Arjita Srivastava

Ionic liquid promoted spiroannulation via hetero-Michael addition and intramolecular heterocyclisation

A sequential efficient method for the synthesis of novel spiro-5-thiazolidin-2-one-indolo[1,5]benzothiazepine from readily available isatin, 4-thioxothiazolidin-2-one and 2-aminothiophenol is reported. The synthesis involves formation of N-methyl-3-(2-oxo-4-thioxothiazolidinon-5-ylidene)-1,3-dihydro indol-2-one by [bmIm]OH promoted Knoevenagel condensation of 4-thioxo-2-thiazolidinone with isatin. The Knoevenagel product on ionic liquid promoted thia-Michael addition with 2-aminothiophenol and intramolecular cyclocondensation yielded the title compounds with high atom economy. The ionic liquid, [bmIm]OH was recovered completely and recycled thrice for the synthesis with no appreciable decrease in the efficiency of the process. The whole sequence of reactions proceeded with quantitative transformation of reactants into spiro [1,5]benzothiazepine at ambient temperature. The sequential reaction pathway is supported by the isolation of the thia-Michael adduct of the knoevenagel product with 2-aminothiophenol and quantitative conversion of the adduct into the final products under the same reaction conditions.

Synthesis of fused pyridines in the presence of thiamine hydrochloride as an efficient and reusable catalyst in aqueous conditions

Efficient and straightforward synthesis of fused pyridine derivatives was achieved from electron-rich amino heterocycles and Knoevenagel products derived from aldehyde and malononitrile under aqueous media at 90 °C in the presence of thiamine hydrochloride as a reusable, green catalyst. The strategy in this protocol involves addition on an activated olefinic bond formed in situ by Knoevenagel condensation between an aromatic aldehyde and an active methylene compound. The Michael product on subsequent cyclo condensation yielded fused pyridine in high yield. It offers several advantages such as inexpensive, easily available and recyclable catalyst, simple operational procedure, excellent yield and use of aqueous medium that is considered to be relatively eco-friendly. Vitamin B1 was recovered and reused thrice.

Diastereoselective synthesis of furopyranopyridine in ionic liquid/water without additional catalyst

3,5-Diarylidene-1-methyl-piperidin-4-one derived in situ from N-methylpiperidinone and benzaldehyde undergoes intermolecular [4 + 2] hetero-Diels–Alder reactions with 2,3-dihydrofuran in [bmim]BF4–H2O (1 : 1) to afford furopyranopyridine derivatives in high to quantitative yields. Heterodienes, 3,5-diaryldiene-1-methylpiperidin-4-one an electron deficient oxadiene added to 2,3-dihydrofuran an electron rich dienophile because of an inverse electron demand, yielding furopyranopyridines with a high atom economy.

[bmim]OH promoted hydroalkynylation of nitrile and intramolecular hydroamination of the carbon–carbon multiple bond: an efficient and eco-compatible strategy for the synthesis of indolizinones

An efficient and novel hydroalkynylation of 2-cyanopyridine with arylacetylene and a subsequent intramolecular hydroamination promoted by a basic ionic-liquid, [bmim]OH, under microwave activation in the absence of an organic solvent and an inorganic base, yielding biodynamic indolizinones has been developed. The protocol involves [bmim]OH mediated in situ generation and addition of a nucleophilic alkynide from the aryl substituted terminal on a carbon alkyne of a polar nitrile group of 2-cyanopyridine. This results in the formation of a 2-pyridylphenylethynyl methimine intermediate which, on subsquent intramolecular nucleophilic addition of a pyridyl nitrogen on the carbon–carbon triple bond of the imine intermediate, heterocyclized into indolizinone with high atom economy. The reaction proceeded smoothly and quantitatively at an ambient temperature. The task specific [bmim]OH was recovered and reused three times without any appreciable decrease in its activity and product yield.

Molecular modeling of pyridine derivatives for COX-2 inhibitors: quantitative structure–activity relationship study

Quantitative structure–activity relationship studies were performed on a set of compounds of pyridine acyl sulfonamide derivative to understand the structural features influencing the affinity toward the COX-2 enzyme inhibition. In the present study, the density functional theory-based descriptors were calculated at B3LYP/6-31+G* level in gas phase. However, empirical molecular descriptors were calculated with the help of different softwares. Number of physicochemical, topological, and electronic descriptors were computed, and the calculated results revealed that the descriptors based on softness (S), hardness (η), chemical potential (μ), and the lowest unoccupied molecular orbital energy seem to be responsible factor for in vitro inhibition activity of COX-2 enzyme. The possible descriptors which we have calculated for the present series of compounds were selected for multiple linear regression analysis. Various regression models have been tested and the regression analysis data indicate that some of the descriptors provide valuable information toward designing of new COX-2 enzyme inhibitors with high efficacy. The predictive ability of the models was cross validated by observation of the low residual activity values and appreciable cross validated R2 values (

Recyclable [bmIm]OH promoted one-pot heterocyclization: synthesis of substituted benzofurans

R_{\text{CV}}^{2}

Highly Diastereoselective NHC-Catalyzed [4+3] Annulation of Enals, Alde­hydes and N-Phenyl Urea/Thiourea for the Synthesis of Monocyclic trans-1,3-Diazepanes

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Basic ionic liquid promoted heterocyclization to access fused imidazopyridines

A quantitative structure–activity relationship (QSAR) study has been performed on 5-hydroxy-1H-pyrazol-3(2H)—ones analogue-based Mur B inhibitors—to understand the structural features influencing the affinity of these inhibitors toward the enzyme. The QSAR results show that antibacterial activity could be modeled using steric parameters such as molecular weight (MW), surface tension (ST), index of refraction (IOR) and electronic parameters such as equalized electro-negativity (χeq). The predictive ability of the models was checked by cross-validation method.