Organocatalytic Desymmetric Double Aza-Michael Addition Cascade: Enantioselective Synthesis of Fused Morpholines

Double aza-Michael addition (DAM) has become an emerging strategy for the construction of two carbon-nitrogen bonds in a single step, which can significantly simplify the synthesis of N-heterocycles. Hitherto, their asymmetric catalytic genre remains unattempted. Herein, we describe the judicious design of an organocatalytic enantioselective desymmetric double aza-Michael addition cascade to access a series of functionalized fused morpholines with excellent yields and diastereo- and enantioselectivities. A one-pot telescopic synthesis was demonstrated for a bridged triheterocyclic compound. In addition, scale-up synthesis and various attractive postsynthetic modifications of the title products amplify the significance of the current methodology.