Synthesis of Indole-Fused Six-, Seven-, or Eight-Membered N,O-Heterocycles via Rhodium-Catalyzed NH-Indole-Directed C–H Acetoxylation/Hydrolysis/Annulation

Abstract

We report herein the facile synthesis of indole-fused six-, seven-, or eight-membered N,O-heterocycles through rhodium-catalyzed C–H acetoxylation/hydrolysis/annulation. The notable features of this method include C–H acetoxylation using NH-indole as the intrinsic directing group, high functional group compatibility, and construction of indole-fused medium-sized rings.

tert-Butyl Nitrite-Induced Radical Nitrile Oxidation Cycloaddition: Synthesis of Isoxazole/Isoxazoline-Fused Benzo 6/7/8-membered Oxacyclic Ketones

“…However, predicting the reactivity of these compounds is challenging due to unfavorable cross-ring tension and entropy effects, making their synthesis both difficult and intriguing. Mediumsized rings, particularly seven-and eight-membered ones, pose significant challenges in synthesis [16][17][18][19]. Numerous methods have been reported for synthesizing small ring (3-6 membered) and large ring (≥12 membered) compounds, including the Diels Alder reaction, Corey Nicolaou macrocycle esterification reaction, Keck macrocycle esterification reaction, and olefin metathesis reaction.…”

“…However, predicting the reactivity of these compounds is challenging due to unfavorable cross-ring tension and entropy effects, making their synthesis both difficult and intriguing. Medium-sized rings, particularly seven- and eight-membered ones, pose significant challenges in synthesis [ 16 , 17 , 18 , 19 ].…”

Selective C–O Bond Forming Reactions at Indole-C2-Position toward Polycyclic Indolone or Indolinone Derivatives Tethered with Medium-Sized Rings

“…Polycyclic indole derivatives are heterocyclic motifs found in various natural products and biologically active molecules . Among them, oxazino-indole derivatives showed good biological activity . [1,3]­Oxazino­[3,2- a ]­indol-4-one derivatives have been known as important heterocycles in pharmaceutical areas (Figure ).…”