Petasis-Ferrier union/rearrangement

Since the late 1990s, the Smith group developed and utilized the Petasis-Ferrier union/rearrangement for the synthesis of 2,6-c -tetrahydropyran-4-ones. This... 

A common strategy for the synthesis of tetrahydropyran rings is C2-C3 disconnection (Scheme 30). The natural order of reactivity typically generates an oxocarbenium ion at C2 while C3 acts as the nucleophile. This strategy is manifested in three general classes of reactions Prins cyclizatiOTis (Eq. 1), Petasis-Ferrier union/rearrangements (Eq. 2), and Panek annulation (Eq. 3). 

Synthesis of Petasis-Ferrier union/rearrangement substrates usually involves the condensation of bis-silylated p-hydroxy acid 169 and aldehyde 94 to afford dioxanone 170 (Scheme 45, Eq. 1) [89, 90]. Carbonyl olefination (typically using Cp2TiMe2) followed by treatment with a Lewis acid (often alkyl aluminum... 

Scheme 45 Synthesis and mechanism of the Petasis-Ferrier union/rearrangement from p-hydroxy acids...

Scheme 48 Petasis-Ferrier union/rearrangement to F ring fragment of spongistatin 1 [36, 92]...

Smith, A.B. III and Simov, V. (2006) Total synthesis of the marine natural product (—)-clavosolide A. A showcase for the Petasis-Ferrier union/rearrangement tactic. Org. Lett., 8, 3315-3318. 

---