LEWIS ACIDS AS CO-REAGENTS IN SULFENYLATION REACTIONS
609
Reactions of ethyl benzenesulfenate with alkenes in the presence of Lewis acids
Reaction conditions
Products
Initial
compound
isomer ratio, %
Lewis acid
solvent
compound no.
yield, %
III
IV
–
V
–
Cyclohexene
AlCl3
TiCl4
SnCl4
ZnCl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
Ia
81
76
70
10
34
84
72
86
90
84
92
46
67
–
–
Ia
–
–
Ia
–
–
–
Ia
–
–
–
II
–
–
–
PBr3
CH2Cl2
CH2Cl2
CH2Cl2
MeNO2
CH2Cl2
MeNO2
CH2Cl2
CH2Cl2
Ib
–
–
–
Norbornene
AlCl3
TiCl4
IIIa
100
100
021
018
000
026
100
00
00
49
23
67
41
00
00
00
30
59
33
33
00
IIIa
IIIa + IV + V
IIIa + IV + V
IV + V
SnCl4
ZnCl2
PBr3
IIIa + IV + V
IIIb
nene in 10 ml of anhydrous nitromethane was slowly
added under vigorous stirring at 0°C in a dry argon
atmosphere to a solution of 2.5 mmol of Lewis acid in
5 ml of anhydrous nitromethane. The mixture was
stirred until the reaction was complete, treated with
an aqueous solution of sodium carbonate, and extract-
ed with chloroform (2×25 ml). The extract was dried
over Na2SO4, and the solvent was removed under
reduced pressure.
(1H each, OCH2, J = 9.2, 7.0 Hz), 7.2–7.4 m (5H,
arom). 13C NMR spectrum, δC, ppm: 15.6 (CH3), 24.3,
24.8, 30.9, 31.5 (CH2), 51.3 (CHS), 64.3 (CH2O), 80.4
(CHO), 126.5, 129.8, 132.6, 135.9 (Carom). Found, %:
C 71.38; H 8.54. C14H20OS. Calculated, %: C 71.18;
H 8.52.
H
exo-2-Chloro-syn-7-phenylsulfanylbicyclo[2.2.1]-
heptane (IV) and exo-2-chloro-anti-7-phenylsul-
fanylbicyclo[2.2.1]heptane (V) (mixture of stereo-
1
Reactions of ethyl benzenesulfenate with alkenes
in the presence of phosphorus(III) bromide (general
procedure). A solution of 2.5 mmol of ethyl benzene-
sulfenate and 2.5 mmol of cyclohexene or norbornene
in 10 ml of anhydrous methylene chloride was cooled
to –30°C, and a solution of 2.5 mmol PBr3 in 10 ml of
methylene chloride was slowly added under vigorous
stirring in an argon atmosphere. The mixture was
stirred for 1 h, allowed to warm up to 20°C, and passed
through a column charged with silica gel, and the
solvent was removed under reduced pressure.
isomers). Rf 0.60. H NMR spectrum, δ, ppm: IV:
2.49 br.s (1H, 4-H), 2.64 br.s (1H, 1-H), 3.32 br.s (1H,
HCS), 3.97 d.d.d (1H, CHCl, J2,endo-3 = 7.7, J2,exo-3
=
3.2, J2,anti-7 = 1.0 Hz); V: 2.39 br.s (1H, 4-H), 2.54 br.s
(1H, 1-H), 3.85 br.s (1H, HCS), 4.03 d.d (1H, CHCl,
J2,endo-3 = 7.8, J2,exo-3 = 2.7 Hz); signals from the C3H2,
C5H2, C6H2 (1.36–2.00 ppm) and aromatic protons
(7.20–7.40 ppm) of compounds IV and V overlapped
each other. Mass spectrum, m/z (Irel, %): IV: 240 (36)
[M + 2]+, 238 (100) [M]+, 203 (40), 136 (36), 123 (56),
110 (41), 93 (49); V: 240 (33) [M + 2]+, 238 (100)
[M]+, 203 (43), 136 (43), 123 (56), 110 (50), 93 (49).
Found, %: C 65.53; H 6.42. C13H15ClS. Calculated, %:
C 65.41; H 6.29. M 238.78.
The yields are given in table. Compounds Ia, Ib,
IIIa, and IIIb were reported previously; their physical
properties coincided with those given in [4].
1
trans-1-Ethoxy-2-phenylsulfanylcyclohexane
The H and 13C NMR spectra were recorded on
1
(II). Rf 0.69. H NMR spectrum, δ, ppm: 1.18 t (3H,
a Bruker Avance 400 spectrometer at 400 and
100 MHz, respectively, using hexamethyldisiloxane as
internal reference. The mass spectra (electron impact,
70 eV) were obtained on a Finnigan MAT TSQ 7000
CH3, J = 7.0 Hz), 1.22–1.48 m (4H, CH2), 1.75 m (2H,
CH2), 2.06 m (2H, CH2), 3.20 t.d and 3.24 t.d (1H
each, 1-H, 2-H, J = 8.4, 3.7 Hz), 3.52 d.q and 3.65 d.q
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 4 2011