Desymmetrizing Enantio- and Diastereoselective Selenoetherification through Supramolecular Catalysis

Abstract

Selenofunctionalization is used for the introduction of aryl- or alkylseleno moieties, which can then be transformed into other functional groups (such as alkenes and carbonyls). However, asymmetric selenofunctionalization of unactivated olefins is often difficult to realize, as aryl- and alkylseleno cations rapidly interchange between olefinic partners. Recently, it has been demonstrated that Lewis bases, assisted by Brønsted acids, induce high levels of enantioselectivity in selenocyclization reactions. The Brønsted acid serves as an activator for the reaction. In this work, we demonstrate an asymmetric selenoetherification and desymmetrization of olefinic 1,3-diols, driven by a unique chiral pairing between a C2-symmetric cyclic selenide catalyst and a chiral Brønsted acid. The resulting substituted tetrahydrofurans contain a phenylselenoether handle and can be transformed into synthetically useful building blocks. A series of experimental and computational investigations suggest that the reaction proceeds via a supramolecular catalytic pathway.