Seven-membered rings Prins reaction

Cyclization via Prins-Type Reactions The intramolecular Prins reaction has been recognized as a powerful method to assemble six- and seven-membered rings from homoallylic alcohols and simple aldehydes under acid catalysis [28]. However, the competing 2-oxo-Cope rearrangement prior to cyclization could lead to a product with partial or total racemization when enantiomerieally enriched secondary alcohols are used [29]. Increasing the nueleophilicity of the alkene reagent... 

---