350 J. CHEM. RESEARCH (S), 1998
J. Chem. Research (S),
1998, 000±000$
Reductive Cleavage of the Se±Si Bond in
Arylselenotrimethylsilanes: Novel Method for
the Synthesis of Unsymmetrical Selenides$
Songlin Zhang and Yongmin Zhang*
Department of Chemistry, Hangzhou University, Hangzhou, 310028, P.R. China
Arylselenotrimethylsilanes are reduced by samarium diiodide to yield samarium areneselenolates, which react with alkyl
halides to give unsymmetrical selenides.
As a powerful and versatile one-electron transfer reducing
and coupling reagent, SmI2 has been applied widely in
organic synthesis.1±3 Our previous work on the reductive
cleavage of S±S, Se±Se and Te±Te bonds with SmI2 led
us to investigate the reductive cleavage of Se±Si bonds by
SmI2.
Scheme 1
4.5
temperature for 3 h. A dilute solution of HCl and diethyl ether
was added. The organic layer was washed with water (20 ml  2)
and dried over anhydrous Na2SO4. The solvent was removed
in vacuo. The crude product was puri®ed by preparative TLC on
silica gel (cyclohexane as eluent). Some results are summarized in
Table 1.
Selenides are involved in important transformations
such as the synthesis of alkanes,6±8 alkenes,9±11 and alkyl
halides,12,13 but relatively few syntheses of selenides have
been described. A useful approach to the synthesis of
selenides is based on the alkylation of selenide ion, which
can easily be prepared from elemental selenium by reduction
with sodium in liquid ammonia,14 sodium tetrahydroborate
in ethanol15 or water16 or with tetraalkylammonium tetra-
hydroborates.17 In another approach, alcohols and selenols
were treated with acid to give selenides.18 Most of these
methods have been applied successfully to the synthesis of
selenides.
Here we report that SmI2 reduces arylselenotrimethyl-
silanes to samarium areneselenolates under a nitrogen atmo-
sphere. This new selenolate anion species reacts with alkyl
halides to give unsymmetrical selenides in good yield under
neutral conditions (Scheme 1).
1.20 mp 34±35 8C, dH (CCl4) 3.93 (2 H, s), 7.00±7.40 (10 H, m);
1
ꢀ~max/cm 3100, 3080, 3040, 2950, 1610, 1590, 1500, 1485, 1460,
1440, 1180, 1080, 1020, 1000, 910, 760, 740, 660, 600
2.21 Oil, dH (CCl4) 0.80 (3 H, t), 1.07±1.60 (12 H, m), 2.75 (2 H,
1
t), 7.00±7.50 (5 H, m); ꢀ~max/cm 3100, 3080, 2980, 2980±2940,
2870, 1590, 1485, 1460, 1440, 1380, 1075, 1020, 1000, 730, 690, 660.
3.22 Oil, dH (CCl4) 0.80 (3 H, t), 1.07±1.57 (16 H, m), 2.77 (2 H,
1
t), 7.00±7.60 (5 H, m); ꢀ~max/cm 3100, 3080, 2980, 2960±2940, 2870,
1590, 1486, 1440, 1380, 1080, 1020, 1000, 730, 690, 665.
4.10 Oil, dH (CCl4) 0.82 (3 H, t), 1.07±1.60 (20 H, m), 2.77 (2 H,
1
t), 7.00±7.60 (5 H, m); ꢀ~max/cm 3100, 3080, 2980, 2960±2940,
2870, 1590, 1485, 1470, 1440, 1380, 1080, 1020, 1000, 730, 690, 660.
5.23 mp 33±34 8C, dH (CCl4) 0.80 (3 H, t), 1.07±1.60 (28 H, m),
1
2.77 (2 H, t), 7.00±7.60 (5 H, m); ꢀ~max/cm 3100, 3080, 2980,
2960±2940, 2870, 1590, 1485, 1470, 1440, 1075, 1020, 1000, 730,
690, 665.
6.24 Oil, dH (CCl4) 2.20 (3 H, s), 3.87 (2 H, s), 6.83±7.40 (9 H,
In summary, a novel method for the preparation of
unsymmetrical selenides has been elucidated, the advantages
of which are simple manipulation, mild and neutral
conditions.
1
m); ꢀ~max/cm 3100, 3080, 3040, 2990, 2950, 2870, 1600, 1500, 1470,
1460, 1385, 1270, 1200, 1180, 1040, 820, 760, 690, 650, 600.
7.25 Oil, dH (CCl4) 2.30 (3 H, s), 2.54 (3 H, s), 6.90±7.40 (4 H,
1
m); ꢀ~max/cm 3100, 3080, 2980, 2950, 2870, 1595, 1485, 1470, 1440,
1380, 1040, 735, 650.
8.25 Oil, dH (CCl4) 1.30 (3 H, t), 2.30 (3 H, s), 2.73 (2 H, q),
Experimental
1
General Procedure.ÐA solution of arylselenotrimethylsilane19
(1 mmol) in THF (1 ml) was added by syringe to a deep blue
solution of SmI2 (2.2 mmol) in THF (10 ml) at re¯ux temperature
under a nitrogen atmosphere. The deep blue solution gradually
became brown within 3 h, which showed that the Se±Si bond had
been reductively cleaved by SmI2 and that the samarium arene-
selenolate (ArSeSmI2)20 had been generated. Alkyl halides (1 mmol)
in THF (1 ml) were then added by syringe and stirred at re¯uxing
6.91±7.45 (4 H, m); ꢀ~max/cm 3100, 3080, 2980, 2960, 2870, 1590,
1485, 1470, 1440, 1380, 1040, 730, 690, 660.
9.25 Oil, dH (CCl4) 1.36 (6 H, d), 2.30 (3 H, s), 3.01±3.08 (1 H, m)
1
6.90±7.40 (4 H, m); ꢀ~max/cm 3100, 3080, 2980±2960, 2870, 1590,
1485, 1470, 1440, 1380, 1040, 730, 690, 665.
1H NMR spectra were recorded on a PMX-60 MHZ instru-
ment (TMS as internal reference), IR spectra on a PE-683 spec-
trometer.
Table 1 Yields of the products ArSeR
Entry
Ar
R±X
Product
Yielda (%)
a
b
c
d
e
f
g
h
i
Ph
Ph
Ph
Ph
Ph
Ph
PhCH2Clb
1 PhSeCH2Ph
1 PhSeCH2Ph
84
84
80
77
79
75
82
82
80
76
68
PhCH2Brb
CH3(CH2)7Br
CH3(CH2)9Br
CH3(CH2)11Br
CH3(CH2)15Br
PhCH2Clb
2 PhSe(CH2)7CH3
3 PhSe(CH2)9CH3
4 PhSe(CH2)11CH3
5 PhSe(CH2)15CH3
6 o-CH3C6H4SeCH2Ph
6 o-CH3C6H4SeCH2Ph
7 o-CH3C6H4SeCH3
8 o-CH3C6H4SeCH2CH3
9 o-CH3C6H4SeCH(CH3)2
o-CH3C6H4
o-CH3C6H4
o-CH3C6H4
o-CH3C6H4
o-CH3C6H4
PhCH2Brb
CH3I
CH3CH2I
CH3CH(Br)CH3
j
k
b
aOf isolated product. Alkylation at room temperature for 4 h.
We are grateful to the National Natural Science
Foundation of China and Laboratory of Organometallic
Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, for ®nancial support.
*To receive any correspondence.
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).
Zhang, Songlin
