Diastereoselective Reductive Cyclization of Allene-Tethered Ketoamines via Copper-Catalyzed Cascade Carboboronation and Protodeborylation

Abstract

A copper-catalyzed cascade process has been developed for the synthesis of 3-hydroxypyrrolidine derivatives in a highly diastereoselective manner. The reaction proceeded via borylative allyl copper intermediate formation from allenes; the intermediate underwent intramolecular diastereoselective cyclization followed by cascade copper-catalyzed protodeborylation, to give 3-hydroxypyrrolidines. This method could be extended to the synthesis of six-membered piperidine analogs. A series of control experiments were carried out to confirm the Cu-catalyzed facile protodeborylation of borylated homoallylic alcohols at room temperature.