234 JOURNAL OF CHEMICAL RESEARCH 2007
sulfide, sodium azide and potassium thiocyanate were commercially
available.
R
R
CH Cl
2
2
NaN
+
_
3
+
I PhBF
N
4
3
1
4
The reaction of vinyl(phenyl)iodonium salts with sodium selenide or
sodium sulfide, general procedure
Scheme 2
UnderaN2 atmosphere, amixtureofseleniumpowderorsulfurpowder
(0.25 mmol) and sodium borohydride (0.50 mmol) in anhydrous
ethyl alcohol (5 ml) was stirred at room temperature until a light
yellow solution was obtained. Then the reaction mixture was cooled
to 0°C and a solution of vinyl(phenyl)iodonium tetrafluoroborate 1
(0.5 mmol) in anhydrous ethyl alcohol (2 ml) was added slowly. The
reaction was fast and completed immediately (monitored by TLC),
sat. aq. NaCl (15 ml) was added to the resulting mixture and which
was then extracted with dichloromethane (2¥10 ml). The extract
was washed with water (10 ml) and dried over anhydrous MgSO4.
After removal of the solvent, the residue was subject to preparative
TLC on a silica gel plate using hexane as developer to give the pure
divinylic selenides 2 or divinylic sulfides 3.
Table 2 Vinylic azides and vinilic thiocyanates
Products
R
Reaction
time/h
Configuration
Yield/%
4a
4b
5a
5b
Ph
0.5
0.2
8
E
E
E
Z
72
78
66
63
n-Bu
Ph
n-Bu
2
R
a
R
H
KSCN
+
-
I+PhBF4
H
The reaction of vinyl(phenyl)iodonium salts with sodium azide,
general procedure
SCN
1
5
a. CH2Cl2, H2O, TBAB
Sodium azide (0.5 mmol) was dissolved in water (5 ml). Then a
solution of vinyl(phenyl)iodonium tetrafluoroborate 1 (0.5 mmol) in
dichloromethane (5 ml) was added slowly at room temperature. The
reaction was fast and completed in about 0.5 h (monitored by TLC).
After reaction was finished, sat. aq. NaCl (15 ml) was added and the
resulting mixture was extracted with dichloromethane (2¥10 ml).
The extract was washed with water (10 ml) and dried over anhydrous
MgSO4. After removal of the solvent, the residue was subject to
preparative TLC on a silica gel plate using hexane as developer to
give the pure vinylic azides 4.
Scheme 2
Divinylic selenides, divinylic sulfides, vinylic azides and
vinylic thiocyanates are important compounds of versatile
utility6 as well as theoretical interest.7 Recently, Silveira et
al.8 reported that divinylic selenides were used to undergo
direct coupling with terminal alkynes in the presence of a
Ni/CuI catalyst to prepare important enyne systems in good
yields and with complete retention of configuration. Divinylic
selenides could be prepared by the reaction of selenium bis-
phosphonate with aldehydes.9,10 There were other methods
for preparation of divinylic selenides and divinylic sulfides, in
which vinyl halides usually were used as starting materials to
react with salts of selenide or sulfide under Pd catalysis.11-13
Y. Masuda et al.14 recently reported a method for preparation
of vinylic azides and vinylic thiocyanates in a one-pot process
from alkynes involving hydroboration. Other methods for
the synthesis vinylic azides have been reported15 e.g. from
2-iodoalkyl azides by elimination of hydrogen iodide to form
2-azidoalk-1-enes.Thereactionbetween1,2-epoxyalkylsilanes
and azidotrimethylsilane only gave (Z)-vinylic azides,16 whilst
the E-isomers were produced in poor yields by the reaction
of 1,2-epoxyalkylsilanes with sodium azide.17 There has been
a report about the preparation of (E)-vinylic thiocyanates by
reaction of (E)-alkenylpentafluorosilicates with copper(||)
thiocyanate in DMF.18 However, using vinyl(phenyl)iodonium
salts as starting materials for synthesis of divinylic selenides,
divinylic sulfides, vinylic azides and vinylic thiocyanates
offers a novel alternative approach.
In summary, we report a novel and efficient method for
stereoselective synthesis of divinylic selenides, divinylic
sulfides, vinylic azides and vinylic thiocyanates by the
reactions of vinyl(phenyl)iodonium salts with sodium selenide,
sodium sulfide, sodium azide and potassium thiocyanate.
The present reactions have some advantages namely the
use of the easily obtainable vinyl(phenyl)iodonium salts,
mild reaction conditions, simple operational procedure and
good yields. Furthermore, the range of useful application of
vinyl(phenyl)iodonium salts as vinylating agents in organic
synthesis has been extended.
The reaction of vinyl(phenyl)iodonium salts with potassium
thiocyanate, general procedure
Potassium thiocyanate (0.6 mmol) was dissolved in water (5 ml).
Then a solution of vinyl(phenyl)iodonium tetrafluoroborate 1
(0.5 mmol) in dichloromethane (5 ml) and phase transfer catalyst
TBAB (0.02 mmol) were added at room temperature. The mixture
was stirred until the reaction was completed (monitored by TLC).
After reaction was finished, sat. aq. NaCl (15 ml) was added and the
resulting mixture was extracted with dichloromethane (2¥10 ml).
The extract was washed with water (10 ml) and dried over anhydrous
MgSO4. After removal of the solvent, the residue was subject to
preparative TLC on a silica gel plate using hexane as developer to
give the pure vinylic thiocyanates 5.
(E, E)-Distyryl selenide (2a): M.p. 42–43°C (Lit.10 43–44°C).
1H NMR (CDCl3): d = 6.75 (d, J = 15 Hz, 2H,), 7.10–7.50 (m, 12H);
IR (film, cm-1): 3040, 1580, 1480, 950, 730, 685; EI-MS (m/z, %):
286 (M+, 42.8), 183 (100); HRMS calcd for C16H14Se 286.0261,
found 286.0235.
(Z,Z)-Di-hex-1-enyl selenide (2b): Oil. 1H NMR (CDCl3): d = 0.95
(t, J = 6 Hz, 6H), 1.16–1.60 (m, 8H), 1.90–2.37 (m, 4H), 5.60–6.00
(m, 2H), 6.41 (d, J = 10 Hz, 2H); IR (film, cm-1): 3020, 1620, 1465,
1320; EI-MS (m/z, %): 246 (M+, 5.3), 57 (100); HRMS calcd for
C12H22Se 246.0887, found 246.0843.
(E,E)-Distyryl sulfide (3a): Oil12. 1H NMR (CDCl3): d = 6.77 (d,
J = 15 Hz, 2H), 7.01–7.42 (m, 12H); IR (film, cm-1): 3040, 1580,
1480, 950, 725, 685; EI-MS (m/z, %): 238 (M+, 41.2), 103 (100);
HRMS calcd for C16H14S 238.0816, found 238.0801.
(Z,Z)-Di-hex-1-enyl sulfide (3b): Oil. 1H NMR (CDCl3): d = 0.93
(t, 6H, J = 6 Hz), 1.16–1.67 (m, 8H), 1.95–2.40 (m, 4H), 5.70-5.91
(m, 2H), 6.13 (d, 2H, J = 10 Hz); IR (film, cm-1): 3020, 1595, 1470,
1320; EI-MS (m/z, %): 198 (M+, 83.7), 83 (100); HRMS calcd for
C12H12S 198.1442, found 198.1433.
(E)-Styryl azide (4a): Oil14. 1H NMR (CDCl3): d = 6.08 (d, J = 14 Hz,
1H), 6.48 (d, J = 14 Hz, 1H), 7.10–7.13 (m, 5H); IR (film, cm-1): 3020,
2105, 1650, 1460, 1270, 930, 750, 690; EI-MS (m/z, %): 145 (M+,
27.1), 103 (100); HRMS calcd for C8H7N3 145.0640, found 145.0621.
(E)-Hex-1-enyl azide (4b): Oil.14 1H NMR (CDCl3): d = 0.88 (t,
J = 6 Hz, 3H), 1.07–1.48 (m, 4H), 1.70–2.20 (m, 2H), 4.83–5.40 (m,
1H), 5.63 (d, J = 13 Hz, 1H); IR (film, cm-1): 3020, 2115, 1670, 1580.
1480, 1260, 940; EI-MS (m/z, %): 125 (M+, 18.3), 57 (100); HRMS
calcd for C6H11N3 125.0953, found 125.0911.
Experimental
(E)-Styryl thiocyanate (5a): Oil.14 1H NMR (CDCl3): d = 6.36 (d,
J = 15 Hz, 1H), 6.93 (d, J = 15 Hz, 1H), 7.27–7.31 (m, 5H); IR (film,
cm-1): 3040, 2160, 1630, 1460, 950, 740, 690; EI-MS (m/z, %): 161
(M+, 100); HRMS calcd for C9H7NS 161.0299, found 161.0278.
(Z)-Hex-1-enyl thiocyanate (5b): Oil. 1H NMR (CDCl3): d = 0.90
(t, J = 6 Hz, 3H), 1.13–1.57 (m, 4H), 1.93–2.43 (m, 2H), 5.87–6.02
Melting points were determined on a digital m.p. apparatus and were
not corrected. IR spectra were recorded on a FT-170 SX instrument,
1H NMR spectra were measured on a Bruker AM-400 FT-NMR
spectrometer, and mass spectra were determined on an HP5989A
mass spectrometer. The vinyl(phenyl)iodonium salts were prepared
according to the literature procedures.4 Sodium selenide, sodium
PAPER: 06/4410