One pot,three component 1,3 dipolar cycloaddition: Regio and diastereoselective synthesis of spiropyrrolidinyl indenoquinoxaline derivatives

A competent and highly discriminating one-pot synthesis of highly diversified novel functionalized indenoquinoxalone grafted spiropyrrolidine linked chromene-3-carbonitrile conjugates accumulating three pharmocophoric cores, heterocyclic indenoquinoxalone, pyrrolidines and chromene-3-carbonitrile in a single molecular framework by means of 1,3-dipolar cycloaddition reaction between indenoquinoxalone, proline/benzyl amine and chromene-3-carbonitrile in ethanol under classical and microwave conditions is described. The three component 1,3-dipolar cycloaddition reaction proceeds via in situ generation of azomethine ylides by the decarboxylative condensation of indenoquinoxalone with proline/benzyl amine and their selectivity towards the endo cyclic double bonds of dipolarophile (chromene-3-carbonitrile) leading to the formation of highly functionalised regio- and diastereoselective molecular hybrids. This methodology exemplifies the green chemistry protocol such as mild reaction conditions, high yields, one-pot procedure and operational simplicity.     

One pot,three component synthesis of spiroindenoquinoxaline pyrrolidine fused nitrochromene derivatives following 1,3-dipolar cycloaddition

An expedient one-pot sequential three-component synthesis of a series of diverse spiroindenoquinoxaline pyrrolidine fused nitrochromene derivatives following 1,3-dipolar cycloaddition of azomethine ylides generated in situ by the condensation of indenoquinoxalone and α-amino acids (L-proline and L-phenyl alanine) with 3-nitrochromenes as dipolarophile under classical as well as microwave irradiation is described. The protocol provides a mild reaction condition, high yield of the products, high regioselectivity, and operational simplicity to assemble complex structural entity in a single operation with good to excellent yield. The regio and stereochemical outcome of the cycloaddition reaction is ascertained by spectroscopic and single crystal X-ray analysis.     

Microwave‐assisted One‐pot,Three‐component Regiospecific and Sterospecific Synthesis of Spiro Indanone Pyrrolidine/Piperidine Fused Nitrochromene Derivatives Through 1,3‐Dipolar Cycloaddition Reactions

A simple, straightforward, and versatile protocol for the synthesis of spiro indanone pyrrolidine/piperidine fused nitrochromene derivatives is described. The synthesis of a new series of spirocyclic molecules has been expediently accomplished via a one‐pot, three component 1,3‐dipolar cycloaddition reaction. 2‐Phenyl‐nitrochromene dipolarophiles were reacted with azomethine ylides, generated in situ by the condensation of dicarbonyl compound indane‐1,3‐dione and secondary amino acid (L‐proline/pipecolic acid), to produce the corresponding cycloadducts in good yields (85–90%) under classical as well as under microwave irradiation. The cycloaddition reaction was found to be highly regiospecific and diasterospecific. The regiochemical and sterochemical outcome of the cycloaddition reaction is ascertained by 2D NMR (COSY and NOESY) studies.     

Microwave‐Assisted Rapid and Efficient Synthesis of New Series of Chromene‐Based 1,2,4‐Oxadiazole Derivatives and Evaluation of Antibacterial Activity with Molecular Docking Investigation

A new series of novel chromene‐based oxadiazole derivatives were synthesized from a variety of chromene‐based amidoximes with readily available carboxylic acids under conventional oil bath heating as well as under microwave irradiation. The use of commercially available EDCI and HOBt as coupling reagents in DMF combined with microwave heating resulted in high yields and purities of the product 1,2,4‐oxadiazoles in an expeditious manner. This methodology is successfully applied to synthesize 18 numbers of new 2H‐chromene‐substituted 1,2,4‐oxadiazole derivatives in good to high yields. The structure of the product was ascertained by X‐ray crystallographic analysis. All the synthesized compounds were evaluated for their in vitro antibacterial activity against two different pathogenic bacterial strains, that is, Escherichia coli (MTCC614) and Klebsiella pneumoniae (MTCC4031). The obtained results from in vitro antimicrobial assays indicated that 6g and 6h exhibited good antibacterial activity nearer to the standard drug, gentamicin. The molecular docking studies showed that compounds 6g and 6h show hydrogen bonding interaction with the bacterial target DNA gyrase of E. coli.     

Microwave-assisted rapid and efficient synthesis of chromene-fused pyrrole derivatives through multicomponent reaction and evaluation of antibacterial activity with molecular docking investigation

The current study aimed to identify a new strategy of FeCl₃ catalyzed multicomponent synthesis of substituted 2H-chromene–fused pyrrole derivatives. A series of chromene-based pyrrole prepared by employing an array of 3-nitro-2H-chromenes, aniline, and acetylacetone in toluene under microwave irradiation. Using FeCl₃ as a prompt catalyst and microwave irradiation to synthesize 2H-chromene–fused pyrrole motifs significantly reduces the reaction time and facilitates to high yields (83%-95%). Structure of all synthesized compounds analyzed by spectroscopic analysis. One-pot reaction, short reaction period, and simple experimental procedure are the fascinating properties associated with this protocol. The in vitro antibacterial activity of the entire series was assessed against Staphylococcus aureus and Escherichia coli. Out of all the compounds, 15b and 15h revealed most excellent potency against both the bacterial strains relative to the reference gentamicin. Docking study was employed to determine the possible binding orientation of DNA gyrase with the active sites of chromene-fused pyrrole analog. The docking results show that compounds 15b and 15h have higher binding affinity with energy −8.00 and −8.80 kcal/mol. These results illuminate the mode of binding progression and provide an esteemed pathway for the design and the structural modification of chromene-fused pyrroles as a newly advanced class of antibacterial agent.