Intermolecular Acetal-Initiated Cationic Polyene Cyclizations

Significance

This report describes the intermolecular acetal-initiated polyene cyclization induced by SnCl₄. The authors do a nice job in optimizing the reaction and find a chiral templated acetal that allows for considerably high dr values. The absolute and relative stereochemistry were determined for the products through derivatization and X-ray crystallography. Some of the cyclization products were also functionalized to various terpenes. Importantly, this report does not require the sometimes difficult and tedious incorporation of the acetal into the cyclization precursor.