Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine1

(DMSO)

[67-68-5]  · C2H6OS  · Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine  · (MW 78.13) (SO3)

[7446-11-9]  · O3S  · Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine  · (MW 80.06) (SO3/pyridine)

[26412-87-3]  · C5H5NO3S  · Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine  · (MW 159.16)

(oxidant for the conversion of primary and secondary alcohols to aldehydes and ketones, respectively; avoids overoxidation to carboxylic acids; gives very good yields with short reaction times near rt with minimal formation of byproducts)

Alternate Name: Parikh-Doering reagent.

Physical Data: DMSO: mp 18.4 °C; bp 189 °C; d 1.101 g cm-3. SO3: mp 16.8 °C; bp 44.7 °C; d 1.970 g cm-3. SO3/pyridine: mp 175 °C.

Solubility: DMSO: sol H2O, alcohol, acetone, THF, CH2Cl2. SO3: reacts with H2O. SO3/pyridine: sol DMSO; reacts with H2O.

Form Supplied in: DMSO is a colorless liquid; SO3 is a low-boiling liquid, and the SO3/pyridine complex is a crystalline solid; widely available, including SO3/pyridine complex and anhydrous grades of DMSO packed under N2. For the preparation of SO3/pyridine complex see Sulfur Trioxide-Pyridine.

Preparative Method: the active oxidant, formulated as Me2+SOSO3-,2d is generated in situ by mixing DMSO and the SO3/pyridine complex.

Purification: DMSO: distillation from CaH2 at 56-57 °C/5 mmHg2a or 83-85 °C/17 mmHg;2b storage over 3Å molecular sieves.

Handling, Storage, and Precautions: Dimethyl Sulfoxide is readily absorbed through the skin and should always be handled with gloves in a fume hood; Sulfur Trioxide and SO3/pyridine are toxic and corrosive, and react strongly with H2O; reactions with DMSO 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 and dimethyl sulfone above 90 °C.2c

DMSO-SO3/pyridine3a is a convenient oxidant for the conversion of primary and secondary alcohols to aldehydes and ketones, respectively. The complex Me2+SOSO3- evidently forms on mixing DMSO and SO3/pyridine, and upon addition of the alcohol and Triethylamine this forms the RO+SMe2 species common to most DMSO oxidations; this alkoxysulfonium ion then reacts with added Et3N, leading to the carbonyl product. This procedure involves operation near rt, which can be an advantage relative to the use of Dimethyl Sulfoxide-Oxalyl Chloride and usually gives fast reactions and good yields with minimal formation of byproducts. Some examples are shown in eqs 1 and 2.3b,c Oxidation with DMSO-SO3/pyridine avoids the side reaction of chlorination of a pyrrole nucleus encountered with DMSO/(COCl)2, but it was found necessary to add the SO3/pyridine complex as a solid and not as a DMSO solution to the alcohol in DMSO-Et3N-THF for oxidation to occur.3d

In the procedure of eq 3, Et3N and SO3/py were added to 0.1 mol of (1) at 0 °C, and after stirring the solution was diluted with EtOAc, extracted, and evaporated, and the crude product was dissolved in THF and added to Wittig reagent to give (2).4

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-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: 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. (d) Varkey, T. E.; Whitfield, G. F.; Swern, D. JOC 1974, 39, 3365.
3. (a) Parikh, J. R.; Doering, W. v. E. JACS 1967, 89, 5505. (b) Schiehser, G. A.; White, J. D. JOC 1980, 45, 1864. (c) Godfrey, J. D., Jr.; Gordon, E. M.; Von Langen, D. J. TL 1987, 28, 1603. (d) Baker, R.; Castro, J. L. JCS(P1) 1990, 47.
4. Nicolaou, K. C.; Reddy, K. R.; Skokotas, G.; Sato, F.; Xiao, X.-Y.; Hwang, C.-K. JACS 1993, 115, 3558.

Thomas T. Tidwell

University of Toronto, Ontario, Canada



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