Org. Synth. 1966, 46, 78
DOI: 10.15227/orgsyn.046.0078
METHYL PHENYL SULFOXIDE
Submitted by Carl R. Johnson and Jeffrey E. Keiser
1.
Checked by Wayland E. Noland, Leonard J. Czuba, and William E. Parham.
1. Procedure
In a 500-ml. round-bottomed flask equipped with a magnetic stirrer are placed 22.5 g. (0.105 mole) of powdered sodium metaperiodate and 210 ml. of water. The mixture is stirred and cooled in an ice bath (Note 1), and 12.4 g. (0.100 mole) of thioanisole (Note 2) is added. The reaction mixture is stirred for 15 hours at ice-bath temperature and is then filtered through a Büchner funnel. The filter cake of sodium iodate is washed with three 30-ml. portions of methylene chloride. The water-methylene chloride filtrate is transferred to a separatory funnel, the lower methylene chloride layer is removed, and the water layer is extracted with three 100-ml. portions of methylene chloride. The combined methylene chloride extracts are treated with activated carbon (Note 3) and dried over anhydrous sodium sulfate (Note 4). The solvent is removed at reduced pressure to yield 13.6–13.9 g. of a slightly yellow oil (Note 5) which crystallizes on cooling. The crude sulfoxide is transferred to a 25-ml. distillation flask with the aid of a small amount of methylene chloride. After removal of the solvent, a pinch of activated carbon is added to the distillation flask (Note 6). Simple vacuum distillation (Note 7) of the crude product through a short path still affords 12.7–12.8 g. (91%) of pure methyl phenyl sulfoxide, b.p. 78–79° (0.1 mm.), m.p. 33–34° (Note 8) and (Note 9).
2. Notes
1.
The periodate oxidation of aryl sulfides to sulfoxides may be carried out at room temperature; however, an
ice bath is necessary to prevent overoxidation of dialkyl sulfides.
2.
Thioanisole (methyl phenyl sulfide) supplied by Aldrich Chemical Company, Milwaukee, Wisconsin, was used without further purification.
3.
The checkers used
1 g. of activated carbon.
4.
The checkers used
3–5 g. of sodium sulfate.
5.
Gas-phase chromatography shows this crude material to be sulfide-free sulfoxide containing a small amount of
methylene chloride.
6.
The simple technique of adding a pinch of activated
carbon to the distillation pot affords a more nearly colorless distillate.
7.
No fore-run is observed other than a small amount of
methylene chloride which does not condense. The pot is taken nearly to dryness.
8.
Methyl phenyl sulfoxide is extremely hygroscopic. The melting point is best taken by rapid transfer of the easily supercooled oil to a melting-point capillary by means of a finely drawn pipet. The sealed capillary is then cooled to effect crystallization of the sulfoxide.
9.
This procedure, with slight modifications depending on the physical properties of the sulfide and sulfoxide in question, has been used to prepare a variety of sulfoxides as illustrated by examples provided in Table I. In the case of very insoluble sulfides, co-solvents such as
methanol or dioxane may be employed. Very soluble sulfoxides are best isolated by continuous extraction with
chloroform or methylene chloride.
TABLE I PREPARATION OF SULFOXIDES
|
|
Products
|
Yields, %
|
M.P. [B.P.], °C.
|
|
|
Methyl 4-ketopentyl sulfoxide
|
98
|
22.5–23.5 [99–101 (0.12 mm.)]
|
|
Thian 1-oxide
|
99
|
67–68
|
|
1,4-Oxathian 1-oxide
|
83
|
46–47
|
|
Bis(2-diethylaminoethyl)sulfoxide
|
85
|
Dipicrate 146–148
|
|
Acetoxymethyl methyl sulfoxide
|
72
|
[85–90 (0.1 mm.)]
|
|
1-Benzylsulfinyl-2-propanone
|
89
|
126.0–126.5
|
|
Phenylsulfinylacetic acid
|
99
|
118.0–119.5
|
|
Benzyl sulfoxide
|
96
|
135–136
|
|
Ethyl sulfoxide
|
65
|
[45–47 (0.15 mm.)]
|
|
Ethyl phenyl sulfoxide
|
93
|
[101–102 (1.5 mm.)]
|
|
3. Discussion
Methyl phenyl sulfoxide has also been prepared from
thioanisole by the action of
hydrogen peroxide,
2,3 lead tetraacetate,
4 and
dinitrogen tetroxide,
5,6 and from
methanesulfinyl chloride and
benzene with
anhydrous aluminum chloride.
7
4. Merits of the Preparation
The present procedure is a specific example of the method generalized by Leonard and Johnson.
8 The method employs extremely mild reaction conditions and affords high yields of sulfoxides
(Note 9) free of contamination by sulfides or sulfones.
Sodium periodate is easily and safely handled; however, the higher cost of this reagent in comparison to certain other oxidants,
e.g.,
hydrogen peroxide, may prohibit its use in large-scale reactions.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
dinitrogen tetroxide
Benzene (71-43-2)
methanol (67-56-1)
chloroform (67-66-3)
sodium sulfate (7757-82-6)
carbon (7782-42-5)
aluminum chloride (3495-54-3)
hydrogen peroxide (7722-84-1)
methylene chloride (75-09-2)
dioxane (123-91-1)
Methanesulfinyl chloride (676-85-7)
Methyl phenyl sulfoxide (1193-82-4)
sodium metaperiodate,
Sodium periodate (7790-28-5)
thioanisole,
methyl phenyl sulfide (100-68-5)
water-methylene chloride
Methyl 4-ketopentyl sulfoxide
Thian 1-oxide
1,4-Oxathian 1-oxide
Bis(2-diethylaminoethyl)sulfoxide
Acetoxymethyl methyl sulfoxide
1-Benzylsulfinyl-2-propanone
Phenylsulfinylacetic acid
Benzyl sulfoxide (621-08-9)
Ethyl sulfoxide (70-29-1)
Ethyl phenyl sulfoxide (4170-80-3)
lead tetraacetate (546-67-8)
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