Pchelintseva, 2015, published in Zhurnal Organicheskoi Khimii, 2015, Vol. 51,
No. 1, pp. 69–71.
Chemistry of 1,5-Diketones:
IV.* New Aspects of the Chemistry of 1,5-Dioxo Compounds
of the 2H-Pyran-2-one Series
O. V. Fedotova, A. A. Shkel’, O. A. Mazhukina, and N. V. Pchelintseva
Institute of Chemistry, Chernyshevskii Saratov State University,
ul. Astrakhanskaya 83, Saratov, 410012 Russia
e-mail: ee1402@mail.ru
Received April 24, 2014
Abstract—Reactions of 3,3′-(phenylmethanediyl)bis(4-hydroxy-6-methyl-2H-pyran-2-one) with electrophilic
(PCl5, CF3COOH, BF3·Et2O) and nucleophilic reagents (P2S5) in different solvents were studied. The reactions
with boron trifluoride–diethyl ether complex in acetic acid and with trifluoroacetic acid gave 4a-hydroxy-3,7-di-
methyl-10-phenyl-10,10a-dihydro-1H,4aH,9H-dipyrano[4,3-b:3′,4′-e]pyran-1,9-dione, while 3,7-dimethyl-10-
phenyl-1,9-dioxo-1H,9H-dipyrano[4,3-b:3′,4′-e]pyran-5-ium tetrafluoroborate was obtained in the reaction
with BF3·Et2O in diethyl ether. Conditions were found for the synthesis of 4-hydroxy-6-methyl-3-[(6-methyl-2-
oxo-4-sulfanyl-2H-pyran-3-yl)(phenyl)methyl]-2H-pyran-2-one by reaction of 3,3′-(phenylmethanediyl)bis-
(4-hydroxy-6-methyl-2H-pyran-2-one) with diphosphorus pentasulfide.
DOI: 10.1134/S1070428015010108
Reactions of 4-hydroxy-3-(3-oxo-1,3-diphenylpro-
pyl)-2H-chromen-2-one, 3,3′-(phenylmethanediyl)bis-
(4-hydroxy-3,4,4a,8a-tetrahydro-2H-chromen-2-one),
and 3-(6-oxo-6H,7H-chromeno[4,3-b]chromen-7-yl)-
2H-chromene-2,4(3H)-dione with phosphorus penta-
chloride, diphosphorus pentasulfide, hydrogen sulfide
generated in situ in acid medium, and boron trifluo-
ride–diethyl ether complex could give rise to new
fused polyheterocyclic compounds of the (thio)pyrano-
chromene series and trioxabenzonaphthotetracenium
salts [2, 3].
2H-pyran-2-one) (1) possessing lactone and enolized
ketone moieties toward the above listed reagents.
Compound 1 was synthesized in 70% yield by con-
densation of 4-hydroxy-6-methyl-2H-pyran-2-one
with benzaldehyde at a ratio of 2:1 in acetic acid
(Scheme 1); unlike the conditions reported in [4], no
base catalyst (piperidine) was used. The dienol struc-
1
ture of 1 was confirmed by the IR and H NMR data.
1
Its H NMR spectrum contained two singlets from
magnetically nonequivalent protons of the enolic hy-
droxy groups in position 4 of the pyran rings at δ 10.73
and 10.94 ppm (CDCl3) (a broadened singlet at
δ 11.5 ppm in CD3COOD-d4), by analogy with the
spectra of 3,3′-(arylmethanediyl)bis(4-hydroxy-2H-
chromen-2-ones) and 3-oxopropyl-substituted
In continuation of our studies on the chemistry of
fused systems containing a 2,4-dioxopyran fragment,
in the present work we examined the behavior of
3,3′-(phenylmethanediyl)bis(4-hydroxy-6-methyl-
Scheme 1.
O
O
OH
HO
OH
O
Ph
Ph
CHO
AcOH
+
Me
Me
Me
Me
O
O
O
O
Me
O
O
O
O
O
1
* For communication III, see [1].
65

FEDOTOVA et al.
66
Scheme 3.
2H-chromen-2-ones [5]. These findings allowed us to
predict the behavior of 1 under selected conditions.
O
Ph
O
The reaction of 1 with phosphorus pentachloride in
acetic acid involved intramolecular heterocyclization
with formation of 4a-hydroxy-3,7-dimethyl-10-phenyl-
10,10a-dihydro-1H,4aH,9H-dipyrano[4,3-b:3′,4′-e]py-
ran-1,9-dione (2) in 72% yield (Scheme 2). Hemi-
Et2O· BF3
1
3
O
O
–H2O
–H+
Me
O
Me
A
1
ketal 2 displayed in the H NMR spectrum a singlet
The products were identified by IR and NMR spec-
from the hydroxy proton at δ 3.68 ppm, two singlets
due to vinylic protons at δ 6.63 and 6.82 ppm, and two
doublets from 10-H and 10a-H at δ 4.69 and 5.70 ppm
with a coupling constant 3J of 8.0 Hz.
1
troscopy. The H NMR spectrum of mixture 2/3 con-
tained signals belonging to hemiketal 2 together with
a one-proton singlet at δ 6.27 ppm due to olefinic
protons in the equivalent pyran rings of symmetric
compound 3; thus, the ratio of products 2 and 3 was
estimated at 2:1.
Scheme 2.
PCl5, AcOH
or CF3COOH
O
Ph
O
Heterocyclization of 1 to hemiketal 2 in acetic acid
in the presence of diphosphorus pentasulfide also pre-
dominated over nucleophilic reaction at the carbonyl
group, and compound 2 was formed in 71% yield
(Scheme 2). Analogous transformations were reported
previously for structurally related systems [6, 7].
or Et2O· BF3, AcOH
or P2S5, AcOH
O
O
1
Me
O
Me
HO
2
O
Ph
O
Only by reaction of 1 with P2S5 in benzene we ob-
tained 75% of 4-hydroxy-6-methyl-3-[(6-methyl-2-
oxo-4-sulfanyl-2H-pyran-3-yl)(phenyl)methyl]-2H-py-
ran-2-one (4) (Scheme 4).
Et2O· BF3, Et2O
O
O
1
2
+
BF4
Me
O
Me
3
Scheme 4.
O
O
Ph
Compound 2 was also formed in 81 and 75% yield
in the reactions of 1 with boron trifluoride–diethyl
ether complex in acetic acid and with trifluoroacetic
acid, respectively. These data indicated very high sta-
bility of the cyclic system, which is intrinsic to benzo-
fused analogs [2] and carbocyclic 1,3- and 1,5-dicar-
bonyl structures [3, 6]. The IR and 1H NMR spectra of
the products obtained by reactions of 1 with BF3·Et2O
and CF3COOH were identical to those of a sample of
2 prepared by reaction of 1 with PCl5. Presumably,
the described reactions involve attack on one of
the two enolic hydroxy groups by electrophilic species
(proton or aprotic reagent), followed by elimination of
hydroxy group and heterocyclization, so that the final
structure retains both lactone fragments.
O
O
P2S5, PhH
1
Me
Me
HO SH
4
1
Compound 4 displayed in the H NMR spectrum
singlets from the methyl protons at δ 2.29 ppm and CH
proton at δ 5.77 ppm, a broadened singlet from the
vinylic protons at δ 6.07 ppm, and signals from the OH
and SH protons at δ 10.89 and 4.18 ppm, respectively.
EXPERIMENTAL
The IR spectra were recorded in KBr on an FSM
1201 spectrometer with Fourier transform. The 1H and
13C NMR spectra were measured on a Varian 400 spec-
trometer at 25°C at 400 and 100 MHz, respectively,
using tetramethylsilane as internal reference. The ele-
mental analyses were obtained on a Vario MICRO ana-
lyzer. The melting points were determined in capil-
laries. The progress of reactions and the purity of prod-
In the reaction of 1 with BF3·Et2O in diethyl ether
we observed for the first time salt formation. Due to
poor solubility of the products in diethyl ether, apart
from hemiketal 2, we detected 3,7-dimethyl-1,9-dioxo-
10-phenyl-1H,9H-dipyrano[4,3-b:3′,4′-e]pyran-5-ium
tetrafluoroborate (3) resulting from aromatization of
intermediate A (Scheme 3).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 1 2015

CHEMISTRY OF 1,5-DIKETONES: IV.
67
ucts were monitored by TLC on Silufol UV-254 plates
using hexane–diethyl ether–acetone (3:1:1) and hex-
ane–ethyl acetate–acetone (2:2:1) as eluents; spots
were visualized by treatment with iodine vapor.
was filtered off and dried. Yield 0.29 g (71%), color-
less crystals, mp 209–210°C.
3,7-Dimethyl-1,9-dioxo-10-phenyl-1H,9H-dipy-
rano[4,3-b:3′,4′-e]pyran-5-ium tetrafluoroborate
(3). A mixture of 20 mL of diethyl ether, 0.4 g
(1.2 mmol) of compound 1, and 5 mL (0.17 g,
1.2 mmol) of boron trifluoride–diethyl ether complex
was stirred for 60 h at room temperature. Yield 0.35 g
(39%), mixture of crystals of 2 and 3. IR spectrum, ν,
cm–1: 3090–3030 br (O–H), 2990–2954 s (CH3),
1720 v.s (C=O), 1262 s (C–O–C), 1063 s (BF4–).
1H NMR spectrum, δ, ppm: 2: 2.25 s and 2.29 s (3H
each, CH3), 3.71 br.s (1H, OH), 4.78 d (1H, 10-H, J =
8.0 Hz), 5.69 (1H, 10a-H, J = 8.0 Hz), 6.58 s (1H,
6-H), 6.79 s (1H, 4-H); 3: 2.58 s (6H, CH3), 6.27 br.s
(2H, 4-H, 6-H), 7.20–7.40 m (10H, Harom). 13C NMR
spectrum, δC, ppm: 2: 17.45 and 18.78 (CH3), 02.36
(C10), 58.76 (C10a), 96.29 (C4), 105.01 (C5a), 115.61
(C6); 124.09, 124.57, 126.49, 138.02 (Carom); 145.28
(C7), 146.23 (C9a), 159.21 (C3), 165.48 (C1), 170.73
(C9), 170.34 (C4a); 3: 15.53 (CH3), 96.51 (C4, C6),
125.34 (C9a, C10a); 121.33, 123.21, 127.68, 130.22
(Carom); 138.59 (C10), 153.65 (C3, C7), 164.32 (C4a,
C5a), 172.02 (C1, C9).
4-Hydroxy-6-methyl-3-[(6-methyl-2-oxo-4-sul-
fanyl-2H-pyran-3-yl)(phenyl)methyl]-2H-pyran-
2-one (4). A mixture of 0.4 g (1.2 mmol) of compound
1 and 20 mL of benzene was stirred at 60–70°C until
dissolution. The solution was cooled to 20–30°C, 0.8 g
(3.6 mmol) of diphosphorus pentasulfide was added,
and the mixture was heated for 80 h under reflux. The
inorganic precipitate was filtered off, the filtrate was
evaporated, the residue was treated with water, and the
crystals were filtered off and dried. Yield 0.31 g (75%),
light yellow crystals, mp 171–172°C. IR spectrum, ν,
cm–1: 3500–3000 br (O–H), 2987–2950 s (CH3), 2593–
2555 w (CH), 1725 v.s (C=O), 1253 s (C–O–C).
1H NMR spectrum, δ, ppm: 2.29 br.s (6H, CH3), 4.18 s
(1H, SH), 5.77 br.s (2H, 5-H, 5′-H) 6.07 s (1H, PhCH),
7.15–7.34 m (5H, Harom), 10.89 br.s (1H, OH).
13C NMR spectrum (primed locants refer to the thiol
fragment), δC, ppm: 15.13 (6′-CH3), 18.37 (6-CH3),
40.20 (C1), 94.47(C5′), 95.82 (C5), 106.54 (C3′), 120.55
(C3); 126.48, 128.97, 129.76, 139.63 (Carom); 162.35
(C6), 163.87 (C2), 165.32 (C2′), 167.12 (C6′), 167.40
(C4), 169.56 (C4′). Found, %: C 64.03; H 4.46; S 9.00.
C19H16O5S. Calculated, %: C 63.94; H 4.54; S 8.92.
3,3′-(Phenylmethanediyl)bis(4-hydroxy-6-
methyl-2H-pyran-2-one) (1). A 50-mL flask was
charged with 15 mL of acetic acid and 1 g (8 mmol) of
4-hydroxy-6-methyl-2H-pyran-2-one, the mixture was
heated to 70°C until dissolution, 0.4 mL (4 mmol) of
benzaldehyde was added, and the mixture was cooled
to room temperature and stirred for 14 h. The pre-
cipitate was filtered off and washed with water. Yield
0.87 g (70%), colorless crystals, mp 214–215°C [4].
4a-Hydroxy-3,7-dimethyl-10-phenyl-10,10a-di-
hydro-1H,4aH,9H-dipyrano[4,3-b:3′,4′-e]pyran-1,9-
dione (2). a. Compound 1, 1 g (3 mmol), and phos-
phorus pentachloride, 0.61 g (3 mmol), were dissolved
in 20 mL of acetic acid on heating to 70°C, and
the mixture was stirred for 72 h. Yield 0.73 g (72%),
colorless crystals, mp 209–210°C. IR spectrum, ν,
cm–1: 3140–3080 br (O–H), 3000–2960 s (CH3),
1
1721 v.s (C=O), 1269 s (C–O–C). H NMR spectrum,
δ, ppm: 2.27 s and 2.31 s (3H each, CH3), 3.68 br.s
(1H, OH), 4.69 d (1H, 10-H, J = 8.0 Hz), 5.70 d (1H,
10a-H, J = 8.0 Hz), 6.63 s (1H, 6-H), 6.82 s (1H, 4-H),
7.09–7.37 m (5H, Harom). 13C NMR spectrum, δC, ppm:
18.55 and 19.97 (CH3), 42.55 (C10), 59.97 (C10a),
98.53 (C4), 107.11 (C5a), 117.75 (C6); 125.21, 125.87,
127.71, 130.11 (Carom); 147.52 (C7), 148.45 (C9a),
160.44 (C3), 167.70 (C1), 171.92 (C9), 172.53 (C4a).
Found, %: C 67.09; H 4.69. C19H16O6. Calculated, %:
C 67.05; H 4.74.
b. A solution of 0.3 g (0.9 mmol) of compound 1
was dissolved in 15 mL of trifluoroacetic acid, and
the mixture was stirred for 70 h at room temperature.
The precipitate was filtered off and dried. Yield 0.22 g
(75%), colorless crystals, mp 209–210°C.
c. A mixture of 15 mL of acetic acid, 0.4 g
(1.2 mmol) of compound 1, and 5 mL (0.17 g,
1.2 mmol) of boron trifluoride–diethyl ether complex
was stirred for 65 h at room temperature. The crystals
were filtered off and dried. Yield 0.32 g (81%), color-
less crystals, mp 209–210°C.
d. Diphosphorus pentasulfide, 0.8 g (3.6 mmol),
was added to a solution of 0.4 g (1.2 mmol) of com-
pound 1 in 20 mL of acetic acid, heated to 70–80°C,
and the mixture was kept for 60 h. The inorganic
precipitate was filtered off, the filtrate was evaporated,
the residue was treated with water, and the precipitate
This study was performed under financial support
by the Ministry of Education and Science of the
Russian Federation (state contract no. 4.1212.2014/K).
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FEDOTOVA et al.
4. de March, P., Moreno-Mañas, M., and Roca, J.L.,
68
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