Org. Synth. 1970, 50, 75
DOI: 10.15227/orgsyn.050.0075
2,2'-DITHIENYL SULFIDE
[Thiophene, 2,2'-thiobis-]
Submitted by E. Jones and I. M. Moodie
1.
Checked by Jerry G. Kohlhoff, Wayland E. Noland, and William E. Parham.
1. Procedure
Caution! Benzene has been identified as a carcinogen; OSHA has issued emergency standards on its use. All procedures involving benzene should be carried out in a well-ventilated hood, and glove protection is required.
A
three necked, 250-ml. flask fitted with a reflux condenser stirrer and a thermometer pocket with a nitrogen inlet is charged with
100 ml. of N,N-dimethylformamide,
5.6 g. (0.10 mole) of potassium hydroxide (Note 1), and
7.15 g. (0.0500 mole) of freshly precipitated copper(I) oxide2 (Note 2).
2-Bromothiophene (16.4 g., 0.101 mole) (Note 3) is added, and the apparatus is flushed with
nitrogen (Note 4).
2-Thiophenethiol3 [11.6 g., 0.100 mole;
Org. Synth., Coll. Vol. 6, 979 (1988)] is then added slowly through the condenser; an exothermic reaction begins, and the temperature may rise to 50–60°. The flask is heated in an
oil bath at 130–140° for 16 hours
(Note 5). The mixture is cooled to room temperature before the contents of the flask are poured into
100 ml. of 6 N hydrochloric acid in ice. The mixture is stirred vigorously for 2 hours
(Note 6); the oily black paste obtained is removed by filtration and thoroughly extracted in a
Soxhlet extractor with
benzene until a colorless extract is obtained. The filtrate is also extracted with two
100-ml. portions of benzene. These extracts are combined, washed with water until neutral, and dried over
anhydrous sodium sulfate. Removal of the solvent gives a yellow-colored oil which, on vacuum distillation, yields
11.5–12.5 g. (
58–63%) of
2,2'-dithienyl sulfide as a pale yellow oil, b.p.
75–78° (0.06 mm.) nD25 1.6643.
2. Notes
1.
The presence of an equivalent of
potassium or sodium hydroxide is necessary to promote the substitution reaction of the
2-bromothiophene with
copper(I) oxide.
2.
Freshly precipitated
copper(I) oxide was dried at 110° before use. Commercial grades were found to give lower yields (
ca. 35–40%) of the desired sulfide. The checkers dried
copper(I) oxide in a
vacuum oven at 100° for 6 hours.
3.
2-Bromothiophene was supplied by Columbia Organic Chemicals, Inc. 2-Chloro- or 2-iodothiophenes may be used; however, the former gives poorer yields of the sulfide.
4.
Nitrogen is passed through the system to provide an inert atmosphere, preventing possible oxidation of the
2-thiophenethiol to the corresponding disulfide.
5.
Reaction is sluggish at temperatures below 130°.
6.
Vigorous stirring helps to break up the thick sludge formed on addition of the reaction mixture to the acid and also removes soluble inorganic salts.
3. Discussion
The submitters have also prepared
2,2'-dithienyl sulfide in
34% yield by condensation of
2-thiophenethiol with
2-bromothiophene in the presence of
copper(I) oxide in a
quinoline-pyridine mixture.
4 Challenger and Harrison
5 have obtained
2,2'-dithienyl sulfide in
50–55% yield by treatment of
2-thienylmagnesium bromide with excess
sulfur. This sulfide may also be obtained in
20% yield by condensation of
thiophene with
sulfur monochloride, followed by pyrolysis of the resultant disulfide.
6This synthetic process offers a route to the preparation of the isomeric dithienyl sulfides
7 (2,3- and 3,3-) which cannot be prepared readily by any of the standard methods. Thus, condensation of
2-thiophenethiol with
3-bromothiophene or
3-thiophenethiol with
2-bromothiophene gives
2,3'-dithienyl sulfide in
63.0 and
73.5% yields, respectively. Similarly,
3,3'-dithienyl sulfide is obtained in
48% yield. The method has also been extended to the synthesis of the isomeric
bis-(thienylthio)thiophenes in 40–50% yield.
4This method may also be used for the preparation in high yields of other aromatic sulfides.
8
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
2,2'-DITHIENYL SULFIDE
potassium or sodium hydroxide
2-Chloro- or 2-iodothiophenes
quinoline-pyridine
2,3'-dithienyl sulfide
3,3'-dithienyl sulfide
hydrochloric acid (7647-01-0)
Benzene (71-43-2)
sodium sulfate (7757-82-6)
nitrogen (7727-37-9)
sulfur (7704-34-9)
copper(I) oxide
potassium hydroxide (1310-58-3)
sulfur monochloride
Thiophene (110-02-1)
N,N-dimethylformamide (68-12-2)
2-thiophenethiol (7774-74-5)
2-Bromothiophene (1003-09-4)
2-thienylmagnesium bromide
3-Bromothiophene (872-31-1)
3-thiophenethiol
Thiophene, 2,2'-thiobis- (3988-99-6)
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