Gold/Chiral Amine Relay Catalysis Enables Asymmetric Synthesis of C2-Quaternary Indolin-3-ones

A mild and effective strategy for the asymmetric synthesis of C2-quaternary indolin-3-ones from 2-alkynyl arylazides and ketones by gold/chiral amine relay catalysis is described. In this reaction, 2-alkynyl arylazides undergo gold-catalyzed cyclization, nucleophilic attack, and oxidation to form intermediate 2-phenyl-3H-indol-3-ones, followed by an l-proline-catalyzed asymmetric Mannich reaction with ketones, to afford corresponding products in satisfactory yields with excellent enantio- and diastereoselectivities.

A general approach to 2,2-disubstituted indoxyls: total synthesis of brevianamide A and trigonoliimine C

The indoxyl unit is a common structural motif in alkaloid natural products and bioactive compounds. Here, we report a general method that transforms readily available 2-substituted indoles into 2,2-disubstituted indoxyls via nucleophile coupling with a 2-alkoxyindoxyl intermediate and showcase its utility in short total syntheses of the alkaloids brevianamide A (7 steps) and trigonoliimine C (6 steps). The developed method is operationally simple and demonstrates broad scope in terms of nucleophile identity and indole substitution, tolerating 2-alkyl substituents and free indole N-H groups, elements beyond the scope of most prior approaches. Spirocyclic indoxyl products are also accessible via intramolecular nucleophilic trapping.

FeCl3-Promoted ring size-dictating diversity-oriented synthesis (DOS) of N-heterocycles using in situ-generated cyclic imines and enamines

The FeCl₃-promoted ring size-controlled oxidative activation of o-alkynylanilines opens up a complementary appealing protocol for poly-N-heterocycle synthesis.