A Green Aerobic Oxidative Synthesis of Pyrrolo[1,2-a]quinoxalines from Simple Alcohols without Metals and Additives

Abstract

A practical and concise protocol for the efficient preparation of pyrrolo[1,2-a]quinoxalines through a cascade of alcohol oxidation/imine formation/intramolecular cyclization/oxidative dehydrogenation has been established. A series of substituted pyrrolo[1,2-a]quinoxaline derivatives were constructed readily in yields of 53-93% from the cheap primary alcohols by using dioxygen as the terminal oxidant. Remarkably, the fact that no extra metals and additives were necessary makes this unprecedented aerobic oxidation process highly step- and atom-economical. The usefulness of this transformation was further demonstrated with the gram-scale synthesis of compound 3aa under standard conditions.

KI‐Mediated One‐Pot Transition‐Metal‐Rree Synthesis of 4‐Phenylpyrrolo[1,2‐a]quinoxalines

“…All reactions were monitored by TLC (thin-layer chromatography). 1 H NMR and was recorded on a Bruker Advance 500 (500 MHz), 400 (400 MHz) or 300 (300 MHz) spectrometer, and 13 C NMR spectra was recorded on a Bruker Advance (125 MHz), (100 MHz) or (75 MHz) in CDCl 3 and tetramethylsilane (TMS) as an internal standard. HRMS (High Resolution Mass Spectrometry) spectra were determined on an Agilent Q-TOF6510 spectrograph.…”

“…Firstly, the cyclization of 2-(1H-pyrrol-1-yl)anilines with the compounds that offer one carbon atom. [12][13][14] Secondly, the cyclization of 2-haloanilines with 2-acylpyrrole/2acylindole derivatives. [15][16][17] Early in 1966, Cheeseman and Tuck's group reported the synthesis of pyrrolo[1,2-a]quinoxaline starting from 2-(1H-pyrrolo-1-yl)anilines and HCO 2 H [18] for the first time.…”

TFAA‐Catalyzed Annulation Synthesis of Spiro Pyrrolo[1,2‐a]quinoxaline Derivatives from 1‐(2‐Aminophenyl)pyrroles and Benzoquinones/Ketones

“…[6] The group of Jiang reported ac oncise oxidative strategyf or the synthesis of pyrrolo[1,2-a]quinoxalined erivatives from simple primary alcohols under dioxygen atmosphere. [7] Afterwards, Ma's group developed as imple and environmental friendly approacht og enerate pyrrolo[1,2a]quinoxalines from 2-(1H-pyrrol-1-yl)anilines and dimethyl sulfoxide. [8] In the past decades, although many methods have been appliedi nt he synthesis of pyrrolo[1,2-a]quinoxalines,t he formationo fs piro pyrrolo[1,2-a]quinoxalines is very rare.…”

Iron Catalyzed Cascade Protocol for the Synthesis of Pyrrolo[1, 2‐a]quinoxalines: A Powerful Tool to Access Solid State Emissive Organic Luminophores

“…discovered Brønsted acid for the same. Recently, Zhai and co‐workers developed additive as well as catalyst free protocol whereas Jiang et al . described metal‐free aerobic oxidative synthesis of pyrrolo[1, 2‐ a ]quinoxalines.…”