Synthesis of Naphtho-Fused Imidazo[1,2-a]pyridines through Copper-Catalyzed Cascade Reactions

Current Market Potential and Prospects of Copper-based Pyridine Derivatives: A Review

Nicotine, minodronic acid, nicotinamide (niacin), zolpidem, zolimidine, and other pyridine-based chemicals play vital roles in medicine and biology. Pyridinecontaining drugs are widely available on the market to treat a wide range of human ailments. As a result of these advances, pyridine research is continually expanding, and there are now higher expectations for how it may aid in the treatment of numerous ailments. This evaluation incorporates data acquired from sources, like PubMed, to provide a thorough summary of the approved drugs and bioactivity data for compounds containing pyridine. Most of the reactions discussed in this article will provide readers with a deeper understanding of various pyridine-related examples, which is necessary for the creation of copper catalysis-based synthetic processes that are more accessible, secure, environmentally friendly, and practical, and that also have higher accuracy and selectivity. This paper also discusses significant innovations in the multi-component copper-catalyzed synthesis of N-heterocycles (pyridine), with the aim of developing precise, cost-effective, and environmentally friendly oxygenation and oxidation synthetic methods for the future synthesis of additional novel pyridine base analogs. Therefore, the review article will serve as a novel platform for researchers investigating copperbased pyridine compounds.

Synthesis of fused imidazo[1,2-a]pyridines derivatives through cascade C(sp2)-H functionalizations

An efficient and convenient synthesis of diversely substituted naphtho[1',2':4,5]imidazo[1,2-a]-pyridine derivatives from the cascade reactions of 2-arylimidazo[1,2-a]pyridines with a-diazo carbonyl compounds via Rh(iii)-catalyzed regioselective C(sp2)-H alkylation followed by intramolecular annulation is presented. Interestingly, when simple 2-arylimidazo[1,2-a]pyridines were used as the substrates, 5,6-disubstituted naphtho[1',2':4,5]imidazo[1,2-a]pyridines were efficiently obtained, whereas using 2-arylimidazo[1,2-a]pyridine-3-carbaldehydes as the substrates afforded naphtho[1',2':4,5]imidazo[1,2-a]-pyridine-5-carboxylates as the dominating products. Compared with literature methods for the synthesis of naphtho[1',2':4,5]imidazo[1,2-a]pyridine derivatives, the protocol presented herein has advantages such as easily obtainable substrates, simple operational procedure, high efficiency and excellent regio- and chemoselectivity.

Metal-free synthesis of aminomethylated imidazoheterocycles: dual role of tert-butyl hydroperoxide as both an oxidant and a methylene source

A novel and efficient aminomethylation approach has been developed for the regioselective functionalization of imidazoheterocycles under metal-free conditions. A wide range of imidazoheterocycles and 2/4-aminoazaheterocycles successfully provided corresponding aminomethylated imidazoheterocycles in moderate to excellent (33-80%) yields. The isotopic labelling study suggested that TBHP played a dual role as both an oxidant and a methylene source in this transformation. The developed protocol follows a radical pathway which is supported by radical trapping experiments.

One-Pot Tandem Amidation, Knoevenagel Condensation, and Palladium-Catalyzed Wacker Type Oxidation/C-O Coupling: Synthesis of Chromeno-Annulated Imidazopyridines

A direct one-pot synthesis of chromeno-annulated imidazo[1,2- a]pyridines is achieved by the reaction of 2-amino-1-(2-ethoxy-2-oxoethyl)pyridinium salts with 2-bromoarylaldehydes using Pd(TFA)₂ as a catalyst and Cu(OAc)₂ as an oxidant. The overall strategy involves tandem base-mediated amidation and Knoevenagel condensation, followed by palladium-catalyzed Wacker type oxidation and intramolecular C-O coupling reaction. The method is simple, tolerates different functional groups, and gives moderate to good yields of chromeno[2',3':4,5]imidazo[1,2- a]pyridin-12-one derivatives. The developed tandem reaction was also successfully applied for the synthesis of pyrano-fused imidazo[1,2- a]pyridines by using 3-bromo-3-arylacrylaldehydes.

Copper(ii) catalyzed synthesis of novel helical luminescent benzo[4,5]imidazo[1,2-a][1,10]phenanthrolines via an intramolecular C–H amination reaction

Novel helical luminescent benzoimidazophenanthrolines were prepared using a Cu(ii) catalyzed C–H amination reaction.

Copper-catalyzed tandem Ullmann type C-N coupling and dehydrative cyclization: synthesis of imidazo[1,2-c]quinazolines

A simple and efficient one-pot protocol has been demonstrated for the synthesis of imidazo[1,2-c]quinazoline derivatives through a copper catalyzed tandem reaction between substituted 2-(2-bromophenyl)-1H-imidazoles and formamide. The synthetic protocol involves initial Ullmann-type C-N coupling followed by intramolecular dehydrative cyclization. The method uses readily available 2-(2-bromophenyl)-1H-imidazoles as the starting materials to afford imidazo[1,2-c]quinazolines in moderate to good yields and provided 610 mg (71%) yield of 3a from a gram scale reaction.