Iodine(III)-Mediated C-C Bond Coupling to Construct Spirocyclic Indolenines of Various Ring Sizes.

Herein, we report a novel iodine(III)-mediated intramolecular dearomative spirocyclization of indole derivatives to generate highly strained spirocyclobutyl, spirocyclopentyl, and spirocyclohexyl indolenines in moderate to good yields. A set of structurally novel, densely functionalized spiroindolenines with broad functional group compatibility was efficiently constructed in this way under mild reaction conditions. Moreover, the ß-enamine ester as a versatile functional group in the product provides great convenience for the synthesis of bioactive compounds and related natural products.

Short, enantioselective, gram-scale synthesis of (-)-zephyranthine.

A reasonable synthesis design by strategically integrating functional group manipulation into the ring system construction resulted in a short, enantioselective, gram-scale total synthesis of (-)-zephyranthine. The concise route includes a catalytic Michael/Michael cascade for the asymmetric synthesis of a penta-substituted cyclohexane with three contiguous stereogenic centers, a remarkable 8-step one-pot operation to easily assemble the zephyranthine tetracyclic skeleton, the regioselective construction of a double bond in the C ring and an asymmetric dihydroxylation. This synthesis is also flexible and paves a potential path to a variety of cyclohexylamine-fused tricyclic or polycyclic alkaloids.