We present a simple approach to bipyridine macrocycles in remarkable yields (typically >65%) and demonstrate their application in efficient rotaxane synthesis.
We report the unexpected discovery of a tandem active template CuAAC‐rearrangement process, in which N
2
is extruded on the way to the 1,2,3‐triazole product to give instead acrylamide rotaxanes. Mechanistic investigations suggest this process is dictated by the mechanical bond, which stabilizes the Cu
I
‐triazolide intermediate of the CuAAC reaction and diverts it down the rearrangement pathway; when no mechanical bond is formed, the CuAAC product is isolated.
An asymmetric pathway to the caged tetracyclic pyrrolidine alkaloid, dendrobine, is reported. The successful synthetic strategy features a one-pot, sequential palladium-catalyzed enyne cycloisomerization and rhodium-catalyzed diene-assisted pyrrolidine formation by allylic CH activation. The developed transition-metal-catalyzed cascade process permits rapid access to the dendrobine core structure and circumvents the handling of labile intermediates. An intramolecular aldol condensation under carefully defined reaction conditions takes place with a concomitant detosylation, followed by reductive amine methylation, to afford a late-stage intermediate (previously identified by several prior dendrobine syntheses) in only 10 synthetic steps overall.
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