Domino Oxidative Cyclization for the One-Pot Synthesis of Pyrrolo[1, 2- a ]quinoxaline Derivatives

Iodoxybenzoic Acid (IBX) in Organic Synthesis: A Septennial Review

This study reviews the oxidative applications of 2-iodoxybenzoic acid (IBX) in organic synthesis, focusing on C-H functionalization, hetero-hetero bond formations, ring cleavage reactions, dehydrogenation, heterocyclic ring formations, and some miscellaneous reactions in a comprehensive and critical way. It compiles the literature starting from mid-2015 to date.

Recent advances in the transition-metal-free synthesis of quinoxalines

Quinoxalines, also known as benzo[a]pyrazines, constitute an important class of nitrogen-containing heterocyclic compounds as a result of their widespread prevalence in natural products, biologically active synthetic drug candidates, and optoelectronic materials. Owing to their importance and chemists' ever-increasing imagination of new transformations of these products, tremendous efforts have been dedicated to finding more efficient approaches toward the synthesis of quinoxaline rings. The last decades have witnessed a marvellous outburst in modifying organic synthetic methods to create them sustainable for the betterment of our environment. The exploitation of transition-metal-free catalysis in organic synthesis leads to a new frontier to access biologically active heterocycles and provides an alternative method from the perspective of green and sustainable chemistry. Despite notable developments achieved in transition-metal catalyzed synthesis, the high cost involved in the preparation of the catalyst, toxicity, and difficulty in removing it from the final products constitute disadvantageous effects on the atom economy and eco-friendly nature of the transformation. In this review article, we have summarized the recent progress achieved in the synthesis of quinoxalines under transition-metal-free conditions and cover the reports from 2015 to date. This aspect is presented alongside the mechanistic rationalization and limitations of the reaction methodologies. The scopes of future developments are also highlighted.

Copper-catalyzed aerobic oxidative domino cyclization of methyl azaarenes with 6-amino-pyrimidine-2,4-diones and pyrazol-5-amines: access to dipyrimidine/dipyrazolo-fused pyridines

An aerobic copper-catalyzed oxidative domino cyclization of methyl azaarenes with 6-amino-pyrimidine-2,4-diones and pyrazol-5-amines for the synthesis of dipyrimidine/dipyrazolo-fused pyridines was reported.

Acid-Catalyzed Multicomponent Rearrangements via 2-((Quinoxalin-3(4H)-on-2-yl)(aryl)methylene)malononitriles, Generated In Situ, for Divergent Synthesis of Pyrroles with Different Substitution Patterns

New three-component domino reactions, providing divergent approaches to multifunctionalized pyrroles with different substitution patterns, have been established (47 examples). In this work, a new rearrangement of quinoxalinones with the participation of the in situ-generated 2-en-1-imine moiety of the substituent at C3 makes it possible to construct two new heterocyclic systems, namely, a benzimidazolone and a pyrrole, simultaneously under one-pot reaction conditions. The reaction is easy to perform simply by mixing three common reactants of acetic acid with heating. Secondary amines or primary alcohols as the third component of the reaction, along with quinoxalin-3(4H)-ones and malononitrile, not only initiate the rearrangement but also are responsible for the nature of substituents at position 5 of the pyrrole ring in the newly formed new biheterocyclic system. The reaction proceeds smoothly and can be finished within 7 h, which makes workup convenient to give up to 97% chemical yields.