[2,3]-Sigmatropic Rearrangements of Allyl Sulfides
J . Org. Chem., Vol. 65, No. 8, 2000 2535
vacuum and then back-filled with nitrogen. Chloroform was
washed three times with water, dried over potassium carbon-
ate, distilled from P2O5 under nitrogen, and stored over 4 Å
molecular sieves in the dark. Portions were then distilled from
P2O5 under nitrogen immediately prior to use. Dichlo-
romethane was distilled from calcium hydride under a nitrogen
atmosphere. Ethyl ether was distilled from sodium benzophe-
none ketyl under a nitrogen atmosphere. Pentane and hexanes
were fractionally distilled before use. Hexamethylphosphor-
amide (Aldrich) and ethanol, denatured with methanol and
2-propanol (Fisher), were used as purchased. Copper(I) tri-
fluoromethanesulfonate benzene complex and the chiral ligands,
2,2′-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline] (5a ), 2,2′-
isopropylidenebis[(4S)-4-phenyl-2-oxazoline] (5b), and 2,2′-
methylenebis[(4S)-4-tert-butyl-2-oxazoline] (5c) were pur-
chased (Aldrich), stored in a MBraun LabMaster100 inert-
atmosphere box, and used as received. Ethyl diazoacetate was
also purchased (Aldrich), refrigerated, and used without
further purification. 1-Adamantylthiol11 and allyl phenyl
sulfide (2e)12 were prepared according to reported procedures.
Allyl methyl sulfide (2a ), 2-methylbenzenethiol, 4-methoxy-
benzenethiol, 2-isopropylbenzenethiol (90%), 2,6-dimethylben-
zenethiol, 1,2-ethanedithiol (tech), (-)-menthone (90%), and
2.5 M butyllithium were used as received (Aldrich) as were
triphenylmercaptan (Fisher) and thiophenol (Fisher).
The catalytic reactions were maintained at a constant
temperature using a Neslab Exatrol heater. A model 365 ATI
Orion pump was used for the injection of ethyl diazoacetate.
All reactions were monitored by TLC carried out on UV-active
250-µm Whatman silica gel plates using a 15:1 hexanes/ethyl
ether mobile phase. Liquid chromatography was done using a
Selecto Scientific silica gel column (63-200 µm). Routine 1H
and 13C NMR spectra were obtained on Anasazi Aii FT-NMR
(60 MHz) and General Electric GN 300 spectrometers. The
COSY and proton-decoupling experiments were done on a
Varian VXN 500 spectrometer. Splitting patterns are desig-
nated as follows: s, singlet; d, doublet; t, triplet; q, quartet;
quint, quintet; sext, sextet; m, multiple; b, broad. Infrared
spectroscopy was done using a Nicolet Avatar 360 FT-IR. GC/
MS data were obtained on a Perkin-Elmer Autosystem XL/
Turbomass instrument using a PE-5MS fused silica capillary
column (20 m × 0.180 mm) with helium as the carrier (1.0
mL/min, split ratio ) 50:1). As referenced in the detailed data
section for each of the sulfides, the GC temperature program
was as follows: method 1, 50 °C (5 min), 2.5 °C/min ramp,
110 °C (31 min); method 2, 50 °C (10 min), 5.0 °C/min ramp,
75 °C (20 min); method 3, 100 °C (5 min), 4.0 °C/min ramp,
200 °C (20 min); or method 4, 100 °C (180 min), 2.0 °C/min
ramp, 150 °C. The data were reported as relative intensity
versus m/z. Enantiomeric excess determination was done on
a Beckman System Gold HPLC instrument with the 166 UV
detector. Baseline separation of the enantiomers was achieved
with a Chiracel OD column (250 × 4.6 mm) using a 0.15%
2-propanol/hexane mobile phase at a flow rate of 1.0 mL/min.
Ad a m a n tyl Allyl Su lfid e (2b). Adamantanethiol11 (5.0 g,
0.030 mol) was added to a solution of sodium ethoxide in
ethanol (prepared by adding sodium (12 g, 0.052 mol) to 600
mL of ethanol). Allyl bromide (3.9 mL, 0.045 mol) was then
added by an addition funnel over a 5 min period and the
reaction mixture stirred at reflux under a nitrogen atmosphere
for 1 h. A white solid gradually formed leaving a clear yellow
solution. The mixture was gravity filtered and the filtrate
combined with 1/3 amount of ethyl ether as well as 1/3 amount
of saturated NaCl. The opaque yellow organic layer was sep-
arated and dried with anhydrous Na2CO3 and then Na2SO4.
Rotary evaporation (20 mmHg, 30 °C) of the solvent gave a
clear yellow oil that was further purified by distillation (bp
89.6-92.5 °C1.0 mmHg) to give a clear and colorless oil (4.0 g,
64%): IR (neat) 3079 (w), 1636 (w), 987 (m), 912 (m); 1H NMR
(60 MHz, CDCl3) δ 1.5-2.3 (m, 15H), 3.0-3.3 (m, 2H), 4.8-
5.3 (m, 2H), 5.5-6.2 (m, 1H); 13C NMR (15 MHz, CDCl3) 29.16,
29.50, 36.08, 43.24, 44.18, 115.07, 134.61; GS/MS (method 1,
tR ) 54.8 min) 210 (1), 209 (2), 208 (11), 135 (100). Anal. Calcd
for C13H20S: C, 74.94; H, 9.67. Found: C, 74.56; H, 9.83.
Allyl 2-Meth ylp h en yl Su lfid e (2f). This compound was
synthesized on the basis of the published procedure for allyl
phenyl sulfide.12 A mixture of 2-methylbenzenethiol (5.0 g,
0.040 mol) and 15% aqueous NaOH (12 mL, 0.045 mol) was
heated to 50 °C. To the rapidly stirring mixture was added
allyl bromide (3.8 mL, 0.044 mol) dropwise over a 5 min period.
The cloudy mixture was heated an additional 40 min and then
allowed to cool. The two-phase mixture was separated and the
upper organic layer dried with anhydrous CaCl2 until it was
clear, and then distilled (bp 50.2-52.2 °C1.0 mmHg (lit.13 42 °C1.0
mmHg)) to give a clear and colorless oil (3.8 g, 58%): IR (neat)
3082 (w), 3060 (w), 1636 (w), 1589 (m), 1469 (s), 987 (m), 919
(m) 743 (s); 1H NMR (60 MHz, CDCl3) δ 2.37 (s, 3H), 3.3-3.6
(m, 2H), 4.8-5.3 (m, 2H), 5.5-6.3 (m, 1H), 6.9-7.4 (m, 4H).
Allyl 4-Meth oxyp h en yl Su lfid e (2i). This compound was
synthesized in the same manner as 2f. A clear and colorless
oil (3.2 g, 54%) was isolated after vacuum distillation (bp 66.0-
1
67.8 °C1.0 mmHg). H NMR and IR spectroscopic analyses were
consistent with the literature.14
Allyl Men th yl Su lfid es (2d a n d 7). This compound was
synthesized from menthyl mercaptan9 on the basis of a
published procedure.9 Under a nitrogen atmosphere, 2.5 M
n-butyllithium (16 mL, 0.040 mol) was added dropwise over a
10 min period to an ice-cooled solution of menthyl mercaptan
(4.0 g, 23.2 mmol) in 50 mL of ethyl ether. The ice bath was
removed and the yellow solution allowed to warm. After 30
min, the solution was again cooled in an ice bath. Allyl bromide
(2.2 mL, 25.4 mmol) and then HMPA (3.0 mL) were added to
the flask resulting in a dark colored mixture. After being
warmed to room temperature, the reaction mixture was
quenched with 100 mL of water, the layers were separated,
and the aqueous layer was extracted twice with 20 mL portions
of pentane. The combined organic layers were dried with
anhydrous Na2SO4 to give a clear and colorless solution. Rotary
evaporation (20 mmHg, 30 °C) of the solvent gave a clear and
colorless oil (4.8 g) that was further purified by vacuum
distillation (bp 52.9-58.0 °C1.0 mmHg) to give a diastereomeric
mixture of 2d and 7. The diastereomers were separated by
column chromatography (4 × 45 cm silica; hexanes eluant):
major isomer (1.09 g, 22%), minor isomer (0.614 g, 13%).
Major isomer (2d ): [R]2D ) 76.8 (c ) 10.00, CHCl3); IR (neat)
3080 (w), 1634 (w), 989 (m), 913 (m); 1H NMR (300 MHz,
CDCl3) δ 0.85 (d, 3H, J ) 6.6 Hz), 0.86 (d, 3H, J ) 6.9 Hz),
0.89 (d, 3H, J ) 6.6 Hz), 0.97-1.21 (m, 4H), 1.52-1.76 (m,
3H), 1.81-2.00 (m, 2H), 3.06 (b, 1H), 3.09 (bd, 2H, J ) 7.1
Hz), 5.00-5.13 (m, 2H), 5.71-5.86 (m, 1H); 13C NMR (15 MHz,
CDCl3) 20.59, 20.91, 22.08, 26.12, 26.21, 29.61, 33.95, 35.21,
40.14, 44.49, 48.55, 115.13, 134.85; GS/MS (method 1, tR
34.4 min) 214 (1), 213 (3), 212 (20), 95 (100). Anal. Calcd for
)
C
13H24S: C, 73.52; H, 11.39. Found: C, 73.23; H, 11.64.
Minor isomer (7): [R]2D ) -77.1 (c ) 7.38, CHCl3); IR (neat)
3080 (w), 1634 (w), 989 (m), 913 (m); 1H NMR (500 MHz,
CDCl3) δ 0.74 (d, 3H, J ) 7.0 Hz), 0.83-0.94 (m, 1H), 0.87 (d,
3H, J ) 7.0 Hz), 0.89 (d, 3H, J ) 7.0 Hz), 0.95-1.05 (m, 1H),
1.09 (q, 1H, J ) 12.4 Hz), 1.18 (tt, 1H, J ) 12.2 Hz, 2.8 Hz),
1.29-1.40 (m, 1H), 1.67-1.74 (m, 2H), 2.05-2.12 (m, 1H), 2.38
(dh, 1H, J ) 2.8 Hz, 7.0 Hz), 2.44 (dt, 1H, J ) 2.8 Hz, 12.2
Hz), 3.12 (ab, 1H, J ) 13.9 Hz, 6.7 Hz), 3.18 (ab, 1H, J ) 13.9
Hz, 7.9 Hz), 5.03-5.13 (m, 2H), 5.76-5.88 (m, 1H,); 13C NMR
(15 MHz, CDCl3) 15.10, 22.14, 22.16, 24.56, 26.94, 32.63, 33.00,
34.54, 43.49, 45.40, 46.52, 115.05, 133.96; GS/MS (method 1,
tR ) 34.5 min) 214 (1), 213 (4), 212 (25), 95 (99), 41 (100). Anal.
Calcd for C13H24S: C, 73.52; H, 11.39. Found: C, 73.31; H,
11.62.
Allyl 2-Isop r op ylben zen e Su lfid e (2g). Under a nitrogen
atmosphere, 2.5 M n-butyllithium (21 mL, 0.053 mol) was
added dropwise to an ice-cooled solution of 2-isopropylben-
zenethiol (7.2 g, 0.047 mol) in 100 mL of ethyl ether. The ice
bath was removed and the yellow solution allowed to warm.
(11) Khullar, K. K.; Bauer, L. J . Org. Chem. 1971, 36, 3038.
(12) Onishi, A.; Fujiyama, H.; Oda, R. J P Patent 54040527, 1979.
(13) Vizgert, R. V.; Sendega, R. V. Zh. Org. Khim. 1969, 5, 488.
(14) Crudden, C. M.; Alper, H. J . Org. Chem. 1995, 60, 5579.