generated in Heck reaction via nucleophilic addition prior to the step of migratory insertion, which leads to a new palladium-catalyzed difunctionalization of enol ethers with aminals and alcohols to afford amino acetals. Mechanistic studies suggested that the cationic cyclometalated Pd(II) complex generated by the oxidative addition of aminal to a Pd(0) species was crucial for this unusual transformation
Tetrahydropyran Rings from a Mukaiyama−Michael Cascade Reaction
作者:Megan L. Bolla、Brian Patterson、Scott D. Rychnovsky
DOI:10.1021/ja056483u
日期:2005.11.23
A new annulation reaction leading to tetrahydropyrans has been discovered. The reaction of homoallylic enol ethers (e.g., 1) with alpha,beta-unsaturated ketones or esters begins with a Mukaiyama-Michael addition. The intermediate oxocarbenium ion undergoes a rapid 2-oxonia-Cope rearrangement, and the resulting zwitterion collapses to form a tetrahydropyran. The reaction is stereoselective with 3-butene-2-one