Exploration of novel TOSMIC tethered imidazo[1,2-a]pyridine compounds for the development of potential antifungal drug candidate

HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines

The imidazo[1,2-a]pyridine moiety is present in drugs with several biological activities. The most direct way of obtaining this nucleus is the Groebke-Blackburn-Bienaymé three-component reaction (GBB-3CR) between aminopyridines, aldehydes, and isocyanides under both Lewis and Brønsted acid catalysis. However, several catalysts for this reaction have major drawbacks such as being expensive, extremely dangerous, strong oxidizing, and even explosive. In this scenario, heteropolyacids emerge as greener and safer alternatives due to their very strong Brønsted acidity. In particular, phosphotungstic acid (HPW) is an economical and green attractive catalyst for being cheap, non-toxic, and is known for its chemical and thermal stability. Herein, we report a straightforward approach to the GBB-3CR using HPW as catalyst in ethanol under microwave (μw) heating. This convenient environmentally benign methodology is broad in scope, provides the heterobicyclic products in high yields (up to 99%), with a low catalyst loading (2 mol %) in only 30 minutes, and allows the successful use of aliphatic aldehydes, substrates not so frequently explored with most usual catalysts for this reaction. Furthermore, the aforementioned advantages make this methodology very attractive and superior to the existing ones.

Chemoselectivity of the CuAAC/Ring Cleavage/Cyclization Reaction between Enaminones and α-Acylketenimine

Ketenimines represent an important class of reactive species, useful synthetic intermediates, and synthons. However, in general, ketenimines preferentially undergoes nucleophilic addition reactions with hydroxyl and amino groups, and carbon functional groups remain a less studied subset of such systems. Herein, we develop a straightforward syntheses of pyridin-4(1H)-imines that is achieved by cyclization of a reacting enaminone unit with α-acylketenimine which is generated from the reactions of sulfonyl azides and terminal ynones in situ (CuAAC/Ring cleavage reaction). The cascade process preferentially starts with the nucleophilic α-C of the enaminone unit instead of an amino group, attacking the electron-deficient central carbon of ketenimine, and the chemoselectivity unconventional products pyridin-4(1H)-imines were formed by intramolecular cyclization.

Antifungal activity of novel azetidine tethered chitosan synthesized via multicomponent reaction approach

The increasing incidences of fungal infections among Covid-19 infected patients is a global public concern and urgently demands novel antifungals. Biopolymers like chitosan hold unique structural properties and thus can be utilized in the synthesis of biologically important scaffolds. To address the current scenario, the author's synthesized novel chitosan-azetidine derivative by adopting one-pot multicomponent reaction approach. The influence of chemical modification on the structural characteristics was investigated by means of spectroscopic techniques viz. FT-IR and 1HNMR and elemental analysis. Additionally, the authors investigated the antifungal potential of chitosan-azetidine derivative against Aspergillus fumigatus 3007 and the results indicated higher antifungal effect with an antifungal inhibitory index of 26.19%. The SEM and confocal microscopy images also reflected a significant inhibitory effect on the morphology of fungal mycelia, thus reflecting the potential of synthesized chitosan-azetidine derivativeas a potential antifungal agent.

Multicomponent synthesis of chromophores – The one-pot approach to functional π-systems

Multicomponent reactions, conducted in a domino, sequential or consecutive fashion, have not only considerably enhanced synthetic efficiency as one-pot methodology, but they have also become an enabling tool for interdisciplinary research. The highly diversity-oriented nature of the synthetic concept allows accessing huge structural and functional space. Already some decades ago this has been recognized for life sciences, in particular, lead finding and exploration in pharma and agricultural chemistry. The quest for novel functional materials has also opened the field for diversity-oriented syntheses of functional π-systems, i.e. dyes for photonic and electronic applications based on their electronic properties. This review summarizes recent developments in MCR syntheses of functional chromophores highlighting syntheses following either the framework forming scaffold approach by establishing connectivity between chromophores or the chromogenic chromophore approach by de novo formation of chromophore of interest. Both approaches warrant rapid access to molecular functional π-systems, i.e. chromophores, fluorophores, and electrophores for various applications.

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

Many heterocyclic compounds can be synthetized using diaza-1,3-butadienes (DADs) as key structural precursors. Isolated and in situ diaza-1,3-butadienes, produced from their respective precursors (typically imines and hydrazones) under a variety of conditions, can both react with a wide range of substrates in many kinds of reactions. Most of these reactions discussed here include nucleophilic additions, Michael-type reactions, cycloadditions, Diels–Alder, inverse electron demand Diels–Alder, and aza-Diels–Alder reactions. This review focuses on the reports during the last 10 years employing 1,2-diaza-, 1,3-diaza-, 2,3-diaza-, and 1,4-diaza-1,3-butadienes as intermediates to synthesize heterocycles such as indole, pyrazole, 1,2,3-triazole, imidazoline, pyrimidinone, pyrazoline, -lactam, and imidazolidine, among others. Fused heterocycles, such as quinazoline, isoquinoline, and dihydroquinoxaline derivatives, are also included in the review.

Utility of arylglyoxal hydrates in synthesis of 4-aroyl-[1,3,5]triazino[1,2-a]benzimidazol-2(1H)-imines and 5-aryl-2-phenyl-4H-imidazol-4-imines

Nucleophilic substitution reaction for arylglyoxal hydrates (AGs-hydrate) was studied via their reaction with some mono- and multi-nucleophilic reagents in the presence of sodium ethoxide as basic catalyst. Thus, reaction of phenylglyoxal hydrate (1a) with hydrogen sulfide and/or ammonium acetate afforded the corresponding 2-hydroxy-2-mercapto-1-phenylethanone (2) and 2-oxo-2-phenylethanimidamide (3), respectively. Heterocyclization reaction of AGs-hydrate 1a-f with 1-(1H-benzimidazol-2-yl)guanidine (4) gave 4-aroyl-[1,3,5]triazino[1,2-a]benzimidazol-2(1H)-imines 5a-f. Also, a series of 5-aryl-2-phenyl-4H-imidazol-4-imines 7a-d was synthesized via one-pot multicomponent reaction of AGs-hydrate 1a-d, benzonitrile (6) and ammonium acetate. Imidazole-4-imines 7a-d can be also prepared using other route via multicomponent reaction of AGs-hydrate 1a-d, benzenecarboximidamide acetate (8) and ammonium acetate.