Selectivity Switch in a Rhodium(II) Carbene Triggered Cyclopentannulation: Divergent Access to Three Polycyclic Indolines

Triple whammy: Effective regio‐ and diastereoselectivity control of a cyclopentannulation affording three polycyclic indolines from the same starting materials has been realized. Access to either the three products derives from a simple change of solvent and reaction temperature.

Abstract

A selectivity switch in a Rh^II/carbene‐triggered cyclopentannulation with catalytic InCl₃ is reported for the first time, affording both diastereomers of the fused spiroindolines and an unusual bridged tetracyclic indoline in high yields with excellent selectivities. Mechanistic studies indicate an intramolecular annulation of the indole with an in situ formed aminocyclopropane. The stepwise thermal conversions from the kinetic spiroindoline to the metastable bridged indoline, and then to the thermodynamic spiroindoline, involving a ring‐opening rearrangement of a cyclopentane, is crucial for selectivity control.

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