Sequencing [3+2]-cycloaddition and multicomponent reactions: A regioselective microwave-assisted synthesis of 1,4-disubstituted 1,2,3-triazoles using ionic liquid supported Cu(II) precatalysts in methanol

A microwave assisted tandem synthesis of quinazolinones using ionic liquid supported copper(II) catalyst with mechanistic insights

Quinazolinone is a preferred structural motif with notable pharmacological activity that is present in a wide range of naturally occurring compounds. A microwave assisted tandem cyclooxidative method has been developed to afford quinazolinones via a recyclable ionic liquid supported copper catalyst. This sustainable method exhibits operational simplicity through a rapid, clean, and energy-efficient route and a variety of 2-substituted quinazolinones are obtained in excellent yields. In addition, this innovative approach enables us to develop a library of nitriles in an environment-friendly synthetic protocol. Moreover, the catalyst can be recycled and reused up to three consecutive cycles without any significant loss of catalytic activity. Further organic transformation of the synthesized quinazolinones was carried out to afford reported as well as novel bioactive heterocyclic compounds.

Recent advances in the application of alkynes in multicomponent reactions

Alkynes have two active positions to carry out chemical reactions: C[triple bond, length as m-dash]C and C-H. These two positions are involved and activated in different reactions using different reagents. In this study, we investigated the reactions of alkynes that are involved in multi-component reactions through the C-C and C-H positions and examined the progress and gaps of each reaction by carefully studying the mechanism of the reactions. Firstly, we investigated and analyzed the reactions involving the C[triple bond, length as m-dash]C position of alkynes, including the reactions between derivatives of alkynes with RN3, sulfur compounds (RSO2R', DMSO, S8, DABCO(SO2)2 and DABSO), barbituric acids, aldehydes and amines, COOH, α-diazoesters or ketones, and isocyanides. Then, we examined and analyzed the important reactions involving the C-H position of alkynes and the progress and gaps in these reactions, including the reaction between alkyne derivatives with amines and aldehydes for the synthesis of propargylamines, the reaction between alkynes with CO2 and the reaction between alkynes with CO.

Multicomponent cyclization with azides to synthesize N-heterocycles

Heterocyclic compounds, both naturally derived and synthetically produced, constitute a wide variety of biologically active and industrially important compounds. The synthesis and application of heterocyclic compounds have garnered significant attention and experienced rapid growth in recent decades. Organic azides, due to their unique properties and distinctive reactivity, have become a convenient chemical tool for achieving a wide range of heterocycles such as triazoles and tetrazoles. Importantly, the field of multicomponent reaction (MCR) chemistry provides a convergent approach to access various N-heterocyclic scaffolds, offering novelty, diversity, and complexity. However, the exploration of MCR pathways to N-heterocyclic compounds remains incomplete. Here, we review the use of multicomponent reactions for the preparation of N-heterocycles. A wide range of reactions based on azides for the synthesis of various types of N-heterocyclic systems have been developed.

Copper Catalyzed Synthesis of Heterocyclic Molecules via C-N and C-O Bond Formation under Microwaves: A Mini-Review

Heterocyclic moieties play a significant role in the field of drug discovery. C-N and C-O bond formation reactions are the primary synthetic sequence for the generation of heterocyclic molecules. The generation of C-N and C-O bonds involves the use of mostly Pd or Cu catalysts although other transition metal catalyst's are also involved. However, in C-N and C-O bond formation reactions, several problems were faced such as catalytic systems containing costly ligands, lack of substrate scope, lots of waste generation, and high temperature conditions. So it is imperative to uncover new eco-friendly synthetic strategies. In view of enormous drawbacks, it is important to develop an alternate microwave-assisted synthesis of heterocycles via C-N and C-O bond formation, which provides a short reaction time, tolerance for functional groups, and less waste production. Numerous chemical reactions have been accelerated using microwave irradiation which provides a cleaner reaction profile, lower energy consumption, and higher yields. This review article highlights a comprehensive overview on the potential application of microwave assisted synthetic routes for the synthesis of diverse heterocycles via mechanistic pathways covering the year ranges from 2014 to 2023, along with possible biological interests.

A practical flow synthesis of 1,2,3-triazoles

A robust and versatile protocol for synthesis of 1-monosubstituted and 1,4-disubstituted 1H-1,2,3-triazoles was established under continuous flow conditions using copper-on-charcoal as a heterogeneous catalyst. This methodology allowed for the synthesis of a diverse set of substituted 1,2,3-triazoles with good functional group tolerance and high yields. 2-Ynoic acids were also used as small-chain alkyne donors in a decarboxylation/cycloaddition cascade, allowing gaseous reagents to be bypassed, delivering desired triazoles in high yields. The developed methodology was used to synthesize an antiepileptic agent, rufinamide, which was obtained in 96% isolated yield.

Copper-on-charcoal is an excellent heterogeneous catalyst for the alkyne–azide cycloaddition reaction performed under continuous flow conditions. 2-Ynoic acids undergo decarboxylation/cycloaddition cascade giving triazoles bearing small alkyl chains.

Recent developments and perspectives in the copper-catalyzed multicomponent synthesis of heterocycles

Heterocyclic compounds have become an inevitable part of organic chemistry due to their ubiquitous presence in bioactive compounds. Copper-catalyzed multicomponent synthesis of heterocycles has developed as the most convenient and facile synthetic route towards complex heterocyclic motifs. In this review, we discuss the advancements in the field of copper-catalyzed multicomponent reactions for the preparation of heterocycles since 2018.

Heterocycles are abundant in several pharmaceutical and naturally occurring compounds. Copper-catalyzed multicomponent reactions are a convenient method for easy access to heterocycles. In this review, we focus on the advancement in this field for the past two years.