Swern oxidation



The Swern oxidation is a chemical reaction whereby a primary or secondary alcohol is functional groups.[4][5][6] [7]


The by-products are oxone, whereupon the sulfide is converted to dimethyl sulfoxide, which has no odor.

Several reviews have been published.[8][9][10]

The reaction is named after Daniel Swern.

Mechanism

The first step of the Swern oxidation is the low-temperature reaction of CO and producing dimethylchlorosulfonium chloride, 4.

After addition of the alcohol 5, the dimethylchlorosulfonium chloride 4 reacts with the alcohol to give the key alkoxysulfonium ion intermediate, 6. The addition of at least 2 equivalents of base — typically dimethyl sulfide and the desired ketone (or aldehyde) 8.

Variations

When using oxalyl chloride as the dehydration agent, the reaction must be kept colder than -60 °C to avoid side reactions. With trifluoroacetic anhydride instead of oxalyl chloride, the reaction can be warmed to -30 °C without side reactions.

In some cases, the use of diisopropylethylamine (i-Pr2NEt, Hünig's base) can mitigate this side reaction.

Considerations

Dimethyl sulfide, a byproduct of the Swern oxidation is one of the foulest odors known in organic chemistry. Human olfactory glands can detect this compound in concentrations as low as parts per billion. A simple remedy for this bothersome problem is to rinse used glassware with bleach (NaClO), which will oxidize the dimethyl sulfide, eliminating the hideous scent.

See also

References

  1. ^ Omura, K.; Swern, D. Tetrahedron 1978, 34, 1651. (doi:10.1016/0040-4020(78)80197-5)
  2. ^ Mancuso, A. J.; Huang, S.-L.; Swern, D. J. Org. Chem. 1978, 43, 2480–2482. (doi:10.1021/jo00406a041)
  3. ^ Mancuso, A. J.; Brownfain, D. S.; Swern, D. J. Org. Chem. 1979, 44, 4148. (doi:10.1021/jo01337a028)
  4. ^ Dondoni, A.; Perrone, D. Org. Syn., Coll. Vol. 10, p.320 (2004); Vol. 77, p.64 (2000). (Article)
  5. ^ Bishop, R. Org. Syn., Coll. Vol. 9, p.692 (1998); Vol. 70, p.120 (1992). (Article)
  6. ^ Leopold, E. J. Org. Syn., Coll. Vol. 7, p.258 (1990); Vol. 64, p.164 (1986). (Article)
  7. ^ Gabriel Tojo and Marcos Fernández. Oxidation of Alkohols to Aldehydes and Ketones: A Guide to Current Common Practice. Springer, 2006.
  8. ^ Mancuso, A. J.; Swern, D. Synthesis 1981, 165-185. (Review)
  9. ^ Tidwell, T. T. Org. React. 1990, 39, 297-572. (Review)
  10. ^ Tidwell, T. T. Synthesis 1990, 857-870. (Review) (doi:10.1055/s-1990-27036)
 
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