Facile synthesis of 2-aroyl-3,5-diarylthiophene

Article abstract of DOI:10.1081/SCC-120022174

2-Aroyl-3,5-diarylthiophenes were prepared in very good yields by reaction of 2,4,6-triarylpyrylium salts or 2,4,6-triarylthiopyrylium salts with an aqeous solution of sodium sulfide and iodine at room temperature.

Full text of DOI:10.1081/SCC-120022174

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Facile Synthesis of 2-Aroyl-3,5-diarylthiophene
Jin-Xian Wang a , Xiaoning Shi a , Xiuqin Men a & Lianbiao Zhao a
a Institute of Chemistry, Department of Chemistry, Northwest Normal University, Lanzhou,
P.R. China
Published online: 19 Aug 2006.
To cite this article: Jin-Xian Wang , Xiaoning Shi , Xiuqin Men & Lianbiao Zhao (2003): Facile Synthesis of 2-Aroyl-3,5-
diarylthiophene, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 33:16, 2849-2856
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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 16, pp. 2849–2856, 2003
Facile Synthesis of 2-Aroyl-3,5-diarylthiophene
*
Jin-Xian Wang, Xiaoning Shi, Xiuqin Men,
and Lianbiao Zhao
Institute of Chemistry, Department of Chemistry,
Northwest Normal University, Lanzhou, P.R. China
ABSTRACT
2-Aroyl-3,5-diarylthiophenes were prepared in very good yields by
reaction of 2,4,6-triarylpyrylium salts or 2,4,6-triarylthiopyrylium
salts with an aqeous solution of sodium sulfide and iodine at room
temperature.
Key Words: Ring-chain transformation; Synthesis; 2-Aroyl-3,5-
diarylthiophene.
Ring-chain transformation reactions of heterocycles have been
proven to be a powerful tool for the synthesis of a wide range of
carbocyclic as well as heterocyclic compounds.[1] The ring transforma-
tion reactions of pyryliums and thiopyryliums have been known for a
*Correspondence: Jin-Xian Wang, Institute of Chemistry, Department of
Chemistry, Northwest Normal University, 805 An Ning Road (E.) Lanzhou,
730070, P.R. China; Fax: þ86 931-7768159; E-mail: Wangjx@nwnu.edu.cn.
2849
DOI: 10.1081/SCC-120022174
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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2850
Wang et al.
long time.[2] Many reactions about this method also have been stu-
died.[3] The previous article by Pedersen[4,5] concerning the reaction of
2,4,6-triphenylpyrylium tetrafluoroborate with sodium sulfide and
iodine that give the product of 2-benzoyl-3,5-diphenylthiophene. The
mechanism of this reaction is thought to 2,4,6-triphenylpyrylium tetra-
fluoroborate when treated with an aqeous solution of sodium sulfide
gives an intensely colored solution, possibly due to formation of the
anion of II (Sch. 1). Upon addition of iodine, the reaction is thought to
involve iodination of the anion of the pseudobase followed by intra-
molecular displacement of iodide ion. But the scope of this reaction was
notexplored.
Sulfide-containing heterocyclic compounds, especially, sulfide
substituted five-member heterocyclic compounds are very important in
both organic synthesis and industrial fields.[6] It has been reported that
2-aroylthiophene derivatives are the materials for the preparation of
2-diaroylaminothiophene, the later is the most interesting developments
in dye chemistry.[7]
R1
O
R2
2
R1
BF3 OEt2
.
MV
C
CHO
CH3
+
+
O
R2
1
R2
2
BF4-
I
Na2S
R1
R1
H+
+
BF4-
R2
S
R2
O
s
R2
R2
III
II
R1
Na2S/I2
I2
Method B
Method A
R2
R2
S
O
3
Scheme 1.

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2-Aroyl-3,5-diarylthiophene
2851
Keeping in view the above facts, we have explored the scope of this
reaction. We have found the reaction to be general for a variety of sub-
stitutents on the aryl rings and to proceed to give reasonable yields
(65–72%) of 2-aroyl-3,5-diarylthiophene 3a–j. The reactions are shown
in Sch. 1 and the corresponding results are summarized in Table 1.
Table 1. The products of 2,4,6-triarylpyryliums or 2,4,6-triarylthiopyryliums
with sodium sulfide and iodine.d
Yielda,c
(%)
Yieldb,c
(%)
Entry
R1
R2
Product
3a
H
H
68
71
64
67
60
83
92
89
85
77
S
O
3b
3c
3d
3e
H
H
4-Br
4-Cl
4-CH3
H
Br
Br
Cl
S
O
Cl
S
O
H
CH3
CH3
S
O
OCH3
4-OCH3
S
O
OCH3
3f
4-OCH3
4-OCH3
4-Cl
4-Cl
4-CH3
H
68
66
72
80
78
90
Cl
Cl
S
O
OCH3
3g
3h
CH3
CH3
S
O
Cl
Cl
Cl
S
O
3i
3j
4-Cl
4-Cl
4-Cl
75
69
93
93
Cl
Cl
S
O
4-CH3
CH3
CH3
S
O
aThe yield of the product of Method A.
bThe yield of the product of Method B.
c Isolated yield.
1
dAll new compounds were determined by H NMR, MS, and microanalyses.

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2852
Wang et al.
At the same time, we have observed the same reaction sequence for a
series of 2,4,6-triarylthiopyrylium salts. Thus, reaction of the salts IIIa–j
with sodium sulfide and iodine in acetone led to the formation of the
corresponding 2-aroyl-3,5-diarylthiophene 3a–j in excellentyields
(See Table 1).
Compared to the reaction of 2,4,6-triarylpyryliums with sodium
sulfide and iodine, this reaction formed only desired thiophene
derivatives and no other byproducts (pseudobase) were isolated.
To determine suitable reaction conditions, using the synthetic reac-
tion of 2,4,6-triphenylthiopyrylium salt with aqeous sodium sulfide and
iodine as an example, we investigated the efficiency of various solvents
on the formation of 2-benzoyl-3,5-diphenylthiophene, and acetone was
found to be the best solvent. Other solvents were also studied and
their efficiency are in the order: acetone ꢀ trichloromethane> benzene>
dichloromethane>ethanol>DMF. Specially, when DMF is used as
solvent in this reaction, the yield of compound 3a is considerably
poor. In addition, we have investigated the effect of different substitu-
tents for this reaction, and found that the presence of either very strong
electron groups or electron withdrawers represents apparent limitations
of this method. For example, in our hands, 2,4,6-tris(4-nitrophenyl)-
and 2,4,6-tris-(4-cyanophenyl)pyrylium tetrafluoroborate were unstable,
and could notbe used in htis process, and 2,4,6- tris(4-N,N-dimethyl-
aminophenyl)pyrylium tetrafluoroborate is formed only in very low
yields.
In summary, we suggest that the present reaction is a convenient
synthetic method of preparing 2-aroyl-3,5-diarylthiophenes.
EXPERIMENTAL
Melting points were determined with an Electrothermal
1
Micromelting point apparatus and are uncorrected. H NMR data were
recorded on an FT-80 spectrometer with CDCl3 as solventand TMS as
internal reference. Mass spectra were obtained on a Nippon Shimadzu
QP-100 GC-MS spectrometer. Elemental analysis was performed on a
Carlo-Erba 1106 Elemental Analysis Instrument.
2,4,6-Triarylpyrylium salts Ia–j and 2,4,6-triarylpyrylium salts IIIa–j
were prepared according to literature procedures.[8]

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2-Aroyl-3,5-diarylthiophene
2853
Typical Produce for Preparation of
2-Benzoyl-3,5-diphenylthiophene
Method A. 2,4,6-Triphenylpyrylium tetrafluoroborate (0.5 g,
1.26 mmol) was suspended in acetone (15 mL) and an aqeous solution
of sodium sulfide (0.6 g, 2.0 mmol) was added. The mixture was
stirred for 0.5 h. Iodine (1.0 g, 3.89 mmol) was then added, and stirring
was continued until the mixture turned into pale-yellow. After
addition of chloroform, excess iodine was removed by extraction with
dilute sodium thiosulfate. The organic phase was separated and dried
over sodium sulfate. After evaporation of the chloroform, the
crude productwas purified by column chromaotgraphy on silica gel
(petroleum/ethyl acetate 10:1) to give 3a (68%). M.p. 109–110
(Lit.[4] 103–104). 1H NMR (CDCl3): ꢀ 7.74–7.62 (t, 4H, J ¼ 6.2 Hz),
7.50–7.33 (m, 5H, J ¼ 6.8 Hz), 7.31–7.14 (m, 7H, J ¼ 4.9 Hz). MS
(m/e, %): 340 (Mþ, 100), 263 (52), 234 (28), 105 (26), 77 (78). Anal.
calcd. for C23H16OS: C, 81.14; H, 4.74; S, 9.42. Found: C, 81.16; H,
4.72; S, 9.38.
Method B. A mixture of 2,4,6-triphenylthiopyrylium tetrafluoro-
borate (0.2 g, 0.5 mmol) in acetone (10 mL) and sodium sulfide non-
ahydrate (0.2 g, 1.0 mmol) in water (5 mL) was stirred for 5 min.
Iodine (0.4 g, 1.5 mmol) was then added and stirring was continued
for 2 min. The pale-yellow mixture was poured into a solution of
Na2S2O3 (4 mmol) in water (10 mL) and the aqeous phase was extrac-
ted with CHCl3. The organic phase was washed with water, dried
with anhydrous Na2SO4, and evaporated in vacuo. The crude
productwas purified by simple crysatllizaiotn (hexane/benzene) ot
give 3a (83%).
3b. M.p. 188–189ꢁC (hexane/benzene). 1H NMR (CDCl3): ꢀ 7.55–7.39
(m, 6H, J ¼ 5.3 Hz), 7.29–7.17 (m, 8H, J ¼ 3.0 Hz). MS (m/e, %): 497
(M þ 1, 87), 343 (33), 234 (57), 185 (60), 155 (100), 103 (51), 89 (83), 75
(88). Anal. calcd. for C23H14OSBr2: C, 55.45; H, 2.83; S, 6.44. Found: C,
55.58; H, 2.86; S, 6.41.
3c. M.p. 181.5–182ꢁC (hexane/benzene). 1H NMR (CDCl3): ꢀ
7.65–7.51 (m, 4H, J ¼ 7.0 Hz), 7.44–7.36 (m, 3H, J ¼ 5.3 Hz), 7.26–7.11
(m, 7H, J ¼ 4.3 Hz). MS (m/e, %): 408 (Mþ, 62), 297 (22), 139 (48), 111
(100), 89 (48), 75 (66). Anal. calcd. for C23H14OSCl2: C, 76.40; H, 3.45;
S, 7.83. Found: C, 67.45; H, 3.32; S, 7.79.
3d. M.p. 157–158ꢁC (hexane/benzene). 1H NMR (CDCl3):
ꢀ
7.62–7.56 (m, 4H, J ¼ 6.0 Hz), 7.40 (s, 1H), 7.31–7.16 (m, 7H,
J ¼ 4.3 Hz), 7.02–6.98 (d, 2H, J ¼ 4.0 Hz), 2.40–2.30 (d, 6H, J ¼ 3.3 Hz).
MS (m/e, %): 368 (Mþ, 100), 277 (25), 249 (9), 119 (12), 91 (27), 77 (19),

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2854
Wang et al.
65 (10). Anal. calcd. for C25H20OS: C, 81.49; H, 5.47; S, 8.70. Found: C,
81.64; H, 5.35; S, 8.64.
3e. M.p. 90ꢁC (hexane/benzene). H NMR (CDCl3): ꢀ 7.73–7.62 (m,
1
4H, J ¼ 7.3 Hz), 7.47–7.12 (m, 10H, J ¼ 7.0 Hz), 6.72–6.67 (d, 1H), 3.74
(s, 3H). MS (m/e, %): 370 (Mþ, 100), 339 (4), 293 (31), 265 (91), 105 (17),
77 (35). Anal. calcd. for C24H18O2S: C, 77.81; H, 4.89; S, 8.66. Found: C,
77.90; H, 4.95; S, 8.63.
3f: M.p. 146–147ꢁC (hexane/benzene). 1H NMR (CDCl3): ꢀ 7.65–7.53
(m, 6H, J ¼ 4.0 Hz), 7.26 (s, 1H), 7.19–7.12 (m, 4H, J ¼ 3.5 Hz), 6.73–6.69
(d, 2H, J ¼ 4.0 Hz), 3.76 (s, 3H). MS (m/e, %): 438 (Mþ, 100), 407 (5); 327
(23), 139 (29), 111 (36), 81 (5). Anal. calcd. for C24H16O2SCl2: C, 65.61;
H, 3.67; S,7.30. Found: C, 65.61; H, 3.60; S, 7.24.
3g. M.p. 156–157ꢁC (hexane/benzene). 1H NMR (CDCl3): ꢀ 7.61–7.57
(d, 4H, J ¼ 4.0 Hz), 7.36–7.20 (m, 5H, J ¼ 6.4 Hz), 7.04–6.95 (d, 2H),
6.74–6.70 (d, 2H, J ¼ 4.0 Hz), 3.75 (s, 3H); 2.39–2.31 (d, 6H,
J ¼ 8.0 Hz). MS (m/e, %): 398 (Mþ, 100), 383 (10), 307 (21), 119 (16),
91 (30). Anal. calcd. for C26H22O2S: C, 78.36; H, 5.56; S, 8.05. Found: C,
78.34; H, 5.50; S, 8.02.
3h. M.p. 108–109ꢁC (hexane/benzene). 1H NMR (CDCl3): ꢀ 7.73–7.63
(m, 4H, J ¼ 5.0 Hz), 7.50–7.36 (m, 5H, J ¼ 5.6 Hz), 7.27–7.12 (m, 6H,
J ¼ 5.0 Hz). MS (m/e, %): 374 (Mþ, 31), 297 (16), 111 (10), 105 (33), 77
(100). Anal. calcd. for C23H15OSCl: C, 73.69; H, 4.03; S, 8.55. Found: C,
73.58; H, 4.01; S, 8.49.
3i. M.p. 190–191ꢁC (hexane/benzene). 1H NMR (CDCl3): ꢀ 7.64–7.56
(m, 2H, J ¼ 8.0 Hz), 7.44–7.36 (m, 2H, J ¼ 8.0 Hz), 7.26–7.19 (m, 9H,
J ¼ 4.7 Hz). MS (m/e, %): 443 (M þ 1, 100), 331 (38), 139 (47), 111 (60),
81 (10), 75 (26). Anal. calcd. for C23H13OSCl3: C, 62.25; H, 2.95; S, 7.23.
Found: C, 62.58; H, 2.98; S, 7.18.
3j. M.p. 155–157ꢁC (hexane/benzene). 1H NMR (CDCl3): ꢀ 7.60–7.56
(d, 4H, J ¼ 8.0 Hz), 7.35 (s, 1H), 7.26–7.14 (m, 6H, J ¼ 4.0 Hz), 7.07–7.03
(d, 2H, J ¼ 4.0 Hz), 2.40–2.34 (d, 6H, J ¼ 6.0 Hz). MS (m/e, %): 402 (Mþ,
51), 387 (3), 367 (2), 311 (16), 119 (50), 91 (100), 65 (52). Anal. calcd.
for C25H19OSCl: C, 74.52; H, 4.75; S, 7.96. Found: C, 74.41; H, 4.91;
S, 7.93.
ACKNOWLEDGMENTS
We thank the National Natural Science Foundation of China and
the Northwest Normal University Science and Technology Development
Foundation of China for financial support.

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2-Aroyl-3,5-diarylthiophene
2855
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Received in Japan October 17, 2002