Zinc-mediated cleavage of diselenides: A novel synthesis of unsymmetrical diorganyl selenides in aqueous media

Article abstract of DOI:10.1055/s-2004-835650

A convenient synthetic method has been developed for the preparation of unsymmetrical selenides through a one-pot zinc-mediated reaction of diselenides and active organic halides in aqueous media.

Full text of DOI:10.1055/s-2004-835650

LETTER
121
Zinc-Mediated Cleavage of Diselenides: A Novel Synthesis of Unsymmetrical
Diorganyl Selenides in Aqueous Media
Zinc-Mediated
Cl
eavage of
D
iselenid
a
e
s
hman Movassagh,* Mojgan Shamsipoor
Department of Chemistry, K. N. Toosi University of Technology, P. O. Box 15875-4416, Tehran, Iran
Fax +98(21)2853650; E-mail: bmovass1178@yahoo.com
Received 28 August 2004
We found that under mild, atmospheric, and neutral con-
Abstract: A convenient synthetic method has been developed for
the preparation of unsymmetrical selenides through a one-pot zinc-
mediated reaction of diselenides and active organic halides in
aqueous media.
ditions, zinc benzyl and arylselenolates 2, readily pre-
pared in situ from the reductive cleavage of the Se-Se
bond of dibenzyl and diaryl diselenides, reacted readily
with the above halides in acetonitrile–water to give un-
symmetrical selenides 3. All of the reactions studied pro-
ceeded smoothly to give the corresponding selenides with
yields ranging from 64–98% (Table 1).11 The reaction of
diaryl diselenides with benzyl bromide (entries 1 and 3)
took place faster with higher yields than the others. The
results clearly show the need for longer reaction times for
benzyl chloride (entries 9 and 10), giving the products
with lower yields. The effects of several solvents were ex-
amined and the best results were obtained with an aceto-
nitrile–water (7:1) system. It is noteworthy that, while
diaryl diselenides reacted conveniently with the halides
merely in the presence of metallic zinc, the reaction of
dibenzyl diselenide (entries 2 and 5) with these halides did
not take place in the absence of aluminum chloride. An
important feature of this method was seen with bromo-
acetic acid, which reacted directly with the zinc phenyl-
selenolate intermediate to give a-phenylselenoacetic acid
in 73% yield. No evidence was found for the formation of
benzeneselenol.
Key words: diselenides, selenides, zinc, zinc selenolate, halides
Organoselenium compounds are of considerable interest
because of their wide involvement as key intermediates in
organic synthesis and use as a food supplement.1 These
compounds are no longer systematically classified as tox-
ic and, thus, much effort is being devoted to accomplish-
ing the synthesis of organic selenides. Although numerous
reports on the synthesis of organoselenium compounds
have already been published,1,2 most of them, with the ex-
ception of two recent reports,3 usually require the han-
dling of unstable reagents, strongly acidic or basic
reaction conditions, and two-step procedures. Hence, the
development of a one-step synthetic method using stable
reagents under neutral conditions is in demand.
In the last decade, organometallic reactions in aqueous
media have attracted considerable attention in organic
synthesis.4 Recently, transition metal selenolates or com-
plexes have been widely used in synthesis of organo-
selenium compounds,5–7 but reports exploring zinc
selenolates are rare.8–10
To conclude, an efficient one-pot synthetic method of un-
symmetrical selenides has been developed through the
zinc-mediated reaction of diselenides with active organic
halides. The present method has the advantages of opera-
tional simplicity, neutral, mild reaction conditions, high
isolated yields of products, lack of toxicity, and low costs.
As a part of our work in aqueous organometallic reactions,
we wish to report herein that zinc powder promotes cleav-
age of the Se-Se bond to form selenide anion (RSe–). This
species can then react with active organic halides such as
benzyl halides, a-haloesters, a-haloacids, and chloroace-
tonitrile to afford unsymmetrical selenides in good to
excellent yields at 65 °C (Scheme 1). To our knowledge
Reformatsky-type reactions in aqueous organometallic
reaction conditions are not generally successful.4b
Acknowledgment
We thank the K. N. Toosi University of Technology Research
Council for financial support.
References
(1) (a) Krief, A.; Hevesi, L. Organoselenium Chemistry, Vol. 1;
Springer-Verlag: Berlin, 1988. (b) Krief, A. In
Comprehensive Organometallic Chemistry; Trost, B. M.,
Ed.; Pergamon: Oxford, 1991, 85; and references therein.
(2) (a) Krief, A.; Derock, M. Tetrahedron Lett. 2002, 43, 3083;
and references therein. (b) Paulmier, C. Selenium Reagents
and Intermediates in Organic Synthesis; Pergamon: Oxford,
1986. (c) Patai, S.; Rappoport, Z. The Chemistry of Organic
Selenium and Tellurium Compounds, Vol. 1; Wiley and
Sons: New York, 1986. (d) Patai, S.; Rappoport, Z. The
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Vol. 2; Wiley and Sons: New York, 1987.
Scheme 1
SYNLETT 2005, No. 1, pp 0121–0122
Advanced online publication: 08.11.2004
DOI: 10.1055/s-2004-835650; Art ID: D25704ST
© Georg Thieme Verlag Stuttgart · New York
0
5.
0
1.
2
0
0
5

122
B. Movassagh, M. Shamsipoor
LETTER
Table 1 Preparation of Unsymmetrical Selenides via Zinc Selenolate Anion Intermediate
Entry
1
R1
R2X
Reaction time (h) Producta
Yield (%)b
Ph
PhCH2Br
0.2
5
PhSeCH2Ph12
98
72
98
89
70
71
82
87
64
66
77
73
2c
3
PhCH2
p-ClC6H4
Ph
PhCH2Br
PhCH2SeCH2Ph12
p-ClC6H4SeCH2Ph13
PhSeCH2CO2Et14
PhCH2SeCH2CO2Et15
p-ClC6H4SeCH2CO2Et15
PhSeCH2CN14
PhCH2Br
0.5
1
4
BrCH2CO2Et
BrCH2CO2Et
BrCH2CO2Et
ClCH2CN
ClCH2CN
PhCH2Cl
5c
6
PhCH2
p-ClC6H4
Ph
5.5
3
7
4
8
p-ClC6H4
Ph
6
p-ClC6H4SeCH2CN15
PhSeCH2Ph12
9
3
10
11
12
p-ClC6H4
Ph
PhCH2Cl
2
p-ClC6H4SeCH2Ph12
16
CH3CHBrCO2CH3
BrCH2CO2H
5.5
6
PhSeCH(CH3)CO2CH3
Ph
PhSeCH2CO2H14
a References of the known compounds.
b Yields refer to those of pure isolated products characterized by IR and 1H NMR spectroscopic data.
c In the presence of AlCl3.
(3) (a) Ranu, B. C.; Mandal, T.; Samanta, S. Org. Lett. 2003, 5,
1439. (b) Nishino, T.; Okada, M.; Kuroki, T.; Watanabe, T.;
Nishiyama, Y.; Sonoda, N. J. Org. Chem. 2002, 67, 8696.
(4) (a) Li, C. J. Chem. Rev. 1993, 93, 2023. (b) Lubineau, A.;
Auge, J.; Queneau, Y. Synthesis 1994, 741.
(5) Meunier, P.; Gaotheron, B.; Mazouz, A. J. Chem. Soc.,
Chem. Commun. 1986, 424.
(6) Osuka, A.; Ohmasa, N.; Suzuki, H. Synthesis 1982, 857.
(7) Bao, W.; Zhang, Y. Synth. Commun. 1995, 25, 1825.
(8) Movassagh, B.; Mirshojaei, F. Monatsh. Chem. 2003, 134,
831.
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Res., Synop. 2004, 148.
(10) Huang, X.; Xu, X.-H. Synth. Commun. 1998, 28, 807.
(11) General Experimental Procedure. In a 50 mL round-
bottom flask, fitted with a reflux condenser, were placed zinc
powder (0.5 mmol), diorganyl diselenide (4 mmol), and
MeCN (14 mL). (In the case of dibenzyl diselenide, AlCl3
(1.5 mmol) was also added at this stage.) The mixture was
stirred at 65 °C for 1 h until the zinc powder was almost
consumed and the solution became turbid; organic halide
(1.8 mmol) and H2O (2 mL) were then added at once to the
solution and stirring was continued for the specified time
(Table 1) at 65 °C. Progress of the reaction was monitored
by TLC. When the reaction was complete, MeCN was
evaporated, Et2O (30 mL) was added, the mixture washed
with H2O (3 × 20 mL), and the organic layer was dried over
anhyd Na2SO4. The solvent was evaporated in vacuo to give
the corresponding selenide which was purified by
preparative TLC (silica gel, eluent petroleum ether–
CCl4 = 1:1 or petroleum ether–Et2O = 9:1 or CCl4–
Et2O = 4:1).
(12) Gladysz, J. A.; Hornby, J. L.; Garbe, J. J. Org. Chem. 1978,
43, 1204.
(13) Lu, G.; Zhang, Y. Synth. Commun. 1998, 28, 4479.
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160.
(16) Qian, W.; Bao, W.; Zhang, Y. Synlett 1997, 393.
Synlett 2005, No. 1, 121–122 © Thieme Stuttgart · New York