Organic Syntheses, CV 9, 662
Submitted by Daniel S. Reno
1 and Richard J. Pariza
2.
Checked by David A. Barda and William R. Roush.
1. Procedure
CAUTION! The intermediate,
1-phenylthio-2-bromoethane, produced in the first step of this one pot reaction sequence is a strong alkylating agent, and some
bromine escapes from the reaction vessel. Therefore the reaction should be run in a properly operating ventilation hood, and care must be exercised to avoid exposure to these substances.
A
2-L, three-necked, round-bottomed flask fitted with a
reflux condenser, an
addition funnel, a
magnetic stirring bar,
thermometer, and
nitrogen inlet is charged with
diphenyl disulfide (200 g, 917 mmol) and
dichloromethane (320 mL) (Note
1). The addition funnel is charged with
bromine (161 g, 52 mL, 1.01 mol). After the
diphenyl disulfide dissolves, the nitrogen inlet is replaced with a
calcium sulfate-packed drying tube, and the flask is fitted with a gas-dispersion tube.
Ethylene (73.1 g, 2.61 mol) (Note
2), (Note
3) is slowly bubbled into the solution through a gas dispersion tube, and the
bromine is added in 2–3-mL portions over 5 hr (Note
4), (Note
5). After addition of the
bromine and
ethylene is complete, the drying tube is replaced with the nitrogen inlet, and the flask is fitted with a clean addition funnel. The addition funnel is charged with
1,8-diazabicyclo[5.4.0]undec-7-ene, DBU, (306 g, 300 mL, 2.01 mol) (Note
6). DBU is added at a rate such that the temperature of the reaction mixture does not exceed 55°C. After the DBU is added the reaction mixture is maintained at about 50°C for 15–18 hr. A
1.0 M ammonium hydroxide solution (600 mL) is added to the reaction mixture, and the mixture is transferred to a
separatory funnel. The layers are separated, and the aqueous layer is extracted with
300 mL of dichloromethane. The organic fractions are combined, washed with water (600 mL), and dried with
10 g of magnesium sulfate. The mixture is filtered, and the solvent is evaporated under reduced pressure. Distillation of the residue affords
162–184 g (
65–74%) of
phenyl vinyl sulfide, bp
80–84°C/11–12 mm (Note
7), (Note
8), (Note
9) and (Note
10). The purity is greater than 98% by GC analysis (Note
11), (Note
12).
2. Notes
1. All the materials used in this process were obtained from the Aldrich Chemical Company, Inc., and were used as received.
2. Initiation of the
ethylene addition should precede the introduction of the first portion of
bromine by 2–4 min.
Ethylene is then added continuously at a slow rate until all the
bromine is consumed (see (Note
4)).
3. The submitters reported that use of less than
1.41 equiv (2.62 mol) of ethylene reduces the yield of product. The checkers used a
145–174-μm fritted gas dispersion tube, and up to
1.84 equiv of ethylene (3.38 mol) was required to consume all the
bromine (see (Note
4)). However, on one occasion the checkers obtained excellent results (83% yield) using only
1.26 equiv of ethylene (2.30 mol). In this instance, a
25–50-μm fritted gas dispersion tube was used, which permitted a slower and more efficient rate of
ethylene introduction.
4. The first
2–3-mL portion of bromine is added until the reaction mixture is intensely violet. Subsequent portions of
bromine are added when the reaction mixture fades to an amber color. After all the
bromine has been added,
ethylene addition is continued until the color fades to amber.
5. A competing process involving halogenation of the phenyl substituent occurs when the
bromine concentration becomes too high. The slow addition of
bromine specified here minimizes the competing aromatic bromination.
6. The submitters report that use of less than this amount of DBU reduces the yield of
phenyl vinyl sulfide.
8.
Phenyl vinyl sulfide has the following spectral properties: EI MS 136;
1H NMR (400 MHz, CDCl
3) δ:5.35 (d, 1 H, J = 16.9), 5.36 (d, 1 H, J = 9.8), 6.55 (dd, 1 H, J = 9.8, 16.9), 7.22–7.40 (m, 5H);
13C NMR (100 MHz, CDCl
3) δ: 115.4, 127.1, 129.1, 130.4, 131.8, 134.2.
9.
Phenyl vinyl sulfide prepared using this procedure is stable at room temperature under a
nitrogen atmosphere for months. The submitters have kept samples for over nine months at ambient temperature without any visible degradation.
11. The GC analysis was performed with a Hewlett-Packard, HP-1 column (10 m × 0.53 mm × 2.65 μm). The temperature program was as follows: initial temperature, 50°C; initial time, 2.0 min; rate, 20°C/min; final temperature, 250°C; final time, 8 min.
Waste Disposal Information
All toxic materials were disposed of in accordance with "Prudent Practices in the Laboratory"; National Academy Press; Washington, DC, 1995.
3. Discussion
Phenyl vinyl sulfide possesses a number of synthetically useful attributes. It participates as an electron-rich alkene in 1+2,
3 2+2,
4 3+2,
5 and 4+2
6 cycloaddition reactions. Deprotonation of
phenyl vinyl sulfide with strong base affords an α-metallated sulfide that reacts with electrophiles.
7 The metallation-electrophile sequence and the cycloaddition reactions afford products amenable to further synthetic manipulation via the sulfide functionality. Furthermore,
phenyl vinyl sulfide is a convenient precursor to the synthetically useful
phenyl vinyl sulfoxide and
phenyl vinyl sulfone.
8
The procedure described here affords
phenyl vinyl sulfide in a high yield using common reagents and mild conditions. The material obtained via this procedure is stable at room temperature under a
nitrogen atmosphere for months. As indicated in (Note
10), this process is readily scaled up. Other methods either afford lower yields,
8,9,10 less stable product,
8 or require more extreme conditions.
11,12
This preparation is referenced from:
Copyright © 1921-2002, Organic Syntheses, Inc. All Rights Reserved