Studies on the Synthesis of 2,6-Disubstituted Dihydropyrans: Intervention of Oxonia-Cope Rearrangements in the Lewis Acid Mediated Cyclodehydrative Reactions of Aldehydes and β-Hydroxyallylsilanes

Abstract

The dehydrative coupling reactions of anti-b-hydroxyallylsilanes 5 and aldehydes provide 2,6-cis-dihydropyrans 27 by pathways involving oxonium ions that cyclize via boat-like transition state 21, with the intervention of oxonia-Cope rearrangements (21 29).