Catalytic Enantioselective and Divergent Total Synthesis of (+)-10-Oxocylindrocarpidine, (+)-Cylindrocarpidine, (−)‑<i>N</i>‑Acetylcylindrocarpinol, and (+)-Aspidospermine

The catalytic enantioselective and divergent total syntheses of Aspidosperma alkaloids (+)-10-oxocylindrocarpidine <b>7</b>, (+)-cylindrocarpidine <b>1</b>, (−)-<i>N</i>-acetylcylindrocarpinol <b>6</b>, and (+)-aspidospermine <b>8</b> have been accomplished in 11 steps from a common precursor (<b>15</b>) on the basis of a highly concise route. The route features three metal-catalyzed reactions, including the key Pd-catalyzed decarboxylative asymmetric allylation of carbazolones developed in our laboratory. Our syntheses, using a combination of C–H activation, enantioselective catalysis, and collective synthesis, represent the first total synthesis of 10-oxocylindrocarpidine and the first asymmetric total synthesis of cylindrocarpidine and <i>N</i>-acetylcylindrocarpinol

Rhodium(III)-Catalyzed Cascade [5 + 1] Annulation/5-exo-Cyclization Initiated by C–H Activation: 1,6-Diynes as One-Carbon Reaction Partners

The catalytic [5 + 1] annulation/5-exo-cyclization reaction of amidines with diynes is reported herein. This protocol provides highly atom-economical access to fabricate two nitrogen-containing heterocycles in one step with high efficiency and selectivity. Significantly, this reaction represents the first example of using diyne as a one-carbon reaction partner in C–H functionalization. Kinetic isotope effects suggested that the catalytic cycle of this reaction is initiated by the cleavage of the <i>ortho</i> C–H bond in the <i>N</i>-phenyl ring of amidines, which is likely involved in the rate-limiting step. Calculations based on density functional theory (DFT) indicated that C–H activation and the formation of Rh­(V) species via 5-exo-cyclization could be vital processes for this cascade transformation