Ankita Chaudhary

An expedient four-component domino protocol for the synthesis of novel benzo[a]phenazine annulated heterocycles and their photophysical studies

A new one pot two-step domino protocol for the efficient synthesis of novel fluorescent benzo[a]phenazine fused derivatives has been developed. The synthesis was achieved by reacting 2-hydroxynaphthalene-1,4-dione, ortho-phenylenediamines, aromatic aldehydes and cyclic 1,3-dicarbonyl compounds in the presence of a catalytic amount of p-TSA in PEG-400 at 70 °C. The structural assignment has been unambiguously confirmed by X-ray analysis. The present finding provides an efficient and promising synthetic strategy for the synthesis of libraries with functional group diversity.

Efficient and green synthesis of 4H-pyrans and 4H-pyrano[2,3-c] pyrazoles catalyzed by task-specific ionic liquid [bmim]OH under solvent-free conditions

Abstract A facile and convenient procedure for the synthesis of 4H-pyrans from aldehydes, malononitrile, and ethyl acetoacetate/acetylacetone and also synthesis of 4H-pyrano[2,3-c]pyrazoles from three-component condensation of aldehydes, malononitrile, and pyrazolone or four-component condensation of aldehydes, malononitrile, ethyl acetoacetate, and hydrazine monohydrate using [bmim]OH as task-specific ionic liquid has been described. The protocol proves to be efficient and environmentally benign in terms of high yields, low reaction times, ease of recovery, and reusability of reaction medium.

Synthesis and in vitro evaluation of antioxidant activity of diverse naphthopyranopyrimidines, diazaanthra[2,3-d][1,3]dioxole-7,9-dione and tetrahydrobenzo[a]xanthen-11-ones

A green and efficient one pot three component protocol has been developed for the synthesis of naphthopyranopyrimidines, diazaanthra[2,3-d][1,3]dioxole-7,9-dione and tetrahydrobenzo[a]xanthen-11-ones in PEG-400 catalyzed by alum (KAl(SO4)2·12H2O). Single crystal X-ray diffraction studies have been performed for naphthopyranopyrimidine (5). The synthesized compounds were screened for in vitro antioxidant activity by DPPH scavenging assay and compounds 3 and 4 manifested profound antioxidant potential.

Efficient and Green Approaches for the Synthesis of 4H-Benzo[g]chromenes in Water, Under Neat Conditions, and Using Task-Specific Ionic Liquid

Abstract Facile and convenient procedures have been described for the synthesis of 4H-benzo[g]chromenes by one-pot condensation of aromatic aldehydes, malononitrile/ethyl cyanoacetate, and 2-hydroxy-1,4-naphthoquinone. The reaction has been accomplished using catalytic cetyltrimethylammonium bromide (CTAB) in water under reflux or under neat conditions at 110 °C. A task-specific ionic liquid, 1-butyl-3-methyl imidazolium hydroxide ([bmim]OH), has also been found to be an effective catalyst for this transformation. The protocols prove to be environmentally benign and offer advantages of good yields, short reaction times, and simple workup procedures. The ionic liquid could be recycled and reused for up to four runs without appreciable loss in the activity. GRAPHICAL ABSTRACT

Efficient and Green Syntheses of 12-Aryl-2,3,4,12-tetrahydrobenzo[b]xanthene-1,6,11-triones in Water and Task-Specific Ionic Liquid

Abstract Facile and convenient one-pot cascade/tandem approaches for the syntheses of privileged medicinal scaffolds, 12-aryl-2,3,4,12-tetrahydrobenzo[b]xanthene-1,6,11-trione derivatives, have been reported under extremely mild reaction conditions using a catalytic amount of H2SO4 in water or in the presence of the acidic ionic liquid bmim[HSO4], which could be recycled. Supplemental materials are available for this article. Go to the publishers online edition of Synthetic Communications® to view the free supplemental file. GRAPHICAL ABSTRACT

Multicomponent Domino Process for the Synthesis of Some Novel Benzo[a]chromenophenazine Fused Ring Systems Using H2SO4, Phosphotungstic Acid, and [NMP]H2PO4

Abstract Efficient, mild, and quantitative procedures for the synthesis of functionalized benzo[c]chromeno[2,3-a]phenazine derivatives by one-pot, four-component condensation of 2-hydroxynaphthalene-1,4-dione, 1,2-phenylenediamines, aromatic aldehydes, and cyclic 1,3-dicarbonyl compounds have been developed using catalytic amounts of H2SO4 and phosphotungstic acid in EtOH/H2O (1:1) under reflux and also with [NMP]H2PO4, which acts as catalyst and medium at 80 °C. The reaction avoids tedious workup procedure due to the direct precipitation of products from the reaction medium. The present finding provides promising synthetic strategies for the synthesis of libraries with functional group diversity. GRAPHICAL ABSTRACT

Rapid Oxidation of 1,2-Diols, α-Hydroxyketones and Some Alcohols using N-Bromosuccinimide in Ionic Liquid

Oxidation of 1,2-diols, α-hydroxyketones and alcohols to carbonyl compounds is of great importance in organic synthesis1 and can be achieved with an array of reagents such as chromium(VI)-based reagents,2 hypervalent iodine reagents,3 and DABCO/Br2, DMSO/N2H4.H2O/I2/H2O/CH3CN. The oxidation of α-hydroxyketones to 1,2-diketones has also been reported by a variety of reagents including pyridinium chlorochromate,6 ammonium chlorochromate,7 iodine,8 Fe(NO3)2.9H2O and Fe(NO3)3/4-OH-TEMPO. The conversion of 1,2-diols to 1,2-diketones has been performed with 4-MeO-TEMPO,11 (4AcNH-TEMPO)-OTs-TsOH,12 CrO3-NH4Cl, NBS-CCl4-Py, NBS-Al2O3. The oxidation of alcohols has also been reported by NBS/2,6-lutidine in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4). This method involves the use of stoichiometric amount of base and suffers from narrow substrate generality and is limited to benzylic alcohols. Ionic liquids have emerged as efficient alternatives to conventional solvents, owing to their favorable properties, such as good solvating capability, wide liquid range, negligible vapor pressure, tunable polarity, high thermal stability, and ease of recyclability.17–19 We now report the oxidation of a variety of 1,2-diols, α-hydroxyketones and alcohols using NBS (N-bromosuccinimide) in different ionic liquids in the absence of any catalyst. The appropriate reaction conditions were optimized by initially investigating the oxidation of hydrobenzoin (1a) with NBS in different ionic liquids and by changing the substrate:NBS ratio. The reaction using 1:2 molar ratio of substrate:NBS in [bmim]BF4 gave the best results with respect to reaction time (2.5 h) and yield (92%) at 70◦C. The yield of benzil was low in other ionic liquids such as [bmim]PF6, [bmim]Br and [bmim]Cl. It was further observed that although the reaction of hydrobenzoin was complete using 1:1 molar ratio (substrate:NBS), it yielded a mixture of benzoin and benzyl (51:35% yields respectively); however, increasing the molar ratio of 1a: NBS to 1:3 had no marked effect on the yield or time of the reaction. Subsequently, oxidation of different hydrobenzoins, naphthoins and aliphatic 1,2-diols was carried out under the optimized reaction conditions. All reactions were rapid, clean and no side-products from ring bromination or α-bromination,

Synthesis and characterization of hybrid chloroquinoline–xanthene derivatives

Abstract A novel series of chloroquinoline-xanthene hybrids were prepared by one-pot multicomponent cyclo-condensation reaction of 2,7-dihydroxynaphthalene, aromatic aldehydes, and cyclic 1,3-dicarbonyl compounds followed by condensation reaction with 4,7-dichloroquinoline. The synthesized compounds were characterized by various spectroscopic techniques and single crystal X-ray analysis.

Expedient Synthesis of Diverse Spirooxindoles via Multicomponent Approach in Presence of Green Catalyst

An efficient, convenient and environmentally benign procedure for the construction of various bioactive spirooxindoles has been developed by condensation reactions of isatins, malononitrile and α-methylene carbonyl compounds/enols in the presence of starch solution as expedient, eco-friendly and biodegradable catalyst at 60 °C. The prominent features of the above protocol are short reaction time, high atom economy, simple work-up, cost-effectiveness, avoidance of toxic chemicals.

Synthesis of Spiro[Indene-2,2′-Naphthalene]-4′-Carbonitriles and Spiro[Naphthalene-2,5′-Pyrimidine]-4-carbonitriles via One-pot Three Component Reaction Using Task Specific Ionic Liquid

A novel and efficient methodology has been developed for synthesizing indane-1,3-dione and pyrimidine based spirocyclic compounds. The synthesis has been achieved via multicomponent reaction of indane-1,3-dione/1.3-dimethylbarbituric acid, variously substituted aromatic aldehydes and cyclohexylidene malononitrile in presence of catalytic amount of TSIL [bmim]OH. Short reaction time, high yields and use of non-chromatographic purification techniques are some of the advantages of this methodology.