The reaction of N-tosyl imines with heteroaromatic compounds: A new access to triheteroarylmethanes

Article abstract of DOI:10.1016/j.tet.2010.06.070

Useful triheteroarylmethanes were prepared by the double Friedel-Crafts reaction of a wide variety of aromatic N-tosyl imines with furan, thiophene, and pyrrole in the presence of Cu(OTf)₂ and Montmorillonite K-10 clay catalysts.

Full text of DOI:10.1016/j.tet.2010.06.070

Tetrahedron 66 (2010) 6765e6768
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The reaction of N-tosyl imines with heteroaromatic compounds: a new
access to triheteroarylmethanes
*
Baris Temelli, Dilek Isik Tasgin, Canan Unaleroglu
Hacettepe University, Department of Chemistry, Beytepe Campus, 06800, Ankara, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Useful triheteroarylmethanes were prepared by the double FriedeleCrafts reaction of a wide variety of
aromatic N-tosyl imines with furan, thiophene, and pyrrole in the presence of Cu(OTf)2 and Montmo-
rillonite K-10 clay catalysts.
Received 9 March 2010
Received in revised form
10 June 2010
Accepted 24 June 2010
Available online 3 July 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Triarylmethane
N-tosyl imine
Metal triflate
Montmorillonite clay
1. Introduction
Recent work in our laboratories have shown that metal tri-
flates are effective reusable catalysts for the addition of pyrrole
Triarylmethanes have attracted much attention as leuco dyes,1
protecting groups2 and photochromic agents.3 Furthermore, the
ring hydroxylated triarylmethanes show antitumor and antioxidant
properties.4 Within the context of wide-ranging applications of
triarylmethanes, triheteroarylmethanes find many applications in
non-linear optics and conducting polymers.5 Diheteroarylmethanes
are also used in the food industry as natural components of certain
food and beverage items.6 While many methods, such as the direct
condensation of arenes with aldehydes and the reaction of benz-
hydroles with aromatic compounds7are available for the prepara-
tion of triarylmethanes, the synthesis of triheteroarylmethanes is
less developed. These compounds have been prepared through the
condensation of heteroaromatic compounds with (i) aldehydes,8aef
(ii) vinyl aromatic compounds8g and (iii) triethylorthoformate8h,i in
the presence of different catalysts, such as P2O5,8e AuCl3,8d,f NaHSO4.
SiO2,8c Montmorillonite clays8a,c,h and ionic liquids.8b The quest for
cheap, environmentally friendly catalysts and mild reaction condi-
tions is still a major challenge for the synthesis of triheteroaryl-
methanes. Herein we report a convenient and practical method for
the synthesis of these compounds by the condensation of hetero-
aromatic compounds with N-tosyl imines using two reusable and
efficient catalysts, Cu(OTf)2 and Montmorillonite K-10 clay.
to a,b
-unsaturated compounds and N-tosyl imines.9 meso-
Substituted dipyrromethanes were obtained by double Frie-
deleCrafts reaction of pyrrole with N-tosyl imines and these
compounds were used in the synthesis of meso-substituted tet-
raphenylporphyrins.10 In an effort to further broaden the reper-
toire of applications of metal triflates as environmentally benign
catalysts for organic reactions, we decided to extend our studies
to the synthesis of triheteroarylmethanes.
2. Results and discussion
The condensation of N-((1H-pyrrol-2-yl)methylene)-4-methyl-
benzenesulfonamide (1a) with pyrrole was selected as a model
reaction to determine the optimum reaction conditions (Scheme 1).
Our attempt was started by investigating the effect of different N-
tosyl imine/pyrrole ratios on the yield of product 2a. Reactions with
1e10 equiv of pyrrole were performed in THF in the presence of Cu
(OTf)2 (10 mol %) at room temperature and resulted in low yields
(<20%). When the amount of pyrrole was increased and used as
both reagent and solvent, the highest yield (85%) was obtained with
40 equiv of pyrrole. Further increasing the equivalents of pyrrole
did not affect the yield of 2a.
Then the activity of a number of catalysts was determined using
the model reaction (Scheme 1). A control experiment showed that
no reaction was observed in the absence of catalyst even after
a long reaction time (48 h) (Table 1, entry 1). Screening of a series of
* Corresponding author. Tel.: þ90 312 297 7962; fax: þ90 312 299 2163; e-mail
address: canan@hacettepe.edu.tr (C. Unaleroglu).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.06.070

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B. Temelli et al. / Tetrahedron 66 (2010) 6765e6768
Table 2
Ts
H
Cu(OTf)2 and Mont. K-10 catalyzed reactions of N-tosyl imines with heteroaromatic
compounds
HN
N
10% Cu(OTf)2
rt
H
N
Ts
Ar-H (40 equiv),
+
N
Ar
Cu(OTf)2 (10 mol %) or
Mont. K-10(0.5 g), rt.
N
H
NH
Ar-H
+
NH
R
H
R
Ar
1
1a
2
2a
Scheme 1. Synthesis of tri(1H-pyrrol-2-yl)methane.
Entry
1
R
Ar
Product Catalyst
Time Yielda
(h)
(%)
Cu(OTf)2
1
85
1a
metal triflate catalysts for the model reaction revealed that Nd and
La-triflates catalyzed the reaction with low yields (Table 1, entries 8
and 9). Gd, Y, Yb, Sc, and Zn-triflates gave the product with mod-
erate yields (Table 1, entries 3e7). The highest yield of 2a (85%) was
obtained with Cu(OTf)2 (Table 1, entry 2).
2a
N
N
H
H
2
Mont. K-10
Cu(OTf)2
2
1
4
1
85
60
40
62
40
80
75
87
94
55
66
60
26
30
d
3
1b
1b
1b
1c
2b
2c
2d
2e
2f
S
O
4
Mont. K-10
Cu(OTf)2
Table 1
Effects of catalysts on the synthesis of 2aa
5
Entry
Catalyst
Time/h
Yieldb (%) of 2a
1
2
3
4
5
6
7
8
None
48
1
1
1
1
1
1
1
1
0.5
0.5
0.5
1
3
3
2
48
2
d
S
S
S
6
Mont. K-10 2b
Cu(OTf)2
Gd(OTf)3
Y(OTf)3
Yb(OTf)3
Sc(OTf)3
Zn(OTf)2
Nd(OTf)3
La(OTf)3
H2SO4
HCl
TFA
TsOH
CuBr2
85
65
58
77
54
65
23
24
65
55
82
84
82
44
80
d
7
Cu(OTf)2
1
2
N
H
8
Mont. K-10
Cu(OTf)2
9
10
11
12
13
14
15
16
17
18
9
1
N
H
O
10
11
12
13
14
15
Mont. K-10
Cu(OTf)2
6
AlCl3
FeCl3
1
Mont. KSFc
Mont. K-10c
1d
N
H
85
N
H
Mont. K-10
Cu(OTf)2
4
a
Reaction conditions: N-tosyl imine (0.5 mmol), pyrrole (20 mmol), catalyst
(10 mol %), room temperature.
b
Yield refers to pure product after column chromatography.
Clay (0.5 g) was used.
1
c
2g
1e
O
Mont. K-10
Cu(OTf)2
4
These variations in the product yields prompted us to
examine other Lewis acids or protic acids and compare their
activity with Cu(OTf)2. Two liquid acid catalysts, H2SO4 and HCl,
yielded the product with 65% and 55% yields, respectively
(Table 1, entries 10 and 11). Some traditional catalysts, such as
CuBr2, FeCl3, and p-toluenesulfonic acid catalyzed the reaction
with comparable yields to Cu(OTf)2 (80e84% yields). Two clays,
KSF and K-10, having wide applications in organic synthesis
were also tested. Although Montmorillonite K-10 clay gave the
product with 85% yield, KSF clay did not provide any product at
all (Table 1, entries 17 and 18).
Having found that two non-toxic, environmentally benign,
reusable compounds, Cu(OTf)2 and Montmorillonite K-10 clay, are
the most effective catalysts in the synthesis of triheteroaryl-
methanes, we then tested the applicability of the current method
to the reaction of different N-tosyl imines with heteroaromatic
compounds. As shown in Table 2, Cu(OTf)2 catalyst formed all
products within a shorter time than Montmorillonite K-10 did. In
all cases except 2e and 2f, the reactions gave higher yields with
Cu(OTf)2 than with Montmorillonite K-10. Cu(OTf)2 promoted the
reaction of phenyl substituted N-tosyl imine with thiophene in
low yields, while Montmorillonite K-10 failed to catalyze this
reaction (Table 2, entries 15 and 16).
4b
2h
1e
S
16
Mont. K-10 24
a
Yield refers to pure product after column chromatography.
The reaction was carried out at 60 ꢀC.
b
The same method was applied to the addition of furane and thio-
phene to N-(furan-2-ylmethylene)-4-methylbenzenesulfonamide
(1c). However, studies with Cu(OTf)2 and Montmorillonite K-10 cat-
alysts proved ineffective, providing recovered starting materials.
Taking account of this failure, other catalysts and harsher reaction
conditions were carried out. 2i and 2j were synthesized in the pres-
ence of aqueous HCl at room temperature in 89% and 30% yields,
respectively (Scheme 2).
Moreover, we tested Cu(OTf)2 and Montmorillonite K-10 clay on
the reaction of 2-pyridyl substituted N-tosyl imine 1f with pyrrole
under the conditions given in Table 2. Montmorillonite K-10 did not
provide any product and only the starting materials were recovered
after long reaction times. Surprisingly, Cu(OTf)2 catalyzed the
reaction by affording a triple arylation product 3 at 60 ꢀC in 25%
yield (Scheme 3).

B. Temelli et al. / Tetrahedron 66 (2010) 6765e6768
6767
4.2. General procedure for Cu(OTf)2 and Montmorillonite
K-10 clay catalyzed synthesis of triarylmethanes (2aeh)
Ts
H
O
N
HCl (aq)
rt
N-Tosyl imine (0.5 mmol) was dissolved in excess hetero-
aromatic compound (20 mmol) and catalyst (0.05 mmol Cu(OTf)2
or 0.5 g Montmorillonite K-10) was added to the reaction mixture
at the temperature indicated in Table 2. The reaction was monitored
with TLC and completed at the appropriate time indicated in Table
2. The catalyst was removed from the reaction medium by sub-
jecting the mixture to a short flash silica gel chromatography using
ethyl acetate as an eluent. The eluent was removed under reduced
pressure and the residue was purified by flash silica gel
chromatography.
+
O
O
O
O
O
S
1c
2i
Ts
H
O
S
N
HCl (aq)
rt
+
S
4.3. General procedure for HCl (aq) catalyzed synthesis of
triarylmethanes (2i and 2j)
1c
2j
N-(Furan-2-ylmethylene)-4-methylbenzenesulfonamide
(1c)
Scheme 2. Synthesis of triheteroarylmethanes 2i and 2j.
(0.5 mmol) was dissolved in excess heteroaromatic compound
(20 mmol) and then 1 mL of concd HCl (aq) was added to the
reaction mixture at room temperature. The reaction was moni-
tored with TLC and completed after 24 h. The mixture was
subjected to a short flash silica gel chromatography using ethyl
acetate as an eluent. The eluent was removed under reduced
pressure and the residue was purified by flash silica gel
chromatography.
Ts
N
HN
H
N
10% Cu(OTf)2
60 oC
H
+
N
H
N
N
NH
4.4. Experimental procedure for the synthesis of 2-(tri(1H-
pyrrol-2-yl)methyl)pyridine (3)
1f
3
4-Methyl-N-(pyridin-2-ylmethylene)benzenesulfonamide (1f)
(0.5 mmol) was dissolved in excess pyrrole (20 mmol) and then Cu
(OTf)2 (0.05 mmol) was added to the reaction mixture at room
temperature. The reaction was heated at 60 ꢀC by monitoring with
TLC. After 6 h, the mixture was cooled to room temperature and
subjected to a short flash silica gel chromatography using ethyl
acetate as an eluent. The eluent was removed under reduced
pressure and the residue was purified by flash silica gel
chromatography.
Scheme 3. Synthesis of tetraheteroarylmethane 3.
3. Conclusion
In summary, we have described a new method for the prepa-
ration of triheteroarylmethanes through the double FriedeleCrafts
reaction of a wide variety of aromatic N-tosyl imines with furan,
thiophene, and pyrrole in the presence of Cu(OTf)2 and Montmo-
rillonite K-10 clay catalysts. The notable features of this method are
the mild reaction conditions, cleaner reaction profiles, and the use
of recoverable environmentally friendly catalysts.
4.5. Spectroscopic data of the products
4.5.1. Tri(1H-pyrrol-2-yl)methane (2a)8g. Pale yellow crystals; mp
133e134 ꢀC; yield: 90 mg, 85%; Rf 0.34 (1:3 EtOAc/hexane); IR
(ATR): 3449, 3369, 3106, 1559, 1464, 1403, 1315, 1258, 1125, 1087,
1030, 973, 878, 821, 772, 722, 661 cmꢁ1; 1H NMR (400 MHz, CDCl3):
4. Experimental
4.1. General
d
5.35 (s, 1H), 5.92 (br s, 3H), 6.06 (dd, J¼2.8, 5.6, 3H), 6.50e6.52 (m,
3H), 7.68 (br s, 3H); 13C NMR (100 MHz, CDCl3):
d
37.3, 106.9, 108.6,
Commercially available reagents and solvents were used
without further purification. 1H NMR (400 MHz) and 13C NMR
(100 MHz) spectra were recorded using SiMe4 as an internal
reference with Bruker 400 FT NMR spectrometer. Data for 1H are
reported as follows: chemical shift (ppm) and multiplicity
(s¼singlet, d¼doublet, t¼triplet, dd¼doublet of doublet,
m¼multiplet, br s¼broad singlet). Coupling constants are
expressed as J values in hertz. Data for 13C NMR are reported as
parts per million. Infrared spectra were taken by ATR (Nicolet
iS10) and are reported in cmꢁ1. Elemental analysis experiments
were performed by Elementar Micro Vario CHNS. Melting points
were recorded on Gallenkamp melting-point apparatus.
Reactions were monitored by thin layer chromatography using
60F silica gel plates. Flash column chromatography was per-
formed on silica gel 60 F254 (230e400 mesh). The spots were
117.3, 131.1. Anal. Calcd for C13H13N3: C, 73.91; H, 6.20; N, 19.89.
Found: C, 73.60; H, 6.42; N, 19.98.
4.5.2. 2,20-(Thiophen-2-ylmethylene)difuran (2b). Brown viscous
oil; yield: 69 mg, 60%; Rf 0.77 (1:3 EtOAc/hexane); IR (ATR): 3118,
2963, 2927, 2852, 1731, 1592, 1501, 1434, 1378, 1228, 1164, 1147,
1073, 1009, 946, 885, 760, 731, 695 cmꢁ1 1H NMR (400 MHz,
;
CDCl3):
6.82e6.83 (m, 1H), 6.85e6.89 (m, 1H), 7.13 (dd, J¼1.2, 5.2, 1H),
7.29e7.31 (m, 2H); 13C NMR (100 MHz, CDCl3):
40.0, 107.3,
d
5.65 (s, 1H), 6.07 (d, J¼3.2, 2H), 6.26 (dd, J¼1.6, 3.2, 2H),
d
110.3, 124.8, 125.8, 126.7, 142.0, 142.3, 153.7. Anal. Calcd for
C13H10O2S: C, 67.80; H, 4.38; S, 13.92. Found: C, 67.55; H, 4.42; S,
14.06.
4.5.3. Trithiophen-2-ylmethane (2c). Brown viscous oil; yield:
81 mg, 62%; Rf 0.80 (1:3 EtOAc/hexane); IR (ATR): 3102, 2963, 2927,
visualized with UV light (l¼254 nm). N-tosyl imines (1aef) are
synthesized in high yields by the reaction of p-toluenesulfona-
mide and aldehydes in the presence of p-toluenesulfonic acid.
2852, 1735, 1457, 1378, 1271, 1231, 1104, 1016, 862, 806, 691 cmꢁ1
;
1H NMR (400 MHz, CDCl3):
d 6.04 (s, 1H), 6.86e6.88 (m, 6H), 7.14

6768
B. Temelli et al. / Tetrahedron 66 (2010) 6765e6768
(dd, J¼1.6, 4.8, 3H); 13C NMR (100 MHz, CDCl3):
d
42.5, 124.8, 125.8,
2856, 1728, 1616, 1509, 1457, 1414, 1229, 1144, 1076, 1010, 929, 853,
756, 732, 693 cmꢁ1; 1H NMR (400 MHz, CDCl3):
5.79 (s, 1H), 6.09
126.6, 147.2. Anal. Calcd for C13H10S3: C, 59.50; H, 3.84; S, 36.66.
Found: C, 59.29; H, 4.15; S, 36.56.
d
(d, J¼3.2, 1H), 6.26 (dd, J¼2.0, 3.2, 1H), 6.83e6.84 (m, 2H), 6.88 (dd,
J¼3.6, 4.8, 2H), 7.14e7.15 (m, 2H), 7.31 (br s,1H); 13C NMR (100 MHz,
4.5.4. 2,20-(Thiophen-2-ylmethylene)bis(1H-pyrrole) (2d)11a,b. Brown
crystals; mp 119e120 ꢀC; yield: 91 mg, 80%; Rf 0.56 (1:3 EtOAc/
hexane); IR (ATR): 3349, 3106, 2959, 2915, 2844, 1716, 1561, 1461,
CDCl3): d 41.2, 107.4, 110.3, 124.8, 125.8, 126.6, 142.1, 144.8, 155.4.
Anal. Calcd for C13H10OS2: C, 63.38; H, 4.09; S, 26.03. Found: C,
63.12; H, 4.23; S, 26.24.
1263, 1235, 1112, 1096, 1023, 798, 733, 710, 675 cmꢁ1 1H NMR
;
(400 MHz, CDCl3):
2H), 6.54e6.56 (m, 2H), 6.77e6.78 (m, 1H), 6.84e6.86 (m, 1H),
7.10e7.11 (m, 1H), 7.78 (br s, 2H); 13C NMR (100 MHz, CDCl3):
39.1,
107.1, 108.5, 117.4, 124.5, 125.5, 126.7, 131.9, 145.7. Anal. Calcd for
C13H12N2S: C, 68.39; H, 5.30; N, 12.27; S, 14.04. Found: C, 68.51; H,
5.18; N, 12.07; S, 14.24.
d
5.60 (s, 1H), 5.94 (br s, 2H), 6.06 (dd, J¼2.8, 6.0,
4.5.11. 2-(Tri(1H-pyrrol-2-yl)methyl)pyridine (3). White powder;
mp 172e173 ꢀC; yield: 36 mg, 25%; Rf 0.61 (1:3 EtOAc/hexane);
IR (ATR): 3444, 3399, 3330, 2962, 2929, 2860, 1712, 1540, 1426,
d
1266, 1209, 1091, 1029, 886, 800, 719 cmꢁ1 1H NMR (400 MHz,
;
CDCl3):
4H), 7.11e7.14 (m, 1H), 7.50e7.52 (m, 1H), 8.57e8.58 (m, 1H),
8.90 (br s, 3H); 13C NMR (100 MHz, CDCl3):
51.6, 107.8, 108.3,
d
5.73 (br s, 3H), 6.08 (dd, J¼2.8, 6.0, 3H), 6.67 (br s,
d
4.5.5. 2,20-(Furan-2-ylmethylene)bis(1H-pyrrole) (2e)11b,c. Pale yel-
low oil; yield: 100 mg, 94%; Rf 0.56 (1:3 EtOAc/hexane); IR (ATR):
3388, 3094, 2967, 2923, 2852, 1708, 1569, 1509, 1461, 1430, 1406,
117.5, 122.0, 122.9, 134.1, 136.9, 148.3, 164.6. Anal. Calcd for
C18H16N4: C, 74.98; H, 5.59; N, 19.43. Found: C, 74.66; H, 5.73;
N, 19.61.
1259, 1092, 1028, 1012, 893, 711 cmꢁ1 1H NMR (400 MHz, CDCl3):
;
d
5.45 (s, 1H), 5.94 (br s, 2H), 6.08e6.11 (m, 3H), 6.29e6.31 (m, 1H),
6.61 (br s, 2H), 7.36 (br s, 1H), 7.95 (br s, 2H); 13C NMR (100 MHz,
CDCl3): 37.8, 106.9, 107.0, 108.5, 110.3, 117.5, 129.9, 141.9, 154.5.
Acknowledgements
d
Anal. Calcd for C13H12N2O: C, 73.56; H, 5.70; N, 13.20. Found: C,
73.88; H, 5.67; N, 13.24.
The authors thank Hacettepe University for financial support
(BAP project 07A601004).
4.5.6. 3-(Di(1H-pyrrol-2-yl)methyl)-1H-indole (2f). Pale yellow oil;
yield: 86 mg, 66%; Rf 0.55 (1:3 EtOAc/hexane); IR (ATR): 3404, 3110,
3058, 2959, 2923, 2856, 1676, 1561, 1461, 1414, 1342, 1259, 1227,
Supplementary data
1092, 1024, 885, 778, 718 cmꢁ1 1H NMR (400 MHz, CDCl3):
; d 5.71
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tet.2010.06.070.
(s, 1H), 6.00 (br s, 2H), 6.11 (br s, 2H), 6.57 (br s, 2H), 6.86 (br s, 1H),
7.00 (t, J¼7.2, 1H), 7.14 (t, J¼7.2, 1H), 7.28e7.30 (m, 2H), 7.92 (br s,
3H); 13C NMR (100 MHz, CDCl3):
d 35.5, 106.6, 108.6, 111.2, 116.6,
117.5, 119.7, 120.0, 122.5, 123.0, 126.7, 132.5, 136.7. Anal. Calcd for
C17H15N3: C, 78.13; H, 5.79; N, 16.08. Found: C, 77.88; H, 5.92; N,
16.20.
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2967, 2935, 2860, 1728, 1596, 1502, 1453, 1374, 1227, 1175, 1144,
1084, 1010, 953, 889, 780, 725, 697 cmꢁ1 1H NMR (400 MHz,
;
CDCl3):
2H), 7.20e7.29 (m, 5H), 7.33 (br s, 2H); 13C NMR (100 MHz,
CDCl3): 45.1, 107.6, 110.3, 127.2, 128.5, 128.6, 139.6, 141.9, 154.5.
d
5.41 (s, 1H), 5.98 (d, J¼2.8, 2H), 6.28 (dd, J¼1.6, 2.8,
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A.; Dwivedy, I.; Ray, S. Synth. Commun. 1997, 27, 2877.
8. (a) Chakrabarty, M.; Sarkar, S. Tetrahedron Lett. 2002, 43, 1351; (b) Yadav, J. S.;
Reddy, B. V. S.; Sunitha, S. Adv. Synth. Catal. 2003, 345, 349; (c) Ramesh, C.;
Banerjee, J.; Pal, R.; Das, B. Adv. Synth. Catal. 2003, 345, 557; (d) Nair, V.; Ab-
hilash, K. G.; Vidya, N. Org. Lett. 2005, 7, 5857; (e) Nair, V.; Thomas, S.; Mathew,
S. C.; Vidya, N.; Rath, N. P. Tetrahedron 2005, 61, 9533; (f) Nair, V.; Nidya, N.;
Abhilash, K. G. Synthesis 2006, 21, 3647; (g) Hong, S.-J.; Lee, M.-H.; Lee, C.-H.
Bull. Korean Chem. Soc. 2004, 25, 1545; (h) Chakrabarty, M.; Sarkar, S.; Linden,
A.; Stein, B. K. Synth. Commun. 2004, 34, 1801; (i) Reese, C. B.; Yan, H. Tetra-
hedron Lett. 2001, 42, 5545.
4.5.8. 2,20-(Phenylmethylene)dithiophene (2h)11d. Pale yellow crys-
tals; mp 67e68 ꢀC; yield: 38 mg, 30%; Rf 0.84 (1:3 EtOAc/hexane);
IR (ATR): 3068, 3027, 2959, 2919, 2848, 1728, 1457, 1374, 1231,
1076, 1024, 854, 802, 695 cmꢁ1
;
1H NMR (400 MHz, CDCl3):
d
5.82
(s, 1H), 6.78 (d, J¼3.6, 2H), 6.90 (dd, J¼3.6, 5.2, 2H), 7.17 (d, J¼5.2,
2H), 7.21e7.31 (m, 5H); 13C NMR (100 MHz, CDCl3):
47.6, 124.6,
d
126.1, 126.6, 127.2, 128.4, 128.6, 143.7, 147.7. Anal. Calcd for
C15H12S2: C, 70.27; H, 4.72; S, 25.01. Found: C, 69.92; H, 4.95; S,
25.13.
4.5.9. Trifuran-2-ylmethane (2i)11e. Colorless viscous oil; yield:
95 mg, 89%; Rf 0.85 (1:3 EtOAc/hexane); IR (ATR): 3114, 2927, 2852,
1728, 1596,1502,1381, 1235,1147, 1009, 946, 881, 773, 726 cmꢁ1; 1H
9. (a) Unaleroglu, C.; Temelli, B.; Demir, A. S. Synthesis 2004, 15, 2574; (b) Temelli,
B.; Unaleroglu, C. Tetrahedron Lett. 2005, 46, 7941; (c) Unaleroglu, C.; Yazici, A.
Tetrahedron 2007, 63, 5608; (d) Unaleroglu, C.; Aytac, S.; Temelli, B. Heterocycles
2007, 71, 2427; (e) Tasgin, D. I.; Temelli, B.; Yazici, A.; Aytac, S.; Unaleroglu, C.
Lett. Org. Chem. 2008, 5, 165.
NMR (400 MHz, CDCl3):
6.20e6.22 (m, 3H), 7.24e7.26 (m, 3H); 13C NMR (100 MHz, CDCl3):
39.0,107.4,110.4,141.9,152.0. Anal. Calcd for C13H10O3: C, 72.89; H,
d 5.43 (s, 1H), 5.99e6.00 (m, 3H),
10. (a) Temelli, B.; Unaleroglu, C. Tetrahedron 2006, 62, 10130; (b) Temelli, B.;
Unaleroglu, C. Tetrahedron 2009, 65, 2043.
d
11. (a) Papamicael, C. A.; Mongin, O.; Gossauer, A. J. Heterocycl. Chem. 2007, 44,
1071; (b) D’Auria, M.; De Luca, E.; Esposito, V.; Mauriello, G.; Racioppi, R. Tet-
rahedron 1997, 53, 1157; (c) Zhang, Y.; Liang, J.; Shang, Z. Chin. J. Chem. 2010, 28,
259; (d) Cho, W.-S.; Lee, C.-H. Bull. Korean Chem. Soc. 1998, 19, 314; (e) Kurata,
H.; Oki, Y.; Matsumoto, K.; Kawase, T.; Oda, M. Chem. Lett. 2005, 34, 910.
4.71. Found: C, 73.10; H, 4.55.
4.5.10. 2-(Dithiophen-2-ylmethyl)furan (2j). Pale brown oil; yield:
37 mg, 30%; Rf 0.76 (1:3 EtOAc/hexane); IR (ATR): 3106, 2955, 2922,