Lewis Acid Promoted Mukaiyama Aldol-Prins (MAP) Cyclizations of Acetals, Ketals, α-Acetoxy Ethers, and Orthoformates
作者:Scott Rychnovsky、Michael Gesinski、Lori Van Orden
DOI:10.1055/s-2008-1032053
日期:2008.2
The Mukaiyama aldol-Prins (MAP) cyclization of acetals stereoselectively provided substituted tetrahydropyrans. The scope of the reaction has been expanded to include other electrophiles, including ketals and α-acetoxy ethers. Finally, a double MAP cyclization with orthoformates is described.
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
作者:Brian Patterson、Shinji Marumoto、Scott D. Rychnovsky
DOI:10.1021/ol035303n
日期:2003.8.1
[reaction: see text] A new version of the Mukaiyamaaldol-Prins (MAP) cyclization has been developed. Unsaturated enol ethers such as 3 were found to couple with aldehydes in the presence of TiBr(4) to give 4-bromotetrahydropyran products. This cascadereaction sequence leads to the formation of two new carbon-carbon bonds, a ring, and three new stereogenic centers. We expect this reaction to be a