Electrophilic 2-thienylselenenylation of thiophene. Preparation of oligo(seleno-2,5-thienylenes)

Article abstract of DOI:10.1016/S0040-4020(00)00245-3

The substitution reactions of thiophene and 2-methylthiophene with the electrophilic selenenylating agent produced from the 2,2'-dithienyl diselenide by oxidation with iodobenzene diacetate involve only the α- positions and give rise to the formation of oligo(seleno-2,5-thienylenes). Products deriving from the attack at the α-positions of thiophene and 2- methylthiophene were also observed starting from the 5,5'-dimethyl-2,2'- dithienyl diselenide. The same electrophilic reagents reacted with furan and 2-methylfuran to afford a mixture of the mono- and di-substituted compounds. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00245-3

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 3255±3260
Electrophilic 2-Thienylselenenylation of Thiophene.
Preparation of Oligo(seleno-2,5-thienylenes)
*
Marcello Tiecco, Lorenzo Testaferri, Luana Bagnoli, Francesca Marini, Andrea Temperini,
Cristina Tomassini and Claudio Santi
Á Á
Istituto di Chimica Organica, Facolta di Farmacia, Universita di Perugia, I-06100 Perugia, Italy
Received 28 December 1999; revised 28 February 2000; accepted 16 March 2000
AbstractÐThe substitution reactions of thiophene and 2-methylthiophene with the electrophilic selenenylating agent produced from the
2,20-dithienyl diselenide by oxidation with iodobenzene diacetate involve only the a-positions and give rise to the formation of oligo(seleno-
2,5-thienylenes). Products deriving from the attack at the a-positions of thiophene and 2-methylthiophene were also observed starting from
the 5,50-dimethyl-2,20-dithienyl diselenide. The same electrophilic reagents reacted with furan and 2-methylfuran to afford a mixture of the
mono- and di-substituted compounds. q 2000 Elsevier Science Ltd. All rights reserved.
We have recently reported that the strongly electrophilic
phenylselenenyl sulfate, which is easily produced from
the oxidation of diphenyl diselenide with ammonium
persulfate,1,2 can be conveniently employed to effect
electrophilic aromatic phenylselenenylation reactions on
activated substrates. Once introduced, the PhSe group acti-
vates the aromatic substrate to further substitution. Thus, for
instance, in the case of thiophene 1, substitution can take
place at the b-positions also. Under controlled experimental
conditions, it was thus possible to introduce the desired
number of PhSe groups and to produce mono 2, bis 3, tris
4 or tetrakis(phenylseleno)thiophene 5 (Scheme 1).3 Similar
results were also obtained by Engman and coworkers, who
found that the same reactions can be effected with alkyl-
selenenyl sulfates also.4 Tetrasubstituted thiophenes were
obtained in good yields with methyl, 1-butyl and 1-octyl-
selenenyl sulfates.
are treated with the electrophilic selenenylating agent
derived from the 2,20-dithienyl diselenide the substitution
reaction involves only the a-positions and gives rise to
the formation of oligo(seleno-2,5-thienylenes). Products
deriving from the attack at the a-positions of thiophene
and 2-methylthiophene were also observed starting from
the 5,50-dimethyl-2,20-dithienyl diselenide. Small amounts
of products in which substitution occurred at the b-position
also were obtained only in the case of the reaction of this
latter reagent with equimolecular amounts of 2-methyl-
thiophene. The same electrophilic reagents reacted with
furan and 2-methylfuran to afford a mixture of the mono-
and di-substituted compounds.
2,20-Dithienyl diselenide 6 was prepared, as reported in the
literature,5 from 2-thienyllithium6 and selenium metal
(Scheme 2). 5,50-Dimethyl-2,20-dithienyl diselenide 7 was
similarly obtained from 2-methylthiophene. The electro-
philic selenenylating agents were prepared by oxidation of
We now report that when thiophene and 2-methylthiophene
Scheme 1.
Keywords: dithienyl diselenides; electrophilic 2-thienylselenenylation; oligo(seleno-2,5-thienylenes).
* Corresponding author. Tel.: 139-075-5855100; fax: 139-075-5855116; e-mail: tiecco@unipg.it
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00245-3

3256
M. Tiecco et al. / Tetrahedron 56 (2000) 3255±3260
Scheme 2.
these diselenides. Preliminary experiments showed that in
the present case ammonium persulfate gave rise to several
secondary products. Oxidation was therefore effected under
milder conditions using iodobenzene diacetate, according to
the procedure recently proposed by us for the oxidation of
diphenyl diselenide.7 Under these conditions the electro-
philic reagents are suggested to be the 2-thienylselenenyl
acetates 8 and 9 (Scheme 2).
diselenide 6 employed. As expected, using a larger amount
of thiophene (100 mmol) the formation of compound 10 was
favored (50%). The amount of 11 was also increased to 30%
and compound 12 was still present, although in low yield
(8%).
The formation of compounds 11 and 12 even in the presence
of a large excess of thiophene indicates that the introduction
of the 2-thienylseleno groups activate the thiophene ring to
further electrophilic substitution.
The ®rst experiments were carried out with 6 and thiophene
in equimolecular amounts (1 mmol). These were treated
with iodobenzene diacetate (2 mmol) in acetonitrile
(6 ml) at room temperature for 24 h. Under these con-
ditions only polymeric material was obtained which was
not further investigated. A further experiment in which
10 mmol of thiophene were employed gave similar results.
The reaction was therefore repeated using a larger amount
of thiophene (50 mmol). A clean reaction mixture was
obtained in this case. This was composed of the 2-(2-
thienylseleno)thiophene 10, the 2,5-di(2-thienylseleno)thio-
phene 11 and the 2-(2-thienylseleno)-5-{[5-(2-thienyl-
seleno)-2-thienyl]seleno}thiophene 12 which could be
easily separated by column chromatography (Scheme 3).
Under these conditions the oligomer containing four thio-
phene rings 12 was the major reaction product, the three
products being formed in 8, 10 and 52% yield, respectively.
Reaction yields were calculated on the amount of the
Some interesting differences were observed when 6 was
allowed to react with the 2-methylthiophene under reaction
conditions identical to those reported above in the case of
thiophene.
An experiment carried out with 1 mmol of 6 and 100 mmol
of 2-methylthiophene afforded a mixture of the two
selenides 13 (78%) and 14 (15%) (Scheme 4). The yields
of these products changed to 62 and 31%, respectively,
when the amount of 2-methylthiophene was reduced to
50 mmol. It can be observed that the yield of the mono-
substituted product 13 was considerably greater than that
of the corresponding product 10 isolated from the reaction
in thiophene. Moreover the oligomer containing four thio-
phene rings 15, analogous to 12, was not formed at all in
either case. These results indicate that 2-methylthiophene is
Scheme 3.
Scheme 4.

M. Tiecco et al. / Tetrahedron 56 (2000) 3255±3260
3257
Scheme 5.
considerably more reactive than thiophene and therefore in
this case the reaction stops at the ®rst stages and affords
compound 13 together with small amounts of 14.8 Thus,
in order to obtain the product of further substitution the
amount of 2-methylthiophene must be greatly reduced.
Indeed, from an experiment in which 1 mmol only of 2-
methylthiophene was employed, leaving the amounts of
all the other reagents unchanged, a 27% yield of the selenide
15 was isolated together with a 42% yield of 14. Compound
15 could also be obtained as the sole reaction product, in
78% yield, from the reaction of 11 with an equimolecular
amount of the 5,50-dimethyl-2,20-dithienyl diselenide 7,
under experimental conditions identical to those reported
above for the reactions of 6 with thiophene and 2-
methylthiophene.
tions are still more reactive and the substitution selectively
affords the oligo(seleno-2,5-thienylene) compounds 12 and
15, respectively.
Starting from the diselenide 7, i.e. using the 2-methyl-2-
thienylselenenyl acetate 9 as the electrophilic reagent, the
formation of the oligo(seleno-2,5-thienylenes) should be
avoided and the reaction could give rise to polysubstituted
thiophenes as observed in the reactions of thiophene with
phenylselenenyl sulfate.3 In the presence of iodobenzene
diacetate (2 mmol), the 5,50-dimethyl-2,20-dithienyl
diselenide 7 (1 mmol) reacted with thiophene (50 mmol)
or with 2-methylthiophene (50 mmol), at room temperature
for 24 h, to give exclusively the products deriving from the
substitution at the a-positions. Thus, as indicated in Scheme
5 compound 13 (5%) and 16 (72%) were isolated from the
reaction of thiophene and compound 17 (78%) was obtained
from the reaction with 2-methylthiophene. The formation of
small amounts of the products deriving from substitution at
the b-position was observed only in the reaction carried out
with 1 mmol of 2-methylthiophene and 1 mmol of the
diselenide 7. In this case, in the initially formed selenide
The results reported in Schemes 3 and 4 indicate that the
attack of the electrophilic 2-thienylselenenylating agent
exclusively occurs at the very reactive a-positions. Thus,
for instance, in compounds 11 and 14, although the b-posi-
tions of the central thiophene rings are activated by the
presence of two thienylseleno groups,3 the available a-posi-
Scheme 6.

3258
M. Tiecco et al. / Tetrahedron 56 (2000) 3255±3260
Scheme 7.
17 no a-positions are available and the attack of the
selenenylating agent occurred at the b-positions to afford
two further products which were identi®ed as 18 (15%) and
19 (15%) (Scheme 5).
Mps were determined on a Ko¯er melting point apparatus
and are uncorrected.
Synthesis of 2,20-dithienyl diselenide (6) and of
5,50-dimethyl-2,20-dithienyl diselenide (7)
Finally, the electrophilic selenenylation of furan and
2-methylfuran was also examined. These experiments
were all carried out using 50 mmol of furan or 2-methyl-
furan and 1 mmol of diselenides 6 or 7 at room temperature.
The results obtained are summarised in the Schemes 6 and
7. In every case the reactions afforded good yields of the
substitution products deriving from attack at the available
a-positions of furan. Mixtures of compounds 20 and 21 and
22 and 23 were obtained from the reactions of furan with 6
and 7, respectively. These products were easily separated by
column chromatography and reaction yields are indicated in
parentheses in the Scheme.
22 ml (35 mmol) of 1.6 M n-butyllithium in hexane was
added to a solution of 3 g (35 mmol) of thiophene or 3.4 g
(35 mmol) of 2-methylthiophene in 25 ml of anhydrous
tetrahydrofuran under nitrogen at 2408C. After 1 h at
2308C the temperature of the reaction mixture was lowered
to 2708C and 2.8 g (35 mg atom) of powdered selenium
was added. After 30 min at 2708C the mixture was stirred
for 1 h at 2108C. The reaction was quenched with 20 ml of
10% aqueous NH4Cl solution and 2 g of potassium ferri-
cyanide were added. Stirring was continued overnight at
room temperature. The mixture was extracted with ether,
dried over Na2SO4 and evaporated. The dithienyl
diselenides were isolated in pure form after column chro-
matography on silica gel using light petroleum as eluant.
Physical and spectroscopic data of the two diselenides are
reported below.
As indicated in Scheme 7, the reactions of the two disele-
nides with 2-methylfuran gave rise to the formation of the
single products 24 and 25, respectively, which were isolated
in very good yields.
1
2,20-Dithienyl diselenide (6). Mp 60±628C; H NMR d
The results described in this paper demonstrate that the
diselenides 6 and 7 can be conveniently employed to
produce electrophilic 2-thienylselenenylating agents which
easily effect substitution reactions on thiophene and furan
derivatives. Of particular interest are the reactions of 6 with
thiophene and 2-methylthiophene since they represent a
very simple method to effect the syntheses of oligo(seleno-
2,5-thienylenes) which can have some practical interest as a
selenium rich donors from which ion radical salts could be
prepared.9
7.40 (dd, 2H, Jˆ1.2, 5.3 Hz), 7.18 (dd, 2H, Jˆ1.2,
3.5 Hz), 6.94 (dd, 2H, Jˆ3.5, 5.3 Hz); 13C NMR d 136.7
(two carbons), 132.7 (two carbons), 127.9 (two carbons),
125.5 (two carbons). MS m/z (relative intensity) 326 (22),
324 (19), 246 (20), 166 (100), 163 (65), 161 (32), 159 (12),
121 (15), 119 (19), 117 (13), 92 (11). Anal. Calcd for
C8H6S2Se2: C, 29.65; H, 1.87. Found: C, 29.51; H, 1.21.
5,50-Dimethyl-2,20-dithienyl diselenide (7). Mp 49±518C;
1H NMR d 6.98 (d, 2H, Jˆ3.5 Hz), 6.59 (dq, 2H, Jˆ0.9,
3.5 Hz), 2.47 (d, 6H, Jˆ0.9 Hz); 13C NMR d 147.7 (two
carbons), 137.1 (two carbons), 126.3 (two carbons), 122.9
(two carbons), 15.5 (two carbons). MS m/z (relative inten-
sity) 354 (2), 274 (16), 194 (100), 193 (39), 177 (12), 161
(19), 97 (26), 53 (8). Anal. Calcd for C10H10S2Se2: C, 34.11;
H, 2.86. Found: C, 34.01, H; 2.75.
Experimental
Starting materials were commercially available and were
used without further puri®cation. New compounds were
characterized by MS, 1H, and 13C NMR spectroscopy.
GLC analyses and MS spectra were carried out with an
HP 5890 gas chromatograph (dimethyl silicone column,
12.5 m) equipped with an HP 5971 Mass Selective Detector.
In the cases of the ions containing one or more selenium
Electrophilic thienylselenenylation of thiophene
derivatives
A mixture of dithienyl diselenide (6 or 7) (1 mmol),
PhI(OAc)2 (2 mmol) and thiophene derivatives was stirred
in acetonitrile (6 ml) at room temperature. As indicated
previously, the experiments with the diselenide 6 were
effected using 1, 50 or 100 mmol of thiophene or
2-methylthiophene. The reactions of the diselenide 7 were
1
atoms only the most prominent peaks are reported. H and
13C NMR spectra were recorded at 200 and 50.32 MHz,
respectively, on a Bruker AC 200 instrument; CDCl3 was
used as solvent and TMS as standard. Elemental analyses
were carried out on a Carlo Erba 1106 Elemental Analyzer.

M. Tiecco et al. / Tetrahedron 56 (2000) 3255±3260
3259
carried out using 50 mmol of thiophene and 50 or 1 mmol of
2-methylthiophene. The progress of the reactions was moni-
tored by TLC and GC±MS. The reaction mixture was
poured into a 10% aqueous Na2CO3 solution and extracted
with dichloromethane. The organic layer was dried over
Na2SO4 and evaporated. The reaction products were isolated
in pure form after column chromatography on silica gel
using light petroleum as eluant. Reaction times and yields
are reported in the discussion section. Physical and spectro-
scopic data of the reaction products, 10±19, are reported
below.
2-({5-[(5-Methyl-2-thienyl)seleno]-2-thienyl}seleno)-5-
(2-thienylseleno)thiophene (15). Mp 103±1058C; 1H NMR
d 7.38 (dd, 1H, Jˆ1.2, 5.3 Hz), 7.27 (dd, 1H, Jˆ1.2,
3.5 Hz), 7.08 (d, 1H, Jˆ3.5 Hz), 7.05±7.01 (m, 4H), 6.95
(dd, 1H, Jˆ3.5, 5.3 Hz), 6.61 (dq, 1H, Jˆ1.0, 3.5 Hz), 2.46
(d, 3H, Jˆ1.0 Hz); 13C NMR d 146.5, 136.0, 135.3 (two
carbons), 135.2, 134.5, 133.9, 132.8, 131.9, 131.3, 130.5,
129.8, 128.0, 126.2, 125.2, 121.9, 15.4. Anal. Calcd for
C17H12S4Se3: C, 35.15; H, 2.08. Found: C, 35.28; H, 2.09.
2-Methyl-5-({5-[(5-methyl-2-thienyl)seleno]-2-thienyl}-
seleno)thiophene (16). Mp 74±758C; H NMR d 7.05 (d,
1
1
2-(2-Thienylseleno)thiophene (10). Oil; H NMR d 7.36
2H, Jˆ3.5 Hz), 7.01 (s, 2H), 6.59 (dq, 2H, Jˆ1.0, 3.5 Hz),
2.44 (d, 6H, Jˆ1.0 Hz); 13C NMR d 146.3 (two carbons),
135.7 (two carbons), 134.2 (two carbons), 131.7 (four
carbons), 126.2 (two carbons), 15.4 (two carbons). MS
m/z (relative intensity) 436 (30), 431 (26), 356 (4), 276
(98), 261 (26), 259 (100), 257 (49), 194 (15), 178 (22),
138 (38), 97 (19), 35 (13). Anal. Calcd for C14H12S3Se2:
C, 38.72; H, 2.79. Found: C, 38.65; H, 2.63.
(dd, 2H, Jˆ1.2, 5.3 Hz), 7.27 (dd, 2H, Jˆ1.2, 3.5 Hz), 6.95
(dd, 2H, Jˆ3.5, 5.3 Hz); 13C NMR d 134.6 (two carbons),
130.8 (two carbons), 127.8 (two carbons), 126.3 (two
carbons). MS m/z (relative intensity) 246 (28), 244 (13),
167 (11), 166 (100), 121 (12), 82 (6), 45 (4). Anal. Calcd
for C8H6S2Se: C, 39.19; H, 2.47. Found: C, 39.02, H;
2.30.
1
2,5-Di(2-thienylseleno)thiophene (11). Mp 62±638C; H
2-Methyl-5-[(5-methyl-2-thienyl)seleno]thiophene (17).
1
NMR d 7.37 (dd, 2H, Jˆ1.2, 5.2 Hz), 7.26 (dd, 2H,
Jˆ1.2, 3.5 Hz), 7.06 (s, 2H), 6.95 (dd, 2H, Jˆ3.5,
5.2 Hz); 13C NMR d 135.2 (two carbons), 134.6 (two
carbons), 131.3 (two carbons),128.0 (two carbons), 125.3
(four carbons). MS m/z (relative intensity) 408 (13), 406
(13), 328 (3), 249 (18), 248 (100), 243 (34), 241 (16), 166
(16), 164 (21), 162 (16), 124 (25), 121 (16), 82 (14). Anal.
Calcd for C12H8S3Se2: C, 35.47; H, 1.98. Found: C, 35.65;
H, 2.10.
Oil; H NMR d 7.06 (d, 2H, Jˆ3.5 Hz), 6.59 (dq, 2H,
Jˆ1.0, 3.5 Hz), 2.49 (d, 6H, Jˆ1.0 Hz); 13C NMR d 145.5
(two carbons), 134.6 (two carbons), 125.9 (two carbons),
123.7 (two carbons), 15.3 (two carbons). MS m/z (relative
intensity) 274 (19), 194 (100), 193 (35), 161 (18), 97 (18),
45 (5). Anal. Calcd for C10H10S2Se: C, 43.96; H, 3.69.
Found: C, 43.80, H, 3.15.
5-Methyl-2,3-di[(5-methyl-2-thienyl)seleno]thiophene (18).
Oil; 1H NMR d 7.05 (d, 1H, Jˆ3.5 Hz), 7.04 (d, 1H,
Jˆ3.5 Hz), 6.62 (dq, 1H, Jˆ1.0, 3.5 Hz), 6.55 (dq, 1H,
Jˆ1.0, 3.5 Hz), 6.30 (q, 1H, Jˆ1.0 Hz), 2.44 (d, 3H,
Jˆ1.0 Hz), 2.40 (d, 3H, Jˆ1.0 Hz), 2.27 (d, 3H,
Jˆ1.0 Hz); 13C NMR d 146.5, 145.9, 144.7, 136.7, 135.6,
134.1 (two carbons), 128.7, 126.3, 126.0, 122.5, 120.7, 15.5,
15.3 (two carbons). MS m/z (relative intensity) 450 (32),
447 (28), 290 (14), 273 (100), 269 (26), 257 (45), 256
(24), 240 (13), 192 (24), 177 (12), 97 (14), 59 (10). Anal.
Calcd for C15H14S3Se2: C, 40.19; H, 3.15. Found: C, 39.95,
H, 3.01.
2-(2-Thienylseleno)-5-{[5-(2-thienylseleno)-2-thienyl]-
seleno}thiophene (12). Mp 122±1238C; H NMR d 7.38
1
(dd, 2H, Jˆ1.1, 5.3 Hz), 7.27 (dd, 2H, Jˆ1.1, 3.5 Hz),
7.05 (s, 4H), 6.96 (dd, 2H, Jˆ3.5, 5.3 Hz); 13C NMR d
135.4 (two carbons), 135.3 (two carbons), 134.5 (two
carbons), 132.1 (four carbons), 131.4 (two carbons), 130.4
(two carbons), 128.0 (two carbons). Anal. Calcd for
C16H10S4Se3: C, 33.87, H, 1.78. Found: C, 33.52; H, 1.73.
2-Methyl-5-(2-thienylseleno)thiophene (13). Oil; 1H
NMR d 7.33 (dd, 1H, Jˆ1.2, 5.2 Hz), 7.21 (dd, 1H,
Jˆ1.2, 3.5 Hz), 7.08 (d, 1H, Jˆ3.4 Hz), 6.92 (dd, 1H,
Jˆ3.5, 5.2 Hz), 6.59 (dq, 1H, Jˆ1.0, 3.4 Hz), 2.44 (d, 3H,
Jˆ1.0 Hz); 13C NMR d 145.7, 135.1, 134.0, 130.4, 127.7,
126.8, 126.0, 123.1, 15.3. MS m/z (relative intensity) 260
(25), 257 (12), 180 (100), 147 (18), 97 (7), 45 (7). Anal.
Calcd for C9H8S2Se: C, 41.71; H; 3.11. Found: C, 41.65; H,
3.02.
5-Methyl-2-({5-methyl-3-[(5-methyl-2-thienyl)seleno]-2-
thienyl}seleno-3-[(5-methyl-2-thienyl)seleno]thiophene
1
(19). Oil; H NMR d 6.94 (d, 2H, Jˆ3.5 Hz), 6.61(q, 2H
Jˆ1.0 Hz), 6.51 (dq, 2H, Jˆ1.0, 3.5 Hz), 2.45 (d, 12H,
Jˆ1.0 Hz); 13C NMR d 145.6 (two carbons), 144.2 (two
carbons), 134.7 (two carbons), 132.1 (two carbons), 128.8
(two carbons), 126.7 (two carbons), 126.0 (two carbons),
123.7 (two carbons), 15.5 (two carbons), 15.3 (two carbons).
Anal. Calcd for C20H18S4Se3: C, 38.54; H, 2.91. Found: C
38.15; H, 2.70.
2-[(5-Methyl-2-thienyl)seleno]-5-(2-thienylseleno)thio-
phene (14). Mp 55±578C; 1H NMR d 7.37 (dd, 1H, Jˆ1.2,
5.3 Hz), 7.26 (dd, 1H, Jˆ1.2, 3.5 Hz), 7.07 (d, 1H,
Jˆ3.5 Hz), 7.06 (d, 1H, Jˆ3.5 Hz), 7.03 (d, 1H,
Jˆ3.5 Hz), 6.94 (dd, 1H, Jˆ3.5, 5.3 Hz), 6.61 (dq, 1H,
1.0, 3.5 Hz), 2.45 (d, 3H, Jˆ1.0 Hz); 13C NMR d 146.4,
135.8, 135.1, 134.7, 134.0, 132.2, 131.2, 130.9, 127.9,
126.2, 125.5, 122.1, 15.4. MS m/z (relative intensity) 422
(1), 262 (100), 261 (33), 259 (54), 257 (27), 245 (28), 243
(16), 229 (13), 179 (17), 178 (14), 162 (14), 131 (41), 97
(14), 82 (14), 45 (8). Anal. Calcd for C13H10S3Se2: C; 37.16;
H, 2.40. Found: C 37.01, H, 2.20.
Electrophilic thienylselenenylation of furan derivatives
These experiments were carried out under reaction condi-
tions identical to those described above for the reactions of
the thiophene derivatives. Physical and spectroscopic data
of the reaction products, 20±25, are reported below.
1
2-(2-Thienylseleno)furan (20). Oil; H NMR d 7.50 (dd,

3260
M. Tiecco et al. / Tetrahedron 56 (2000) 3255±3260
1H, Jˆ1.0, 1.9 Hz), 7.36 (dd, 1H, Jˆ1.1, 5.2 Hz), 7.26 (dd,
1H, Jˆ1.1, 3.3 Hz), 6.96 (dd, 1H, Jˆ3.3, 5.2 Hz), 6.64 (dd,
1H, Jˆ1.0, 3.2 Hz), 6.36 (dd, 1H, Jˆ1.9, 3.2 Hz); 13C NMR
d 146.3, 143.1, 134.5, 130.7, 127.8, 123.9, 118.5, 111.6. MS
m/z (relative intensity) 230 (38), 228 (18), 202 (20), 163 (6),
150 (100), 122 (30), 121 (72), 116 (16), 93 (13), 45 (6).
Anal. Calcd for C8H6OSSe: C, 41.94; H, 2.64. Found: C,
41.65; H, 2.38.
(19), 201 (7), 164 (100), 135 (12), 121 (19), 117 (4), 82 (4),
43 (7). Anal. Calcd for C9H8OSSe: C, 44.46; H, 3.32.
Found: C, 44.21; H, 3.15.
2-Methyl-5-[(5-methyl-2-thienyl)seleno]furan (25). Oil;
1H NMR d 7.03 (d, 1H, Jˆ3.4 Hz), 6.58 (dq, 1H, Jˆ1.1,
3.4 Hz), 6.52 (d, 1H, Jˆ3.1 Hz), 5.93 (dq, 1H, Jˆ1.0,
3.1 Hz), 2.43 (d, 3H, Jˆ1.1 Hz), 2.29 (d, 3H, Jˆ1.0 Hz);
13C NMR d 156.2, 145.2, 137.4, 134.5, 125.9, 121.6, 119.8,
107.7, 15.2, 13.4. MS m/z (relative intensity) 258 (16), 179
(16), 178 (100), 177 (30), 135 (25), 89 (9), 53 (10). Anal.
Calcd for C10H10OSSe: C, 46.71; H, 3.92. Found C, 46.51;
H, 3.81.
2,5-Di(2-thienylseleno)furan (21). Mp 99±1018C; 1H
NMR d 7.35 (dd, 2H, Jˆ1.2, 5.3 Hz), 7.25 (dd, 2H,
Jˆ1.2, 3.6 Hz), 6.91 (dd, 2H, Jˆ3.6, 5.3 Hz), 6.51 (s,
2H); 13C NMR d 143.5 (two carbons), 134.9 (two carbons),
130.9 (two carbons), 127.8 (two carbons), 123.3 (two
carbons), 119.8 (two carbons). MS m/z (relative intensity)
392 (10), 229 (81), 227 (39), 203 (18), 201 (74), 199 (37),
197 (14), 163 (17), 121 (100), 117 (23), 116 (43), 71 (17).
Anal. Calcd for C12H8OS2Se2: C, 36.95; H, 2.07. Found: C,
36.68; H, 1.89.
Acknowledgements
Á
Financial support from Ministero dell'Universita e della
Ricerca Scienti®ca e Tecnologica, Italy, National Project
Stereoselezione in Sintesi Organica. Metodologie ed Appli-
cazioni, University of Perugia, Progetti di Ateneo, and CNR,
Rome, is gratefully acknowledged.
2-[(5-Methyl-2-thienyl)seleno]furan (22). Oil; 1H NMR d
7.42 (dd, 1H, Jˆ0.8, 1.9 Hz), 7.09 (d, 1H, Jˆ3.5 Hz), 6.58-
6.60 (m, 2H), 6.28 (dd, 1H, Jˆ1.9, 3.2 Hz), 2.47 (d, 3H,
Jˆ1.1 Hz); 13C NMR d 146.2, 145.8, 144.5, 135.7, 135.1,
126.1, 118.1, 111.6, 15.4. MS m/z (relative intensity) 244
(23), 242 (13), 215 (7), 164 (100), 163 (21), 135 (44), 117
(6), 97 (9), 45 (6). Anal. Calcd for C9H8OSSe: C, 44.46, H,
3.32. Found: C, 44.30; H, 3.11.
References
1. Tiecco, M.; Testaferri, L.; Tingoli, M.; Chianelli, D.; Bartoli, D.
Tetrahedron Lett. 1989, 30, 1417±1420.
2. Tiecco, M.; Testaferri, L.; Tingoli, M.; Bagnoli, L.; Marini, F.
J. Chem. Soc. Perkin Trans. 1 1993, 1989±1993 and references
cited therein.
Á
3. Tiecco, M.; Testaferri, L.; Tingoli, M.; Marini, F.; Mariggio, S.
Tetrahedron 1994, 50, 10549±10554.
2,5-Di[(5-methyl-2-thienyl)seleno]furan (23). Mp 72±748C;
1H NMR d 7.06 (d, 2H, Jˆ3.4 Hz), 6.60 (dq, 2H, Jˆ0.9,
3.4 Hz), 6.48 (s, 2H), 2.48 (d, 6H, Jˆ0.9 Hz); 13C NMR d
145.9 (two carbons), 143.8 (two carbons), 135.4 (two
carbons), 126.1 (two carbons), 120.2 (two carbons), 119.4
(two carbons), 15.3 (two carbons). MS m/z (relative inten-
sity) 420 (11), 418 (11), 340 (2), 260 (61), 244 (10), 243
(100), 217 (15), 215 (67), 213 (29), 177 (16), 135 (69), 134
(19), 97 (21), 91 (7), 53 (9). Anal. Calcd for C14H12OS2Se2:
C, 40.21, H, 2.89. Found: C, 40.01; H, 2.55.
4. Engman, L.; Erikson, P. Heterocycles 1996, 43, 861±871.
5. Jen, K.-Y.; Benfaremo, N.; Cava, M. P.; Huang, W.-S.;
MacDiarmid, A. G. J. Chem. Soc., Chem. Commun. 1983, 633±
634.
6. Jones, E.; Moodie, I. M. In Org. Synth., Breslow, R., Ed.;
Wiley: New York, 1970; Vol. 50, pp 104±106.
7. Tingoli, M.; Tiecco, M.; Testaferri, L.; Temperini, A. Synth.
Commun. 1998, 28, 1769±1778.
1
2-Methyl-5-(2-thienylseleno)furan (24). Oil; H NMR d
7.32 (dd, 1H, Jˆ1.1, 5.3 Hz), 7.22 (dd, 1H, Jˆ1.1,
3.5 Hz), 6.92 (dd, 1H, Jˆ3.5, 5.3 Hz), 6.55 (d, 1H,
Jˆ3.1 Hz), 5.94 (dq, 1H, Jˆ0.9, 3.1 Hz), 2.29 (d, 3H,
Jˆ0.9 Hz); 13C NMR d 156.6, 137.1, 134.0, 130.3, 127.8,
125.1, 120.3, 107.8, 13.8. MS m/z (relative intensity) 244
8. A competitive experiment carried out with the 5,50-dimethyl-
2,20-dithienyl diselenide and iodobenzene diacetate showed that
2-methylthiophene is about 150 times more reactive than
thiophene.
9. Bryce, M. R. Chem. Soc. Rev. 1991, 20, 355±390.