Dimethyl Sulfoxide-Triphosgene1

(DMSO)

[67-68-5]  · C2H6OS  · Dimethyl Sulfoxide-Triphosgene  · (MW 78.13) ((CCl3O)2CO)

[32315-10-9]  · C3Cl6O3  · Dimethyl Sulfoxide-Triphosgene  · (MW 296.75)

(oxidant for the conversion of primary and secondary alcohols to aldehydes and ketones, respectively; avoids overoxidation to carboxylic acids; suitable for large-scale oxidation; gives good yields of high-purity products; more convenient than the use of phosgene)

Physical Data: DMSO: mp 18.4 °C; bp 189 °C; d 1.101 g cm-3. (CCl3O)2CO: bp 203-206 °C; mp 79-83 °C.

Solubility: DMSO: sol H2O, alcohol, acetone, THF, CH2Cl2. (CCl3O)2CO: reacts H2O; sol CH2Cl2, THF, o-dichlorobenzene.

Form Supplied in: DMSO: colorless liquid; widely available, including anhydrous grades of DMSO packed under N2. (CCl3O)2CO: crystalline solid, widely available.

Preparative Method: the active reagent is not known, but may be Me2+SCl, formed from DMSO and triphosgene at -78 °C in CH2Cl2, or may be Me2+SOCO2CHRR1, generated after addition of the alcohol, as in the case of phosgene.

Purification: DMSO: distillation from calcium hydride at 56-57 °C/5 mmHg,2a or 83-85 °C/17 mmHg;2b storage over 3Å molecular sieves. (CCl3O)2CO: drying at 0.1 mmHg.3a

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;2c (CCl3O)2CO is a lachrymator, is moisture sensitive, and decomposes to Phosgene; it therefore should be used with the same precautions as used for phosgene, which is highly toxic;3b use in a fume hood.

Triphosgene, or Bis(trichloromethyl) Carbonate, is a solid reagent that is easier to handle than phosgene,3c and that can be used as a phosgene substitute in many applications.3 However, triphosgene forms highly toxic phosgene on heating and should be used with due precautions.3b DMSO-triphosgene has been used in the oxidation of alcohols on a 0.1 M scale (eqs 1, 2).4 The reactions are carried out by adding DMSO to triphosgene in CH2Cl2 at -78 °C, followed by addition of the alcohol and then Triethylamine. Presumably the alkoxysulfonium ion Me2+SOR common to most DMSO base oxidations is formed, but the mechanism has not been studied.

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-Phosgene; Dimethyl Sulfoxide-Phosphorus Pentoxide; Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine; Dimethyl Sulfoxide-Trifluoroacetic Anhydride; 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: London, 1988. (e) Hudlicky, M. Oxidations in Organic Chemistry; ACS: Washington, 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) 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.
3. (a) Eckert, H.; Forster, B. AG(E) 1987, 26, 894. (b) Damle, S. B. Chem. Eng. News 1993, 71 (6), 4. (c) Barton, D. H. R.; Garner, B. J.; Wightman, R. H. JCS 1964, 1855.
4. (a) Palomo, C.; Cossio, F. P.; Ontoria, J. M.; Odriozola, J. M. JOC 1991, 56, 5948. (b) Palomo, C.; Aizpurua, J. M.; Urchegui, R.; Garcia, J. M. JOC 1993, 58, 1646.

Thomas T. Tidwell

University of Toronto, Ontario, Canada



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