CuH-Catalyzed Synthesis of 3-Hydroxyindolines and 2-Aryl-3H-indol-3-ones from o-Alkynylnitroarenes, Using Nitro as Both the Nitrogen and Oxygen Source

Abstract

CuH-catalyzed diasterospecific synthesis of 3-hydroxyindolines and 2-aryl-3H-indol-3-ones have been developed from o-alkynylnitroarenes in the presence of hydrosilane as the reductant. The protocol employs nitro as both nitrogen and oxygen sources for the intramolecular simultaneous construction of C–N and C–O bonds.

Access to Polycyclic Indol(en)ines viaBase‐Catalyzed Intramolecular Dearomatizing 3‐Alkenylation of Alkynyl Indoles

“…Specifically, we subjected spiroindolenine 2a to the standard conditions shown in Scheme 4 and obtained corresponding product 4a in 99% yield (Scheme 5a). On the basis of this outcome, previously reported results on dearomatizing alkenylation reactions of indoles [5][6][7][8] and CuH-catalyzed reduction reactions, [14] we propose the mechanism as shown in Scheme 5b. First, indolenine anion intermediate A is generated by reaction of 1a or 5a with the alkoxide.…”

“…This transformation would avoid the necessity of isolating the intermediate spiroindolenines, which tend to decompose during silica gel chromatography. [13] For a reductant, we chose copper(I) hydride (CuH), which is frequently used in reduction reactions [14] and is generated by the reaction of a copper salt, an alkoxide, and a silane. We envisioned that the alkoxide might also simultaneously catalyze the dearomatizing alkenylation step.…”

Gold‐Catalysed Nitroalkyne Cycloisomerization – Synthetic Utility

“…The reaction mechanism involves the formation of the LCuÀ H active catalyst that promotes the key nitroalkyne cycloisomerization resulting in the isatogen, which upon reduction by hydrosilane furnishes 2-aryl-3H-indol-3-one, the further reduction of which gives the 3-hydroxyindoline 31. [15]…”

Recent Progress on Reductive Coupling of Nitroarenes by Using Organosilanes as Convenient Reductants

“…[26] In 2019, Yin and co-workers reported a Cucatalyzed diasterospecifific synthesis of 3-hydroxyindolines 21 and 2-aryl-3H-indol-3-ones 22 from oalkynylnitroarenes 20 with hydrosilane as a reductant (Scheme 13). [27] This protocol employs nitro as both nitrogen and oxygen sources for the intramolecular Recently, a novel Cu-catalyzed reductive aminocarbonylation of alkyl iodides 25 by using nitroarenes as amine source and PhSiH 3 as final reductant has been reported by Mankad and Zhao (Scheme 15a). [28] This three components reaction provides a facile access to N-aryl alkylamides 26 from readily available nitro- arenes, alkyl iodides, and carbon monoxide (CO).…”