Tandem addition-cyclization of o-ethynylphenyllithiums and isoselenocyanates: A convenient preparation of functionalized benzo[c]selenophenes

Article abstract of DOI:10.1016/j.tetlet.2011.04.057

The o-bromoethynylbenzenes were lithiated with tert-BuLi in Et₂O followed by treatment with isoselenocyanate, and then EtOH was added as a proton source, producing the desired (Z)-3-methylidenebenzo[c]selenophenes as the sole 5-exo-dig mode cyc

Full text of DOI:10.1016/j.tetlet.2011.04.057

Tetrahedron Letters 52 (2011) 3279–3282
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Tetrahedron Letters
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Tandem addition–cyclization of o-ethynylphenyllithiums
and isoselenocyanates: a convenient preparation of functionalized
benzo[c]selenophenes q
⇑
Mamoru Kaname, Haruki Sashida
Faculty of Pharmaceutical Sciences, Hokuriku University, Kanagawa-machi, Kanazawa 920-1181, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The o-bromoethynylbenzenes were lithiated with tert-BuLi in Et2O followed by treatment with isoselen-
Received 4 March 2011
Revised 10 April 2011
Accepted 13 April 2011
Available online 28 April 2011
ocyanate, and then EtOH was added as
a proton source, producing the desired (Z)-3-meth-
ylidenebenzo[c]selenophenes as the sole 5-exo-dig mode cyclization products in one-pot with yields
ranging from 54–87%. The iodocyclization of the o-ethynylphenyllithium with isoselenocyanate stereose-
lectively gave the (E)-10-iodo-3-methylidenebenzo[c]selenophene, which was converted into the more
functionalized benzo[c]selenophenes via the Suzuki- and Sonogashira-coupling reactions.
Ó 2011 Published by Elsevier Ltd.
Keywords:
o-Ethynylphenyllithium
Isoselenocyanate
Benzo[c]selenophene
Tandem addition–cyclization
Iodocyclization
Recently, considerable attention has focused on the synthetic
studies of various selenium-containing heterocycles not only be-
cause of their attractive chemical properties and reactivities, but
also because of their pharmaceutical applications.2 In contrast to
many reports on the benzo[b]selenophenes,3 which are quite sta-
ble, the synthesis of the benzo[c]selenophenes4 has been the objec-
tive of considerable chemical interest, both from synthetic and
theoretical points of views, but is limited, as the hydrogenated
derivatives have not yet been examined.5
per-catalyzed one-pot reaction of 2-iodoanilines and isoselenocya-
nates was also described. Furthermore, in 1998,17,18 we published
two reports of the synthesis of benzo[b]chalcogenophenes17a
involving benzo[b]selenophenes and (Z)-3-methylideneselenoph-
thalides18 obtained from the o-bromoethynylbenzenes. The former
involved the quite useful, simple, and versatile one-pot 5-endo-dig
mode cyclization of the selenol, which is generated through the o-
ethynylphenyllithiums. The latter included the stereospecific prep-
aration of the (Z)-3-methylideneselenophthalides through the 2-
ethynylbenzoselenoic Se-acid. To the best of our knowledge, there
is no report on the reaction of isoselenocyanates with a carbanion
except for active methylene compounds,19 such as malononitrile
and cyanoacetate. It is known that alkyl and phenyllithiums react
with isothiocyanates to give the corresponding thioamides,20 but
do not react at low temperature (ꢀ78 °C).21
On the other hand, the isoselenocyanates6 are powerful syn-
thetic precursors for the preparation of selenium-containing het-
erocycles because they are easy to prepare and store, and are safe
to handle. Thus, many reports concerning the synthesis of sele-
nium-containing heterocycles using isoselenocyanates with nucle-
ophiles, such as amines,7 alcohols,8 thiols,9 selenolates,10 and
others; for example, azodicarboxylates,11 diazo compounds12 have
been published. Previously, we have also focused on the synthesis
of the 1,3-benzoselenazines,13 which are six-membered heterocy-
cles containing nitrogen and selenium atoms; the synthetic method
involved the catalyst- and solvent-free intramolecular cyclization
of the selenols, which were generated from isoselenocyanates used
as the selenium source, into a triple bond.14,15 Very recently, the
simple preparation of the 2-aminobenzoselenazoles16 by the cop-
In this Letter, the simple preparation of the benzo[c]selenoph-
enesbythetandemaddition–cyclizationof theo-ethynylphenyllith-
iums, generated from the same starting o-bromoethynylbenzenes,
and the isoselenocyanates as the selenium source were evaluated.
In addition, the iodocyclization of the o-ethynylphenyllithiums
and the isoselenocyanates, followed by the transformation of the
iodomethylideneselenophenes to the more functionalized com-
pounds via the palladium-catalyzed reactions is also described.
The o-bromoethynylbenzene 1a was lithiated with 1.2 equiv of
t-BuLi in anhydrous THF at ꢀ80 °C under an argon atmosphere, fol-
lowed by treatment with 1.5 equiv of cyclohexyl isoselenocyanate
2A at room temperature, and then ethanolyzed to give the desired
q
See Ref. 1.
⇑
Corresponding author. Tel.: +81 76 229 6211; fax: +81 76 229 2781.
E-mail address: h-sashida@hokuriku-u.ac.jp (H. Sashida).
0040-4039/$ - see front matter Ó 2011 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2011.04.057

3280
M. Kaname, H. Sashida / Tetrahedron Letters 52 (2011) 3279–3282
Table 1
3-Methylidenebenzo[c]selenophenes 3
1) t-BuLi
2)
R1
R1
R2 NCSe
2
Se
3) EtOH
Br
N
R2
1
3
Entry
Substrate
Isoselenocyanate
Solvent (temp)
Product
Yielda (%)
1
2
3
4
5
6
7
8
9
10
1a (R1 = n-Bu)
1a
1a
1a
2A (R2 = cyclohexyl)
THF (rt)
3Aa
3Aa
3Ba
3Ca
3Da
3Da
3Ab
3Ac
3Ad
3Ae
13
87
54
0
2A
Et2O (rt)
Et2O (rt)
Et2O (rt)
Et2O (rt)
Et2O (reflux)
Et2O (rt)
Et2O (rt)
Et2O (rt)
Et2O (rt)
2B (R2 = n-Bu)
2C (R2 = t-Bu)
1a
1a
2D (R2 = Ph)
2
2D
2A
2A
2A
2A
64
71
85
83
69
1b (R1 = Me)
1c (R1 = t-Bu)
1d (R1 = TMS)
1e (R1 = Ph)
a
Isolated yield.
R1
R1
R1
R1
R2 NCSe
t-BuLi
2
and/or
Se
SeLi
Br
Li
LiN
N
1'
R2
R2
1
6
4
5
EtOH
R1
R1
R1
4
3
5-exo-dig
6-endo-dig
Se
2
Se
R2
SeH
R2
1
N
N
R2
N
8
7
3
Scheme 1.
(Z)-3-methylidenebenzo[c]selenophene 3Aa in only 13% yield in
one-pot; no starting material was recovered (Table 1, entry 1).
When 1a was similarly treated with 2A in anhydrous Et2O, 3Aa
was produced in 87% yield (entry 2).22 The reaction of 1a with n-
butyl isoselenocyanate 2B, the primary aliphatic isoselenocyanate,
also occurs under the same conditions to afford the selenophene
3Ba in 54% yield (entry 3). On the other hand, the use of tert-butyl
isoselenocyanate 2C gave a complex mixture; no corresponding
selenophene 3Ca was obtained (entry 4). The lower reactivity of
tert-butyl isoselenocyanate 2C may be due to the steric hindrance
by the bulky tertiary butyl group. Although 1a also reacted with
phenyl isoselenocyanate 2D to produce the phenylimino derivative
3Da in Et2O at room temperature in only 2% yield, 3Da was
obtained in refluxing Et2O in 64% yield (entry 5 vs 6). The extension
of this tandem addition–cyclization of the substrates having an
alkyl or phenyl group at the triple bond with cyclohexyl isoselen-
ocyanate 2A was also carried out. The treatment of o-propynylb-
romobenzene 1b and tert-butyl derivative 1c with t-BuLi,
followed by the addition of isoselenocyanate 2A gave the corre-
sponding selenophenes 3Ab and 3Ac in 71 and 85% yields, respec-
The configuration of the olefin moiety of 3 was determined by
the NOE, which was observed between the 10-H and the aromatic
4-H in the 500 MHz 1H NMR spectra of 3Aa. Thus the olefin moiety
was determined to have a (Z)-configuration. The stereospecific
intramolecular trans-addition of phenylselenols, alkylselenols and
relative compounds to an acetylene group, forming (Z)-vinylsele-
nides, is well known.23 These results support the proposed mecha-
nism described below.
A
plausible mechanism for the formation of (Z)-3-meth-
ylidenebenzo[c]selenophene 3 from o-bromoethynylbenzene 1
with isoselenocyanate 2 is shown in Scheme 1. The successful
intramolecular cyclization of the initial adduct 5 or 6, which is gen-
erated by the attack of the carbanion 4 on the sp carbon of the
isoselenocyanate 2, may be protonated by EtOH to give selenol 7.
The resulting selenol 7 cyclized to afford the sole 5-exo-dig mode
product 3; no 6-endo-dig mode cyclization products 8 were ob-
tained. In case of the absence of a proton source, no products and
starting isoselenocyanates were obtained; EtOH as a proton source
gave the best results. Therefore, it is clear that the addition of carb-
anion 4 to the isoselenocyanate 2 gave the adduct 5 or 6, which
was gradually decomposed during the isolation operation or on
standing.
tively (entries
7 and 8). The TMS methylidene 3Ad and
benzylideneselenophene 3Ae were also obtained from the corre-
sponding o-bromoethynylbenzenes in good to high yields (entries
9 and 10).
Next, the iodocyclization of o-ethynylphenyllithium 4 with
isoselenocyanate
2 was found to proceed stereoselectively

M. Kaname, H. Sashida / Tetrahedron Letters 52 (2011) 3279–3282
3281
H
n-Bu
n-Bu
n-Bu
Se
N
Br
Se
1a
3Aa
(30%)
PhB(OH)2
N
Pd(OAc)2, Cs2CO3
HCOOH, Et3N
PdCl2(Ph3P)2
t-BuLi
10
(56%)
I
1)
NCSe
n-Bu
n-Bu
2A
PhC CH
n-Bu
Se
2) t-BuOH
3) I2 or NIS
PdCl2(Ph3P)2
CuI
Li
N
Se
N
9
4a
5-exo-dig
11
(84%)
Scheme 2.
affording the (E)-10-iodo-3-methylidenebenzo[c]selenophene 9 as
shown in Scheme 2. o-Ethynylphenyllithium 4a generated from
1a was similarly treated with cyclohexyl isoselenocyanate 2A,
and then protonated with t-BuOH, followed by iodination with I2,
giving the desired (E)-10-iodobenzo[c]selenophene 9 in one-pot in
40% yield24; NIS gave a somewhat lower yield (25% yield) com-
pared to that of I2. This iodobenzo[c]selenophene 9 can be reduced
to 3Aa by treatment with HCOOH/Et3N in the presence of a palla-
dium-catalyst, and further functionalized by palladium-catalyzed
coupling reactions. The (E)-10-phenyl-3-methylidenebenzo[c]sel-
enophene 10 was produced in 56% isolated yield by the Suzuki
cross coupling of 9 with phenylboric acid. The Sonogashira reaction
of 9 with phenylacetylene gave 11 in 84% yield.
2. (a)Selenium in Biology and Medicine; Wengel, A., Ed.; Springer: Berlin, 1989; (b)
Burk, R. F. Selenium in Biology and Human Health; Springer: New York, 1994; (c)
Xu, Y.; Kool, E. T. J. Am. Chem. Soc. 2000, 122, 9040–9041; (d) Mugesh, G.; du
Mont, W.-W.; Sies, H. Chem. Rev. 2001, 101, 2125–2180; (e) Soriano-Garcia, M.
Curr. Med. Chem. 2004, 11, 1657–1669.
3. Recent works on benzo[b]selenophenes: (a) Lyons, J. E.; Schiesser, C. H.; Sutej,
K. J. Org. Chem. 1993, 58, 5632–5638; (b) Kloc, K.; Młochowski, J. Tetrahedron
Lett. 2001, 42, 4899–4902; (c) Stefani, H. A.; Petragunani, N.; Ascenso, M. F. C.;
Zeni, G. Synth. Commun. 2003, 33, 2161–2166; (d) Okamoto, T.; Kudoh, K.;
Wakamiya, A.; Yamaguchi, S. Org. Lett. 2005, 7, 5301–5304; (e) Kesharwani, T.;
Worlikar, S. A.; Larock, R. C. J. Org. Chem. 2006, 71, 2307–2312; (f) Takimiya, K.;
Kunugi, Y.; Konda, Y.; Ebata, H.; Toyoshima, Y.; Otsubo, T. J. Am. Chem. Soc.
2006, 128, 3044–3055; (g) Bui, C. T.; Flynn, B. L. J. Comb. Chem. 2006, 8, 163–
167; (h) Rosa, C. D.; Kneeteman, M.; Mancini, O. Tetrahedron Lett. 2007, 48,
7075–7078; (i) Sato, T.; Nakamura, I.; Terada, M. Eur. J. Org. Chem. 2009, 5509–
5512; (j) Kashiki, T.; Shinamura, S.; Kohara, M.; Miyazaki, E.; Takimiya, K.;
Ikeda, M.; Kuwabara, H. Org. Lett. 2009, 11, 2473–2475.
4. (a) Saris, L. E.; Cava, M. P. J. Am. Chem. Soc. 1976, 98, 867–868; (b) Aqad, E.;
Lakshmikantham, M. V.; Cava, M. P.; Broker, G. A.; Rogers, R. D. Org. Lett. 2003,
5, 2519–2521; (c) Mohanakrishnan, A. K.; Amaladass, P. Tetrahedron Lett. 2005,
46, 7201–7204; (d) Mohanakrishnan, A. K.; Kumar, N. S.; Amaladass, P.
Tetrahedron Lett. 2008, 49, 4792–4795; (e) Kumar, N. S.; Mohanakrishnan, A. K.
Tetrahedron 2010, 66, 5660–5670.
5. Sashida, H.; Ohyanagi, K.; Minoura, M.; Akiba, K. J. Chem. Soc., Perkin Trans. 1
2002, 606–612.
6. (a) Garud, D. R.; Koketsu, M.; Ishihara, H. Molecules 2007, 12, 504–535; (b)
Heimgartner, H.; Zhou, Y.; Atanassov, P. K.; Sommen, G. L. Phosphorus, Sulfur
Silicon Relat. Elem. 2008, 183, 840–855; (c) Ninomiya, M.; Garud, D. R.; Koketsu,
M. Heterocycles 2010, 81, 2027–2055.
In summary, the one-pot catalyst- and ligand-free tandem
addition–cyclization of the 2-ethynylphenyllithiums with the
isoselenocyanates for the practical synthesis of the (Z)-3-meth-
ylidenebenzo[c]selenophenes via the 5-exo-dig mode cyclization
smoothly occurred; the reaction of the phenylcarbanion with the
isoselenocyanate is the first such example. The iodocyclization in
a
similar manner also proceeded to give the (E)-10-
iodobenzo[c]selenophene.
A variety of 3-methylidenebenzo[c]selenophenes was easily ob-
tained in almost good yields.
ˇ
7. Amines: (a) Kristian, P.; Košcik, D.; Gonda, J. Collect. Czech. Chem. Commun.
1983, 48, 3567–3574; (b) Banert, K.; Hückstädt, H.; Vrobel, K. Angew. Chem., Int.
Ed. Engl. 1992, 31, 90–92; (c) Banert, K.; Toth, C. Angew. Chem., Int. Ed. Engl.
1995, 34, 1627–1629; (d) Matsumoto, H.; Hara, S.; Nagata, N.; Ikeda, K.;
Mizuno, Y. Heterocycles 1995, 41, 47–56; (e) Hashim Nizar, P. N.; Parkash, S.;
Chauhan, S. M. S. J. Indian Chem. Soc. 1997, 74, 161–162; (f) Atanassov, P. K.;
Linden, A.; Heimgartner, H. Helv. Chim. Acta 2003, 86, 3235–3243; (g) Ueda, S.;
Terauchi, H.; Yano, A.; Matsumoto, M.; Kubo, T.; Kyoya, Y.; Suzuki, K.; Ido, M.;
Kawasaki, M. Bioorg. Med. Chem. Lett. 2004, 12, 4101–4116; (h) Ueda, S.;
Terauchi, H.; Yano, A.; Ido, M.; Matsumoto, M. Bioorg. Med. Chem. Let. 2004, 14,
313–316; (i) Atanassov, P. K.; Linden, A.; Heimgartner, H. Heterocycles 2003, 61,
569–579; (j) Atanassov, P. K.; Linden, A.; Heimgartner, H. Helv. Chim. Acta 2004,
87, 1873–1887; (k) Ueda, S.; Terauchi, H.; Suzuki, K.; Yano, A.; Matsumoto, M.;
Kubo, T.; Minato, H.; Arai, Y.; Tsuji, J.; Watanabe, N. Bioorg. Med. Chem. Lett.
2005, 15, 1361–1366; (l) Sommen, G. L.; Linden, A.; Heimgartner, H. Eur. J. Org.
Chem. 2005, 3128–3137; (m) Sommen, G. L.; Linden, A.; Heimgartner, H.
Tetrahedron Lett. 2005, 46, 6723–6725; (n) Koketsu, M.; Yamamura, Y.; Ishihara,
H. Heterocycles 2006, 68, 1191–1200; (o) Koketsu, M.; Sakai, T.; Kiyokuni, T.;
Garud, D. R.; Ando, H.; Ishihara, H. Heterocycles 2006, 68, 1607–1615; (p)
Sommen, G.; Linden, A.; Heimgartner, H. Helv. Chim. Acta 2006, 89, 1322–1329;
(q) Koketsu, M.; Takahashi, A.; Ishihara, H. J. Heterocyclic Chem. 2007, 44, 79–81.
8. Alcohols: (a) Mizuno, T.; Nakamura, F.; Ishino, Y.; Nishiguchi, I.; Hirashima, T.;
Ogawa, A.; Kambe, N.; Sonoda, N. Synthesis 1989, 770–771; (b) Silks, L. A.; Peng,
J.; Odom, J. D.; Dunlap, R. B. J. Chem. Soc., Perkin Trans. 1 1991, 2495–2498; (c)
Fujiwara, S.; Shikano, Y.; Shin-ike, T.; Kambe, N.; Sonoda, N. J. Org. Chem. 2002,
67, 6275–6278; (d) Asanuma, Y.; Fujiwara, S.; Shin-ike, T.; Kambe, N. J. Org.
Chem. 2004, 69, 4845–4848.
Acknowledgments
This work was supported in part by a Grant-in Aid for Scientific
Research from the Ministry of Education, Science and Culture, Ja-
pan (19590022). Thanks are due to Ms. Sayuri Ando and Yuko Usa-
mi (Hokuriku University) for their technical assistances.
Supplementary data
Supplementary data (experimental procedures, IR, 1H NMR, 13
NMR, MS and HR-MS data of all obtained new products) associated
with this article can be found, in the online version, at doi:10.1016/
j.tetlet.2011.04.057.
C
References and notes
1. This paper constitutes Part 34 in the series ‘Studies on Chalcogen-Containing
Heterocycles’, which was changed from ‘Studies on Tellurium-Containing
Heterocycles’ since this Letter. For Part 33: Ref. 16.

3282
M. Kaname, H. Sashida / Tetrahedron Letters 52 (2011) 3279–3282
9. Thiols: Sommen, G. L.; Linden, A.; Heimgartner, H. Heterocycles 2005, 65, 1903–
1915.
10. Selenolates: (a) Zmitrovich, N. I.; Petrov, M. L.; Potekhim, K. A.; Balashva, E. V.
Zhurmal Obshchei Khimii 1996, 66, 1684–1687; (b) Zmitrovich, N. I.; Petrov, M.
L. Zhurmal Organicheskoi Khim. 1996, 32, 1870–1874.
of o-bromoethynylbenzene 1a (236 mg, 1 mmol) in anhydrous Et2O (10 mL) at
ꢀ80 °C under argon atmosphere was slowly added t-BuLi (1.6 M in pentane
solution, 0.76 mL, 1.2 mmol). After stirring under same conditions 2 h, a
solution of cyclohexyl isoselenocyanate 2A (1.5 mmol) in Et2O (3 mL) was
slowly added to the mixture, and then the cooling bath was removed to allow
to warm up to room temperature for 1 h. EtOH (1 mL) was added to the
mixture. The whole mixture was stirred (refluxed for phenyl isoselenocyanate)
for further 12 h, and then poured into ice-water (20 mL). The aqueous mixture
was extracted with Et2O (10 mL ꢁ 3). The combined organic layer was washed
with brine, (20 mL ꢁ 2) dried over anhydrous Na2SO4, and concentrated in
vacuo. The obtained residue was chromatographed on silica gel using CHCl3–
hexane (1:1) as an eluent to give pure 3Aa. Yield: 301 mg (87%). Yellow oil. IR
11. Azodicarboxylates: Favero, F.; Sommen, G.; Linden, A.; Heimgartner, H.
Heterocycles 2006, 67, 749–762.
12. Diazo compounds: (a) Suchár, G.; Kristian, P. Chemicke Zvesti 1975, 29, 244–
249; (b) Zhou, Y.; Heimgartner, H. Helv. Chim. Acta 2000, 83, 539–553.
13. Sashida, H.; Pan, C.; Kaname, M.; Minoura, M. Synthesis 2010, 3091–3096.
14. Reviews: (a) Sashida, H. Rev. Heteroat. Chem. 2000, 22, 59–78; (b) Sashida, H. J.
Syn. Org. Chem. Jpn. 2001, 59, 355–362; (c) Sashida, H. Mini-Rev. Org. Chem.
2007, 4, 105–114; (d) Sashida, H.; Minoura, M. J. Syn. Org. Chem. Jpn. 2009, 67,
714–723.
15. Recent works: (a) Sashida, H.; Nakayama, A.; Kaname, M. Synthesis 2008, 3229–
3236; (b) Sashida, H.; Nakabayashi, S.; Kaname, M.; Minoura, M. Heterocycles
2010, 80, 1339–1352; (c) Sashida, H.; Satoh, H.; Ohyanagi, K.; Kaname, M.
Molecules 2010, 15, 1466–1472; (d) Sashida, H.; Kaname, M.; Ohyanagi, K.
Heterocycles 2010, 82, 441–447; (e) Sashida, H.; Kaname, M.; Nakayama, A.;
Suzuki, H.; Minoura, M. Tetrahedron 2010, 66, 5149–5157; (f) Sashida, H.;
Nakabayashi, S.; Suzuki, H.; Kaname, M.; Minoura, M. Tetrahedron Lett. 2010,
51, 5395–5398.
16. Kaname, M.; Minoura, M.; Sashida, H. Tetrahedron Lett. 2011, 52, 505–508.
17. (a) Sashida, H.; Sadamori, K.; Tsuchiya, T. Synth. Commun. 1998, 28, 713–727;
(b) Sashida, H.; Yasuike, S. J. Heterocycl. Chem. 1998, 35, 725–726.
18. Sashida, H.; Kawamukai, A. J. Heterocycl. Chem. 1998, 35, 165–167.
19. Carbanions: (a) Maeda, H.; Kambe, N.; Sonoda, N.; Fujiwara, S.; Shin-ike, T.
Tetrahedron 1997, 53, 13667–13680; (b) Klika, K. D.; Janovec, L.; Imrichi, J.;
Suchár, G.; Kristian, P.; Sillanpää, R.; Pihlaja, K. Eur. J. Org. Chem. 2002, 1248–
1255; (c) Atanassov, P. K.; Linden, A.; Heimgartner, H. Helv. Chim. Acta 2004, 87,
1452–1466; (d) Sommen, G. L.; Comel, A.; Kirsch, G. Phosphorus, Sulfur Silicon
Relat. Elem. 2005, 180, 939–943; (e) Sommen, G.; Linden, A.; Heimgartner, H.
Tetrahedron 2006, 62, 3344–3354.
(KBr-neat): 1635 (C@N) cmꢀ1 1H NMR (CDCl3) d: 0.94, 1.83–1.93, 2.32 (3H, t,
.
J = 7.3 Hz, 4H, m, 2H, td, J = 7.4, 7.3 Hz, n-Bu), 1.26–1.47, 1.51–1.72, 2.93–3.02
(5H, m, 5H, m, 1H, m, cyclohexyl-H), 6.64 (1H, t, J = 7.3 Hz, C = CH-), 7.28, 7.38,
7.70, 8.00 (1H, dd, J = 7.9, 7.0 Hz, 1H, dd, J = 8.0, 7.0 Hz, 1H, d, J = 8.0 Hz, 1H, d,
J = 7.9 Hz, Ph-H). 13C NMR (CDCl3) d: 14.0 (t), 22.5 (t), 24.7 (t), 25.7 (t), 31.1 (t),
32.9 (t), 34.1 (t), 71.8 (d), 120.8 (d), 124.1 (d), 124.9 (d), 127.9 (d), 130.4 (d),
134.0 (s), 140.0 (s), 142.7 (s), 159.0 (s). EI-MS: m/z (%) = 347 (M+, 100), 345 (47),
266 (43), 222 (40), 209 (45), 184 (80). EI-HR-MS: m/z calcd for C19H25N80Se
[M+]: 347.1153; found: 347.1157.
23. (a) Comasseto, J. V. J. Organomet. Chem. 1983, 253, 131–181. and references
cited therein; (b) Potapov, V. A.; Amosova, V. S.; Kashik, A. S. Tetrahedron Lett.
1989, 30, 613–616.
24. A typical experimental procedure for iodocyclization of o-ethynylphenyllithium
with isoselenocyanate is as follows: o-Bromoethynylbenzene 1a (236 mg,
1 mmol) was similarly treated with t-BuLi followed by addition of cyclohexyl
isoselenocyanate 2A as described for the preparation of 3Aa, and then treated
with t-BuOH (1 mL) and I2 (380 mg, 1.5 mmol) instead of EtOH and worked up
to give 9. Yield: 189 mg (40%). Yellow oil. IR (KBr-neat): 1635 (C@N) cmꢀ1 1H
.
NMR (CDCl3) d: 0.98, 1.81–1.90, 2.89 (3H, t, J = 7.4 Hz, 4H, m, 2H, t, J = 7.7 Hz,
n-Bu), 1.28–1.48, 1.55–1.64, 1.64–1.75, 2.92–2.98 (5H, m, 2H, m, 3H, m, 1H, m,
cyclohexyl-H), 7.38, 7.48, 8.08, 9.14 (1H, dd, J = 7.8, 7.2 Hz, 1H, dd, J = 8.2,
7.2 Hz, 1H, d, J = 7.8 Hz, 1H, d, J = 8.2 Hz, Ph-H). 13C NMR (CDCl3) d: 14.0 (q),
21.8 (t), 24.6 (t), 25.7 (t), 30.7 (t), 33.0 (t), 52.6 (t), 71.3 (d), 89.8 (s), 123.8 (d),
124.2 (d), 128.9 (d), 129.6 (d), 131.7 (s), 140.7 (s), 143.1 (s), 156.7 (s). EI-MS:
m/z (%) = 473 (M+, 83), 471 (42), 391 (35), 346 (100), 264 (82), 222 (48), 182
(60), 140 (45). EI-HR-MS: m/z calcd for C19H24NI80Se [M+]: 473.0120; found:
473.0125.
20. (a) Cambie, R. C.; Chambers, D.; Rutledge, P.; Woodgate, P. D. J. Chem. Soc.,
Perkin Trans. 1 1981, 40–51; (b) Tsuge, O.; Kanemasa, S.; Matsuda, K. J. Org.
Chem. 1986, 51, 1997–2004.
21. Kobayashi, K.; Yokoi, Y.; Komatsu, T.; Konishi, H. Tetrahedron 2010, 66, 9336–
9339.
22.
A
typical experimental procedure for tandem addition–cyclization of 2-
ethynylphenyllithium with isoselenocyanate is as follows: To a stirring solution