Asymmetric Cyclopropanation and Epoxidation via a Catalytically Formed Chiral Auxiliary

For the enantioselective diversification of a single starting material, a different chiral catalyst is usually required for each transformation. Herein, we extend the concept of catalytically formed chiral auxiliary from hydrogenation to the asymmetric cyclopropanation and epoxidation of tetra-substituted olefins, alleviating the need for different chiral catalysts in the alkene functionalization step. The chiral auxiliary is catalytically constructed from propargylic amines in a Pd-catalyzed enantioselective carboetherification step using a commercially available trifluoroacetaldehyde hemiacetal tether. The installed auxiliary is then controlling the stereochemistry of the cyclopropanation and the epoxidation using standard highly reactive reagents to give enantioenriched spirocyclic aminomethylcyclopropanols and alpha-amino-alpha-hydroxy ketones.

Automated summary

The paper explores the enantioselective diversification of a single starting material by extending the concept of catalytically formed chiral auxiliary from hydrogenation to cyclopropanation and epoxidation reactions. This approach eliminates the need for different chiral catalysts in alkene functionalization and allows for the control of stereochemistry using a catalytically constructed chiral auxiliary.