The Mukaiyama aldol-Prins (MAP) cyclization with ketones is described. These reactions produce substituted tetrahydropyrans efficiently and in some cases with high stereoselectivity. Cyclizations with E- and Z-alkenes are shown to be stereospecific. These studies extend the scope of the MAP cyclizations promoted by titanium tetrabromide.
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