[4+2] Annulatlon - Convenient synthesis of substituted dihydropyranones in aqueous media

Article abstract of DOI:10.1002/ejoc.200801257

A facile and convenient synthesis of dihydropyranones has been developed by a formal [4+2] annulation of readily available α-acetyl ketene S,S-acetals with various aldehydes, involving a tandem aldol reaction and conjugate addition-elimination reaction, i

Full text of DOI:10.1002/ejoc.200801257

FULL PAPER
DOI: 10.1002/ejoc.200801257
[4+2] Annulation – Convenient Synthesis of Substituted Dihydropyranones in
Aqueous Media
Yan Ouyang,[a,c] Jie Huang,[a,b] Wei Pan,[a] Yongjiu Liang,[b] Yang Yang,[a] and
Dewen Dong*[a,b]
Keywords: Aldol reactions / Annulation / α-Oxo ketene S,S-acetals / Dihydropyranones / Water
A facile and convenient synthesis of dihydropyranones has
been developed by a formal [4+2] annulation of readily avail-
able α-acetyl ketene S,S-acetals with various aldehydes, in-
volving a tandem aldol reaction and conjugate addition-eli-
mination reaction, in the presence of NaOH in water.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
Over the past decades, the utility of α-oxo ketene S,S-
acetals as versatile three-carbon 1,3-electrophilic intermedi-
ates in organic synthesis has been recognized.[13] During the
course of our studies on the chemistry of α-oxo ketene S,S-
acetals, we successfully developed novel strategies for highly
substituted six-membered-ring carbocycles and heterocy-
cles, relying upon the utilization of α-alkenoyl ketene S,S-
acetalsϪaldol condensation products of α-acetyl ketene S,S-
acetalsϪas a five-carbon 1,5-bielectrophilic species in the
formal [5+1] annulation with various nucleophiles.[14] Con-
sidering the important synthetic utility of α-alkenoyl ketene
S,S-acetals, we recently investigated the aldol condensation
reaction of 3-(1,3-dithiolan-2-ylidene)pentane-2,4-dione in
water and obtained both mono- and double-condensed
products,[15] which were further used for the synthesis of
thiopyrano[2,3-b]thiopyran-4,5-diones by a double formal
[5+1] annulation.[16] In connection with our previous work
and our continuing interest in the synthesis of valuable het-
erocycles, we examined the aldol reactions of α-oxo ketene
S,S-acetals 1 with aldehydes 2 in aqueous media. As a re-
sult, we achieved a convenient one-pot synthesis of substi-
tuted dihydropyranones by a base-promoted formal [4+2]
annulation of 1 with 2 in the presence of NaOH in water.
Herein, we wish to report our results and propose a mecha-
nism for the reactions.
Introduction
2,3-Dihydro-4H-pyran-4-ones have attracted consider-
able research attention for their presence in a diverse array
of natural products and their useful bio-, physio-, and phar-
macological activities.[1,2] In addition, their rich source of
functionalities renders them versatile intermediates in the
synthesis of a variety of biologically important compounds,
such as carbohydrates,[3] antibiotics,[4] and toxins.[5] The de-
velopment of efficient syntheses of 2,3-dihydro-4H-pyran-
4-ones has been the focus of much research for many dec-
ades and continues to be an active area of research today.
A pioneering synthetic approach for such heterocycles was
established through the hetero-Diels–Alder reaction of car-
bonyl compounds and activated dienes by Danishefsky and
co-workers.[6] Many papers and reviews subsequently re-
ported on the variations and improvements of the originally
published Danishefsky synthesis, which provides the basis
for a number of synthetic strategies.[7] Particularly, the ap-
plication of asymmetric catalysis to this protocol makes it
a very powerful synthetic tool.[8] Other methods, such as
Claisen rearrangements, ring opening of epoxides, iodo-
cyclisation, olefin metathesis, and Prins cyclization have
also been developed.[9] The synthesis of 2,3-dihydro-4H-
pyran-4-ones has also been achieved by nucleophilic ad-
dition to β-ethoxy-α,β-unsaturated lactones,[10] the oxidat-
ive cyclization of β-hydroxyenones with PdII,[4] the intramo-
lecular cyclization of a keto acid onto a cyclohexenone,[11]
and the aldol reaction of enones.[12]
Results and Discussion
α-Oxo ketene S,S-acetals 1a and 1b were prepared from
commercially available acetylacetone with carbon disulfide,
methyl iodide, and ethyl bromide in water in excellent yields
according to our reported procedure.[17]
We initially investigated the reaction of 3-[bis(methyl-
thio)methylene]pentane-2,4-dione (1a) with benzaldehyde
(2a, 2.0 equiv.) at room temperature in the presence of
[a] Department of Chemistry, Northeast Normal University,
Changchun 130024, China
[b] Changchun Institute of Applied Chemistry, Chinese Academy
of Sciences,
Changchun 130022, China
[c] Department of Chemistry, Yili Normal University,
Yining 835000, China
Fax: +86-431-85098635
E-mail: dongdw663@nenu.edu.cn
Eur. J. Org. Chem. 2009, 2003–2009
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2003

Y. Ouyang, J. Huang, W. Pan, Y. Liang, Y. Yang, D. Dong
FULL PAPER
K2CO3 (4.0 equiv.) in water. Unfortunately, the reaction
proceeded very sluggishly, and most of the substrate 1a re-
mained intact after one week. We then subjected 1a and 2a
(1.0 equiv.) to NaOH (1.0 equiv.) in water at room tempera-
ture, and the reaction proceeded smoothly as indicated by
TLC. As shown in Scheme 1, we filtered the resulting mix-
ture to furnish a white solid, which was quite pure after
being washed with water, and characterized it as 5-acetyl-
6-(methylthio)-2-phenyl-2,3-dihydropyran-4-one (3a) on the
basis of its spectra and analytical data (55% yield, Table 1,
Entry 1). We acidified the filtrate with 10% aqueous HCl
(to pH ≈ 1). We collected the resulting precipitate by fil-
tration, washed it with water and petroleum ether several
times, and dried it in vacuo to give another white solid,
characterized as 3-acetyl-4-hydroxy-6-phenyl-5,6-dihy-
dropyran-2-one (4a, 18% yield). We dried the combined or-
ganic washings with anhydrous Na2SO4 and filtered and
concentrated them to afford the third white solid, which
we characterized as (2E,4E)-S-methyl 2-acetyl-3-hydroxy-5-
phenylpenta-2,4-dienethioate (5a, 21% yield). We estab-
lished the structure of 4a by X-ray single-crystal analyses
(Figure 1) and confirmed it by NMR spectroscopy. Further
experiments revealed that both high reaction temperature
and excess NaOH resulted in lower yields of 3a. It is worth
noting that the one-pot reaction is associated with a very
simple separation process.
Scheme 1. Reaction between 1a and 2a in aqueous media.
Under the conditions used for 3a in Table 1, Entry 1, we acetyl-4-hydroxy-5,6-dihydropyran-2-one (4i) in high yield
carried out a range of reactions of 1a with a variety of se- (Table 1, Entry 9). We could not isolate products 3i and 5i,
lected aldehydes 2, and some results are listed in Table 1. which might have been present in trace amounts in the reac-
We observed that all the reactions of 1a with aromatic and tion mixture. Based on the reaction times and yields, it
heterocyclic aldehydes proceeded smoothly under the essen- seems the reactivity of aldehydes 2 follows the sequence:
tially mild basic conditions in water to afford the corre- aromatic aldehydes with electron-withdrawing groups Ͼ
sponding substituted dihydropyranones 3 and 4 and 2,4- heterocyclic aldehydes Ͼ halogenated aromatic aldehydes Ͼ
dienethioesters 5 (Table 1, Entries 2–8). Interestingly, the re- benzaldehyde Ͼ aromatic aldehydes with electron-donating
action of 1a with aqueous formaldehyde (2i) afforded 3- groups. In the case of 4-nitrobenzaldehyde (2d), the reaction
Table 1. Reactions of α-oxo ketene S,S-acetals 1 with selected aldehydes 2 in aqueous media.
Entry
1
R1
2
R2
Time
[h]
3
Yield
[%][a]
4
Yield
[%][a]
5
Yield
[%][a]
1
2
3
4
5
6
7
8
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1b
1b
1b
1b
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Et
2a
2b
2c
2d
2e
2f
2g
2h
2i
2d
2a
2b
2c
2d
Ph
8.0
12.0
3.0
0.5
14.0
6.0
1.5
1.0
8.0
1.0
3a
3b
3c
3d
3e
3f
3g
3h
3i
3d
3j
3k
3l
3m
55
53
79
81
46
45
47
56
0
95
48
54
63
69
4a
4b
4c
4d
4e
4f
4g
4h
4i
4d
4a
4b
4c
4d
18
17
10
6
13
19
20
16
92
0
5a
5b
5c
5d
5e
5f
5g
5h
5i
5d
5j
5k
5l
5m
21
26
7
4-MeC6H4
4-ClC6H4
4-O2NC6H4
4-MeOC6H4
PhCH=CH
2-thienyl
2-furyl
8
33
26
29
23
0
9
H
10[b]
11
12
13
14
4-O2NC6H4
Ph
4-MeC6H4
4-ClC6H4
4-O2NC6H4
0
16.0
20.0
8.0
9
27
25
18
12
Et
Et
Et
13
12
14
1.0
[a] Isolated yields. [b] Aqueous K2CO3 (1.0 equiv.) was employed in this case.
2004
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2003–2009

Convenient Synthesis of Substituted Dihydropyranones in Aqueous Media
Scheme 2. Proposed mechanism for the reaction of 1 and 2 in aqueous media.
groups, and in particular an α,β-unsaturated carbonyl moi-
ety, which may render them extremely versatile as synthetic
scaffolds in the preparation of natural and synthetic com-
pounds with important biological and pharmacological ac-
tivities.
To obtain insight into the mechanism of the one-pot re-
action, we conducted a separate experiment, in which we
treated 3c with 1.0 equiv. of NaOH at room temperature
for 16 h and obtained 4c and 5c in 64% and 33% yield,
respectively. On the basis of these results, a mechanism for
the reaction of 1 and 2 in water is proposed as depicted in
Scheme 2. Under the basic conditions, the aldol reaction of
1 and 2 generates A, which undergoes an intramolecular
addition-elimination (nucleophilic vinylic substitution,
SNV) reaction to afford 3.[12a,14,18] With the attack of OH–,
3 undergoes competitive SNV and ring-opening reactions to
give 4 and intermediate C, respectively. In another pathway,
C can be formed by the SNV reaction of B, derived from
the aldol condensation of 1 and 2. Finally, C is converted
into its isomer 5.
Figure 1. ORTEP drawing of 4a.
could even proceed in aqueous K2CO3 (1.0 equiv.) at room
temperature and exclusively furnished 2,3-dihydropyran-4-
one 3d in 95% yield (Table 1, Entry 10). It should be men-
tioned that we confirmed the structure of 5b by X-ray sin-
gle-crystal analysis (Figure 2).
Conclusions
In summary, a convenient one-pot synthesis of substi-
tuted dihydropyranones of types 3 and 4 and 2,4-diene thio-
esters 5 was developed by a tandem aldol reaction and con-
jugate addition-elimination of α-acetyl ketene S,S-acetals 1
with aldehydes 2 in the presence of NaOH in water. The
simple reaction procedure and product separation, mild
conditions, readily available substrates, and potentially use-
ful products make this synthetic protocol very attractive.
Figure 2. ORTEP drawing of 5b.
Next, we extended the synthesis of dihydropyranones by
subjecting 1b and selected aldehydes 2 to the identical con-
ditions. These reactions of 1b required longer reaction times
than was required for a complete conversion of 1a (Table 1,
Entries 11–14). However, the reaction of 1a or 1b with ali-
phatic aldehydes, such as acetaldehyde, under the identical
conditions could not produce the corresponding substituted
dihydropyranones 3 and/or 4. All the results shown above
demonstrated the efficiency and versatility of the cyclization
reaction with respect to a range of heterocyclic and aro-
matic aldehydes. Thus, we provided a novel one-pot synthe-
sis of substituted dihydropyranones from α-oxo ketene S,S-
acetals and aldehydes in aqueous media. It is worth noting
that the dihydropyranones of type 3 and 4 possess very rich
Experimental Section
Typical Procedure for the Synthesis of 3–5 (3a–5a as Examples): To
aqueous NaOH (0.2 , 10 mL) were added 1a (409 mg, 2.0 mmol)
and 2a (212 mg, 2.0 mmol). The mixture was stirred at room tem-
perature for 12.0 h. After the substrate 2a was consumed as indi-
cated by TLC, the resulting mixture was filtered. The precipitate
was washed with water (3ϫ20 mL) and dried in vacuo to give 3a
as a white solid (289 mg, 55%). The aqueous filtrate was acidified
with 10% aqueous HCl (to pH ≈ 1), and a white solid precipitated.
The resulting precipitate was collected by filtration, washed with
functionality, such as acetyl and alkylthio or hydroxy water (3ϫ20 mL) and petroleum ether (4ϫ20 mL), and dried in
Eur. J. Org. Chem. 2009, 2003–2009
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2005

Y. Ouyang, J. Huang, W. Pan, Y. Liang, Y. Yang, D. Dong
FULL PAPER
vacuo to give 4a as a white solid (84 mg, 18%). The combined
organic washings were dried with anhydrous Na2SO4, filtered and
concentrated to afford 5a as a white solid (110 mg, 21%).
(2E,4E)-S-Methyl 2-Acetyl-3-hydroxy-5-p-tolylpenta-2,4-dienethio-
ate (5b): White solid; m.p. 112–114 °C. 1H NMR (CDCl3,
500 MHz): δ = 2.27 (s, 3 H), 2.37 (s, 3 H), 2.50 (s, 3 H), 6.76 (d, J
= 15.5 Hz, 1 H), 7.18 (d, J = 7.5 Hz, 2 H), 7.41 (d, J = 7.5 Hz, 2
H), 7.72 (d, J = 15.5 Hz, 1 H), 16.69 (s, 1 H) ppm. 13C NMR
(CDCl3, 125 MHz): δ = 13.6, 21.7, 25.9, 117.1, 118.8, 128.7, 129.9,
In most cases, products 3–5 were obtained as quite pure solids
without purification, while in some cases, oily products required
further purification, which was carried out by flash chromatog-
raphy over silica gel (for products 3: ethyl acetate/petroleum ether
10%; for products 4: ethyl acetate/petroleum ether 20%; for prod-
ucts 5: petroleum ether only).
132.3, 141.3, 142.9, 177.5, 194.0, 196.4 ppm. IR (KBr): ν = 1740,
˜
1652, 1539, 1515, 1385, 1178, 882 cm–1. C15H16O3S (276.08): calcd.
C 65.19, H 5.84; found C 65.08, H 5.92.
Crystal Data for 5b: C15H16SO3, colourless crystal, M = 276.34,
monoclinic, P21/n, a = 7.8916(19) Å, b = 10.404(3) Å, c =
17.376(4) Å, α = 90.00°, β = 93.162(4)°, γ = 90.00°, V =
1424.5(6) Å3, Z = 4, T = 273(2) K, F000 = 584, R1 = 0.0493, wR2
= 0.1177. CCDC-694976 contains the supplementary crystallo-
graphic data for 5b. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.a-
c.uk/data_request/cif.
Selected Data for 3–5:
5-Acetyl-6-methylthio-2-phenyl-2,3-dihydropyran-4-one (3a): White
solid; m.p. 119–121 °C. H NMR (CDCl3, 500 MHz): δ = 2.29 (s,
3 H), 2.56 (s, 3 H), 2.78 (dd, J = 3.0, 17.0 Hz, 1 H), 2.98 (dd, J =
14.0, 17.0 Hz, 1 H), 5.55 (dd, J = 3.0, 14.0 Hz, 1 H), 7.40–7.43 (m,
2 H), 7.44–7.47 (m, 3 H) ppm. 13C NMR (CDCl3, 125 MHz): δ =
14.4, 32.2, 43.1, 83.4, 115.8, 126.3, 129.3, 129.7, 136.7, 187.4, 188.5,
1
196.8 ppm. IR (KBr): ν = 1658, 1634, 1500, 1428, 1344, 1185, 879
˜
5-Acetyl-2-(4-chlorophenyl)-6-methylthio-2,3-dihydropyran-4-one
(3c): White solid; m.p. 132–134 °C. H NMR (CDCl3, 500 MHz):
δ = 2.29 (s, 3 H), 2.56 (s, 3 H), 2.76 (dd, J = 3.0, 17.0 Hz, 1 H),
2.95 (dd, J = 14.0, 17.0 Hz, 1 H), 5.53 (dd, J = 3.0, 14.0 Hz, 1 H),
7.34 (d, J = 8.0 Hz, 2 H), 7.43 (d, J = 8.5 Hz, 2 H) ppm. 13C NMR
(CDCl3, 125 MHz): δ = 14.4, 32.2, 43.0, 82.7, 115.9, 127.7, 129.6,
cm–1. C14H14O3S (262.07): calcd. C 64.10, H 5.38; found C 64.24,
H 5.29.
1
3-Acetyl-4-hydroxy-6-phenyl-5,6-dihydropyran-2-one (4a): White so-
1
lid; m.p. 122–124 °C. H NMR (CDCl3, 500 MHz): δ = 2.66 (s, 3
H), 2.87 (dd, J = 3.0, 17.0 Hz, 1 H), 3.05 (dd, J = 12.0, 17.0 Hz, 1
H), 5.43 (dd, J = 3.0, 12.0 Hz, 1 H), 7.39–7.42 (m, 5 H), 17.78 (s,
1 H) ppm. 13C NMR (CDCl3, 125 MHz): δ = 25.5, 38.8, 74.1,
102.7, 124.9, 127.8, 128.0, 136.2, 163.1, 193.8, 200.3 ppm. IR
135.2, 135.7, 186.9, 188.2, 196.7 ppm. IR (KBr): ν = 1655, 1497,
˜
1449, 1352, 1249, 1089, 864 cm–1. C14H13ClO3S (296.03): calcd. C
56.66, H 4.42; found C 56.45, H 4.53.
(KBr): ν = 1705, 1645, 1515, 1454, 1224, 1066, 763 cm–1. C H O
˜
3-Acetyl-6-(4-chlorophenyl)-4-hydroxy-5,6-dihydropyran-2-one (4c):
White solid; m.p. 162–164 °C. 1H NMR (CDCl3, 500 MHz): δ =
2.66 (s, 3 H), 2.85 (dd, J = 3.0, 17.0 Hz, 1 H), 3.01 (dd, J = 12.0,
17.0 Hz, 1 H), 5.41 (dd, J = 3.0, 12.0 Hz, 1 H), 7.35 (d, J = 8.5 Hz,
2 H), 7.39 (d, J = 8.5 Hz, 2 H), 17.8 (s, 1 H) ppm. 13C NMR
(CDCl3, 125 MHz): δ = 26.8, 40.0, 74.6, 103.8, 127.6, 129.4, 135.1,
13 12
4
(232.07): calcd. C 67.23, H 5.21; found C 67.48, H 5.15.
Crystal Data for 4a: C13H12O4, colourless crystal, M = 232.23, mo-
noclinic, P21/c, a = 11.911(3) Å, b = 16.494(4) Å, c = 5.7210(15) Å,
α = 90.00°, β = 91.806(4) °, γ = 90.00°, V = 1123.4(5) Å3, Z = 4, T
= 293(2) K, F000 = 488, R1 = 0.0471, wR2 = 0.1110. CCDC-694975
contains the supplementary crystallographic data for 4a. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
136.0, 164.1, 194.9, 201.6 ppm. IR (KBr): ν = 1645, 1549, 1497,
˜
1422, 1317, 1090, 826 cm–1. C13H11ClO4 (266.03): calcd. C 58.55,
H 4.16; found C 58.71, H 4.05.
(2E,4E)-S-Methyl 2-Acetyl-5-(4-chlorophenyl)-3-hydroxypenta-2,4-
(2E,4E)-S-Methyl 2-Acetyl-3-hydroxy-5-phenylpenta-2,4-dienethio-
ate (5a): White solid; m.p. 93–95 °C. 1H NMR (CDCl3, 500 MHz):
δ = 2.28 (s, 3 H), 2.51 (s, 3 H), 6.81 (d, J = 15.5 Hz, 1 H), 7.38–
7.39 (m, 3 H), 7.51–7.52 (m, 2 H), 7.75 (d, J = 16.0 Hz, 1 H), 16.65
(s, 1 H) ppm. 13C NMR (CDCl3, 125 MHz): δ = 12.4, 24.7, 116.0,
118.6, 127.4, 127.9, 129.4, 133.7, 141.5, 175.9, 192.7, 195.4 ppm.
1
dienethioate (5c): White solid; m.p. 104–106 °C. H NMR (CDCl3,
500 MHz): δ = 2.28 (s, 3 H), 2.51 (s, 3 H), 6.76 (d, J = 15.5 Hz, 1
H), 7.35 (d, J = 8.0 Hz, 2 H), 7.43 (d, J = 8.0 Hz, 2 H), 7.68 (d, J
= 15.5 Hz, 1 H), 16.61 (s, 1 H) ppm. 13C NMR (CDCl3, 125 MHz):
δ = 13.7, 26.1, 117.4, 120.3, 129.4, 129.7, 133.4, 136.6, 141.2, 176.7,
193.8, 197.0 ppm. IR (KBr): ν = 1740, 1596, 1540, 1383, 1269,
˜
IR (KBr): ν = 1656, 1547, 1446, 1338, 1018, 841 cm–1. C H O S
˜
1091, 854 cm–1. C14H13ClO3S (296.03): calcd. C 56.66, H 4.42;
found C 56.78, H 4.35.
14 14
3
(262.07): calcd. C 64.10, H 5.38; found C 64.27, H 5.34.
5-Acetyl-6-methylthio-2-p-tolyl-2,3-dihydropyran-4-one (3b): White
solid; m.p. 116–118 °C. H NMR (CDCl3, 500 MHz): δ = 2.27 (s,
5-Acetyl-6-(methylthio)-2-(4-nitrophenyl)-2,3-dihydropyran-4-one
(3d): White solid; m.p. 180–182 °C. H NMR (CDCl3, 500 MHz):
1
1
3 H), 2.39 (s, 3 H), 2.56 (s, 3 H), 2.74 (dd, J = 3.0, 17.0 Hz, 1 H),
2.98 (dd, J = 14.0, 17.0 Hz, 1 H), 5.51 (dd, J = 3.0, 14.0 Hz, 1 H),
7.25 (d, J = 8.0 Hz, 2 H), 7.29 (d, J = 8.0 Hz, 2 H) ppm. 13C NMR
(CDCl3, 125 MHz): δ = 14.3, 21.5, 32.2, 43.0, 83.4, 115.7, 126.4,
δ = 2.34 (s, 3 H), 2.56 (s, 3 H), 2.83 (dd, J = 3.0, 17.0 Hz, 1 H),
2.94 (dd, J = 14.0, 17.0 Hz, 1 H), 5.68 (dd, J = 3.0, 14.0 Hz, 1 H),
7.61 (d, J = 8.5 Hz, 2 H), 8.33 (d, J = 8.5 Hz, 2 H) ppm. 13C NMR
(CDCl3, 125 MHz): δ = 14.5, 32.3, 43.2, 81.9, 116.0, 124.7, 127.0,
123.0, 133.7, 139.8, 187.6, 188.6, 196.8 ppm. IR (KBr): ν = 1740,
˜
143.6, 148.5, 186.1, 188.0, 196.6 ppm. IR (KBr): ν = 1740, 1659,
˜
1658, 1515, 1438, 1351, 1038, 860 cm–1. C15H16O3S (276.08): calcd.
C 65.19, H 5.84; found C 65.48, H 5.76.
1514, 1445, 1344, 1042, 854 cm–1. C14H13NO5S (307.05): calcd. C
54.71, H 4.26, N 4.56; found C 54.92, H 4.35, N 4.68.
3-Acetyl-4-hydroxy-6-p-tolyl-5,6-dihydropyran-2-one (4b): White so-
3-Acetyl-4-hydroxy-6-(4-nitrophenyl)-5,6-dihydropyran-2-one (4d):
lid; m.p. 102–104 °C. H NMR (CDCl3, 500 MHz): δ = 2.36 (s, 3 White solid; m.p. 126–128 °C. 1H NMR (CDCl3, 500 MHz): δ =
H), 2.65 (s, 3 H), 2.85 (dd, J = 3.0, 17.0 Hz, 1 H), 3.04 (dd, J = 2.67 (s, 3 H), 2.92 (dd, J = 4.0, 17.0 Hz, 1 H), 2.99 (dd, J = 12.0,
1
12.0, 17.0 Hz, 1 H), 5.40 (dd, J = 3.0, 12.0 Hz, 1 H), 7.21 (d, J =
8.0 Hz, 2 H), 7.28 (d, J = 8.0 Hz, 2 H), 17.77 (s, 1 H) ppm. 13C
NMR (CDCl3, 125 MHz): δ = 21.4, 26.8, 40.0, 75.3, 103.9, 110.0,
17.0 Hz, 1 H), 5.55 (dd, J = 4.0, 12.0 Hz, 1 H), 7.62 (d, J = 8.5 Hz,
2 H), 8.27–8.30 (m, 2 H), 17.79 (s, 1 H) ppm. 13C NMR (CDCl3,
125 MHz): δ = 26.8, 40.1, 74.2, 103.7, 124.5, 126.9, 144.5, 148.4,
126.2, 129.7, 134.5, 139.1, 164.5, 195.2, 201.6 ppm. IR (KBr): ν =
163.6, 194.4, 201.8 ppm. IR (KBr): ν = 1701, 1558, 1520, 1347,
˜
˜
1710, 1549, 1515, 1295, 1220, 1060, 813 cm–1. C14H14O4 (246.09):
calcd. C 68.28, H 5.73; found C 68.52, H 5.61.
1294, 1064, 874 cm–1. C13H11NO6 (277.06): calcd. C 56.32, H 4.00,
N 5.05; found C 56.45, H 3.89, N 5.14.
2006
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2003–2009

Convenient Synthesis of Substituted Dihydropyranones in Aqueous Media
(2E,4E)-S-Methyl 2-Acetyl-3-hydroxy-5-(4-nitrophenyl)penta-2,4- 1660, 1606, 1392, 1281, 1174, 1004, 860 cm–1. C16H16O3S (288.08):
1
dienethioate (5d): White solid; m.p. 146–148 °C. H NMR (CDCl3,
500 MHz): δ = 2.31 (s, 3 H), 2.53 (s, 3 H), 6.92 (d, J = 15.5 Hz, 1
H), 7.65 (d, J = 8.5 Hz, 2 H), 7.73 (d, J = 15.5 Hz, 1 H), 8.24 (d,
J = 9.0 Hz, 2 H), 16.46 (s, 1 H) ppm. 13C NMR (CDCl3, 125 MHz):
δ = 13.8, 26.4, 118.0, 123.9, 124.4, 129.1, 139.3, 141.0, 148.6, 175.2,
calcd. C 66.64, H 5.59; found C 66.47, H 5.75.
5-Acetyl-6-(methylthio)-2-(thiophen-2-yl)-2,3-dihydropyran-4-one
1
(3g): White solid; m.p. 102–104 °C. H NMR (CDCl3, 500 MHz):
δ = 2.30 (s, 3 H), 2.54 (s, 3 H), 2.95 (dd, J = 3.0, 17.0 Hz, 1 H),
3.07 (dd, J = 12.0, 17.0 Hz, 1 H), 5.80 (dd, J = 3.0, 12.0 Hz, 1 H),
7.05–7.06 (m, 1 H), 7.12–7.14 (m, 1 H), 7.42 (d, J = 5.0 Hz, 1 H)
ppm. 13C NMR (CDCl3, 125 MHz): δ = 14.4, 32.1, 42.7, 78.9,
115.9, 126.9, 127.4, 127.6, 139.1, 186.6, 187.8, 196.6 ppm. IR
193.5, 197.9 ppm. IR (KBr): ν = 1740, 1693, 1654, 1515, 1397,
˜
1339, 862 cm–1. C14H13NO5S (307.05): calcd. C 54.71, H 4.26, N
4.56; found C 54.52, H 4.32, N 4.74.
(KBr): ν = 1731, 1659, 1537, 1431, 1342, 1071, 865 cm–1
.
˜
5-Acetyl-2-(4-methoxyphenyl)-6-(methylthio)-2,3-dihydropyran-4-
one (3e): White solid; m.p. 124–126 °C. 1H NMR (CDCl3,
500 MHz): δ = 2.26 (s, 3 H), 2.56 (s, 3 H), 2.72–2.76 (m, 1 H),
3.00–3.04 (m, 1 H), 3.84 (s, 3 H), 5.49–5.51 (m, 1 H), 6.97 (d, J =
7.5 Hz, 2 H), 7.33 (d, J = 7.5 Hz, 2 H) ppm. 13C NMR (CDCl3,
125 MHz): δ = 13.0, 30.9, 41.6, 54.3, 82.1, 113.4, 114.4, 126.9,
C12H12O3S2 (268.02): calcd. C 53.71, H 4.51; found C 53.82, H
4.53.
3-Acetyl-4-hydroxy-6-(thiophen-2-yl)-5,6-dihydropyran-2-one (4g):
White solid; m.p. 80–82 °C. 1H NMR (CDCl3, 500 MHz): δ = 2.50
(s, 3 H), 3.02–3.06 (m, 1 H), 3.14–3.19 (m, 1 H), 5.67–5.70 (m, 1
H), 7.01 (d, J = 4.0 Hz, 1 H), 7.10 (d, J = 3.0 Hz, 1 H), 7.36 (d, J
= 5.0 Hz, 1 H), 17.76 (s, 1 H) ppm. 13C NMR (CDCl3, 125 MHz):
δ = 26.8, 39.8, 71.4, 103.9, 126.3, 126.9, 127.2, 140.3, 163.8, 194.6,
127.2, 159.4, 186.3, 187.2, 195.4 ppm. IR (KBr): ν = 1655, 1516,
˜
1434, 1353, 1244, 1076, 863 cm–1. C15H16O4S (292.08): calcd. C
61.62, H 5.52; found C 61.46, H 5.71.
201.6 ppm. IR (KBr): ν = 1652, 1558, 1540, 1457, 1354, 1062, 887
˜
3-Acetyl-4-hydroxy-6-(4-methoxyphenyl)-5,6-dihydropyran-2-one
(4e): White solid; m.p. 142–144 °C. H NMR (CDCl3, 500 MHz):
cm–1. C11H10O4S (238.03): calcd. C 55.45, H 4.23; found C 55.28,
H 4.31.
1
δ = 2.65 (s, 3 H), 2.82 (dd, J = 3.0, 17.0 Hz, 1 H), 3.05 (dd, J =
14.0, 17.0 Hz, 1 H), 3.82 (s, 3 H), 5.38 (dd, J = 3.0, 14.0 Hz, 1 H),
6.92 (d, J = 8.0 Hz, 2 H), 7.32 (d, J = 8.5 Hz, 2 H), 17.78 (s, 1 H)
ppm. 13C NMR (CDCl3, 125 MHz): δ = 25.5, 38.6, 54.3, 74.0,
102.7, 113.2, 126.5, 128.2, 159.1, 163.3, 194.0, 200.3 ppm. IR
(2E,4E)-S-Methyl 2-Acetyl-3-hydroxy-5-(thiophen-2-yl)penta-2,4-
dienethioate (5g): Yellowish solid; m.p. 84–86 °C. 1H NMR (CDCl3,
500 MHz): δ = 2.26 (s, 3 H), 2.50 (s, 3 H), 6.59 (d, J = 15.0 Hz, 1
H), 7.06–7.08 (m, 1 H), 7.28 (d, J = 4.0 Hz, 1 H), 7.41 (d, J =
5.0 Hz, 2 H), 7.84 (d, J = 15.0 Hz, 1 H), 16.67 (s, 1 H) ppm. 13C
NMR (CDCl3, 125 MHz): δ = 12.4, 24.7, 115.8, 117.5, 127.4, 128.4,
(KBr): ν = 1645, 1514, 1463, 1249, 1173, 1031, 827 cm–1. C H O
˜
14 14
5
(262.08): calcd. C 64.12, H 5.38; found C 64.35, H 5.19.
130.5, 134.0, 139.3, 175.9, 192.7, 195.1 ppm. IR (KBr): ν = 1651,
˜
(2E,4E)-S-Methyl 2-Acetyl-3-hydroxy-5-(4-methoxyphenyl)penta-
2,4-dienethioate (5e): White solid; m.p. 96–98 °C. 1H NMR
(CDCl3, 500 MHz): δ = 2.26 (s, 3 H), 2.50 (s, 3 H), 3.84 (s, 3 H),
6.67 (d, J = 15.5 Hz, 1 H), 6.90 (d, J = 8.0 Hz, 2 H), 7.47 (d, J =
8.0 Hz, 2 H), 7.71 (d, J = 15.0 Hz, 1 H), 16.77 (s, 1 H) ppm. 13C
NMR (CDCl3, 125 MHz): δ = 13.7, 25.9, 55.6, 114.6, 116.9, 117.3,
1614, 1498, 1370, 1226, 1041, 868 cm–1. C12H12O3S2 (268.02):
calcd. C 53.71, H 4.51; found C 53.63, H 4.68.
3-Acetyl-6-(furan-2-yl)-2-(methylthio)-4H-pyran-4-one (3h): White
1
solid; m.p. 100–102 °C. H NMR (CDCl3, 500 MHz): δ = 2.27 (s,
3 H), 2.54 (s, 3 H), 2.83 (dd, J = 3.5, 17.0 Hz, 1 H), 3.15 (dd, J =
12.0, 17.0 Hz, 1 H), 5.60 (dd, J = 3.5, 12.0 Hz, 1 H), 6.43–6.44 (m,
1 H), 6.50 (d, J = 3.0 Hz, 1 H), 7.49–7.51 (m, 1 H) ppm. 13C NMR
(CDCl3, 125 MHz): δ = 14.2, 32.2, 39.3, 76.0, 110.9, 111.0, 115.8,
127.7, 130.5, 142.7, 161.9, 177.8, 194.2, 196.1 ppm. IR (KBr): ν =
˜
1740, 1693, 1514, 1465, 1292, 1024, 821 cm–1. C15H16O4S (292.08):
calcd. C 61.62, H 5.52; found C 61.49, H 5.56.
144.5, 148.9, 186.8, 187.8, 196.7 ppm. IR (KBr): ν = 1641, 1558,
˜
(E)-5-Acetyl-6-(methylthio)-2-styryl-2,3-dihydropyran-4-one (3f):
White solid; m.p. 102–104 °C. 1H NMR (CDCl3, 500 MHz): δ =
2.33 (s, 3 H), 2.55 (s, 3 H), 2.72 (dd, J = 4.0, 17.0 Hz, 1 H), 2.81
(dd, J = 12.0, 17.0 Hz, 1 H), 5.20 (dd, J = 4.0, 12.0 Hz, 1 H), 6.31
(dd, J = 6.5, 16.0 Hz, 1 H), 6.76 (d, J = 16.0 Hz, 1 H), 7.31–7.39
(m, 3 H), 7.43 (d, J = 7.5 Hz, 2 H) ppm. 13C NMR (CDCl3,
125 MHz): δ = 14.2, 32.1, 41.9, 82.6, 115.8, 123.8, 127.2, 129.1,
1446, 1345, 1251, 1036, 834 cm–1. C12H10O4S (252.05): calcd. C
57.13, H 4.79; found C 57.46, H 4.89.
3-Acetyl-6-(furan-2-yl)-4-hydroxy-5,6-dihydropyran-2-one (4h):
White solid; m.p. 78–80 °C. 1H NMR (CDCl3, 500 MHz): δ = 2.64
(s, 3 H), 2.94 (dd, J = 3.5, 17.5 Hz, 1 H), 3.25 (dd, J = 10.0,
17.5 Hz, 1 H), 5.47 (dd, J = 3.5, 10.0 Hz, 1 H), 6.39 (s, 1 H), 6.44
(d, J = 2.5 Hz, 1 H), 7.45 (s, 1 H), 17.79 (s, 1 H) ppm. 13C NMR
(CDCl3, 125 MHz): δ = 26.8, 36.4, 68.7, 109.8, 110.5, 110.9, 143.8,
129.2, 135.3, 135.6, 187.1, 188.2, 196.7 ppm. IR (KBr): ν = 1655,
˜
1541, 1441, 1244, 1043, 747 cm–1. C16H16O3S (288.08): calcd. C
66.64, H 5.59; found C 66.48, H 5.65.
149.7, 163.7, 194.9, 201.4 ppm. IR (KBr): ν = 1721, 1596, 1395,
˜
1235, 1016, 753 cm–1. C11H10O5 (222.05): calcd. C 59.46, H 4.54;
found C 59.21, H 4.67.
(E)-3-Acetyl-4-hydroxy-6-styryl-5,6-dihydropyran-2-one (4f): White
1
solid; m.p. 118–120 °C. H NMR (CDCl3, 500 MHz): δ = 2.65 (s,
3 H), 2.81–2.92 (m, 2 H), 5.06–5.08 (m, 1 H), 6.21–6.26 (m, 1 H),
6.73 (d, J = 15.5 Hz, 1 H), 7.28–7.41 (m, 5 H), 17.75 (s, 1 H) ppm.
13C NMR (CDCl3, 125 MHz): δ = 26.8, 38.5, 74.2, 103.9, 124.8,
127.0, 128.8, 129.0, 134.1, 135.6, 164.5, 195.1, 201.4 ppm. IR
(2E,4E)-S-Methyl 2-Acetyl-5-(furan-2-yl)-3-hydroxypenta-2,4-
dienethioate (5h): White solid; m.p. 92–94 °C. 1H NMR (CDCl3,
500 MHz): δ = 2.26 (s, 3 H), 2.49 (s, 3 H), 6.48 (d, J = 1.5 Hz, 1
H), 6.49–6.70 (m, 2 H), 7.47–7.51 (m, 2 H), 16.59 (s, 1 H) ppm.
13C NMR (CDCl3, 125 MHz): δ = 13.7, 26.0, 112.9, 116.3, 117.2,
(KBr): ν = 1716, 1558, 1507, 1489, 1244, 1062, 885 cm–1. C H O
˜
15 14
4
(258.09): calcd. C 69.76, H 5.46; found C 69.89, H 5.31.
117.5, 128.7, 145.6, 151.7, 176.9, 194.0, 196.5 ppm. IR (KBr): ν =
˜
1651, 1614, 1546, 1296, 1020, 946, 866 cm–1. C12H12O4S (252.05):
calcd. C 57.13, H 4.79; found C 57.01, H 4.95.
(2E,4E,6E)-S-Methyl 2-Acetyl-3-hydroxy-7-phenylhepta-2,4,6-tri-
enethioate (5f): White solid; m.p. 103–105 °C. 1H NMR (CDCl3,
500 MHz): δ = 2.26 (s, 3 H), 2.49 (s, 3 H), 6.36 (d, J = 14.5 Hz, 1 3-Acetyl-4-hydroxy-5,6-dihydropyran-2-one (4i):[9d] White solid;
H), 6.93 (d, J = 8.0 Hz, 2 H), 7.30–7.37 (m, 3 H), 7.47 (d, J = m.p. 91–93 °C. 1H NMR (CDCl3, 500 MHz): δ = 2. 61 (s, 3 H),
8.0 Hz, 2 H), 7.51–7.53 (m, 1 H), 16.51 (s, 1 H) ppm. 13C NMR 2.77 (t, J = 6.0 Hz, 2 H), 4.367 (t, J = 6.0 Hz, 2 H), 17.75 (s, 1 H)
(CDCl3, 125 MHz): δ = 13.6, 26.0, 117.1, 123.2, 127.3, 127.6, 129.1,
129.5, 136.3, 141.6, 143.1, 176.9, 194.1, 196.5 ppm. IR (KBr): ν =
ppm. 13C NMR (CDCl3, 125 MHz): δ = 26.9, 32.9, 62.7, 104.2,
164.4, 195.6, 201.7 ppm. IR (KBr): ν = 2915, 1716, 1652, 1558,
˜
˜
Eur. J. Org. Chem. 2009, 2003–2009
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2007

Y. Ouyang, J. Huang, W. Pan, Y. Liang, Y. Yang, D. Dong
1388, 1056, 931, 869 cm–1. C7H8O4 (156.04): calcd. C 53.85, H 5.16; 17.0 Hz, 1 H), 2.89 (q, J = 7.5 Hz, 2 H), 2.94 (dd, J = 14.0, 17.0 Hz,
FULL PAPER
found C 53.68, H 5.25.
1 H), 5.66 (dd, J = 3.0, 14.0 Hz, 1 H), 7.61 (d, J = 9.0 Hz, 2 H),
8.33 (d, J = 8.5, Hz, 2 H) ppm. 13C NMR (CDCl3, 125 MHz): δ =
13.5, 24.9, 32.0, 42.9, 81.6, 115.7, 124.3, 126.7, 143.3, 148.2, 185.9,
5-Acetyl-6-(ethylthio)-2-phenyl-2,3-dihydropyran-4-one (3j): White
1
solid; m.p. 70–72 °C. H NMR (CDCl3, 500 MHz): δ = 1.27 (t, J
187.3, 196.3 ppm. IR (KBr): ν = 1740, 1661, 1518, 1430, 1342,
˜
= 7.5 Hz, 3 H), 2.56 (s, 3 H), 2.74–2.78 (m, 1 H), 2.87 (q, J =
7.5 Hz, 2 H), 2.96–3.02 (m, 1 H), 5.53 (dd, J = 3.0, 14.0 Hz, 1 H),
6.83 (d, J = 15.0 Hz, 1 H), 7.39–7.41 (m, 2 H), 7.43–7.47 (m, 3 H)
ppm. 13C NMR (CDCl3, 125 MHz): δ = 14.0, 25.2, 32.3, 43.3, 83.5,
1039, 851 cm–1. C15H15NO5S (321.07): calcd. C 56.06, H 4.70, N
4.36; found C 56.15, H 4.57, N 4.38.
(2E,4E)-S-Ethyl 2-Acetyl-3-hydroxy-5-(4-nitrophenyl)penta-2,4-
dienethioate (5m): White solid; m.p. 100–102 °C. 1H NMR (CDCl3,
500 MHz): δ = 1.39 (t, J = 6.0 Hz, 3 H), 2.31 (s, 3 H), 3.07 (q, J =
6.0 Hz, 2 H), 6.92 (d, J = 15.5 Hz, 1 H), 7.62 (d, J = 9.0 Hz, 2
H),7.71 (d, J = 15.5 Hz, 2 H), 8.22 (d, J = 8.0 Hz, 2 H), 16.36 (s,
1 H) ppm. 13C NMR (CDCl3, 125 MHz): δ = 14.5, 25.1, 26.0,
118.3, 123.7, 124.1, 128.7, 138.7, 140.8, 148.3, 174.6, 192.8, 197.5
115.9, 126.4, 129.3, 129.7, 136.8, 187.4, 196.9 ppm. IR (KBr): ν =
˜
1661, 1439, 1402, 1330, 1245, 1041, 988 cm–1. C15H16O3S (276.08):
calcd. C 65.19, H 5.84; found C 65.34, H 5.79.
(2E,4E)-S-Ethyl 2-Acetyl-3-hydroxy-5-phenylpenta-2,4-dienethioate
1
(5j): Liquid. H NMR (CDCl3, 500 MHz): δ = 1.39 (t, J = 7.0 Hz,
3 H), 2.28 (s, 3 H), 3.07 (q, J = 7.0 Hz, 2 H), 6.83 (d, J = 15.0 Hz,
1 H), 7.38–7.39 (m, 3 H), 7.50–7.51 (m, 2 H), 7.73 (d, J = 15.5 Hz,
1 H), 16.57 (s, 1 H) ppm. 13C NMR (CDCl3, 125 MHz): δ = 14.6,
25.0, 25.7,117.2, 119.6, 128.4, 128.9, 130.4, 134.7, 142.2, 176.6,
ppm. IR (KBr): ν = 1740, 1653, 1515, 1417, 1342, 1186, 862 cm–1.
˜
C15H15NO5S (321.07): calcd. C 56.06, H 4.70, N 4.36; found C
56.24, H 4.78, N 4.47.
193.4, 196.4 ppm. IR (KBr): ν = 1727, 1658, 1491, 1410, 1265,
˜
1178, 877 cm–1. C15H16O3S (276.08): calcd. C 65.19, H 5.84; found
C 65.52, H 5.68.
Acknowledgments
5-Acetyl-6-(ethylthio)-2-p-tolyl-2,3-dihydropyran-4-one (3k): Liquid.
1H NMR (CDCl3, 500 MHz): δ = 1.27 (t, J = 8.0 Hz, 3 H), 2.39
(s, 3 H), 2.56 (s, 3 H), 2.73 (dd, J = 3.0, 17.0 Hz, 1 H), 2.82 (q, J
= 8.0 Hz, 2 H), 2.99 (dd, J = 14.0, 17.0 Hz, 1 H), 5.49 (dd, J = 3.0,
14.0 Hz, 1 H), 7.22–7.30 (m, 4 H) ppm. 13C NMR (CDCl3,
125 MHz): δ = 13.9, 21.5, 25.1, 32.2, 43.2, 83.5, 115.8, 126.5, 130.0,
Financial support of this research by the National Natural Science
Foundation of China (20572013 and 20872136), the Ministry of
Education of China (105061), and Yili Normal University
(2007ZD11) is greatly acknowledged.
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in Organic Synthesis academic Press, New York, 1987; b) H. B.
Kagan Comprehensive Organic Chemistry; Pergamon, Oxford,
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Schmidt, Acc. Chem. Res. 1986, 19, 250–259; c) T. L. B. Boivin,
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Helv. Chim. Acta 1993, 76, 1275–1281; e) S. J. Danishefsky,
M. T. Bilodeau, Angew. Chem. Int. Ed. Engl. 1996, 35, 1380–
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Chem. Soc. 1985, 107, 1280–1285; b) S. J. Danishefsky, M. P.
DeNinno, Angew. Chem. Int. Ed. Engl. 1987, 26, 15–23.
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231–234; b) J. M. Cox, J. D. Rainier, Org. Lett. 2001, 3, 2919–
2922; c) Y. Yamashita, S. Saito, H. Ishitani, S. Kobayashi, J.
Am. Chem. Soc. 2003, 125, 3793–3798.
133.7, 139.8, 187.6, 188.1, 196.8 ppm. IR (KBr): ν = 1660, 1442,
˜
1343, 1242, 1185, 1071, 873 cm–1. C16H18O3S (290.10): calcd. C
66.18, H 6.25; found C 66.04, H 6.37.
(2E,4E)-S-Ethyl 2-acetyl-3-hydroxy-5-p-tolylpenta-2,4-dienethioate
1
(5k): White solid; m.p. 56–58 °C. H NMR (CDCl3, 500 MHz): δ
= 1.39 (t, J = 7.5 Hz, 3 H), 2.27 (s, 3 H), 2.38 (s, 3 H), 3.06 (q, J
= 7.5 Hz, 2 H), 6.78 (d, J = 16.0 Hz, 1 H), 7.19 (d, J = 7.0 Hz, 2
H), 7.41 (d, J = 7.5 Hz, 2 H), 7.71 (d, J = 15.5 Hz, 1 H), 16.62 (s,
1 H) ppm. 13C NMR (CDCl3, 125 MHz): δ = 14.9, 21.8, 25.3, 25.9,
117.4, 118.9, 128.6, 129.9, 132.3, 141.3, 142.7, 177.3, 193.9, 196.4
ppm. IR (KBr): ν = 1740, 1645, 1515, 1394, 1174, 851 cm–1
.
˜
C16H18O3S (290.10): calcd. C 66.18, H 6.25; found C 66.41, H 6.22.
5-Acetyl-2-(4-chlorophenyl)-6-(ethylthio)-2,3-dihydropyran-4-one
(3l): White solid; m.p. 120–122 °C. 1H NMR (CDCl3, 500 MHz): δ
= 1.27 (t, J = 7.5 Hz, 3 H), 2.55 (s, 3 H), 2.74 (dd, J = 3.0, 17.0 Hz,
1 H), 2.84 (q, J = 7.5 Hz, 2 H), 2.95 (dd, J = 14.0, 17.0 Hz, 1 H),
5.51 (dd, J = 3.0, 14.0 Hz, 1 H), 7.34 (d, J = 8.5 Hz, 2 H), 7.44 (d,
J = 8.0 Hz, 2 H) ppm. 13C NMR (CDCl3, 125 MHz): δ = 14.0,
25.2, 32.3, 43.1, 82.7, 115.9, 127.8, 129.6, 135.2, 135.7, 187.0, 187.9,
196.8 ppm. IR (KBr): ν = 1655, 1440, 1345, 1241, 1136, 1080, 835
˜
cm–1. C15H15ClO3S (310.04): calcd. C 57.97, H 4.86; found C 58.15,
H 4.78.
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Soc. 1982, 104, 358–360; b) S. J. Danishefsky, J. F. Kerwin, J.
Org. Chem. 1982, 47, 3183–3184.
(2E,4E)-S-Ethyl 2-Acetyl-5-(4-chlorophenyl)-3-hydroxypenta-2,4-
dienethioate (5l): White solid; m.p. 66–68 °C. 1H NMR (CDCl3,
500 MHz): δ = 1.38 (t, J = 7.5 Hz, 3 H), 2.28 (s, 3 H), 3.06 (q, J =
7.5 Hz, 2 H), 6.78 (d, J = 15. 5 Hz, 1 H), 7.35 (d, J = 8.5 Hz, 2 H),
7.43 (d, J = 8.5 Hz, 2 H), 7.66 (d, J = 15.5 Hz, 1 H), 16.53 (s, 1 H)
ppm. 13C NMR (CDCl3, 125 MHz): δ = 13.6, 24.2, 24.8, 116.4,
119.2, 128.2, 128.5, 132.3, 135.4, 139.8, 175.2, 192.4, 195.7 ppm.
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˜
C15H15ClO3S (310.04): calcd. C 57.97, H 4.86; found C 58.22, H
4.67.
5-Acetyl-6-(ethylthio)-2-(4-nitrophenyl)-2,3-dihydropyran-4-one
1
(3m): White solid; m.p. 134–136 °C. H NMR (CDCl3, 500 MHz):
δ = 1.29 (t, J = 7.5 Hz, 3 H), 2.54 (s, 3 H), 2.82 (dd, J = 3.0,
2008
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Received: December 18, 2008
Published Online: March 2, 2009
Eur. J. Org. Chem. 2009, 2003–2009
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2009