Komal Aggarwal

One-Pot Synthesis of Biologically Important Spiro-2-amino-4H-pyrans, Spiroacenaphthylenes, and Spirooxindoles Using DBU as a Green and Recyclable Catalyst in Aqueous Medium

Abstract We have reported DBU-catalyzed one-pot synthesis of biologically and pharmacologically important spiropyrans from condensation of malononitrile/ethyl cyanoacetate, 1,3-dicarbonyl compounds, and ninhydrin/acenaphthequinone/istain in good yields. This new protocol employing DBU, which is a green, recyclable, and inexpensive catalyst, offers advantages such as mild reaction conditions, short reaction times, and easy isolation of products. The structures have been confirmed by x-ray analysis. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] GRAPHICAL ABSTRACT

Synthesis of novel 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthene-11-thiones and evaluation of their biocidal effects.

Novel 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthene-11-thiones have been synthesized in high yields by treatment of the corresponding oxo analogs with Lawessons reagent. The structure has been confirmed by X-ray analysis. The compounds were tested for in vitro antifungal activity against Rhizoctonia bataticola, Sclerotium rolfsii, Fusarium oxysporum and Alternaria porii. The compounds exhibited moderate to good activity against all pathogens. Insecticidal activity of these compounds against Spodoptera litura was observed to be comparable to commercial pyrethroid insecticide, cypermethrin. The urease inhibitory activity has also been studied.

An efficient and confluent approach for the synthesis of novel 3,4-dihydro-2H-naphtho[2,3-e][1,3]oxazine-5,10-dione derivatives by a three component reaction in ionic liquid

A catalyst free multicomponent reaction (MCR) capable of affording a wide range of novel 3,4-dihydro-2H-naphtho[2,3-e][1,3]oxazine-5,10-dione derivatives via one pot three component condensation of 2-hydroxy-1,4-naphthoquinone, aromatic amine and formaldehyde in ionic liquid [bmim]BF4 is reported. Mild reaction conditions, high yields, short reaction time, and easy separation are some of the salient features of the present protocol.

Synthesis, photophysical studies, solvatochromic analysis and TDDFT calculations of diazaspiro compounds.

Diazaspiro[5.5]undecane-1,3,5,9-tetraones and 3-thioxo-diazaspiro[5.5]undecane-1,5,9-trione have been synthesized via double Michael addition of 1,5-diphenyl-1,4-pentadien-3-one with active methylene heterocycles N,N-dimethyl barbituric acid, barbituric acid and thiobarbituric acid in water:ethanol (1:1) using TBAB as catalyst. The solvent effect on photophysical behavior of these compounds showed that stokes shift increases with increase in polarity of solvents. The solvent effect on the spectral properties has been investigated by using the Lippert-Mataga and Reichardt methods. The solvatochromism is analyzed by linear solvation energy relationship using the new four-parameter Catalán polarity scales. The relative fluorescence quantum yield of these diazaspiro compounds varies in solvents of different polarity. The HOMO and LUMO energies have been calculated by TDDFT (B3LYP/6-311G (d, p)) approach. TDDFT calculations were also used to compare the experimental and theoretical absorption spectra.

Efficient catalyst-free synthesis of diversified bis (spirooxindoles) via one-pot, three-component reaction

ABSTRACT A catalyst-free, one-pot synthesis of bis-spirooxindoles has been carried out by a three-component reaction of bis-isatins, malononitrile, and various cyclic enolizable carbonyl compounds in ethylene glycol at 100 °C. The protocol provides an easy and simple route for the synthesis of such complex compounds, in short reaction times and high yields. No chromatographic techniques have been employed for the purification of the compounds. GRAPHICAL ABSTRACT

An efficient catalyst free synthesis of nitrogen containing spiro heterocycles via [5 + 1] double Michael addition reaction

2,4-Diazaspiro[5.5]undecane-1,3,5,9-tetraones and 3-thioxo-2,4-diazaspiro[5.5]undecane-1,5,9-triones have been synthesized via double Michael addition of 1,5-diaryl-1,4-pentadien-3-one with active methylene compounds such as N,N-dimethyl barbituric acid, barbituric acid, thio-barbituric acid and N,N-diphenyl thiobarbituric acid in ethylene glycol at 100 °C in the absence of any catalyst to give high yields within a short reaction time. The structure has been confirmed by X-ray analysis. The single-crystal structure of the diazaspiro compound revealed that the CAr–H⋯π, π–π stacking and intermolecular hydrogen bonding interactions act as major driving forces for crystal packing.

An ampyrone based azo dye as pH-responsive and chemo-reversible colorimetric fluorescent probe for Al3+ in semi-aqueous medium: implication towards logic gate analysis

A novel ampyrone based azo dye, 4-((6-hydroxybenzo[d][1,3]dioxol-5-yl)diazenyl)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (1), was synthesized by coupling sesamol and 4-amino antipyrine (ampyrone) and was characterized spectroscopically. The interaction of azo dye (1) with different metal ions was studied using UV-vis and fluorescence spectra. Chemosensor 1 exhibits high selectivity and sensitivity towards Al3+ over other metal ions by fluorescence enhancement in methanol : water (1 : 1, v/v, at pH = 7.2), which could also be detected directly by the naked eye under visible light. The fluorescence of the 1–Al3+ complex was found to be reversible in the presence of EDTA. The pH-dependent absorption behavior of chemosensor 1 was also investigated. It was observed that chemosensor 1 could also be used as a selective ‘naked-eye’ colorimetric sensor for H+ and displayed a very strong red shift in the absorption band from 492 nm to 540 nm with a notable color change from yellow to violet-blue. Moreover, chemosensor 1 showed keto–enol tautomerization in the presence of acidic media and both forms were confirmed by 1H and 13C NMR spectra. Practical applicability of sensor 1 was further explored using sensing strip analysis, which enables rapid detection of Al3+ and H+ ions. NMR and DFT optimized geometries of chemosensor 1 suggest that the compound is present in the azo form (enol form) in the ground state. In addition, an INHIBIT logic gate was constructed based on the multi-responsive properties of chemosensor 1 induced by Al3+ and EDTA2−, which contained two input signals (In1: Al3+, In2: EDTA) and an output signal (O1: fluorescence intensity at 613 nm). The chemosensor 1 exhibited a high association constant with a detection limit of 3.55 × 10−7 M for Al3+ in MeOH–water solution.

Development of a novel protocol for chemoselective deprotection of N/O-benzyloxycarbonyl (Cbz) at ambient temperature

A novel protocol for the deprotection of N-benzyloxycarbonyl and O-benzyloxycarbonyl groups by nickel boride generated in situ from NaBH4 and NiCl2·6H2O in methanol at room temperature has been developed to give the corresponding amines and phenols. This protocol is chemoselective as groups like chloro, bromo, amide, ester, pyridine, and tert-butyloxycarbonyl moiety are unaffected under these conditions. The deprotection has also been validated in gram scale reactions, to establish the wider appropriateness of this protocol.Graphical abstract