Petasis-Ferrier rearrangement

What is Petasis-Ferrier rearrangement?

The Petasis-Ferrier rearrangement is a Lewis acid induced conversion of enol acetals (such as 4-alkylidenyl-1,3-dioxanes) into tetrahydropyranones, which was first reported by Petasis in 1995.

Petasis-Ferrier rearrangement - general reaction scheme
Petasis-Ferrier rearrangement

This reaction is similar to the Ferrier-II rearrangement and can be promoted by various Lewis acids, including BF3·Et2O, ZnCl2, TiCl2(O-i-Pr)2, MeAlCl2, and Me2AlCl. It can tolerate a variety of functional groups, including silyl ether, and can directly produce cis-2,6-disubstituted tetrahydropyranone when Me2AlCl is used as the Lewis acid. This reaction occurs via fragmentation, followed by endo-cyclization onto an oxocarbenium.

The Petasis-Ferrier rearrangement has been extended to the preparation of compounds containing medium-size rings.