Lewis Acid-Promoted Disproportionation Reaction of Aromatic Vinyl Ethers and Acetals and Its Application to the Synthesis of Paracotoin

Abstract
Aromatic vinyl ethers and acetals underwent a novel addition-fragmentation reaction affording olefins and esters in the presence of a Lewis acid. This reaction was applied to intramolecular cyclization reaction, giving five or six membered ring compounds in good yields. Paracotoin, an intermediate in the biosynthesis of shikimic acid, was synthesized using this cyclization reaction as the key step.