Electro- and Mechanochemical Strategy as a Dual Synthetic Approach for Biologically Relevant 3-Nitro-imidazo-[1,2-a]pyridines

We herein disclose a dual synthetic approach involving electrochemical and mechanochemical strategies for diversely functionalized 3-nitro-2-aryl-immidazo[1,2-a]pyridines. Both methods offer a practical and straightforward alternative route for accessing this important class of biologically promising nitrogen-containing heterocycles. Significant advantages of the newly developed methods include mild and energy-efficient reaction conditions, avoidance of transition metal catalysts, external heating and additional oxidants, shorter reaction times, good to excellent yields, broad substrate scope, gram-scale applicability, operational simplicity, and eco-friendliness. Furthermore, a synthetic application was extended by successfully reducing synthesized 3-nitro-2-aryl-immidazo[1,2-a]pyridines to their corresponding amino derivatives.

Regioselective synthesis and molecular docking studies of functionalized imidazo [1,2-a]pyridine derivatives through MCRs

A efficient protocol has been developed for the synthesis of regioselective imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrimidine derivatives through cascade reaction between 2-aminopyridine, arylelglyoxal, and 4-hydroxypyran via three-component reaction to prepare targeted compounds with good to excellent yields. The advantages of this transformation are a catalyst-free reaction, green solvent, operationally simple, scalable, and eco-friendly. The product collects with simple filtration which avoided tedious and expensive purification techniques. In addition, computational studies like molecular docking were conducted to provide the theoretical possibilities of binding these types of synthesized compounds to the VEGFR2 receptors as potential key inhibitors of tumor cell growth and angiogenesis.

The Application of Microwaves, Ultrasounds, and Their Combination in the Synthesis of Nitrogen-Containing Bicyclic Heterocycles

The use of alternative energy sources, such as microwaves (MW) or ultrasounds (US), and their mutual cross-combination have been widely described in the literature in the development of new synthetic methodologies in organic and medicinal chemistry. In this review, our attention is focused on representative examples, reported in the literature in the year range 2013-2023 of selected N-containing bicyclic heterocycles, with the aim to highlight the advantages of microwave- and ultrasound-assisted organic synthesis.

Molecular Iodine-Catalyzed Synthesis of Imidazo[1,2-a]Pyridines: Screening of Their In Silico Selectivity, Binding Affinity to Biological Targets, and Density Functional Theory Studies Insight

The present paper discloses an ultrasonication strategy assisted by molecular iodine as an environmentally benign catalyst leading to the synthesis of pharmacologically significant imidazo[1,2-a]pyridine scaffolds. The molecular-iodine-catalyzed approach for the synthesis of biologically active synthetic equivalents was achieved through three-component coupling embracing 2-aminopyridine derivatives, pertinent acetophenones, and dimedone in water medium under aerobic conditions. The higher product yield (up to 96%) with a miniature reaction time and modest catalyst loading as demonstrated by higher ecological compatibility and sustainability factors are fascinating features of this protocol. The structures of synthesized compounds were accomplished through FT-IR, ¹H NMR,¹³C NMR, mass, and elemental analysis data. The virtual screening of synthetic moieties was performed to ascertain the in silico selectivity and binding affinities against several biological targets. Lipinski's rules of five, ADMET, and TOPKAT descriptors were used to evaluate the drug-likeness assets. Furthermore, a quantum computational study was computed at the B3LYP/6-311G++(d,p) level of theory to investigate the density functional theory-based chemical reactivity parameters and HOMO-LUMO energy gap of the synthesized derivatives. The present studies open the way for in vitro and in vivo testing of synthesized derivatives as potent inhibitors with an improved pharmacological profile against farnesyl diphosphate synthase, phosphodiesterase III, CXCR4, and GABAa receptor agonists.

Iodine-Catalyzed Multicomponent Synthesis of Highly Fluorescent Pyrimidine-Linked Imidazopyridines

Herein, we report a metal-free one-pot three-component reaction of aryl methyl ketones, 2-aminopyridines, and barbituric acids for the synthesis of pyrimidine-linked imidazopyridines using a catalytic amount of molecular iodine in DMSO medium. This process involves a one-pot C-H oxidation, followed by the formation of one C-C and two C-N bonds. A wide variety of aryl methyl ketones and 2-aminopyridines were found to be suitable for this methodology. The UV and fluorescence properties of the synthesized products were studied in water and DMSO media. Most of the synthesized products exhibited very good to excellent fluorescence quantum yield. Among all the products, compounds 4p and 4q showed the maximum fluorescence quantum yield (0.36) in water medium under basic conditions and compound 4c showed the maximum fluorescence quantum yield (0.75) in DMSO medium.

Series of Functionalized 5-(2-Arylimidazo[1,2-a]pyridin-3-yl)pyrimidine-2,4(1H,3H)-diones: A Water-Mediated Three-Component Catalyst-Free Protocol Revisited

A water-mediated and catalyst-free practical method for the synthesis of a new series of pharmaceutically interesting functionalized 5-(2-arylimidazo[1,2-a]pyridin-3-yl)pyrimidine-2,4(1H,3H)-diones has been accomplished based on a one-pot multicomponent reaction between arylglyoxal monohydrates, 2-aminopyridines/2-aminopyrimidine, and barbituric/N,N-dimethylbarbituric acids under reflux conditions. The salient features of this protocol are avoidance of any additive/catalyst and toxic organic solvents, use of water as reaction medium, clean reaction profiles, operational simplicity, ease of product isolation/purification without the aid of tedious column chromatography, good to excellent yields, and high atom-economy and low E-factor.

Iodine Promoted Efficient Synthesis of 2-Arylimidazo[1,2-a]pyridines in Aqueous Media: A Comparative Study between Micellar Catalysis and an "On-Water" Platform

In a new and environmentally sustainable approach, a series of 2-arylimidazo[1,2-a]pyridine derivatives were synthesized in aqueous media in the presence of iodine as a catalyst. The reaction proceeded by condensation of various aryl methyl ketones with 2-aminopyridines to afford 2-arylimidazo[1,2-a]pyridines in good overall yields. Although several of the reactions were efficiently performed "on water", the addition of a surfactant, namely, sodium dodecyl sulphate , was found effective in terms of substrate scope and yield enhancement. Both methods were successfully used for the gram-scale synthesis of a marketed drug, zolimidine. The simple experimental setup, water as "green" media, and inexpensive catalyst are some of the merits of this protocol.

Synthesis and biological activities of drugs for the treatment of osteoporosis

Osteoporosis is an asymptomatic progressive disease. With the improvement of people's living standard and the aging of population, osteoporosis and its fracture have become one of the main diseases threatening the aging society. The serious medical and social burden caused by this has aroused wide public concern. Osteoporosis is listed as one of the three major diseases of the elderly. At present, the drugs for osteoporosis include bone resorption inhibitors and bone formation promoters. The purpose of these anti-osteoporosis drugs is to balance osteoblast bone formation and osteoclast bone resorption. With the development of anti-osteoporosis drugs, new anti osteoporosis drugs have been designed and synthesized. There are many kinds of new compounds with anti osteoporosis activity, but most of them are concentrated on the original drugs with anti osteoporosis activity, or the natural products with anti-osteoporosis activity are extracted from the natural products for structural modification to obtain the corresponding derivatives or analogues. These target compounds showed good ALP activity in vitro and in vivo, promoted osteoblast differentiation and mineralization, or had anti TRAP activity, inhibited osteoclast absorption. This work attempts to systematically review the studies on the synthesis and bioactivity of anti-osteoporosis drugs in the past 10 years. The structure-activity relationship was discussed, which provided a reasonable idea for the design and development of new anti-osteoporosis drugs.

The microwave-assisted syntheses and applications of non-fused single-nitrogen-containing heterocycles

Microwave technology has emerged as a great tool for the efficient synthesis of organic compounds and it provides opportunities for chemists to achieve chemical transformations that tend to be challenging using classical approaches. Additionally, N-heterocycles are well-known for their medicinal/biological significance, along with their applications as excellent building blocks in chemical synthesis. The dominance of N-heterocycles in drug molecules and other pharmacological agents makes them attractive scaffolds, which encourages chemists to develop a wide range of strategies towards the greener synthesis and functionalization of these heterocycles. In this regard, we have collated and discussed literature relating to the microwave-assisted synthesis and the modification of non-(benzo)fused single-nitrogen-containing N-heterocycles from the past decade. The role of the microwave technique and its benefits over the conventional approach have also been emphasized in terms of overall reaction efficiency, reaction time, yield, reduced side-product generation, neat and clean reactions, chemo-/regio-/enantio-selectivity, and the use of mild reagents/reaction conditions to achieve the objectives of green and sustainable chemistry.

FeCl3or MeSO3H-promoted multicomponent reactions for facile synthesis of structurally diverse furan analogues

The atom-economical characteristics, mild conditions, simple operation and broad substrate scope demonstrated the synthetic value of this protocol.

Synthesis of Novel 5,6-Disubstituted Pyrrolo [2,3-d]Pyrimidine-2,4-Diones Via One-Pot Three-Component Reactions

A simple and novel method for the synthesis of 5,6-disubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones has been reported using arylglyoxal-based three-component reactions. Under microwave heating conditions, arylglyoxal, 6-amino uracil, or its derivatives reacts with various thiols in acetic acid medium to provide a series of pyrrolo[2,3-d]pyrimidine-2,4-diones (4) having a thioether and an aryl ring in 5 and 6 positions, respectively. On the other hand reaction of arylglyoxal, amino uracil and malononitrile in place of thiols, provided corresponding 5,6-disubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones (5) with selectively converting one of the -CN to -CONH₂ group both in conventional (method A) and microwave heating conditions (method B). This methodology is a simple and efficient protocol for the synthesis of diverse 5,6-disubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones from the readily available starting materials in good yields.

Catalyst-free microwave-assisted arylglyoxal-based multicomponent reactions for the synthesis of fused pyrans

A simple and straight forward method has been reported for the synthesis of fused pyrans from the three component reactions of arylglyoxals, cyclic 1,3-dicarbonyls and malononitrile under microwave and catalyst free conditions.

Design, synthesis and in vitro evaluation of coumarin–imidazo[1,2-a]pyridine derivatives against cancer induced osteoporosis

The potential of coumarin–imidazo[1,2-a]pyridine hybrids to prevent bone loss in patients with bone metastases is discussed.