Photoinduced synthesis of unsymmetrical diaryl selenides from triarylbismuthines and diaryl diselenides

Article abstract of DOI:10.3762/bjoc.9.127

A novel method of photoinduced synthesis of unsymmetrical diaryl selenides from triarylbismuthines and diaryl diselenides has been developed. Although the arylation reactions with triarylbismuthines are usually catalyzed by transition-metal complexes, the present arylation of diaryl diselenides with triarylbismuthines proceeds upon photoirradiation in the absence of transition-metal catalysts. A variety of unsymmetrical diaryl selenides can be conveniently prepared by using this arylation method.

Full text of DOI:10.3762/bjoc.9.127

Photoinduced synthesis of unsymmetrical diaryl
selenides from triarylbismuthines
and diaryl diselenides
Yohsuke Kobiki, Shin-ichi Kawaguchi, Takashi Ohe and Akiya Ogawa*
Letter
Open Access
Address:
Beilstein J. Org. Chem. 2013, 9, 1141–1147.
Department of Applied Chemistry, Graduate School of Engineering,
Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka
599-8531, Japan
doi:10.3762/bjoc.9.127
Received: 16 April 2013
Accepted: 22 May 2013
Published: 13 June 2013
Email:
Akiya Ogawa* - ogawa@chem.osakafu-u.ac.jp
This article is part of the Thematic Series "Organic free radical chemistry".
Guest Editor: C. Stephenson
* Corresponding author
Keywords:
arylation; unsymmetrical diaryl selenide; free radical; organobismuth;
photoinduced reaction
© 2013 Kobiki et al; licensee Beilstein-Institut.
License and terms: see end of document.
Abstract
A novel method of photoinduced synthesis of unsymmetrical diaryl selenides from triarylbismuthines and diaryl diselenides has
been developed. Although the arylation reactions with triarylbismuthines are usually catalyzed by transition-metal complexes, the
present arylation of diaryl diselenides with triarylbismuthines proceeds upon photoirradiation in the absence of transition-metal
catalysts. A variety of unsymmetrical diaryl selenides can be conveniently prepared by using this arylation method.
Introduction
A number of organoselenium compounds are known to be bio- has led to several applications in organic synthesis [33]. There-
logically active [1-4]. In particular, diaryl selenides are known fore, numerous transition-metal-catalyzed coupling reactions
to have antioxidative effects [5]. Therefore, many studies on the with organobismuth compounds have been reported [34-53].
synthetic methods for unsymmetrical diaryl selenides have Although triphenylbismuthine can generate a phenyl radical
recently been reported [6-32]. Most of these methods use [33,54] in the absence of a radical initiator simply by photoirra-
coupling reactions catalyzed by transition-metal complexes. To diation, few arylation reactions using this mechanism have been
avoid the contamination of product selenides with transition- reported [55,56]. We presume that a phenyl radical generated
metals, the development of synthetic methods for unsymmet- from triphenylbismuthine can be captured by organic dise-
rical diaryl selenides in the absence of transition-metal catalysts lenides, which have a high carbon-radical-capturing ability [57-
is desirable. On the other hand, triarylbismuthines are gaining 64] and as a result, diaryl selenide will be generated
interest as useful arylation reagents, because organobismuth (Scheme 1). In 1999, Barton and co-workers reported that diaryl
compounds are nontoxic and have excellent reactivity, which selenide was obtained by the reaction of triarylbismuthine with
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Beilstein J. Org. Chem. 2013, 9, 1141–1147.
diphenyl diselenide under heating at high temperature (140 °C) duce the desired arylation reaction (Table 1, entry 2), and in the
[65], but the photoinduced reaction was not investigated. In this dark, the reaction did not proceed at all (Table 1, entry 3).
letter, we will report the radical reaction of diaryl diselenides When 2,2′-azobis(isobutyronitrile) (AIBN) was used as a
with triarylbismuthines from the viewpoint of a photoinduced radical initiator, the desired reaction proceeded ineffectively
reaction in the synthesis of unsymmetrical diaryl selenides.
(Table 1, entry 4). Among several solvents, such as benzene,
DMSO and CH3CN, the use of CH3CN improved the yield of
3aa (Table 1, entries 5–7). Although the solubility of 2a is
different depending on the solvent, the yield of 3aa is not corre-
lated with the solubility of 2a. It may be more important to
choose a solvent that does not react with the generated aryl
radical. Moreover, a lower amount of solvent and the utiliza-
tion of a quartz test tube ( = 9 mm) contributed to the increase
in the yield of 3aa (Table 1, entries 8 and 9).
Scheme 1: Photoinduced radical reaction of diaryl diselenide with
triphenylbismuthine.
Next, we investigated the scope of the synthesis of unsymmet-
rical diaryl selenides by using different diaryl diselenides and
triarylbismuthines (Table 2). The employed diaryl diselenides
Results and Discussion
First, we investigated the photoinduced reaction of diphenyl were diphenyl diselenide (1a), bis(4-fluorophenyl) diselenide
diselenide with triphenylbismuthine. Diphenyl diselenide (1a, (1b), bis(4-(trifluoromethyl)phenyl) diselenide (1c), bis(1-naph-
0.1 mmol) and triphenylbismuthine (2a, 0.5 mmol) were placed thyl) diselenide (1d), and bis(2-naphthyl) diselenide (1e). The
in a Pyrex test tube ( = 9 mm) with CHCl3 (4 mL), and the used triarylbismuthines were triphenylbismuthine (2a), tris(4-
mixture was irradiated by a xenon lamp for 5 h at room methylphenyl)bismuthine (2b), tris(4-chlorophenyl)bismuthine
temperature. As a result, 0.042 mmol (21% yield based on the (2c), and tris(4-fluorophenyl)bismuthine (2d). A number of
amount of selenium atoms) of diphenyl selenide (3aa) was combinations of 1 and 2 were examined and as a result, unsym-
obtained after the isolation by silica gel chromatography (the metrical diaryl selenides 3 were obtained in moderate to high
yield was determined by HPLC). Next, optimization of the reac- yields (45–86%) in every case (Table 2, entries 1–10) after the
tion conditions was investigated as shown in Table 1. Irradi- isolation by preparative TLC on silica gel. The chemical shifts
ation by a tungsten lamp instead of a xenon lamp did not in- of 77Se NMR spectra of diaryl selenides 3 are also shown in
Table 1: Reaction of diphenyl diselenide with triphenylbismuthine under different conditions.
entry
reaction conditions
yield of 3aaa
1
2
3
4
5
6
7
8
9
CHCl3 (4 mL), xenon lamp, Pyrex test tube, 5 h
CHCl3 (4 mL), tungsten lamp, Pyrex test tube, 5 h
CHCl3 (4 mL), dark, 24 h
0.042 mmol, 21%
0.004 mmol, 2%
0%
C6H6 (5 mL), AIBN (1.5 mmol), 80 °C, two-necked flask, 8 h
C6H6 (4 mL), xenon lamp, Pyrex test tube, 5 h
DMSO (4 mL), xenon lamp, Pyrex test tube, 5 h
CH3CN (4 mL), xenon lamp, Pyrex test tube, 5 h
CH3CN (2 mL), xenon lamp, Pyrex test tube, 5 h
CH3CN (2 mL), xenon lamp, quartz test tube, 5 h
0.012 mmol, 6%
0.102 mmol, 51%
0.034 mmol, 17%
0.114 mmol, 57%
0.126 mmol, 63%
0.138 mmol, 69%
aThe yields were determined by HPLC.
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Beilstein J. Org. Chem. 2013, 9, 1141–1147.
Table 2: Syntheses of unsymmetrical diaryl selenides.
entry
(ArSe)2 1
Ar’3Bi 2
product 3 (ArSeAr’)
77Se NMR,
yielda
δ ppm
1b
407
65%
3ab
1a
2b
2b
416
45%
3ac
1a
2c
3c
411
66%
3ad
1a
2d
4b
411
57%
3ba
1b
2a
5b
404
86%
3bb
1b
2b
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Beilstein J. Org. Chem. 2013, 9, 1141–1147.
Table 2: Syntheses of unsymmetrical diaryl selenides. (continued)
6b
427
67%
1c
3ca
2a
7b
418
51%
1c
3cb
2b
2a
2a
8c
355
51%
3da
3ea
1d
9c
418
71%
1e
10c
354
57%
3dc
1d
2c
aThe yields were determined after isolation. b0.5 mmol of triarylbismuthine was used. c0.3 mmol of triarylbismuthine was used.
Table 2, because 77Se NMR is a tool well suited to identify Additionally, air is entrained in the reaction system, since a test
diorganyl monoselenides.
tube with a septum was used in which a needle was inserted.
When the reaction of diaryl diselenide with triarylbismuthine
To get information about the reaction pathway of this arylation, was conducted with a strictly sealed tube in Ar atmosphere, a
we first investigated the arylation of diphenyl diselenide by bismuth mirror was observed and the yield of 3aa decreased.
varying the 1a/2a molar ratio (Table 3). When excess amounts We assume that the reaction proceeds with bismuth residue
of either starting substrate were employed, the yields of 3aa getting oxidized.
increased (Table 3, entries 1, 2 and 5).
A plausible reaction pathway for the photoinduced reaction of
In the case of the reaction of triphenylbismuthine with diphenyl diaryl diselenide with triarylbismuthine is shown in Scheme 3.
disulfide (4) instead of diphenyl diselenide, diphenyl sulfide 5 First, an aryl radical is generated from triarylbismuthine by
was obtained in lower yield with unidentified byproducts, near-UV light irradiation [33,54,55]. The generated aryl radical
unlike in the case of diphenyl selenide 3aa (Scheme 2).
is captured by diaryl diselenide to produce diaryl selenide and a
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Beilstein J. Org. Chem. 2013, 9, 1141–1147.
Table 3: The yield of diphenyl selenide 3aa upon changing the ratio 1a/2a.
entry
amount of 1a
amount of 2a
yield of 3aaa
69%
0.138 mmol
1
2
3
4
5
0.1 mmol
0.1 mmol
0.1 mmol
0.1 mmol
0.2 mmol
0.5 mmol
0.3 mmol
0.1 mmol
69%
0.138 mmol
59%
0.118 mmol
0.067 mmol
(2/3 equiv)
57%
0.118 mmol
88%b
0.263 mmol
0.1 mmol
aThe yields were determined by HPLC based on the amount of 1a. bThe yield was calculated based on the amount of 2a.
Scheme 2: Photoinduced reaction of diphenyl disulfide with triphenylbismuthine.
seleno radical. The seleno radical may dimerize to re-form dise- [57-59].) These facts also support that the reaction starts from
lenide. Diphenyl diselenide has its absorption maximum (λmax) the generation of an aryl radical. On the other hand, a pale
at 340 nm (ε = 103) [66] and accordingly, the seleno radical yellow solid, insoluble in organic solvents, was obtained as a
could be produced by the irradiation with a tungsten lamp. byproduct after the reaction. We assume that this solid is a
However, the irradiation by a tungsten lamp instead of a xenon bismuth residue, which can consist of bismuth oxides and/or
lamp did not result in the desired reaction (Table 1, entry 3). bismuth selenides. Moreover, it may form biaryls (Ar–Ar) as
This fact strongly suggests that the formation of a phenylseleno byproducts, but no biaryl was observed after the reaction.
radical is not important for the formation of diphenyl selenide.
Conceivably, when the reaction proceeds, a phenyl radical may
be formed directly from triphenylbismuthine upon photoirradia-
tion. Moreover, the use of an excess amount of 1, which has a
relatively high carbon-radical-capturing ability, increased the
yield of 3, and the use of diphenyl disulfide (4), which has a
lower carbon-radical-capturing ability than diselenide,
decreased the yield of 5. (The exact capturing abilities of dise-
lenide and disulfide toward the phenyl radical are not known,
Scheme 3: A plausible reaction pathway for the photoinduced reac-
tion of diaryl diselenide with triarylbismuthine.
but they have been reported toward vinyl radicals, where dise-
lenide has a higher capturing ability than disulfide: kSe/kS = 160
1145

Beilstein J. Org. Chem. 2013, 9, 1141–1147.
5. Andersson, C.-M.; Hallberg, A.; Linden, M.; Brattsand, R.; Moldéus, P.;
Cotgreave, I. Free Radical Biol. Med. 1994, 16, 17–28.
doi:10.1016/0891-5849(94)90238-0
Conclusion
We have found that the photoinduced reaction of diaryl dise-
lenides with triarylbismuthines affords unsymmetrical diaryl
selenides in good yields. This method is efficient, because two
arylseleno groups from diaryl selenides can be used as a sele-
nium source, and its advantage is that the reaction proceeds in
the absence of transition-metal catalysts.
6. Campbell, T. W.; Walker, H. G.; Coppinger, G. M. Chem. Rev. 1952,
50, 279–349. doi:10.1021/cr60156a003
7. Greenberg, B.; Gould, E. S.; Burlant, W. J. Am. Chem. Soc. 1956, 78,
4028–4029. doi:10.1021/ja01597a043
8. Cristau, H. J.; Chabaud, B.; Labaudiniere, R.; Christol, H.
Organometallics 1985, 4, 657–661. doi:10.1021/om00123a007
9. Beletskaya, I. P.; Sigeev, A. S.; Peregudov, A. S.; Petrovskii, P. V.
J. Organomet. Chem. 2000, 605, 96–101.
Experimental
General comments
doi:10.1016/S0022-328X(00)00265-5
Compounds 1a, 2a, 3aa, 4, and 5 were obtained from commer-
cially available materials. Diaryl diselenides 1b–e [67] and
triarylbismuthines 2b–d [68] were synthesized according to the
literature procedures.
10.Gujadhur, R. K.; Venkataraman, D. Tetrahedron Lett. 2003, 44, 81–84.
doi:10.1016/S0040-4039(02)02480-2
11.Taniguchi, N.; Onami, T. J. Org. Chem. 2004, 69, 915–920.
doi:10.1021/jo030300+
12.Kumar, S.; Engman, L. J. Org. Chem. 2006, 71, 5400–5403.
doi:10.1021/jo060690a
General procedure for the photoinduced syn-
thesis of unsymmetrical diaryl selenides from
13.Varala, R.; Ramu, E.; Adapa, S. R. Bull. Chem. Soc. Jpn. 2006, 79,
140–141. doi:10.1246/bcsj.79.140
14.Taniguchi, N. J. Org. Chem. 2007, 72, 1241–1245.
doi:10.1021/jo062131+
diaryl diselenide and triarylbismuthine
(Ar1Se)2 (0.1 mmol), and Ar23Bi (0.3 mmol) were dispersed in
CH3CN (2 mL) with a stirring bar in a quartz test tube ( = 9
mm) with a septum in which a needle was inserted. The mix-
ture was stirred and irradiated by a xenon lamp for 5 h at room
temperature. The reaction mixture was filtered through a bed of
celite (Celite 535). The crude product was purified by prepara-
tive TLC on silica gel (eluent: hexane/EtOAc). Details about
compounds 3ab [30], 3ac [14], 3ad [17], 3ba [17], 3bb [31],
3ca [17], 3da [32], 3ea [28] and 3dc [30] were reported in the
corresponding articles.
15.Alves, D.; Santos, C. G.; Paixão, M. W.; Soares, L. C.; Souza, D. D.;
Rodrigues, O. E. D.; Braga, A. L. Tetrahedron Lett. 2009, 50,
6635–6638. doi:10.1016/j.tetlet.2009.09.052
16.Murthy, S. N.; Madhav, B.; Reddy, V. P.; Nageswar, Y. V. D.
Eur. J. Org. Chem. 2009, 5902–5905. doi:10.1002/ejoc.200900989
17.Reddy, V. P.; Kumar, A. V.; Swapna, K.; Rao, K. R. Org. Lett. 2009, 11,
951–953. doi:10.1021/ol802734f
18.Singh, D.; Alberto, E. E.; Rodrigues, O. E. D.; Braga, A. L.
Green Chem. 2009, 11, 1521–1524. doi:10.1039/b916266f
19.Bhadra, S.; Saha, A.; Ranu, B. C. J. Org. Chem. 2010, 75, 4864–4867.
doi:10.1021/jo100755g
20.Li, Y.; Wang, H.; Li, X.; Chen, T.; Zhao, D. Tetrahedron 2010, 66,
8583–8586. doi:10.1016/j.tet.2010.09.061
21.Freitas, C. S.; Barcellos, A. M.; Ricordi, V. G.; Pena, J. M.; Perin, G.;
Jacob, R. G.; Lenardão, E. J.; Alves, D. Green Chem. 2011, 13,
2931–2938. doi:10.1039/c1gc15725f
Supporting Information
Supporting Information File 1
22.Swapna, K.; Murthy, S. N.; Nageswar, Y. V. D. Eur. J. Org. Chem.
2011, 1940–1946. doi:10.1002/ejoc.201001639
Spectral and analytical data of the new compound 3cb.
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-9-127-S1.pdf]
23.Zhao, H.; Hao, W.; Xi, Z.; Cai, M. New J. Chem. 2011, 35, 2661.
doi:10.1039/c1nj20514e
24.Ricordi, V. G.; Freitas, C. S.; Perin, G.; Lenardão, E. J.; Jacob, R. G.;
Savegnago, L.; Alves, D. Green Chem. 2012, 14, 1030–1034.
doi:10.1039/c2gc16427b
Acknowledgements
This work is supported by a Grant-in-Aid for Scientific
Research (C, 23550057) from the Ministry of Education,
Culture, Sports, Science and Technology.
25.Beletskaya, I. P.; Sigeev, A. S.; Peregudov, A. S.; Petrovskii, P. V.;
Khrustalev, V. N. Chem. Lett. 2010, 39, 720–722.
doi:10.1246/cl.2010.720
26.Beletskaya, I. P.; Sigeev, A. S.; Peregudov, A. S.; Petrovskii, P. V.
Russ. J. Org. Chem. 2001, 37, 1463–1475.
References
doi:10.1023/A:1013460213633
1. Klayman, D. L.; Günther, W. H. H. Organic Selenium Compounds:
Their Chemistry and Biology; John Wiley & Sons: New York, 1973.
2. Wirth, T., Ed. Organoselenium Chemistry; Topics in Current Chemistry,
Vol. 208; Springer: Berlin, 2000. doi:10.1007/3-540-48171-0
3. Ogawa, A. Selenium and Tellurium in Organic Synthesis. In Main
Group Metals in Organic Synthesis; Yamamoto, H.; Oshima, K., Eds.;
Wiley-VCH: Weinheim, Germany, 2004; Vol. 2, pp 813–866.
4. Nogueira, C. W.; Rocha, J. B. Arch. Toxicol. 2011, 85, 1313–1359.
doi:10.1007/s00204-011-0720-3
27.Ren, K.; Wang, M.; Wang, L. Org. Biomol. Chem. 2009, 7, 4858–4861.
doi:10.1039/b914533h
28.Reddy, K. H. V.; Satish, G.; Ramesh, K.; Karnakar, K.;
Nageswar, Y. V. D. Chem. Lett. 2012, 41, 585–587.
doi:10.1246/cl.2012.585
29.Wang, M.; Ren, K.; Wang, L. Adv. Synth. Catal. 2009, 351, 1586–1594.
doi:10.1002/adsc.200900095
30.Hayashi, S.; Yamane, K.; Nakanishi, W. J. Org. Chem. 2007, 72,
7587–7596. doi:10.1021/jo070988g
1146

Beilstein J. Org. Chem. 2013, 9, 1141–1147.
31.Beletskaya, I. P.; Sigeev, A. S.; Peregudov, A. S.; Petrovskii, P. V.
Tetrahedron Lett. 2003, 44, 7039–7041.
58.Russell, G. A.; Tashtoush, H. J. Am. Chem. Soc. 1983, 105,
1398–1399. doi:10.1021/ja00343a069
doi:10.1016/S0040-4039(03)01756-8
59.Russell, G. A.; Ngoviwatchai, P.; Tashtoush, H. I.; Pla-Dalmau, A.;
Khanna, R. K. J. Am. Chem. Soc. 1988, 110, 3530–3538.
doi:10.1021/ja00219a030
32.Prasad, C. D.; Balkrishna, S. J.; Kumar, A.; Bhakuni, B. S.; Shrimali, K.;
Biswas, S.; Kumar, S. J. Org. Chem. 2013, 78, 1434–1443.
doi:10.1021/jo302480j
60.Ogawa, A.; Tanaka, H.; Yokoyama, H.; Obayashi, R.; Yokoyama, K.;
Sonoda, N. J. Org. Chem. 1992, 57, 111–115.
33.Suzuki, H.; Matano, Y. Organobismuth Chemistry; Elsevier:
Amsterdam, 2001.
doi:10.1021/jo00027a021
34.Finet, J. P. Chem. Rev. 1989, 89, 1487–1501.
61.Ogawa, A.; Obayashi, R.; Ine, H.; Tsuboi, Y.; Sonoda, N.; Hirao, T.
J. Org. Chem. 1998, 63, 881–884. doi:10.1021/jo971652h
62.Kawaguchi, S.-i.; Shirai, T.; Ohe, T.; Nomoto, A.; Sonoda, M.;
Ogawa, A. J. Org. Chem. 2009, 74, 1751–1754.
doi:10.1021/jo8020067
doi:10.1021/cr00097a005
35.Elliott, G. I.; Konopelski, J. P. Tetrahedron 2001, 57, 5683–5705.
doi:10.1016/S0040-4020(01)00385-4
36.Leonard, N. M.; Wieland, L. C.; Mohan, R. S. Tetrahedron 2002, 58,
8373–8397. doi:10.1016/S0040-4020(02)01000-1
37.Cho, C. S.; Yoshimori, Y.; Uemura, S. Bull. Chem. Soc. Jpn. 1995, 68,
950–957. doi:10.1246/bcsj.68.950
63.Kawaguchi, S.-i.; Ogawa, A. J. Synth. Org. Chem., Jpn. 2010, 68,
705–717. doi:10.5059/yukigoseikyokaishi.68.705
64.Kawaguchi, S.-i.; Ohe, T.; Shirai, T.; Nomoto, A.; Sonoda, M.;
Ogawa, A. Organometallics 2010, 29, 312–316.
doi:10.1021/om9008982
38.Arnauld, T.; Barton, D. H. R.; Doris, E. Tetrahedron 1997, 53,
4137–4144. doi:10.1016/S0040-4020(97)00133-6
39.Arnauld, T.; Barton, D. H. R.; Normant, J.-F.; Doris, E. J. Org. Chem.
1999, 64, 6915–6917. doi:10.1021/jo9905928
65.Arnauld, T.; Barton, D. H. R.; Normant, J.-F. J. Org. Chem. 1999, 64,
3722–3725. doi:10.1021/jo982093x
40.Ohe, T.; Tanaka, T.; Kuroda, M.; Cho, C. S.; Ohe, K.; Uemura, S.
Bull. Chem. Soc. Jpn. 1999, 72, 1851–1855. doi:10.1246/bcsj.72.1851
41.Ikegai, K.; Mukaiyama, T. Chem. Lett. 2005, 34, 1496–1497.
doi:10.1246/cl.2005.1496
66.Ogawa, A.; Obayashi, R.; Doi, M.; Sonoda, N.; Hirao, T. J. Org. Chem.
1998, 63, 4277–4281. doi:10.1021/jo972253p
67.Reich, H. J.; Renga, J. M.; Reich, I. L. J. Am. Chem. Soc. 1975, 97,
5434–5447. doi:10.1021/ja00852a019
42.Moiseev, D. V.; Malysheva, Y. B.; Shavyrin, A. S.; Kurskii, Y. A.;
Gushchin, A. V. J. Organomet. Chem. 2005, 690, 3652–3663.
doi:10.1016/j.jorganchem.2005.04.051
68.Barton, D. H. R.; Bhatnagar, N. Y.; Finet, J. P.; Motherwell, W. B.
Tetrahedron 1986, 42, 3111–3122.
doi:10.1016/S0040-4020(01)87378-6
43.Finet, J.-P.; Fedorov, A. Y. J. Organomet. Chem. 2006, 691,
2386–2393. doi:10.1016/j.jorganchem.2006.01.022
44.Gagnon, A.; St-Onge, M.; Little, K.; Duplessis, M.; Barabé, F.
J. Am. Chem. Soc. 2007, 129, 44–45. doi:10.1021/ja0676758
45.Ikegai, K.; Fukumoto, K.; Mukaiyama, T. Chem. Lett. 2006, 35,
612–613. doi:10.1246/cl.2006.612
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46.Rao, M. L. N.; Venkatesh, V.; Banerjee, D. Tetrahedron 2007, 63,
12917–12926. doi:10.1016/j.tet.2007.10.047
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permits unrestricted use, distribution, and reproduction in
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47.Gagnon, A.; Duplessis, M.; Alsabeh, P.; Barabé, F. J. Org. Chem.
2008, 73, 3604–3607. doi:10.1021/jo702377h
48.Rao, M. L. N.; Jadhav, D. N.; Banerjee, D. Tetrahedron 2008, 64,
5762–5772. doi:10.1016/j.tet.2008.04.011
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49.Rahman, A. F. M. M.; Murafuji, T.; Ishibashi, M.; Miyoshi, Y.;
Sugihara, Y. J. Organomet. Chem. 2004, 689, 3395–3401.
doi:10.1016/j.jorganchem.2004.07.055
(http://www.beilstein-journals.org/bjoc)
50.Chaudhari, K. R.; Wadawale, A. P.; Jain, V. K. J. Organomet. Chem.
2012, 698, 15–21. doi:10.1016/j.jorganchem.2011.09.024
51.Barton, D. H. R.; Ozbalik, N.; Ramesh, M. Tetrahedron 1988, 44,
5661–5668. doi:10.1016/S0040-4020(01)81427-7
52.Rao, M. L. N.; Dasgupta, P. Tetrahedron Lett. 2012, 53, 162–165.
doi:10.1016/j.tetlet.2011.10.156
The definitive version of this article is the electronic one
which can be found at:
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53.Rao, M. L. N.; Awasthi, D. K.; Talode, J. B. Tetrahedron Lett. 2012, 53,
2662–2666. doi:10.1016/j.tetlet.2012.03.059
54.Kopinke, F. D.; Zimmermann, G.; Anders, K. J. Org. Chem. 1989, 54,
3571–3576. doi:10.1021/jo00276a014
55.Hey, D. H.; Shingleton, D. A.; Williams, G. H. J. Chem. Soc. 1963,
5612–5619. doi:10.1039/jr9630005612
56.Yamago, S.; Kayahara, E.; Kotani, M.; Ray, B.; Kwak, Y.; Goto, A.;
Fukuda, T. Angew. Chem., Int. Ed. 2007, 46, 1304–1306.
doi:10.1002/anie.200604473
57.Perkins, M. J.; Turner, E. S. J. Chem. Soc., Chem. Commun. 1981,
139–140. doi:10.1039/C39810000139
1147