Ramberg-Backlund Rearrangement

Ramberg-Backlund Rearrangement

04 April, 2015 / by / in Reactions
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  • General Characteristics

The basic treatment of α-halogenated sulfones leads to the formation of alkenes with the elimination of sulfur dioxide. This reaction is called the Ramberg-Backlund reaction and provides an indirect route to make carbon-carbon bonds.

  • General References

  • Ramberg, L.; Backlund B. Arkiv Kemi, Minerat. Geol. 1940, 13A, 50.
  • Paquett, L. A. Acc. Chem. Res. 1968, 1, 209. DOI: 10.1021/ar50007a003
  • Paquett, L. A. Org. React. 1977, 25, 1. doi:10.1002/0471264180.or025.01
  • Hartman, G. D.; Hartman, R. D. Synthesis 1982, 504.
  • Clough, J. M. Comprehensive Organic Synthesis 1991, 3, 861.
  • Taylor, R. J. K. Chem. Commun. 1999, 217. DOI: 10.1039/a806615i

 

  • Reaction Mechanism

The α-protons of sulfones are reasonably acidic and easily deprotonated. The intramolecular substitution forms three-membered episulfone intermediates, which decompose to give alkenes with SO2 as a leaving group.

ramberg_backlund_2.gif

  • Examples

As shown below, it is possible to generate the anion via conjugate addition to vinyl sulfones and trigger the Ramberg-Backlund reaction in tandem fashion.[1]

ramberg_backlund_3.gif

An example in which the reaction was combined with epoxide ring opening to synthesize allyl alcohols.[2]

ramberg_backlund_4.gif

  • Experimental Procedure

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  • References

[1] Burger, J. J.; Chen, T. B. R. A. ; de Waard, E. R.; Huisman, H. O. Tetrahedron 1981, 37, 417. doi:10.1016/S0040-4020(01)92030-7 [2] (a) Evans, P.; Taylor, R. J. K. Tetrahedron Lett. 1997, 38, 3055. doi:10.1016/S0040-4039(97)00507-8 (b) Evans, P.; Johnson, P.; Taylor, R. J. K. Eur. J. Org. Chem. 2006, 1740.doi: 10.1002/ejoc.200500956

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  • External Links

Ramberg-Backlund reaction (Wikipedia)

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