Dimethyl Sulfoxide-Phosgene1

(DMSO)

[67-68-5]  · C2H6OS  · Dimethyl Sulfoxide-Phosgene  · (MW 78.13) (COCl2)

[75-44-5]  · CCl2O  · Dimethyl Sulfoxide-Phosgene  · (MW 98.92)

(oxidant for the conversion of primary and secondary alcohols to aldehydes and ketones, respectively; avoids overoxidation to carboxylic acids; because of the high toxicity of phosgene and the absence of any clear advantages, the use of this procedure is not recommended)

Physical Data: DMSO: mp 18.4 °C; bp 189 °C; d 1.101 g cm-3. COCl2: bp 8.2 °C/760 mmHg; d 1.432 g cm-3 (4 °C).

Solubility: DMSO: sol H2O, alcohol, acetone, THF, CH2Cl2. COCl2: reacts slowly H2O; sol CH2Cl2, THF, benzene.

Form Supplied in: DMSO is a colorless liquid; widely available, including anhydrous grades of DMSO packed under N2; COCl2 is a gas available in cylinders.

Preparative Method: the active reagent is proposed2 to be (CH3)2+SOCO2CHRR1, formed from the reaction with DMSO of the chloroformate RR1CHO2CCl separately generated from phosgene and the alcohol.

Purification: DMSO: distillation from calcium hydride at 56-57 °C/5 mmHg,3a or 83-85 °C/17 mmHg;3b storage over 3Å molecular sieves. COCl2: distillation.

Handling, Storage, and Precautions: Dimethyl Sulfoxide is readily absorbed through the skin and should always be handled with gloves in a fume hood; its reactions form foul-smelling byproducts and should be carried out with good ventilation, and the waste byproducts and liquids used for washing should be treated with KMnO4 solution to oxidize volatile sulfur compounds; DMSO undergoes appreciable disproportionation to dimethyl sulfide (stench!) and dimethyl sulfone above 90 °C;3c Phosgene, also known as carbonic dichloride, is corrosive, moisture sensitive, and highly toxic, and should only be used with extreme caution.

In this procedure, chloroformates are generated from COCl2 and the alcohols are proposed to react with DMSO to form dimethylsulfonium salts (2) via decarboxylation of the intermediates (1) (eqs 1 and 2). This procedure has been used in the oxidation of various alcohols, including steroids, in 20-80% yields.2 The use of 1,2-epoxypropane as an acid scavenger in the process has been suggested.2b This procedure is inconvenient and dangerous, and offers no apparent advantages.

Related Reagents.

N-Chlorosuccinimide-Dimethyl Sulfide; Chromic Acid; Dimethyl Sulfide-Chlorine; Dimethyl Sulfoxide-Acetic Anhydride; Dimethyl Sulfoxide-Dicyclohexylcarbodiimide; Dimethyl Sulfoxide-Methanesulfonic Anhydride; Dimethyl Sulfoxide-Oxalyl Chloride; Dimethyl Sulfoxide-Phosphorus Pentoxide; Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine; Dimethyl Sulfoxide-Trifluoroacetic Anhydride; Dimethyl Sulfoxide-Triphosgene; Manganese Dioxide; Pyridinium Chlorochromate; Pyridinium Dichromate; Ruthenium(VIII) Oxide; Silver(I) Carbonate; 1,1,1-Triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one.


1. (a) Tidwell, T. T. OR 1990, 39, 297. (b) Tidwell, T. T. S 1990, 857. (c) Lee, T. V. COS 1991, 7, 291. (d) Haines, A. H. Methods for the Oxidation of Organic Compounds; Academic Press: London, 1988. (e) Hudlicky, M. Oxidations in Organic Chemistry; ACS: Washington, DC, 1990. (f) Mancuso, A. J.; Swern, D. S 1981, 165. (g) Moffatt, J. G. In Oxidation, Augustine, R. L.; Trecker, D. J., Eds.; Dekker: New York, 1971; Vol. 2, Chapter 1.
2. (a) Barton, D. H. R.; Garner, B. J.; Wightman, R. H. JCS 1964, 1855. (b) Barton, D. H. R.; Forbes, C. P. JCS(P1) 1975, 1614.
3. (a) Iwai, I.; Ide, J. OSC 1988, 6, 531. (b) Insalaco, M. A.; Tarbell, D. S. OSC 1988, 6, 207. (c) Corey, E. J.; Chaykovsky, M. OSC 1973, 5, 755.

Thomas T. Tidwell

University of Toronto, Toronto, Canada



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