The first aryne evolution from the reactions of selenonium salts with aryllithiums

Article abstract of DOI:10.1016/S0040-4020(99)01090-X

The first example of the benzyne generation was found in the reactions of alkynylselenonium salt 1a with 1.0 equiv. of phenyllithium in THF at room temperature for 3 h. The formation of the aryne intermediate was confirmed in the reactions of alkynylselenonium salt 1b and tri-p-tolylselenonium salt 6b with tolyllithium, which gave a mixture of alkynylbiphenyl derivatives 18 and 19 in 19% yield (18:19=11:8) and a mixture of bitolyls 28 and 29 in 63% yield (28:29=2:1), respectively. The reaction mechanisms of these reactions are discussed. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(99)01090-X

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 855–863
The First Aryne Evolution from the Reactions of Selenonium Salts
with Aryllithiums
Shin-ichi Watanabe, Keiichirou Yamamoto, Yukiko Itagaki, Tatsunori Iwamura, Tetsuo Iwama
*
and Tadashi Kataoka
Gifu Pharmaceutical University, 6-1, Mitahora-higashi 5-chome, Gifu 502-8585, Japan
Received 27 October 1999; accepted 16 December 1999
Abstract—The first example of the benzyne generation was found in the reactions of alkynylselenonium salt 1a with 1.0 equiv. of
phenyllithium in THF at room temperature for 3 h. The formation of the aryne intermediate was confirmed in the reactions of alkynyl-
selenonium salt 1b and tri-p-tolylselenonium salt 6b with tolyllithium, which gave a mixture of alkynylbiphenyl derivatives 18 and 19 in
19% yield (18:19ˆ11:8) and a mixture of bitolyls 28 and 29 in 63% yield (28:29ˆ2:1), respectively. The reaction mechanisms of these
reactions are discussed. ᭧ 2000 Elsevier Science Ltd. All rights reserved.
Introduction
Results and Discussion
First, we examined reactions of diphenyl(phenylethynyl)-
selenonium triflate 1a with phenyllithium in THF (Scheme
1, Table 1). Reactions of the compound 1a with 0.5–
5 equiv. of phenyllithium at room temperature for 3 h
gave complex mixtures in all cases. Yields of the products
except for selenonium salts were analyzed by HPLC.
Compound 7 was isolated and its structure was determined
in comparison with its spectral data with those of
compounds 7 and 8. The authentic samples 7 and 8 were
prepared by the method as shown in Scheme 2. Bromination
of alkene 99 followed by dehydrobromination with t-BuOK
afforded 1-(o-biphenylyl)-2-phenylethyne 7 in 33% yield.
1-(m-Biphenylyl)-2-phenylethyne 8 was similarly prepared
from alkene 1010 in 90% yield. The reactions shown in
Scheme 1 and Table 1 revealed four interesting results:
(1) when 0.5 equiv. of phenyllithium was used, the starting
material 1a was not recovered but triphenylselenonium
triflate 6a was obtained (entry 1); (2) 1,4-diphenylbutadiyne
5 was obtained in all cases; (3) alkynylbiphenyl 7 was given
in low yields (entries 2–5); (4) when the quantity of phenyl-
lithium was increased, the yields of diyne 5 and alkynyl-
biphenyl 7 were decreased and phenylethyne 2 was
increased.
These days, numerous hypervalent chalcogen compounds,
of which the chalcogen atom formally possesses more than
eight valence electrons, have been synthesized.1 Among
them, sulfuranes and selenuranes with only carbon ligands
can be prepared from the reactions of triarylsulfonium and
selenonium salts with aryllithiums, respectively.2 Reactions
of triarylsulfonium salts with aryllithiums have been widely
studied3 and it is well-known that these reactions proceed
via the hypervalent intermediate.4 As a matter of fact, these
reactions also form aryne intermediates because nucleo-
philes attack the o-proton of the aryl group of sulfonium
salts. Khim and Oae reported that the reactions of tritolyl-
sulfonium bromide with phenyllithium proceeded via the
aryne formation as well as the nucleophilic attack of the
phenyl anion on the sulfur.4a Andersen’s group showed
the formation of the benzyne intermediate from the reaction
of tritolylsulfonium salt with p-tolyllithium.5 On the other
hand, few reports on the reactions of triarylselenonium salts
with aryllithiums have been published till now.2,6 Interest-
ingly, there has been no report that aryne intermediates are
generated from the reactions of selenonium salts with
nucleophiles. In the course of our research on diphenyl-
alkynylselenonium salts,7 we have recently found the first
formation of the benzyne intermediate from the reactions of
alkynylselenonium salts with phenyllithium,8 and here we
wish to describe our extensive study on the preliminary
result obtained.
The result (1) implies that ligand exchange would occur in
the first step of this reaction (Scheme 3). Therefore, we
investigated the reaction of alkynylselenonium salt 1a
with 1 equiv. of phenyllithium in THF at Ϫ78ЊC for 3 h
followed by quenching with aqueous TfOH at that tempera-
ture. Triphenylselenonium salt 6a was obtained in 86%
yield as the main product accompanied with the starting
material, alkynylselenonium salt 1a in 5% yield. The finding
Keywords: selenonium ions; arynes; hypervalent elements; lithium and
compounds.
* Corresponding author. Tel.: ϩ81-58-237-3931, ext. 227; fax: ϩ81-58-
237-5979; e-mail: kataoka@gifu-pu.ac.jp
0040–4020/00/$ - see front matter ᭧ 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(99)01090-X

856
S. Watanabe et al. / Tetrahedron 56 (2000) 855–863
Scheme 1.
Table 1. Reactions of alkynylselenonium salt 1a with phenyllithium
Entry
Phenyllithium (equiv.)
Products (% yield)a
1
2
3
4
5
0.5
1.0
2.0
3.0
5.0
2 (10)
4 (56)
4 (92)
4 (99)
4 (100)
4 (100)
5 (34)
5 (25)
5 (13)
5 (2)
6ab (18)
2 (14)
2 (38)
2 (51)
2 (60)
3 (20)
7 (15)
7 (7)
7 (5)
7 (4)
3c
3c
3c
5 (2)
a Determined by HPLC.
b Isolated yield.
c Biphenyl 3 was also obtained from the coupling of phenyllithium and, therefore, the yield of 3 is meaningless.
exchange to form triphenylselenonium salt 6a and phenyl-
ethynyllithium concertedly.
The selenonium salt 6a, generated in situ, reacts with
phenyllithium to form the selenurane A, which subsequently
brings about the ligand coupling reaction to produce
biphenyl 3 and selenide 4 (Scheme 4). On the other hand,
the eliminated phenylethynyllithium reacts with unreacted
alkynylselenonium salt 1a to form selenurane intermediate
B, whose two ethynyl ligands couple with each other to
afford selenide 4 and diyne 5. This route was experimentally
supported by the result that the reaction of alkynyl-
selenonium salt 1a with phenylethynyllithium gave selenide
4 and diyne 5 in 94 and 75% yields, respectively. When the
quantity of phenyllithium was increased, the yield of diyne 5
was decreased and phenylethyne 2 was increased (Table 1).
This is attributed to the fact that alkynylselenonium salt 1a
reacts more rapidly with excess phenyllithium than with
phenylethynyllithium.
Scheme 2.
strongly supported our assumption that ligand exchange
reaction occurred. On the other hand, the reaction of tri-
phenylselenonium salt 6a with phenylethynyllithium was
also examined. Triphenylselenonium salt 6a was prepared
by the reaction of diphenyliodonium triflate 13, derived
from the corresponding chloride 1111,12 and silver triflate,
with diphenyl selenide in the presence of copper(II) benzo-
ate in 74% yield. The reaction of 6a with the phenyl-
ethynyllithium did not proceed and the starting material
6a was recovered (81%). This shows that the ligand
exchange reaction was not an equilibrium reaction because
phenyllithium is much more nucleophilic than phenyl-
ethynyllithium. Thus, the nucleophilic attack of phenyl-
lithium at the selenium of 1a gives rise to ligand
Alkynylbiphenyl 7 would be produced via benzyne. If
phenyllithium abstracts the o-proton of the phenyl group
Scheme 3.

S. Watanabe et al. / Tetrahedron 56 (2000) 855–863
857
Scheme 4.
Scheme 5.
Scheme 6.
of alkynylselenonium salt 1a, benzyne and 1-phenyl-2-
(phenylseleno)ethyne should be obtained. However, the
selenide was not obtained from this reaction. Therefore,
benzyne would be generated from the reaction of triphenyl-
selenonium salt 6a with phenyllithium or phenylethynyl-
lithium (Scheme 5). Two pathways are possible for
formation of alkynylbiphenyl 7. One way goes through
the intermediate 15 which was formed via the reaction of
benzyne with phenylethynyllithium, and the other is a route
via the intermediate 16 which is generated from the reaction
with phenyllithium. In order to confirm these pathways, we
conducted the reactions of selenonium salts 6a and 1a with
o-(phenylethynyl)phenyllithium 15 and o-biphenylyllithium
16, respectively. These aryllithiums were prepared from
n-butyllithium and the corresponding aryl bromides in
THF at room temperature for 3 h (Scheme 6). The former
reaction afforded ligand coupling products 4 (87%) and 7
(61%), while the latter gave a small amount of 7 together
with some other products 2–5. This result showed that
alkynylbiphenyl 7 would be mainly produced from the reac-
tion of 6a with 15. However, the reasons why the selenurane
which was formed from aryllithium 15 and selenonium salt
6a underwent the selective ligand-coupling between the
phenyl and the phenylethynylphenyl groups are not clear
so far. When more than 2 equiv. of phenyllithium were
used, excess phenyllithium, which is more nucleophilic
than ethynyllithium, reacted with benzyne and then with
triphenylselenonium salt 6a faster than phenylethynyl-
lithium, and consequently the yield of alkynylbiphenyl 7
was decreased. Although the reaction of triphenylseleno-
nium salt 6a with phenylethynyllithium at Ϫ78ЊC did not
proceed as mentioned above, the reaction at room tempera-
ture afforded alkynylbiphenyl 7 in 27% yield. It is interest-
ing that benzyne was even evolved from the reaction of
triphenylselenonium salt 6a with phenylethynyllithium, a
much lower nucleophilic carbanion than phenyllithium.13

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S. Watanabe et al. / Tetrahedron 56 (2000) 855–863
Scheme 7. Reagents and conditions: (i) PhCH2PϩPh3BrϪ, n-BuLi, THF, r.t.; (ii) Br2, CH2Cl2, r.t.; (iii) t-BuOK, t-BuOH, reflux; (iv) n-BuLi, (p-tolyl)3SeϩTfOϪ
6b, THF, r.t.
This result indicated that the acidity of the o-proton of the
phenyl group in triphenylselenonium salt 6a was fairly high.
tolylselenonium salt 6b with an aryllithium derivative,
which was derived from alkyne 24 and n-butyllithium,
furnished the desired product 2-(phenylethynyl)-5,40-
dimethyl-1,10-biphenyl 18 in 25% yield. 2-(Phenyl-
ethynyl)-4,40-dimethyl-1,10-biphenyl 19 was similarly
prepared from aldehyde 21.16 Thus, 4-methylbenzyne is
generated from 6b with RLi, and reacts with phenylethynyl-
lithium at both 3- and 4-positions to form the carbanions 26
and 27, respectively (Scheme 8). These tolyllithiums 26 and
27 react with 6b and afford the ligand coupling products 18
and 19, respectively. More than 13% of the reaction went
through aryne and the isomeric ratio of 18 and 19 (ca. 1:1)
was faithfully similar to that of Oae’s report.4a
In order to study the formation of an aryne more precisely,
we planned to conduct the reaction of di-p-tolyl(phenyl-
ethynyl)selenonium triflate 1b7b with p-tolyllithium in
THF. If an unsymmetrical aryne, 4-methylbenzyne is
formed, two types of alkynylbiphenyls 18 and 19 should
be produced (Scheme 7). Actually, the reaction of alkynyl-
selenonium salt 1b with p-tolyllithium in THF at room
temperature afforded a complex mixture and the products
were separated by preparative TLC to give a mixture of
alkynylbiphenyls 18 and 19 in 19% yield (18:19ˆ11:8) as
we had expected. These compounds were identical with
authentic samples 18 and 19. The authentic samples were
prepared by an alternative method shown in Scheme 7. The
Wittig reaction of aldehyde 2015 with benzylphosphorane
gave olefin 22 and subsequent bromination and dehydro-
bromination with t-BuOK afforded o-bromoalkynylbenzene
derivative 24 in 35% yield from 20. The reaction of tri-p-
When the ligands on the selenonium salt and an aryl group
of aryllithium are different, the reaction would be very
complex and several products with similar polarity are
produced and product separation is troublesome. Therefore,
we planned to match effectively tri-p-tolylselenonium salt
6b with p-tolyllithium. Tri-p-tolylselenonium triflate 6b
Scheme 8.
Scheme 9.

S. Watanabe et al. / Tetrahedron 56 (2000) 855–863
859
Scheme 10.
was prepared from 1211 as shown in Scheme 3. The reaction
of the selenonium salt 6b with p-tolyllithium in THF at
room temperature for 3 h was carried out and a mixture of
bitolyls 28 and 2917 was isolated in 63% yield (28:29ˆ2:1)
besides selenide 30 (Scheme 9). Compounds 28 and 29 were
phenylethynyllithium as well as phenyllithium. Treatment
of a triarylselenonium salt with a base would lead to a new
method for the easy formation of aryne.
1
Experimental
determined by comparison of their H NMR spectra with
those of authentic samples. On the basis of the result that
bitolyl 29 was obtained, the reaction mechanism involving
an aryne intermediate is shown in Scheme 10. The nucleo-
philic attack of p-tolyllithium at the selenium atom of
selenonium salt 6b forms tetra-p-tolylselenurane inter-
mediate. The ligand coupling reaction of the selenurane
affords bitolyl 28 and selenide 30 (route A). On the other
hand, p-tolyllithium as a base abstracts an o-aromatic proton
of tri-p-tolylselenonium salt 6b to generate 4-methyl-
benzyne. The aryne reacts with p-tolyllithium at both 3-
and 4-positions to give carbanions 31 and 32, respectively,
and the protonation of them afforded bitolyls 28 and 29. If
the ratio of the p-tolyllithium attack at 3- or 4-position of
4-methylbenzyne was ca. 1:1, the same as that of reaction of
1b with p-tolyllithium, more than 42% of the reaction would
have proceeded via the aryne intermediate. We did not
detect terphenyl derivative 33 which would be generated
by ligand coupling reaction of a selenurane generated
from carbanions 31 or 32 and tri-p-tolylselenonium salt
6b. These results indicated that the reaction of tri-p-tolyl-
selenonium salt 6b with p-tolyllithium proceeded through
both ligand coupling reaction and aryne formation. The
reason why terphenyl derivative 33, which was expected
to be formed, was not obtained would be attributable to
the steric hindrance of carbanions 31 and 32.
Melting points were obtained with a Yanagimoto micro
melting point apparatus and are uncorrected. IR spectra of
solids (KBr) and liquids (NaCl) were recorded on a JASCO
IRA-100 spectrophotometer. 1H NMR spectra were
recorded on a JEOL GX-270 (270 MHz) or a JEOL
EX-400 (400 MHz) spectrometer with tetramethylsilane as
an internal standard. 13C NMR spectra were obtained on a
JEOL EX-400 spectrometer. The J values are given in Hz.
Mass spectra were recorded on a JEOL JMS-SX 102A
spectrometer with a direct-insertion probe at 70 eV.
Elemental analyses of new compounds were performed by
a Yanaco CHN Corder MT-5. All chromatographic
isolations were accomplished with either Kieselgel 60
(Merck) or BW-127ZH (Fuji Silysia) for column chromato-
graphy or Kieselgel 60 PF254 containing gypsum (Merck)
for PTLC. HPLC analyses were carried out using a JASCO
chromatography system (PU–986, UV–970) with monitor-
ing of the 220 nm, DEVELOSIL 60-5 HPLC column with a
flow rate of 1.0 cm3 minϪ1 eluting hexane and their data
were recorded with a System Instruments integrator (Chro-
matocorder 21J). Authentic pure samples of ethynylben-
zene, biphenyl, diphenylselenide and diphenylethyne were
commercially available.
Reactions of alkynylselenonium salt 1a with
phenyllithium: general procedure
Conclusion
Phenyllithium in cyclohexane–ether was added dropwise to
a THF solution (10 ml) of alkynylselenonium salt 1a7b
(290 mg, 0.6 mmol) at room temperature under argon.
After being stirred magnetically for 3 h at ambient tempera-
ture, the reaction mixture was quenched with water (5 ml),
and extracted with hexane. Reaction products were identi-
fied by comparison of the retention times with those of
authentic samples except triphenylselenonium salt 6a.
Yields of the products estimated were determined by
means of HPLC using p-iodoanisole as an internal standard
and described on the basis of starting alkynylselenonium
salt 1a. Products and their yields were summarized in
The reaction of alkynylselenonium salt 1a with phenyl-
lithium produced characteristic compounds, diyne 5 and
alkynylbiphenyl 7, which could not be generated from
only a ligand coupling reaction. The present investigation
showed that this reaction proceeded through both ligand
coupling reaction of a selenurane intermediate and aryne
formation. The aryne formation was elucidated from the
reactions of selenonium salts having tolyl groups. This is
the first example of the aryne formation in the reactions
of selenonium salts with nucleophiles. The o-proton of the
aryl group of a selenonium salt was readily abstracted by

860
S. Watanabe et al. / Tetrahedron 56 (2000) 855–863
Table 1. 1,4-Diphenyl-1,3-butadiyne 5 was prepared by the
method of Hay.18 Alkynylbiphenyl 7 was isolated by
preparative TLC (hexane) and its structure was determined
by comparison of the spectral data and the retention time
with those of an authentic sample. In entry 1, the aqueous
layer was extracted with CHCl3 and the organic phase was
dried over anhydrous MgSO4. After the solvent was evapo-
rated under reduced pressure, the precipitate was washed
several times with ether to give triphenylselenonium salt
6a (50 mg, 18%), which was identical with an authentic
sample.
100%) was obtained as a colorless solid, mp 39–41ЊC;
nmax(film)/cmϪ1 2222; dH(400 MHz; CDCl3) 7.32–7.37 (4
H, m, ArH), 7.39–7.45 (3 H, m, ArH), 7.51–7.60 (6 H, m,
ArH), 7.77 (1 H, s, ArH); dC(100 MHz; CDCl3) 89.4, 89.5,
123.2, 123.7, 127.1, 127.6, 128.28, 128.33, 128.8, 130.3,
131.6, 140.3, 141.4; m/z (EI) 254 (Mϩ, 100%), 252(25);
HRMS: m/z For C20H14 (Calc.: M, 254.1095. Found: Mϩ,
254.1105).
Reaction of alkynylselenonium salt 1a with
phenyllithium at Ϫ78ЊC
1-(o-Biphenylyl)-2-phenylethyne 7. To a stirred solution
of 99 (E:Zˆ1:1) (400 mg, 1.6 mmol) in CH2Cl2 (20 ml)
was added Br2 (0.1 ml, 1.9 mmol) at 0ЊC under argon.
After the reaction mixture was stirred for 2 h, sat.
Na2S2O3 (aq.) was added to it, and the whole was extracted
with CH2Cl2. The extracts were dried (MgSO4) and evapo-
rated under reduced pressure. The residue was purified by
preparative TLC (hexane) to give 1-(o-biphenylyl)-1,2-
dibromo-2-phenylethane (221 mg, 46%) as a mixture of
diastereomers (erythro:threoˆ1:1), dH(400 MHz; CDCl3)
5.45 (1 H, d, Jˆ10.3, CH), 5.53 (1 H, d, Jˆ11.7, CH),
5.62 (1 H, d, Jˆ10.3, CH), 5.69 (1 H, d, Jˆ11.7, CH),
6.84 (2 H, d, Jˆ7.8, ArH), 6.95 (1 H, d, Jˆ7.6, ArH),
7.01–7.09 (3 H, m, ArH), 7.12 (1 H, t, Jˆ7.6, ArH),
7.25–7.30 (8 H, m, ArH), 7.35–7.51 (11 H, m, ArH), 7.60
(1 H, d, Jˆ7.6, ArH), 7.75 (1 H, d, Jˆ7.8, ArH);
dC(100 MHz; CDCl3) 52.2, 56.08, 56.12, 59.7, 126.9,
127.53, 127.59, 127.68, 127.75, 127.79, 128.12, 128.17,
128.30, 128.39, 128.43, 128.48, 128.6, 128.8, 129.2,
130.0, 130.2, 136.3, 137.5, 138.3, 139.7, 139.8, 140.0,
140.7, 141.6; m/z (EI) 418 (1%, Mϩϩ4), 416 (2%,
Mϩϩ2), 414 (1%, Mϩ), 255 (100). To a stirred solution of
this compound (75 mg, 0.2 mmol) in t-BuOH (5 ml), 90%
t-BuOK (60 mg, 0.5 mmol) was added at room temperature.
The mixture was refluxed for 6 h, then quenched with water
and extracted with hexane. The organic phase was dried
over anhydrous MgSO4, and concentrated. The residue
was purified by preparative TLC (hexane) to give 7
(45 mg, 98%) as yellow oil, (Found: C, 94.2; H, 5.67;
C20H14 requires C, 94.45; H, 5.55%); nmax(film)/cmϪ1
2253; dH(400 MHz; CDCl3) 7.25–7.33 (6 H, m, ArH),
7.35–7.46 (5 H, m, ArH), 7.63–7.67 (3 H, m, ArH);
dC(100 MHz; CDCl3) 89.4, 92.2, 121.6, 123.5, 127.0,
127.5, 127.9, 128.1, 128.2, 128.5, 129.4, 129.5, 131.3,
132.8, 140.6, 143.9; m/z (EI) 254 (Mϩ, 88%), 253(100),
252 (65).
Phenyllithium in cyclohexane–ether (0.75 ml, 0.6 mmol)
was added dropwise to a THF solution (10 ml) of alkynyl-
selenonium salt 1a (290 mg, 0.6 mmol) at Ϫ78ЊC under
argon. After being stirred magnetically for 3 h at Ϫ78ЊC,
the reaction mixture was quenched with TfOH (aq.) (5 ml),
and extracted with CHCl3 and the organic phase was dried
over anhydrous MgSO4. After the solvent was evaporated
under reduced pressure, the precipitate was washed several
times with ether to give the mixture of triphenylselenonium
salt 6a and 1a (252 mg) as a colorless oil. The ratio of
1
these compounds was determined by H NMR spectrum
(6a:236 mg, 86%, 1a:16 mg, 5%).
Reaction of triphenylselenonium salt 6a with
phenylethynyllithium at Ϫ78ЊC
n-Butyllithium in hexane (0.42 ml, 0.66 mmol) was added
dropwise to a THF solution (5 ml) of ethynylbenzene
(67 mg, 0.66 mmol) at Ϫ78ЊC under argon. After being
stirred magnetically for 30 min at Ϫ78ЊC, the solution of
phenylethynyllithium thus prepared was added dropwise to
a THF solution (5 ml) of triphenylselenonium salt 6a
(276 mg, 0.60 mmol) at Ϫ78ЊC under argon with a cannula.
After being stirred magnetically for 3 h at Ϫ78ЊC, the reac-
tion mixture was quenched with TfOH (aq.) (5 ml), and
extracted with CHCl3. The organic phase was dried over
anhydrous MgSO4. After the solvent was evaporated
under reduced pressure, the precipitate was washed several
times with ether to give starting material 6a (252 mg) as a
colorless solid.
Diphenyliodonium trifluoromethanesulfonate 13. Di-
phenyliodonium chloride 1111,12 (1.26 g, 4.0 mmol) was
dissolved in MeCN (200 ml) with heating. Silver trifluoro-
methanesulfonate (977 mg, 3.8 mmol) was added to the
solution at room temperature. After the mixture was stirred
magnetically for 2 h at ambient temperature, the precipitate
was filtered and washed with MeCN. The filtrate and wash-
ings were combined and the solvent was removed under
reduced pressure. The residual solid was recrystallized
from MeOH to give 13 (1.66 g, 98%) as a colorless solid,
mp 177–180ЊC (Found: C, 36.46; H, 2.50; C13H10F3IO3S
requires C, 36.30; H, 2.34%); nmax(film)/cmϪ1 3047, 1465,
1442, 1240, 1150; dH(400 MHz; CDCl3) 7.40 (4 H, t, Jˆ7.8,
ArH), 7.55 (2 H, t, Jˆ7.8, ArH), 7.99 (4 H, d, Jˆ7.8, ArH);
dC(100 MHz; CD3OD) 115.9, 121,8, 133.2, 133.6, 136.4;
m/z (FAB) 281 ([MϪTfO]ϩ, 55%).
1-(m-Biphenylyl)-2-phenylethyne 8. A solution of (Z)-1010
(200 mg, 0.8 mmol) in CH2Cl2 (5 ml) was similarly treated
with Br2 (0.1 ml, 1.9 mmol) at 0ЊC under argon. The raw
product was purified by preparative TLC (hexane) to give
1-(m-biphenylyl)-1,2-dibromo-2-phenylethane
(292 mg,
90%) as a single product detected by H, 13C NMR and
mass spectra, dH(400 MHz; CDCl3) 5.51 (1 H, d, Jˆ8.0,
CH), 5.54 (1 H, d, Jˆ8.0, CH), 7.16–7.26 (7 H, m, ArH),
7.32–7.43 (7 H, m, ArH); dC(100 MHz; CDCl3) 59.0, 127.1,
127.4, 127.5, 127.6, 128.2, 128.5, 128.6, 128.7, 137.6,
138.1, 140.4, 141.1; m/z (EI) 418 (3%, Mϩϩ4), 416 (6%,
Mϩϩ2), 414 (3%, Mϩ), 256 (100). The dibromo compound
(292 mg, 0.7 mmol) was similarly dehydrobrominated with
90% t-BuOK (216 mg, 1.7 mmol). Compound 8 (179 mg,
1
Di-p-tolyliodonium trifluoromethanesulfonate 14. Di-p-
tolyliodonium chloride 1211 (1.0 g, 2.9 mmol) was similarly
treated with silver trifluoromethanesulfonate (745 mg,

S. Watanabe et al. / Tetrahedron 56 (2000) 855–863
861
2.9 mmol) and gave 14 (1.24 g, 97%) as a colorless solid,
Reaction of alkynylselenonium salt 1a with
o-biphenylyllithium 16
mp 153–155ЊC (Found: C, 39.15; H, 3.10; C15H14F3IO3S
requires C, 39.32; H, 3.08%); nmax(film)/cmϪ1 3053, 1482,
1264, 1165; dH(400 MHz; CDCl3) 2.45 (9 H, s, Me), 7.41 (6
H, d, Jˆ8.3, ArH), 7.41 (6 H, d, Jˆ8.3, ArH); dC(100 MHz;
CDCl3) 21.3, 110.0, 120.3, 132.9, 135.0, 143.4; m/z (FAB)
309 ([MϪTfO]ϩ, 10%).
o-Biphenylyllithium 16 was prepared from n-butyllithium
in hexane (0.49 ml, 0.78 mmol) and a THF solution (5 ml)
of 2-bromobiphenyl (181 mg, 0.78 mmol) in a similar way
as for phenylethynyllithium, and added dropwise to a THF
solution (5 ml) of alkynylselenonium salt 1a (290 mg,
0.60 mmol) at room temperature. After the mixture was
treated as mentioned above and reaction products were
analyzed by HPLC, ethynylbenzene 2 (13%), biphenyl 3
(63%), diphenyl selenide 4 (48%), 1,3-diphenylbutadiyne
5 (15%) and 1-(o-biphenylyl)-2-phenylethyne 7 (10%)
were obtained.
Triphenylselenonium trifluoromethanesulfonate 6a.
Diphenyliodonium trifluoromethanesulfonate 13 (2.0 g,
4.65 mmol) was added to a mixture of diphenyl selenide
(1.5 g, 6.44 mmol) and copper benzoate (20 mg,
0.07 mmol) at room temperature under argon. After the
mixture was stirred magnetically for 3 h at 120ЊC, the pre-
cipitate was washed several times with ether, and recrystal-
lized from CH2Cl2–ether to give 6a (1.5 g, 70%) as a
colorless solid, mp 87–89ЊC (Found: C, 49.40; H, 3.46;
C19H15F3O3SSe requires C, 49.68; H, 3.29%); nmax(KBr)/
cmϪ1 3091, 1475, 1445, 1248, 1140; dH(400 MHz;
CDCl3) 7.59–7.66 (12 H, m, ArH), 7.70–7.73 (3 H, m,
ArH), 7.63–7.67 (3 H, m, ArH); dC(100 MHz; CDCl3)
120.5, 126.4, 131.2, 131.7, 133.7; m/z (FAB) 311
([MϪTfO]ϩ, 45%).
Reaction of triphenylselenonium salt 6a with
phenylethynyllithium at room temperature
A THF solution (2.5 ml) of triphenylselenonium salt 6a
(138 mg, 0.30 mmol) was allowed to react with phenyl-
ethynyllithium, prepared from n-butyllithium in hexane
(0.21 ml, 0.33 mmol) and ethynylbenzene (34 mg,
0.33 mmol), at room temperature for 3 h under argon.
After the reaction mixture was treated as mentioned
above, reaction products were analyzed by HPLC. Ethynyl-
benzene 2 (75%), diphenyl selenide 4 (87%) and 1-(o-
biphenylyl)-2-phenylethyne 7 (27%) were obtained.
Tri-p-tolylselenonium trifluoromethanesulfonate 6b. Di-
p-tolyliodonium trifluoromethanesulfonate 14 (1.0 g,
2.2 mmol) was similarly treated with di-p-tolyl selenide
(0.57 g, 2.2 mmol) and copper benzoate (12 mg,
0.04 mmol) and gave 6b (0.8 g, 74%) as a colorless solid,
mp 124–126ЊC (Found: C, 52.71; H, 4.12; C22H21F3O3SSe
requires C, 52.70; H, 4.22%); nmax(film)/cmϪ1 3045, 1488,
1259, 1158; dH(400 MHz; CDCl3) 2.45 (9 H, s, Me), 7.41 (6
H, d, Jˆ8.3, ArH), 7.41 (6 H, d, Jˆ8.3, ArH); dC(100 MHz;
CDCl3) 21.5, 120.6, 123.2, 130.8, 132.2, 144.7; m/z (FAB)
353 ([MϪTfO]ϩ, 95%).
Reaction of alkynylselenonium salt 1b with
p-tolyllithium
p-Tolyllithium was prepared from a THF solution (5 ml) of
p-bromotoluene (133 mg, 0.78 mmol) and n-butyllithium in
hexane (0.49 ml, 0.78 mmol), and added dropwise to a THF
solution (5 ml) of alkynylselenonium salt 1b (290 mg,
0.6 mmol) at room temperature under argon. After being
stirred magnetically for 3 h at ambient temperature, the
reaction mixture was treated as mentioned above. The raw
product was purified by preparative TLC (hexane) to give a
mixture of 18 and 19 (32 mg, 19%) as a colorless oil and the
ratio of these compounds was determined by HPLC (18:
19 mg, 11%, 19: 13 mg, 8%).
Reaction of alkynylselenonium salt 1a with
phenylethynyllithium
A THF solution (5 ml) of alkynylselenonium salt 1a
(290 mg, 0.60 mmol) was treated with phenylethynyl-
lithium, which was prepared in a similar way as mentioned
above. Reaction products were analyzed by HPLC in the
same manner as described in the reaction of alkynylseleno-
nium salt 1a with phenyllithium. 1,3-Diphenylbutadiyne 5
(75%) and diphenyl selenide 4 (94%) were obtained.
1-Bromo-2-(phenylethynyl)-5-methylbenzene 22. n-Butyl-
lithium in hexane (3.26 ml, 5.0 mmol) was added dropwise
to a THF solution (20 ml) of benzyltriphenylphosphonium
bromide (2.18 g, 5.0 mmol) at 0ЊC under argon. After the
reaction mixture was stirred magnetically for 30 min at
Ϫ78ЊC, 2-bromo-4-tolualdehyde 2015 (1.0 g, 5.0 mmol)
was added to it. The whole was stirred for 2 h at room
temperature, and extracted with hexane. The extracts were
dried over anhydrous MgSO4 and the solvent was evapo-
rated under reduced pressure. The crude product was puri-
fied by column chromatography (hexane) to yield (E)-22
(640 mg, 47%) and (Z)-22 (574 mg, 42%) as yellow oils.
(E)-22: nmax(film)/cmϪ1 3025, 1597, 1496, 1448, 1038;
dH(400 MHz; CDCl3) 2.29 (3 H, s, CH3), 6.96 (1H, d,
Jˆ16.1, CH), 7.06 (1 H, d, Jˆ7.8, ArH), 7.24 (1 H, t,
Jˆ7.6, ArH), 7.34 (2 H, t, Jˆ7.6, ArH), 7.38 (1 H, s,
ArH), 7.42 (1 H, s, Jˆ16.1, CH), 7.49–7.53 (3 H, m,
ArH); dC(100 MHz; CDCl3) 20.8, 123.9, 126.2, 126.7,
127.3, 127.8, 128.4, 128.7, 130.4, 133.4, 134.2, 137.2,
139.1; m/z (EI) 274 (Mϩϩ2, 42%), 272(Mϩ, 44%), 178
Reaction of triphenylselenonium salt 6a with
2-(phenylethynyl)phenyllithium 15
A THF solution (5 ml) of 1-bromo-2-(phenylethynyl)-
benzene19 (200 mg, 0.78 mmol) was treated with n-butyl-
lithium in hexane (0.49 ml, 0.78 mmol) at Ϫ78ЊC under
argon. After the mixture was stirred magnetically for
30 min at Ϫ78ЊC, the solution of 2-(phenylethynyl)phenyl-
lithium 15 thus prepared was added dropwise to a THF
solution (5 ml) of triphenylselenonium salt 6a (276 mg,
0.60 mmol) at room temperature with a cannula. After
being stirred magnetically for 3 h at ambient temperature,
the reaction mixture was quenched with water (5 ml), and
extracted with hexane. Reaction products were analyzed by
HPLC as mentioned above. Diphenyl selenide 4 (87%) and
1-(o-biphenylyl)-2-phenylethyne 7 (61%) were obtained.

862
S. Watanabe et al. / Tetrahedron 56 (2000) 855–863
(100); HRMS: m/z For C15H13Br (Calc.: M, 272.0401.
Found: Mϩ, 272.0203). (Z)-22: nmax(film)/cmϪ1 3023,
1601, 1485, 1446, 1039; dH(400 MHz; CDCl3) 2.27 (3 H,
s, CH3), 6.58 (1 H, d, Jˆ12.0, CH), 6.63 (1 H, d, Jˆ12.0,
CH), 6.85 (1 H, d, Jˆ7.8, ArH), 7.05 (1 H, d, Jˆ7.8, ArH),
7.12–7.18 (5 H, m, ArH), 7.41 (1 H, s, ArH); dC(100 MHz;
CDCl3) 20.8, 123.8, 127.2, 127.9, 128.1, 128.9, 129.3,
130.4, 130.9, 133.0, 134.8, 136.5, 138.8; m/z (EI) 274
(Mϩϩ2, 52%), 272(Mϩ, 53%), 178 (100); HRMS: m/z For
C15H13Br (Calc.: M, 272.0401. Found: Mϩ, 272.0190).
nmax(film)/cmϪ1 3054, 2213, 1599, 1492, 1469, 1032;
dH(400 MHz; CDCl3) 2.29 (3 H, s, CH3), 6.98 (1 H, dd,
Jˆ2.0 and 8.3, ArH), 7.34–7.37 (4 H, m, ArH), 7.47 (1 H,
d, Jˆ8.3, ArH), 7.56–7.58 (2 H, m, ArH); dC(100 MHz;
CDCl3) 20.7, 88.2, 93.5, 122.3, 123.0, 125.0, 128.4, 128.6,
130.4, 131.7, 132.1, 133.8, 137.0; m/z (EI) 272 (Mϩϩ2,
99%), 270(Mϩ, 100%).
2-(Phenylethynyl)-5,40-dimethyl-1,10-biphenyl 18. n-Butyl-
lithium in hexane (0.43 ml, 0.66 mmol) was added dropwise
to a THF solution (5 ml) of 24 (178 mg, 0.66 mmol) at
Ϫ78ЊC under argon. After being stirred magnetically for
30 min at Ϫ78ЊC, the reaction mixture was added dropwise
to a THF solution (5 ml) of selenonium salt 6b (300 mg,
0.60 mmol) at room temperature. The whole was stirred
magnetically for 3 h at ambient temperature, quenched
with water (5 ml), and extracted with hexane. The organic
phase was dried over anhydrous MgSO4, and the solvent
was evaporated under reduced pressure. The crude product
was purified by preparative TLC (hexane) to give 18
(43 mg, 25%) as a yellow oil, (Found: C, 93.36; H, 6.60;
C22H18 requires C, 93.58; H, 6.42%); nmax(film)/cmϪ1 3023,
2212, 1595, 1497; dH(400 MHz; CDCl3) 2.40 (3 H, s, CH3),
2.42 (3 H, s, CH3), 7.10 (1 H, d, Jˆ7.8, ArH), 7.22–7.27 (6
H, m, ArH), 7.32–7.35 (2 H, m, ArH), 7.52 (1 H, d, Jˆ7.8,
ArH), 7.56 (2 H, d, Jˆ8.3, ArH); dC(100 MHz; CDCl3)
21.2, 21.5, 89.7, 91.4, 118.5, 123.8, 127.6, 127.8, 128.2,
128.6, 129.2, 130.2, 131.3, 132.9, 137.1, 137.7, 138.6,
143.7; m/z (EI) 282 (Mϩ, 100%), 267 (40).
1-Bromo-2-(phenylethynyl)-4-methylbenzene 23.
A
phosphorane was prepared from a THF solution (20 ml) of
benzyltriphenylphosphonium bromide (1.95 g, 4.5 mmol)
and n-butyllithium in hexane (2.8 ml, 4.5 mmol), and
allowed to react with 2-bromo-5-tolualdehyde 2116
(900 mg, 4.5 mmol). The mixture was similarly treated as
described above, and extracted with hexane. The extracts
were dried over anhydrous MgSO4 and the solvent was
evaporated under reduced pressure. The crude product was
purified by column chromatography (hexane) to yield (E)-
23 (350 mg, 29%) as a yellow oil, (Found: C, 65.80; H, 4.73;
C15H13Br requires C, 65.95; H, 4.80%); nmax(film)/cmϪ1
3058, 1599, 1495, 1470, 1025; dH(400 MHz; CDCl3) 2.31
(3 H, s, CH3), 6.91 (1 H, d, Jˆ7.8, ArH), 7.00 (1 H, d,
Jˆ16.1, CH), 7.27 (1 H, t, Jˆ7.3, ArH), 7.35 (2 H, t,
Jˆ7.3, ArH), 7.41–7.45 (3 H, m, ArH), 7.53 (2 H, d,
Jˆ7.3, ArH); dC(100 MHz; CDCl3) 21.9, 120.9, 126.8,
127.3, 127.5, 128.0, 128.7, 129.8, 131.1, 132.7, 136.7,
137.1,137.3; m/z (EI) 274 (Mϩϩ2, 45%), 272(Mϩ, 48%),
178 (100).
2-(Phenylethynyl)-4,40-dimethyl-1,10-biphenyl 19. 2-Phenyl-
ethynyl-4-tolyllithium was prepared from a THF solution
(3 ml) of 25 (96 mg, 0.36 mmol) and n-butyllithium in
hexane (0.23 ml, 0.36 mmol) at Ϫ78ЊC under argon and
added dropwise to a THF solution (3 ml) of selenonium
salt 6b (162 mg, 0.32 mmol) at room temperature. The
reaction mixture was treated in a similar way as for
compound 18. The crude product was purified by prepara-
tive TLC (hexane) to give 19 (25 mg, 25%) as a yellow oil;
nmax(film)/cmϪ1 3022, 2211, 1604, 1492; dH(400 MHz;
CDCl3) 2.38 (3 H, s, CH3), 2.41 (3 H, s, CH3), 7.19 (1 H,
d, Jˆ7.8, ArH), 7.23–7.35 (8 H, m, ArH), 7.46 (1 H, s,
ArH), 7.56 (2 H, d, Jˆ8.3, ArH); dC(100 MHz; CDCl3)
20.8, 21.2, 89.7, 91.7, 121.2, 123.7, 128.0, 128.2, 128.6,
129.2, 129.3, 129.5, 131.4, 133.4, 136.5, 136.9, 137.6,
141.0; m/z (EI) 282 (Mϩ, 100%), 267 (40); HRMS: m/z
For C22H18 (Calc.: M, 282.1409. Found: Mϩ, 282.1403).
1-Bromo-2-(phenylethynyl)-5-methylbenzene 24. To a
stirred solution of 22 (1458 mg, 1.68 mmol) in CH2Cl2
(50 ml) was added Br2 (0.3 ml, 5.7 mmol) at 0ЊC under
argon. After the reaction mixture was stirred for 2 h, sat.
Na2S2O3 (aq.) was added to it, and the whole was extracted
with CH2Cl2. The extracts were dried (MgSO4) and evapo-
rated under reduced pressure. The residue was dissolved in
t-BuOH (25 ml) and treated with 90% t-BuOK (272 mg,
2.2 mmol) under reflux for 6 h. The mixture was quenched
with water and extracted with hexane. The organic phase
was dried over anhydrous MgSO4, and concentrated. The
residue was purified by preparative TLC (hexane) to give 24
(178 mg, 39%) as white prisms, mp 48–50ЊC (Found: C,
66.68; H, 4.18; C15H11Br requires C, 66.44; H, 4.09%);
nmax(film)/cmϪ1 3060, 2221, 1596, 1498, 1442, 1041;
dH(400 MHz; CDCl3) 2.30 (3 H, s, CH3), 7.07 (1 H, d,
Jˆ7.8, ArH), 7.33–7.36 (3 H, m, ArH), 7.43 (2 H, d,
Jˆ7.8, ArH), 7.55–7.58 (2 H, m, ArH); dC(100 MHz;
CDCl3) 21.1, 88.2, 93.1, 122.4, 123.2, 125.4, 128.0, 128.4,
128.5, 131.6, 132.9, 133.0, 140.6; m/z (EI) 272 (Mϩϩ2,
98%), 270(Mϩ, 100%).
Reaction of tri-p-tolylselenonium salt 6b with
p-tolyllithium
Tolyllithium in THF (1.0 ml, 0.20 mmol) was added drop-
wise to a THF solution (2.5 ml) of tri-p-tolylselenonium salt
6b (100 mg, 0.62 mmol) at room temperature under argon.
After being stirred magnetically for 3 h at ambient tempera-
ture, the reaction mixture was hydrolyzed with water (5 ml),
and extracted with hexane. The extracts were dried
(MgSO4) and evaporated under reduced pressure. The resi-
due was purified by preparative TLC (hexane) to give di-p-
tolyl selenide 30 (43 mg, 82%) and a mixture of 28 and 2917
(23 mg, 63%) as a yellow oil. The ratio of these compounds
was determined in comparison with their methyl signals of
1-Bromo-2-(phenylethynyl)-4-methylbenzene 25. A solu-
tion of 23 (506 mg, 2.29 mmol) in CH2Cl2 (25 ml) was
brominated with Br2 (0.5 ml, 9.5 mmol) at 0ЊC under
argon in a similar way as for compound 24. The bromide
thus prepared was dehydrobrominated with 90% t-BuOK
(686 mg, 5.5 mmol) in t-BuOH (20 ml). The raw product
was purified by preparative TLC (hexane) to give 25
(174 mg, 28%) as white prisms, mp 62–65ЊC (Found: C,
66.70; H, 4.10; C15H11Br requires C, 66.44; H, 4.09%);

S. Watanabe et al. / Tetrahedron 56 (2000) 855–863
863
1H NMR with authentic samples (28: 15 mg, 41%, 29: 8 mg,
22%).
(b) Ogawa, S.; Sato, S.; Furukawa, N. Tetrahedron Lett. 1992, 33,
7925–7928.
7. (a)Kataoka, T.; Banno, Y.; Watanabe, S.; Iwamura, T.;
Shimizu, H. Tetrahedron Lett. 1997, 38, 1809–1812. (b) Kataoka,
T.; Watanabe, S.; Yamamoto, K.; Yoshimatsu, M.; Tanabe, G.;
Muraoka, O. J. Org. Chem. 1998, 63, 6382–6386. (c) Kataoka,
T.; Watanabe, S.; Yamamoto, K. Tetrahedron Lett. 1999, 40,
931–934.
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