Development of an Efficient Stereoretentive Para‐Claisen‐Cope Rearrangement

Abstract

A stereoretentive para-Claisen-Cope rearrangement of chiral aryl-allyl ethers is reported, achieving near-perfect chirality transfer thereby furnishing products with exceptional enantiomeric excess (up to > 98% ee) as single regioisomers. This transformation is operationally simple, air- and moisture-tolerant, and catalyzed by a commercially available Europium (III) complex. Mechanistic studies suggest that this para-Claisen-Cope process involves two consecutive [3,3]-sigmatropic rearrangements, resulting in overall retention of stereochemistry. Furthermore, an optimized asymmetric allylic alkylation protocol enables the straightforward preparation of enantioenriched aryl-allyl ether substrates with high enantiomeric purity. Both transformations exhibit broad functional group tolerance, affording the desired products in good to excellent yields.