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Org. Synth. 1978, 58, 143
DOI: 10.15227/orgsyn.058.0143
SULFIDE SYNTHESIS IN PREPARATION OF DIALKYL AND ALKYL ARYL SULFIDES: NEOPENTYL PHENYL SULFIDE
[Benzene, [(2,2-dimethylpropyl)thio]-]
Submitted by D. Landini1 and F. Rolla.
Checked by Ronald L. Sobczak and S. Masamune.
1. Procedure
A 100-ml., two-necked flask fitted with a reflux condenser, a gas-inlet, and a magnetic stirrer is charged with 15.1 g. (12.0 ml., 0.100 mole) of 1-bromo-2,2-dimethylpropane (Note 1), aqueous sodium benzenethiolate (0.1 mole) (Note 2), and 1.67 g. (0.00329 mole) of tributylhexadecylphosphonium bromide (Note 3) and (Note 4). This mixture is heated at 70° with vigorous stirring under nitrogen (Note 5) for 3.5 hours (Note 6). After the mixture has cooled to room temperature, the organic layer is separated, and the aqueous phase is extracted with two 20-ml. portions of diethyl ether. The combined organic phases are washed with 20 ml. of 10% aqueous sodium chloride and dried over calcium chloride. After removal of the solvent, the resulting, residual oil is distilled through a 10-cm. Vigreux column, giving 14.1–15.3 g. (78–85%) of colorless neopentyl phenyl sulfide (Note 7), b.p. 85–87° (5 mm.), 96–98° (8 mm.); nD24 1.5365 (Note 8).
2. Notes
1. 1-Bromo-2,2-dimethylpropane (neopentyl bromide) was obtained from Fluka A G or Tridom Chemical Inc.
2. Aqueous sodium benzenethiolate was prepared by adding 11.0 g. (10.2 ml., 0.100 mole) of commercial benzenethiol (listed as thiophenol by Aldrich Chemical Company, Inc., and Tridom Chemical Inc.) to an ice-cold solution of 4.0 g. of sodium hydroxide in 25 ml. of water.
3. The tributylhexadecylphosphonium bromide was prepared by heating 0.1 mole of 1-bromohexadecane and 0.1 mole of tributylphosphine at 60–70° for three days, according to Starks' procedure.2 The product, while hot, was poured into 300 ml. of hexane and the mixture was stirred for 15 minutes. After cooling of the mixture to 0°, a solid product crystallized, was filtered on a Büchner funnel, and dried under reduced pressure, m.p. 54–56° (84%).
4. When the reaction was carried out using 0.033 mole equivalent of tricaprylylmethylammonium chloride (aliquat 336), obtained from General Mills Company, Chemical Division, Kankakee, Illinois, as catalyst, the reaction required about 10 hours for completion.
5. The nitrogen flow must be as slow as possible to avoid loss of 1-bromo-2,2-dimethylpropane.
6. The reaction time depends on the concentration of the catalyst; e.g., with 0.1 and 0.01 mole equivalents of phosphonium salt, the reaction required 1 and 10 hours, respectively.
7. The catalyst could be recovered (80–90%) from the distillation residue, which also contained some neopentyl phenyl sulfide and diphenyl disulfide. These products were eliminated from the residue by column chromatography on silica (8 g. for 1 g. of phosphonium salt; eluent, ether). Extraction of the silica with two 25-ml. portions of boiling ethanol and evaporation of the solvent afforded the phosphonium salt, m.p. 48–51°. This material could be reused without further purification.
8. The product showed the following 1H NMR spectrum (CDCl3) δ (multiplicity, number of protons, assignment): 1.03 [s, 9H, (CH3)3C], 2.88 (s, 2H, CH2), 7.02–7.52 (m, 5H, C6H5).
Working with Hazardous Chemicals

The procedures in Organic Syntheses are intended for use only by persons with proper training in experimental organic chemistry. All hazardous materials should be handled using the standard procedures for work with chemicals described in references such as "Prudent Practices in the Laboratory" (The National Academies Press, Washington, D.C., 2011; the full text can be accessed free of charge at http://www.nap.edu/catalog.php?record_id=12654). All chemical waste should be disposed of in accordance with local regulations. For general guidelines for the management of chemical waste, see Chapter 8 of Prudent Practices.

In some articles in Organic Syntheses, chemical-specific hazards are highlighted in red "Caution Notes" within a procedure. It is important to recognize that the absence of a caution note does not imply that no significant hazards are associated with the chemicals involved in that procedure. Prior to performing a reaction, a thorough risk assessment should be carried out that includes a review of the potential hazards associated with each chemical and experimental operation on the scale that is planned for the procedure. Guidelines for carrying out a risk assessment and for analyzing the hazards associated with chemicals can be found in Chapter 4 of Prudent Practices.

The procedures described in Organic Syntheses are provided as published and are conducted at one's own risk. Organic Syntheses, Inc., its Editors, and its Board of Directors do not warrant or guarantee the safety of individuals using these procedures and hereby disclaim any liability for any injuries or damages claimed to have resulted from or related in any way to the procedures herein.

The paragraphs above were added in September, 2014. The statements above do not supersede any specific hazard caution notes and safety instructions included in the procedure.

3. Discussion
This procedure3 illustrates a simple and general method for the preparation of primary and secondary dialkyl and alkyl aryl thioethers via alkylation of sodium sulfide, sodium alkyl- or arylthiolates with alkyl chlorides or bromides. The method is an example of phase-transfer catalysis, characterized by mild reaction conditions, high yields, and simple work-up procedure.
Dineopentyl and neopentyl phenyl sulfides are obtained from 1-bromo-2,2-dimethylpropane. Some other examples are given in Table I.
TABLE I
PREPARATION OF DIALKYL AND ALKYL PHENYL SULFIDES

Alkyl Halide

Nucleophile

Catalyst (mole equivalent)

Temperature (°C)

Time (minutes)

Yield of Sulfidea(%)


1-Chloroöctane

Na2Sb

0.1

70

40

91

2-Chloroöctane

Na2Sb

0.1

70

300

90

1-Bromoöctane

Na2Sb

0.1

70

20

91

2-Bromoöctane

Na2Sb

0.1

70

80

91

Neopentylbromide

Na2Sb

0.1

70

500

81c

1-Chloroöctane

C2H5SNad

0.033

40

40

90

2-Chloroöctane

C2H5SNad

0.033

70

250

88

1-Bromoöctane

C2H5SNad

0.033

40

15

91

2-Bromoöctane

C2H5SNad

0.033

70

120

89

1-Chloroöctane

C6H5SNad

0.033

40

30

92

2-Chloroöctane

C6H5SNad

0.033

70

180

90

1-Bromoöctane

C6H5SNad

0.033

40

10

91

2-Bromoöctane

C6H5SNad

0.033

70

60

90


aIsolated products.

bMole ratio of Na2S to alkyl halide is 0.6.

cReaction carried out under nitrogen.

dMole ratio of sodium salt to alkyl halide is 1.

Neopentyl sulfides have been prepared by alkylation of sodium sulfide with neopentyl tosylate in high-boiling polar solvents,4,5 or in low yields by reduction of alkyl 2,2-dimethylpropanethioate with lithium aluminum hydride in a large excess of boron trifluoride-diethyl etherate.6

References and Notes
  1. Centro C.N.R. e Istituto di Chimica Industriale dell'Universita', Via C. Golgi 19, Milano 20133, Italy.
  2. C. M. Starks, J. Am. Chem. Soc., 93, 195 (1971).
  3. D. Landini and F. Rolla, Synthesis, 565 (1974).
  4. F. G. Bordwell, B. M. Pitt, and M. Knell, J. Am. Chem. Soc., 73, 5004 (1951).
  5. W. E. Parham and L. D. Edwards, J. Org. Chem., 33, 4150 (1968).
  6. E. L. Eliel and R. A. Daignault, J. Org. Chem., 29, 1630 (1964).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

silica

ethanol (64-17-5)

calcium chloride (10043-52-4)

ether,
diethyl ether (60-29-7)

sodium hydroxide (1310-73-2)

sodium chloride (7647-14-5)

1-Bromooctane (111-83-1)

nitrogen (7727-37-9)

sodium (13966-32-0)

sodium sulfide (1313-82-2)

Thiophenol,
Benzenethiol (108-98-5)

lithium aluminum hydride (16853-85-3)

hexane (110-54-3)

1-bromohexadecane (112-82-3)

boron trifluoride-diethyl etherate (109-63-7)

diphenyl disulfide (882-33-7)

tributylphosphine (998-40-3)

Neopentyl phenyl sulfide,
Benzene, [(2,2-dimethylpropyl)thio]- (7210-80-2)

1-bromo-2,2-dimethylpropane,
neopentyl bromide,
Neopentylbromide (630-17-1)

sodium benzenethiolate

tributylhexadecylphosphonium bromide (14937-45-2)

tricaprylylmethylammonium chloride (5137-55-3)

neopentyl tosylate

1-Chlorooctane (111-85-3)

2-Chlorooctane

2-Bromooctane

Notes

1. 1-Bromo-2,2-dimethylpropane (neopentyl bromide) was obtained from Fluka A G or Tridom Chemical Inc.

2. Aqueous sodium benzenethiolate was prepared by adding 11.0 g. (10.2 ml., 0.100 mole) of commercial benzenethiol (listed as thiophenol by Aldrich Chemical Company, Inc., and Tridom Chemical Inc.) to an ice-cold solution of 4.0 g. of sodium hydroxide in 25 ml. of water.

3. The tributylhexadecylphosphonium bromide was prepared by heating 0.1 mole of 1-bromohexadecane and 0.1 mole of tributylphosphine at 60–70° for three days, according to Starks' procedure.2 The product, while hot, was poured into 300 ml. of hexane and the mixture was stirred for 15 minutes. After cooling of the mixture to 0°, a solid product crystallized, was filtered on a Büchner funnel, and dried under reduced pressure, m.p. 54–56° (84%).

4. When the reaction was carried out using 0.033 mole equivalent of tricaprylylmethylammonium chloride (aliquat 336), obtained from General Mills Company, Chemical Division, Kankakee, Illinois, as catalyst, the reaction required about 10 hours for completion.

5. The nitrogen flow must be as slow as possible to avoid loss of 1-bromo-2,2-dimethylpropane.

6. The reaction time depends on the concentration of the catalyst; e.g., with 0.1 and 0.01 mole equivalents of phosphonium salt, the reaction required 1 and 10 hours, respectively.

7. The catalyst could be recovered (80–90%) from the distillation residue, which also contained some neopentyl phenyl sulfide and diphenyl disulfide. These products were eliminated from the residue by column chromatography on silica (8 g. for 1 g. of phosphonium salt; eluent, ether). Extraction of the silica with two 25-ml. portions of boiling ethanol and evaporation of the solvent afforded the phosphonium salt, m.p. 48–51°. This material could be reused without further purification.

8. The product showed the following 1H NMR spectrum (CDCl3) δ (multiplicity, number of protons, assignment): 1.03 [s, 9H, (CH3)3C], 2.88 (s, 2H, CH2), 7.02–7.52 (m, 5H, C6H5).

References/EndNotes

Article Compounds

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