Unprecedented Alkene Stereocontrol in the Claisen Rearrangement of Cyclic Bis-Allylic Esters

The Ireland and ester enolate Claisen rearrangements of tertiary substituted bis-allylic esters derived from cyclohexenones afford pentenoic acids that possess tri- and tetrasubstituted alkylidenes with unprecedented levels of stereoselectivity. In some cases the higher energy exocyclic alkene is the major product.