A simple strategy for incorporation, protection, and deprotection of selenium functionality

Article abstract of DOI:10.1055/s-2006-944191

Synthesis of di-2-cyanoethyl diselenide is reported for the first time. Using this reagent, incorporation and protection of selenium functionality can be achieved in one step with high yield, and the deprotection condition is mild, which allows alkylation simultaneously. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2006-944191

1554
LETTER
A Simple Strategy for Incorporation, Protection, and Deprotection of
Selenium Functionality
S
trategy for Incorp
i
oration
a
,
Protection,
a
nd Depro
i
tection
n
of Selenium
a
Functionality Logan,1,a Charity Igunbor,1,a Gue-Xiong Chen,a Hays Davis,a Arlyne Simon,a Jozef Salon,a
Zhen Huang*a,b
a
Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
b
Brooklyn College, Brooklyn, NY 11210, USA
Fax 01(404)6511416; E-mail: huang@gsu.edu
Received 22 February 2006
by NaOH or NH4OH.10 Unfortunately, these protecting
groups did not give satisfactory results in the desired Pd/
Cu-catalyzed reactions.10 To further advance organosele-
nium chemistry, we examined and found 2-cyanoethyl
group as a good protecting group for the selenium func-
tionality, as it is used in oxygen and sulfur protection.11
Therefore, to generate a reagent for both introduction and
protection of selenium functionality, we developed and
report here for the first time the synthesis of di-2-cyano-
ethyl diselenide and the use of this novel reagent in
selenium functionality incorporation, protection and
deprotection of selenol, and its conversion to selenides. In
brief, sodium 2-cyanoethyl selenide, formed by reduction
of di-2-cyanoethyl diselenide with NaBH4, can react with
an alkylating reagent to generate the corresponding cya-
noethyl-protected selenol via a SN2 substitution. Though
it is stable under acidic conditions, we have also demon-
strated that this protecting group can be easily removed by
weak base treatment. The in situ generated selenols can
thus be simultaneously converted to desired selenides in
the presence of an alkylating reagent in the deprotection
reaction using weak bases.
Abstract: Synthesis of di-2-cyanoethyl diselenide is reported for
the first time. Using this reagent, incorporation and protection of
selenium functionality can be achieved in one step with high yield,
and the deprotection condition is mild, which allows alkylation
simultaneously.
Key words: organoselenium compounds, selenium incorporation,
selenol protection, deprotection
In recent years, chemistry of organoselenium compounds
has attracted more and more attention. Organoselenium
compounds have been used in many applications, includ-
ing X-ray crystal structure determination of proteins2 and
nucleic acids,3,4 self-assembled monolayers (SAMs),5 de-
velopment of synthetic methodologies in organic chemis-
try,6 and cancer study and treatment.7 As selenium
chemistry is relatively underdeveloped, there are needs
for novel synthetic strategies in selenium functionality in-
corporation, protection, deprotection, and conversion. For
instance, in our investigation of nucleotide and nucleic
acid derivatization with selenium for X-ray crystal struc-
ture determination,3 we need to site-specifically incorpo-
rate selenium into nucleotide and nucleic acid molecules.
Synthesis of the selenium-derivatized nucleotides and nu-
cleic acids requires synthesis, protection and deprotection
of the selenols and conversion of the selenols to selenides.
In order to generate a reagent for selenol synthesis and
protection, we reduced selenium metal with NaBH4 to di-
sodium diselenide (Scheme 1),12 using ethanol as solvent.
A minimum amount of NaBH4 should be used in this re-
action to avoid formation of sodium selenide, which later
leads to the formation of undesired di-2-cyanoethyl se-
lenide. This reduction reaction needs to be performed un-
der argon to prevent rapid oxidation of the diselenide back
to selenium metal. The generated brown-colored disodi-
um diselenide was then immediately alkylated, without
work-up or purification, with excess 3-bromopropionitrile
to create di-2-cyanoethyl diselenide (3). A satisfactory
yield of di-2-cyanoethyl diselenide (72%) was obtained
after two reactions, the NaBH4 reduction and the alkyla-
tion reactions. Di-2-cyanoethyl diselenide (3) is a stable
liquid with a light-orange color and can be purified by
flash chromatography or distillation. It can be rapidly re-
duced with NaBH4 in ethanol solution, indicated by the
color change from light orange to colorless within five
minutes. Fortunately, the cyano group is not reduced un-
der this reductive condition when an appropriate amount
of NaBH4 is used. When a large excess of NaBH4 was
used, the cyano group was partially reduced to the imine
group. This overreduction problem can be easily avoided
Besides our research, synthesis of selenols (R-SeH), its
protection and deprotection, and its conversion to se-
lenides are often required in the synthesis of organosele-
nium compounds. As selenols can be readily oxidized to
the corresponding diselenides, selenols are usually pro-
tected as the symmetrical diselenides.8 The diselenides
can be later reduced to selenols again by strong reducing
reagents, such as Na/NH3 or NaBH4.3a,8,9 The use of the
strong reducing reagent, however, is not always compati-
ble with organoselenium molecules. In addition, the sele-
nocyanates are developed as the protected selenols,
though the deprotection reaction often causes formation
of HCN.8b It was also reported that selenols can be pro-
tected as the selenocarbamates, selenocarbonates, and
selenoacetates; these protecting groups can be removed
SYNLETT 2006, No. 10, pp 1554–1558
2
1
.0
6
.2
0
0
6
Advanced online publication: 12.06.2006
DOI: 10.1055/s-2006-944191; Art ID: S02106ST
© Georg Thieme Verlag Stuttgart · New York

LETTER
Strategy for Incorporation, Protection, and Deprotection of Selenium Functionality
1555
NC
can be converted quantitatively to a 2-cyanoethyl selenide
(5) when an alkylating compound (R1-X) is added after
the reduction.13–16
Br-CH2CH2CN
NaBH4
Se
Se
NaSe-SeNa
Se
CN
2
3
1
NaBH4
For instance, strong nucleophile 4 reacts with halogenated
alkyl compounds by displacing the halogens via a SN2
reaction. Though it is stable under acidic conditions, the
generated 2-cyanoethyl selenide (5, NCCH2CH2Se-R1,
equivalent to a protected selenol) can be easily deprotect-
ed to give a corresponding selenol (6, HSe-R1) under a
mild condition, such as a weak base (K2CO3/MeOH solu-
tion), which removes the 2-cyanoethyl group in two
hours. This protection and deprotection strategy is com-
plementary to the use of di(methoxymethyl) diselenide,
where the protecting group can be removed under acidic
conditions.6g The deprotection reaction, conducted under
argon to prevent the formation of the diselenide, is quan-
titative. Naturally, it was also found that stronger bases,
such as ammonia and NaOH, can also be used for the
deprotection with high yields. In the presence of another
alkylating reagent (R2-X) during this mild deprotection
using K2CO3, the generated selenol (6, R1-SeH) is quanti-
tatively converted to a selenide (7, R1-Se-R2).17–19 The
alkylation reaction needs to be performed under argon to
prevent rapid oxidation of the selenol to the corresponding
diselenide (8, R1-SeSe-R1). Of course, the formed dise-
lenide (8, R1-SeSe-R1)20,21 can also be converted to the
selenide (7, R1-Se-R2) after the NaBH4 reduction and
alkylation.
R1–X
NC
K2CO3
NC
R1
R1-Se-H
Se–Na+ (or H+)
Se
in MeOH
4
6
5a–d
air
R2–X and K2CO3 in MeOH
1) NaBH4
2) R2-X
R1-Se-Se-R1
R1-Se-R2
7a–c
8a, b
R1 = a:
b:
R2 =
O
O
c:
d:
X = Cl or Br
N
Scheme 1 Synthesis and application of di-2-cyanoethyl diselenide
by adding a solution of NaBH4 dissolved in ethanol drop-
wise into di-2-cyanoethyl diselenide (3) until the dise-
lenide solution just turns colorless. The formed sodium 2-
cyanoethyl selenide or 2-cyanoethyl selenol (4), which
Table 1 Synthesis of Diselenides and Selenides
Entry
a
Reduction or deprotection
Conversion
NaBH4
Alkylation or oxidation
Yield (%)
72
NC
1 to 3
Br
Cl
b
c
3 to 5a
3 to 5b
NaBH4
NaBH4
97
85
Cl
Cl
d
e
3 to 5c
3 to 5d
NaBH4
NaBH4
81
97
O
Br
N
O
Cl
Cl
Cl
f
5a to 7a
5b to 7b
5c to 7c
K2CO3 in MeOH
K2CO3 in MeOH
K2CO3 in MeOH
97
95
84
g
h
i
j
5a to 8a
5b to 8b
K2CO3 in MeOH
K2CO3 in MeOH
air
air
92
89
Synlett 2006, No. 10, 1554–1558 © Thieme Stuttgart · New York

1556
G. Logan et al.
LETTER
(3) (a) Carrasco, N.; Ginsburg, D.; Du, W.; Huang, Z.
To demonstrate this novel strategy, benzyl chloride was
first used as an alkylating reagent for both alkylation steps
(4 to 5 and 5 to 7 in Scheme 1). Quantitative yields were
obtained for both alkylation steps: the first alkylation re-
action and the second alkylation when K2CO3 was used as
the deprotecting reagent. If strong bases, such as ammonia
and NaOH, were used as the deprotecting reagents in the
second step, reduced yields of the selenide formation were
observed because these strong bases reacted with benzyl
chloride. Several other alkylating reagents have also been
used in the investigation, and satisfactory yields were ob-
tained for both alkylation reactions in each case (Table 1).
The selenizing reagent, the intermediates, and the final se-
Nucleosides, Nucleotides Nucleic Acids 2001, 20, 1723.
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Huang, Z. J. Am. Chem. Soc. 2002, 124, 24. (c) Buzin, Y.;
Carrasco, N.; Huang, Z. Org. Lett. 2004, 6, 1099.
(d) Carrasco, N.; Buzin, Y.; Tyson, E.; Halpert, E.; Huang,
Z. Nucleic Acids Res. 2004, 32, 1638. (e) Carrasco, N.;
Huang, Z. J. Am. Chem. Soc. 2004, 126, 448. (f) Salon, J.;
Chen, G.; Portilla, Y.; Germann, M. W.; Huang, Z. Org. Lett.
2005, 7, 5645. (g) Carrasco, N.; Caton-Williams, J.; Brandt,
G.; Wang, S.; Huang, Z. Angew. Chem. Int. Ed. 2006, 45, 94;
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Malinina, L.; Tereshko, V.; Skripkin, E.; Höbartner, C.;
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(5) (a) Samant, M. G.; Brown, C. A.; Gordon, J. G. II Langmuir
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(d) Organoselenium Chemistry; Back, T. G., Ed.; Oxford
University Press: Oxford, 1999. (e) Organoselenium
Chemistry, In Top. Curr. Chem.; Wirth, T., Ed.; Springer:
Berlin, 2000, 208. (f) Wirth, T. Angew. Chem. Int. Ed. 2000,
39, 3742. (g) Uehlin, L.; Wirth, T. Phosphorus, Sulfur
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ChemBioChem 2002, 3, 1061. (i) Yao, Q.; Kinney, E. P.;
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1
lenides were synthesized and fully characterized by H
NMR, 13C NMR, and HRMS.12–21
In conclusion, we have synthesized a novel and stable
reagent (di-2-cyanoethyl diselenide) for the synthesis of
organoselenium compounds and developed a simple
strategy for incorporation, protection and deprotection of
selenium functionality. This novel diselenide reagent is
useful for incorporating 2-cyanoethyl-protected selenol
functionality into molecules containing halogens or other
leaving groups. This cyanoethyl protection can be easily
removed with a weak base to generate the corresponding
selenol in situ, which can then be conveniently converted
to a selenide in the presence of an alkylating reagent dur-
ing the deprotection. Using this strategy, the selenium
functionality incorporation and protection are achieved si-
multaneously, and the deprotection and conversion of the
protected selenols are also accomplished in one step,
which is convenient. This novel and simple strategy of se-
lenol synthesis and its protection, deprotection and con-
version to selenides will have wide applications in
advancement of organoselenium chemistry, synthesis of
organoselenium compounds, including selenium-deriva-
tized nucleotides and nucleic acids for X-ray crystal struc-
ture study.
(7) (a) Abdulah, R.; Miyazaki, K.; Nakazawa, M.; Koyama, H.
J. Trace Elem. Med. Biol. 2005, 19, 141. (b) Rayman, M. P.
Proc. Nutr. Soc. 2005, 64, 527. (c) Wu, Y.; Zhang, H.;
Dong, Y.; Park, Y. M.; Ip, C. Cancer Res. 2005, 65, 9073.
(d) Sonn, G. A.; Aronson, W.; Litwin, M. S. Prostate Cancer
Prostatic Dis. 2005, 8, 304.
Acknowledgment
C.I. and A.S. were supported by the McNair Program. This work
was supported by GSU Research Program, the US National
Institutes of Health (GM069703), and the US National Science
Foundation (MCB-0517092).
(8) (a) Organic Selenium Compounds: Their Chemistry and
Biology, In The Chemistry of Organometallic Compounds;
Klayman, D. L.; Gunther, W. H. H., Eds.; John Wiley and
Sons: New York, 1973, 73. (b) Organic Selenium
Compounds: Their Chemistry and Biology, In The
Chemistry of Organometallic Compounds; Klayman, D. L.;
Gunther, W. H. H., Eds.; John Wiley and Sons: New York,
1973, 42.
(9) (a) Hale, K. J.; Manaviazar, S. Tetrahedron Lett. 1994, 35,
8873. (b) Kawashima, E.; Toyama, K.; Ohshima, K.;
Kainosho, M.; Kyogoku, Y.; Ishido, Y. Tetrahedron Lett.
1995, 36, 6699. (c) Andreadou, I.; Menge, W. M. P. B.;
Commandeur, J. N. M.; Worthington, E. A.; Vermeulen, N.
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References and Notes
(1) These authors have contributed equally to this publication.
(2) (a) Yang, W.; Hendrickson, W. A.; Crouch, R. J.; Satow, Y.
Science 1990, 249, 1398. (b) Ferré-D’Amaré, A. R.; Zhou,
K.; Doudna, J. A. Nature (London) 1998, 395, 567.
(c) Egli, M. Curr. Opin. Chem. Biol. 2004, 8, 580. (d) Liu,
L.; Wei, Z.; Wang, Y.; Wan, M.; Cheng, Z.; Gong, W. J.
Mol. Biol. 2005, 344, 317.
(10) Reinerth, W. A.; Tour, J. M. J. Org. Chem. 1998, 63, 2397.
Synlett 2006, No. 10, 1554–1558 © Thieme Stuttgart · New York

LETTER
Strategy for Incorporation, Protection, and Deprotection of Selenium Functionality
1557
(11) Coleman, R. S.; Arthur, J. C.; McCary, J. L. Tetrahedron
1997, 53, 11191.
(12) Di-2-cyanoethyl Diselenide (3).
(CH2CN), 25.95 (CH2CH2Ph), 36.94 (CH2Ph), 118.87 (CN),
126.59 (p-ar.-C), 128.42 (o-ar.-C), 128.58 (m-ar.-C), 140.53
(ar. CCH2Se). HRMS (MALDI-FTMS): m/z [M with 80Se]+
calcd for C11H13NSe: 239.0213; found: 239.0209.
Solution of dioxane–EtOH (4:1, 100 mL) was injected into a
flask containing selenium metal (7.9 g, 100 mmol; FW = 79)
and NaBH4 (2.7 g) under argon. After stirring the dark
suspension for 1 h, 3-bromopropionitrile (12.4 mL, 150
mmol, 1.5 equiv; MW = 134, r = 1.62 g/mL) was added
dropwise in an ice bath. The reaction was stirred for 1 h
before it was poured into a beaker containing H2O (400 mL).
The suspension (yellow-orange) in the beaker was adjusted
to pH 7 and then extracted with EtOAc (3 × 200 mL). The
combined organic phases were washed with NaCl (sat., 100
mL) and then dried over MgSO4 (s). After evaporation of the
solvent under reduced pressure, the crude product was
purified on silica gel column equilibrated with CH2Cl2–
hexane (30:70). The gradient was run using CH2Cl2 in
hexane (150 mL each, 30%, 40%, 50%, 60%, 70%, and
80%). The eluted product was light orange. The solvents
were evaporated under reduced pressure (using rotary
evaporator, do not use high vacuum) and co-evaporated with
MeOH twice (2 × 30 mL). A light-orange product was
obtained (9.65 g, 72% yield). 1H NMR (300 MHz, CDCl3):
d = 2.84 (t, J = 7.2 Hz, 2 H, CH2Se), 3.04 (t, J = 7.2 Hz, 2 H,
CH2CN). 13C NMR (75 MHz, CDCl3): d = 18.65 (CH2Se),
21.53 (CH2CN), 118.27 (CN). HRMS (MALDI-FTMS):
m/z [M (with 80Se) + Na]+ calcd for C6H8N2Se2: 290.8916;
found: 290.8912. When a large excess of NaBH4 was used in
the reaction, colorless di-2-cyanoethyl selenide was also
isolated. 1H NMR (300 MHz, CDCl3). d = 2.91 (t, J = 7.1 Hz,
2 H, CH2Se), 3.53 (t, J = 7.1 Hz, 2 H, CH2CN). 13C NMR (75
MHz, CDCl3): d = 21.03 (CH2Se), 23.27 (CH2CN), 117.42
(CN). HRMS (MALDI-FTMS): m/z [M with (80Se + Na)]+
calcd for C6H8N2Se: 210.9750; found: 210.9746.
(15) 2-Cyanoethyl (1-Naphthyl)methyl Selenide (5c).
The synthesis (81% yield) is analogous to the synthesis of
5a. 1H NMR (CDCl3): d = 2.53 (t, J = 7.0 Hz, 2 H,
NCCH2CH2Se), 2.66 (t, J = 7.0 Hz, 2 H, NCCH2CH2Se),
4.36 (s, 2 H, CH2C10H7), 7.20–8.10 (m, 7 H, arom.). 13
C
NMR (CDCl3): d = 17.77 (NCCH2CH2Se), 19.48 (CH2CN),
24.47 (CH2C10H9), 118.91 (CN), 123.88, 125.20, 126.14,
126.22, 127.01, 128.39, 128.92, 130.96, 133.57, 134.15 (10
C, arom.). HRMS (ESI-TOF): m/z [M with (80Se + Na)]+
calcd for C14H13NSe: 298.0105; found: 298.0099.
(16) 2-Cyanoethyl 3-(1,3-Dioxoisoindolin-2-yl)propyl
Selenide (5d).
The synthesis (97% yield) is analogous to the synthesis of
5a. In this reaction, mixture of MeOH and toluene (1:9) was
used to dissolve N-(3-bromopropyl)phthalimide. 1H NMR
(CDCl3): d = 2.04–2.11 (m, 2 H, NCH2CH2CH2Se), 2.69–
2.86 (m, 6 H, NCH2CH2CH2SeCH2CH2CN), 3.81 (t, J = 6.8
Hz, 2 H, NCH2CH2CH2Se), 7.72–7.89 (m, 4 H, arom.). 13
NMR (CDCl3): d = 17.8 (NCCH2CH2Se), 20.1 (CH2CN),
21.6 (NCH2CH2CH2), 29.4 (NCH2CH2CH2Se), 38.0
C
(NCH2CH2CH2Se), 123.3 (CN), 132.4, 133.8 and 134.1 (C,
arom.), 169.2 (C=O). ESI-MS: m/z [M with 80Se]+ calcd for
C14H14N2O2Se: 322.0221; found: 322.0218. When a large
excess of NaBH4 was used, reduction of the nitrile to the
corresponding imine was also observed. 1H NMR (CDCl3):
d = 1.99–2.08 (m, 2 H, NCH2CH2CH2Se), 2.66–2.78 (m, 6
H, NCH2CH2CH2SeCH2CH2CH=NH), 3.51 (t, J = 6.8 Hz, 2
H, NCH2CH2CH2Se), 4.05 (br, 1 H, NH), 5.76 (s, 1 H,
SeCH2CH2CH=NH), 7.43–7.62 (m, 4 H, arom.). ESI-MS:
m/z [M with 80Se]+ calcd for C14H16N2O2Se: 324.0377;
found: 324.0371.
(13) Benzyl 2-Cyanoethyl Selenide (5a).
EtOH (5 mL) was added to NaBH4 (317 mg) placed in an
airtight flask under an argon balloon. The supernate of the
mixture was added into a round-bottom flask (100 mL, on an
ice bath) containing di-2-cyanoethyl diselenide (1.48 mL,
2.67 g, 10 mmol, r = 1.8 g/mL) under an argon balloon.
After stirring for 5 min, the reaction turned colorless from
light orange color. Benzyl chloride (0.75 mL, 821 mg, 6.5
mmol, r = 1.1 g/mL) was then injected into the reaction.
After completion in 30 min (monitored on TLC, hexane–
CH2Cl2 = 9:1; the product Rf = 0.61), H2O (50 mL) was
added to quench the reaction, and the pH was adjusted to 7
with 10% AcOH. The crude product was extracted three
times with EtOAc (50 mL each time), and the organic phases
were combined and dried over MgSO4 (s). After removal of
the solvent using rotary evaporator under reduced pressure,
the crude product was purified by several preparative TLC
plates (hexane–CH2Cl2 = 8:2). An oil product (1.412 g) was
obtained (97% yield). 1H NMR (CDCl3): d = 2.48 (t, J = 7.2
Hz, 2 H, CH2Se), 2.55 (t, J = 7.2 Hz, 2 H, CH2CN), 3.83 (s,
2 H, CH2Ph), 7.18–7.32 (m, 5 H, arom. protons). 13C NMR
(CDCl3): d = 17.19 (NCCH2CH2Se), 19.41 (CH2CN), 27.80
(CH2Ph), 118.91 (CN), 127.22 (p-ar.-C), 128.78 (o-ar.-C),
128.94 (m-ar.-C), 138.28 (ar. CCH2Se). MS (ESI): m/z = 91
[benzyl]+, 169, 225 [M + H]+. HRMS (MALDI-FTMS): m/z
[M with 80Se]+ calcd for C10H11NSe: 225.0057; found:
225.0054.
(17) Dibenzyl Selenide (7a).
A solution of K2CO3 (0.05 M in MeOH, 6 mL, 300 mmol,
thoroughly purged with argon) was injected into a round-
bottom flask containing benzyl (2-cyanoethyl) selenide (5a,
35.0 mg, 155 mmol) under argon, followed by injection of
benzyl chloride (38.9 mg, 307 mmol, 2 equiv). When the
reaction was completed over a few hours (monitored on
analytical TLC, hexane–CH2Cl2 = 8:2), the solvent was
evaporated under reduced pressure and the crude product
was purified by preparative TLC (hexanes–CH2Cl2 = 7:3).
An oil product was obtained (39.4 mg, 97% yield). 1H NMR
(CDCl3): d = 3.71 (s, 4 H, CH2Ph), 7.19–7.32 (m, 10 H,
arom. protons). 13C NMR (CDCl3): d = 27.2 (CH2Ph), 127.2
(p-ar.-C), 128.7 (o-ar.-C), 128.9 (m-ar.-C), 138.2 (ar.
CCH2Se). MS (ESI): m/z = 91 [benzyl]+, 171, 260 and 262
[M+]. HRMS (MALDI-FTMS): m/z [M with 80Se]+ calcd for
C14H14Se: 262.0261; found: 262.0264.
(18) Benzyl 2-Phenylethyl Selenide (7b).
The synthesis (95% yield) is analogous to the synthesis of
7a. 1H NMR (CDCl3): d = 2.74 (t, J = 7.3 Hz, 2 H, CH2Se),
2.92 (t, J = 7.3 Hz, 2 H, CH2CH2Ph), 3.78 (s, 2 H, CH2Ph),
7.17–7.36 (m, 10 H, arom.). 13C NMR (CDCl3): d = 26.1
(CH2CH2Ph), 27.9 (CH2Ph), 38.0 (CH2CH2Ph), 126.3 and
126.7 (p-ar.-C), 128.4 and 128.7 (o-ar.-C), 129.6 and 129.9
(m-ar.-C), 139.4 and 141.2 (ar. CCH2). HRMS (MALDI-
FTMS): m/z [M with 80Se]+ calcd for C15H16Se: 276.0417;
found: 276.0419.
(14) 2-Cyanoethyl 2-Phenylethyl Selenide (5b).
The synthesis (85% yield) is analogous to the synthesis of
(19) Benzyl (1-Naphthyl)methyl Selenide (7c).
The synthesis (84% yield) is analogous to the synthesis of
7a. 1H NMR (CDCl3): d = 3.71 (s, 2 H, CH2C10H7), 4.12 (s,
2 H, CH2Ph), 7.19–7.89 (m, 12 H, aromatic). 13C NMR
(CDCl3): d = 25.30 (CH2C10H7), 28.72 (CH2Ph), 124.27,
5a. 1H NMR (CDCl3): d = 2.62–2.81 (m, 4 H,
SeCH2CH2CN), 2.94 (t, J = 7.4 Hz, 2 H, SeCH2CH2Ph),
3.04 (t, J = 7.4 Hz, 2 H, SeCH2CH2Ph), 7.18–7.37 (m, 5 H,
arom.). 13C NMR (CDCl3): d = 17.57 (NCCH2CH2Se), 19.64
Synlett 2006, No. 10, 1554–1558 © Thieme Stuttgart · New York

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G. Logan et al.
LETTER
125.48, 126.11, 126.29, 127.04, 127.10, 128.09, 128.37,
128.66, 128.88, 129.26, 129.34, 131.53, 134.35, 134.91,
139.36 (16 C, arom.). HRMS (MALDI-FTMS): m/z [M with
80Se]+ calcd for C18H16Se: 312.0417; found: 312.0415.
7.38 (m, 10 H, arom. protons). 13C NMR (CDCl3): d = 32.58
(CH2Ph), 127.09 (p-ar.-C), 128.43 (o-ar.-C), 129.01 (m-ar.-
C), 138.18 (ar. CCH2Se). MS (ESI): m/z = 91 [benzyl]+, 169,
181, 262, and 342 [M + H]+. HRMS (MALDI-FTMS): m/z
[M with 80Se]+ calcd for C14H14Se2: 341.9426; found:
341.9428.
(20) Dibenzyl Diselenide (8a).
A MeOH solution of K2CO3 (0.05 M, 6 mL, 300 mmol) was
injected into a round-bottom flask containing benzyl (2-
cyanoethyl) selenide (5a, 20.0 mg, 89 mmol), which was
open to air. When the reaction was complete, (overnight;
monitored by TLC, hexane–CH2Cl2 = 7:3, Rf = 0.38), the
solvent was evaporated under reduced pressure and the
crude product was purified by preparative TLC (hexane–
CH2Cl2 = 6:4). A solid product was obtained (28.1 mg, 92%
yield). 1H NMR (CDCl3): d = 3.86 (s, 4 H, CH2Ph), 7.23–
(21) Di(phenylethyl) Diselenide (8b).
1H NMR (CDCl3): d = 3.06 (t, J = 7.6 Hz, 4 H, CH2Se), 3.18
(t, J = 7.6 Hz, 4 H, CH2Ph), 7.22–7.37 (m, 10 H, arom.). 13
C
NMR (CDCl3): d = 30.72 (CH2Se), 37.54 (CH2Ph), 126.39
(p-ar.-C), 128.50 (o-ar.-C), 128.54 (m-ar.-C), 140.79 (ar.
CCH2Se). HRMS (MALDI-FTMS): m/z [M with 80Se]+
calcd for C16H18Se2: 369.9739; found: 369.9736.
Synlett 2006, No. 10, 1554–1558 © Thieme Stuttgart · New York