Ramberg–Bäcklund reaction

[1] The reaction is named after the two Swedish chemists Ludwig Ramberg and Birger Bäcklund.

The carbanion formed by deprotonation gives an unstable episulfone that decomposes with elimination of sulfur dioxide.

The application of the Ramberg–Bäcklund conditions then leads to an exocyclic vinyl ether that can be reduced to the C-nucleoside [7].In a variation, oxidation of a sulfamide generates a azo compound.

[8] The sulfone group contains an acidic proton in one of the α-positions which is abstracted by a strong base (scheme 1).

The negative charge placed on this position (formally a carbanion) is transferred to the halogen residing on the other α-position in a nucleophilic displacement temporarily forming a three-membered cyclic sulfone.

Scheme 1. The Ramberg–Bäcklund reaction
Scheme 1. The Ramberg–Bäcklund reaction
Scheme 2. Using the Ramberg–Bäcklund reaction to synthesize 1,8-diphenyl-1,3,5,7-octatetraene
Scheme 2. Using the Ramberg–Bäcklund reaction to synthesize 1,8-diphenyl-1,3,5,7-octatetraene
Scheme 3. Small-ring application of the Ramberg–Bäcklund reaction
Scheme 3. Small-ring application of the Ramberg–Bäcklund reaction
Scheme 4. Small-ring application of the Ramberg–Bäcklund reaction
Scheme 4. Small-ring application of the Ramberg–Bäcklund reaction
Scheme 5. Ramberg–Bäcklund synthesis of dimethylene-cyclohexane
Scheme 5. Ramberg–Bäcklund synthesis of dimethylene-cyclohexane
Scheme 6. Ramberg–Bäcklund synthesis of allyl alcohols
Scheme 7. Ramberg–Backlund reaction to synthesize C-nucleoside.