Checked by Bruce A. Carlson and William A. Sheppard.
1. Procedure
B.
Ethyl N-nitroso-N-(p-tolylsulfonylmethyl)carbamate. A solution of
154 g. (0.599 mole) of the ethyl N-(p-tolylsulfonylemthyl)carbamate in
600 ml. of pyridine (Note
6) is placed in a
1-l., four-necked flask equipped with a thermometer, a mechanical stirrer, a gas-inlet tube leading into the solution, and a gas outlet leading to the exhaust. The weight of the flask together with its contents is determined, preferably on a balance placed in the same hood. The solution is cooled to 0° in an ice–salt mixture.
Gaseous nitrosyl chloride (Note
7) is introduced,
via a
mineral oil bubbler and a
trap, into the stirred solution at such a rate that the temperature is kept between 0° and 5°. After
52–65 g. (0.79–0.99 mole) of nitrosyl chloride has been taken up (Note
8), the reaction is completed by stirring for 30 minutes at about 0°, at which point the reaction mixture is poured in a thin stream into a hand-stirred mixture of 4 l. of ice and water, giving a pale-yellow oil that readily solidifies (Note
9). The solid is collected by suction filtration after standing for 1 hour at 0°. Any lumps present are pulverized, and the solid is washed thoroughly in a beaker with four 500-ml. portions of cold water, removing
pyridine. The moist product is dissolved in sufficient
dichloromethane (
ca. 1.5 l.) and the water layer is removed. The
dichloromethane solution is dried over
anhydrous magnesium sulfate and concentrated to dryness under reduced pressure, giving
157–171 g. (
92–100%) of crude
ethyl N-nitroso-N-(p-tolylsulfonylmethyl)carbamate, m.p.
86–89° (slight dec.). The crude nitroso compound can be used without purification in the next step of the reaction, provided that it is free of starting material (Note
10).
If the nitrosocarbamate is to be stored (preferably at −20°) for periods longer than a month, it should be recrystallized once from
1:2 dichloromethane-diethyl ether (Note
11), m.p.
87–89°. In this purified form it can be stored for several months at −20° without noticeable decomposition.
C.
p-Tolylsulfonyldiazomethane.
Warning! α-Diazosulfones slowly decompose under the influence of light. Exposure to light should therefore be kept at a minimum in all stages of the reaction. A
3-l., three-necked, round-bottomed flask equipped with a condenser, an efficient mechanical stirrer, and a stopper, is charged with
570 g. of alumina (Note
12). The flask is wrapped with
aluminum foil or covered with dark cloth or black paper. With stirring,
1.5 l. of ether (Note
13) is added. The mixture is cooled to 10–15° with a
water–ice bath, and a solution of
57.3 g. (0.200 mole) of ethyl N-nitroso-N-(p-tolylsulfonylmethyl)carbamate in
150 ml. of dichloromethane (Note
14) is added in one portion. Stirring is continued for 2 hours at 10–15° (Note
15); during this time the
ether solution soon develops the bright-yellow color of
p-tolylsulfonyldiazomethane. The
ether solution is decanted from the
alumina. The
alumina is extracted thoroughly by stirring for periods of 5 minutes with two portions of
500 ml. and three portions of 250 ml. of ether. The combined
ether solutions are filtered through coarse filter paper and concentration is a
vacuum rotary flash evaporator. The temperature of the water bath must not exceed 25°. When the volume is reduced to about 200 ml., the water bath is removed entirely and concentration is continued until the cold residue crystallizes spontaneously (Note
16). The crystal mass is stirred for about 2 minutes in
50 ml. of ice-cold petroleum ether (40–60°). The crystals are collected on a
sintered-glass filter and washed on the filter with two
25-ml. portions of cold petroleum ether. Drying overnight at 0° in a
vacuum desiccator over
anhydrous calcium chloride, yields
26–30 g. (
66–76%) of yellow
p-tolylsulfonyldiazomethane, m.p.
35–38° (slight dec.) (Note
17). Recrystallization from
anhydrous ether-pentane (Note
18) will raise the melting point to
36–38° (slight dec.) at the expense of 5–10% of material.
p-Tolylsulfonyldiazomethane should be stored at or below 0° in the absence of light in an
unsealed container (Note
19).
2. Notes
Alternatively, sulfinates can be synthesized conveniently by the method of Truce and Roberts,
2 or by that of Oxley and colleagues.
3
3.
Ethyl carbamate (J. T. Baker Chemical Company), with a reporter melting point of
48–50° (
46–49° was found), was used without purification. The solid was added to the reaction mixture.
4.
Formic acid (97%) from J. T. Baker Chemical Company was used.
5. By cooling and stirring as described, the product is obtained in a finely divided form, which can be removed from the flask easily and washed efficiently.
6.
Commercial pyridine (J. T. Baker Chemical Company) was used without purification.
7.
Nitrosyl chloride (Matheson Gas Products) with a purity specified as >97% was used. Occasionally, the needle valve of the
nitrosyl chloride tank clogs. After closing the tank, the valve is disconnected and flushed with
acetone until the
acetone remains colorless. The needle valve is reconnected after being dried with compressed air.
8. The color of the
pyridine solution changes rapidly from blue and green to yellow. After roughly
I equivalent (0.6 mole) of nitrosyl chloride has been taken up (
ca. 1 hour), the color of the solution changes to dark red-brown. During the reaction a precipitate of
pyridinium chloride is formed; however, it will disappear during the workup with water as described. A large excess of
nitrosyl chloride (up to 3 equivalents) has been used occasionally without any disadvantages.
9. Preferably, a few drops of the
pyridine solution are rubbed first with a little water, providing seed crystals so that the product will solidify immediately, giving a finely divided material which can be washed more easily.
10. The presence of
ethyl N-(p-tolylsulfonylemthyl)carbamate in the reaction product is most readily detected by the N-H IR absorption band at 3370 cm.
−1. If the nitrosation is incomplete, the reaction with
nitrosyl chloride should be repeated on the mixture of compounds, rather than to try to purify the product by recrystallization.
11.
Ether (ca. 1.4 l.) is added to a warm, filtered solution of
100 g. of the crude nitroso compound in
ca. 0.7 l. of dichloromethane until the solution becomes slightly turbid. The nitrosocarbamate is collected after cooling overnight at −20° and dried under reduced pressure at 0°, providing
88–93 g. of yellow crystals with a pink luster, m.p.
87–89.
12.
Alumina Number 1076, "aktiv basisch," for chromatography (E. Merck, Darmstadt) was usually employed. Occasionally, when alumina Number 1077, "aktiv neutral," from the same company, was used, a longer reaction time was required (compare (Note
15)).
13. Commercial
ether was stored over
potassium hydroxide pellets and used without distillation. Because some heat is evolved when the
ether is added to the
alumina, the flask is equipped with a condenser.
15. The time necessary for completion of the reaction may vary from 0.5 to 4 hours, depending on the actual activity of the
alumina. The progress of conversion should be monitored by IR analysis of a concentrated sample of the solution. Stirring should be continued for 15 minutes after the nitroso band at 1540 cm.
−1 has disappeared. A strong diazo band at about 2100 cm.
−1 will then be present. The carbonyl band a 1750 cm.
−1, initially due to nitrosocarbamate, will usually not disappear completely during the reaction, because some
diethyl carbonate is formed in addition to
carbon dioxide and
ethanol.
Diethyl carbonate is removed during the workup procedure.
During the reaction the alumina usually attains a pink color, due to some decomposition of
p-tolylsulfonyldiazomethane. However, the colored decomposition products adhere strongly to the alumina and will not, therefore, contaminate the final product. If the alumina becomes reddish rather than pink, the type of the alumina in use may be too basic, causing more extensive decomposition of the
p-tolylsulfonyldiazomethane; the reaction time should then be reduced as much as possible to prevent a considerable decrease in yield.
16. If crystallization does not occur, it can be induced readily by scratching.
17. Spectral data of
p-tolylsulfonyldiazomethane; IR (Nujol) cm.
−1: 2125 (C=N=N), 1330 (SO
2), 1150 (SO
2);
1H NMR (CDCl
3), δ (multiplicity, number of protons, assignment): 2.46 (s, 3H, C
H3), 5.36 (s, 1H, C
H), 7.30, 7.43, 7.73, 7.87 (AB q, 4H, C
6H4); visible (
40% dioxane-water) nm. max. (log ε): 394 (1.8).
19.
p-Tolylsulfonyldiazomethane is insensitive to impact detonation; however, it decomposes on warming, evolving significant quantities of
nitrogen at temperature as low as 32°. It should never be stored for any length of time in a sealed container and should be stored at or below 0° if not used immediately.
3. Discussion
Appendix
Compounds Referenced (Chemical Abstracts Registry Number)
alumina
petroleum ether
N-(p-tolylsulfonylemthyl)carbamate
J. T. Baker Chemical Company
ethyl N-(p-tolylsulfonylemthyl)carbamate
N-hydroxy-1-(p-tolysulfonyl)methanimidoyl chloride
1-(1-tert-butoxy-1-chloromethysulfonyl)-4-methylbenzene
p-tolylsulfonylacetaldehyde hemihydrate
ethanol (64-17-5)
calcium chloride (10043-52-4)
hydrochloric acid (7647-01-0)
ammonia (7664-41-7)
methanol (67-56-1)
ether,
diethyl ether (60-29-7)
formaldehyde (630-08-0)
ethyl (2025-56-1)
formic acid (64-18-6)
nitrogen (7727-37-9)
sodium nitrite (7632-00-0)
sulfur (7704-34-9)
aluminum (7429-90-5)
carbon dioxide (124-38-9)
acetone (67-64-1)
pyridine (110-86-1)
potassium hydroxide (1310-58-3)
Pentane (109-66-0)
dichloromethane (75-09-2)
nitrosyl chloride (2696-92-6)
2,3-dimethyl-2-butene (563-79-1)
magnesium sulfate (7487-88-9)
dioxane (5703-46-8)
ethyl carbamate (51-79-6)
diethyl carbonate (105-58-8)
tert-butyl alcohol (75-65-0)
perchloric acid (7601-90-3)
p-tolylsulfonyl azide (941-55-9)
Benzene, 1-[(diazomethyl)sulfonyl]-4-methyl-,
p-Tolylsulfonyldiazomethane (1538-98-3)
nitrosonium tetrafluoroborate (14635-75-7)
pyridinium chloride (628-13-7)
1-(1-chloro-1-ethoxymethylsulfonyl)-4-methylbenzene
1-(4-methoxyphenylsulfonyl)-2,2,3,3-tetramethylcyclopropane
4-methoxybenzenesulfonyldiazomethane
4-carboxybenzenesulfonyl azide (17202-49-2)
Sodium p-toluenesulfinate
tert-Butyl hypochlorite (507-40-4)
p-Toluenesulfenyl chloride (933-00-6)
sodium p-toluenesulfinate dihydrate (7257-26-3)
trans-2-Butene (624-64-6)
ethyl N-(p-toluenesulfonylmethyl)carbamate,
ethyl N-(p-tolylsulfonylmethyl)carbamate (2850-26-2)
Ethyl N-nitroso-N-(p-tolylsulfonylmethyl)carbamate (2951-53-3)
chloro-p-tolylsulfonyl-p-tolylthiomethane
(d,l)-1-(4-methoxyphenylsulfonyl)-trans-2,3-dimethylcyclopropane
p-tolylsulfonylacetaldehyde enol acetate
p-tolylsulfonylmethylenetriphenylphosphorane
N-nitroso-N-(p-tolylsulfonylmethyl)carbamate
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