Insight into the Ferrier Rearrangement by Combining Flash Chemistry and Superacids

The transformation of glycals into 2,3-unsaturated glycosyl derivatives, reported by Ferrier in 1962, is supposed to involve an alpha,beta unsaturated glycosyl cation, an elusive ionic species that has still to be observed experimentally. Herein, while combination of TfOH and flow conditions failed to observe this ionic species, its extended lifetime in superacid solutions allowed its characterization by NMR-based structural analysis supported by DFT calculations. This allyloxycarbenium ion was further exploited in the Ferrier rearrangement to afford unsaturated nitrogen-containing C-aryl glycosides and C-alkyl glycosides under superacid and flow conditions, respectively.

Automated summary

Ferrier's research in 1962 on the transformation of glycals into unsaturated glycosyl derivatives involved an alpha,beta unsaturated glycosyl cation. Through NMR-based structural analysis and DFT calculations, this elusive ionic species was characterized, leading to the synthesis of unsaturated nitrogen-containing C-aryl glycosides and C-alkyl glycosides under different conditions.