Department of Chemistry

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1,3,5-Trisubstituted benzenes as fluorescent photoaffinity probes for human carbonic anhydrase II capture
(RSC, 2013) Addy, Partha Sarathi
The ‘capture’ of proteins by small molecules via irreversible cross-linking mediated by photo-irradiation is of interest in the field of proteomics (for reviews see ref. 1). The technique has the potential for profiling protein-binding by small molecules, an objective of importance both for basic cell biology and in pharmaceutical science. Capture compounds, or photoaffinity probes, are typically endowed with three functions comprising (i) a selectivity function, such as an enzyme inhibitor, (ii) a photo-cross linking group (capture function) and (iii) a sorting group to enable separation of the captured protein from biological mixtures, such as biotin or an alkyne for subsequent modification. The captured protein(s) can be isolated using streptavidin beads and identified by mass spectrometry or Western blotting (for examples see ref. 2)
1,3-Carbon D–A strategy for [3 + 2] cycloadditions/annulations with imines: synthesis of functionalized pyrrolidines and related alkaloids
(RSC, 2014) Kumar, Indresh
Cycloaddition/annulation reactions remain the most attractive methods for the synthesis of five membered heterocyclic ring systems. Among the three possible strategies for [3 + 2] cycloaddition, this review focuses on 1,3-carbon donor–acceptor (C3, D–A) cycloaddition/annulation reactions with imines to synthesize pyrrolidines. The formal [3 + 2] cycloaddition, which includes the in situ 1,3-carbon D–A precursor generation through metal catalysis, Lewis acid catalysis and organocatalysis approaches is highlighted. The scope and limitations of this strategy along with its applications in the synthesis of natural product alkaloids reported during the last decade are outlined.
1-Butyl-3-methylimidazolium p-toluenesulfinate: a novel reagent for synthesis of sulfones and β-ketosulfones in ionic liquid
(Elsiever, 2011-10-12) Kumar, Anil
A novel task-specific ionic liquid, 1-butyl-3-methylimidazolium p-toluenesulfinate, [bmim][p-TolSO2] has been synthesized and used as a nucleophile for the reaction with alkyl bromides and phenacyl bromides to prepare sulfones and β-ketosulfones in excellent yields (80–93%) in [bmim][BF4] ionic liquid. The isolated yields of sulfones and β-ketosulfones were higher in [bmim][BF4] than other organic solvents at room temperature.
1-Methyl-3-butylimidazolium Decatungstate in Ionic Liquid: An Efficient Catalyst for the Oxidation of Alcohols
(Thieme, 2005) Kumar, Anil
An excellent system for the selective oxidation of benzylic and secondary alcohols with hydrogen peroxide catalyzed by 1-methyl-3-butylimidazolium decatungstate in [bmim][BF4] ionic liquid is described. The catalytic system is reusable and products are obtained in excellent yield under environmentally benign conditions.
A 1D thiocyanato bridge nickel(II) system: crystal structure and magnetic property
(Elsiever, 2001-04) Laskar, Inamur Rahaman
A one-dimensional coordination polymer of nickel(II), [(μN,S-NCS)2{Ni(ampy)}]n (ampy=1-(2-aminoethyl)pyrrolidine) has been synthesized and characterized by X-ray single crystal analysis. Structure analysis reveals that each nickel(II) center is coordinated in a distorted octahedral fashion with four bridging thiocyanato ligands and one mesocyclic diamine ligand. The low temperature (300–18 K) magnetic measurement shows that the system is ferromagnetically coupled. The magnetic data are fitted to the de Neef equation, giving the parameters J=1.4 cm−1 and g=2.08.
1O2 Mediated Conversion of β-Enaminonitriles to α-Keto Amides Photosensitized by Recyclable H2TPP in Visible Light
(ACS, 2024-03) Grover, Nitika
We report a one-step approach for the conversion of β-enaminonitriles to synthetically versatile α-keto amides in moderate to high yields under visible light irradiation photosensitized by porphyrins. The method is mild, cost-effective, and sustainable and requires air as the sole reagent/oxidant. The reaction is believed to proceed via an ene-type pathway initiated by 1O2, followed by dehydration, imine hydrolysis, and subsequent nucleophilic substitution of the cyanide group by amine. The method offers a broad substrate scope and has also been extended for synthesis of α-keto esters with aliphatic alcohols as nucleophiles. The porphyrin recovered after the reaction can be reused multiple times.
2-(3'-Indolyl)-N-arylthiazole-4-carboxamides: Synthesis and evaluation of antibacterial and anticancer activities
(Elsiever, 2015-10) Kumar, Dalip; Kumar, Anil
A new series of 2-(3′-indolyl)-N-arylthiazole-4-carboxamides 17a–p has been designed and synthesized. Initial reaction of readily available thioamides 15 with bromopyruvic acid under refluxing conditions produced different thiazole carboxylic acids 16 which upon coupling with arylamines by using EDCI·HCl and HOBt afforded diverse arylthiazole-4-carboxamides 17a–p in 78–87% yields. Antibacterial activity evaluation against Gram-positive and Gram-negative bacterial strains led to compounds 17i–k and 17o as potent and selectively (Gram-negative) antibacterial agents. The cytotoxicity of thiazole carboxamides 17a–p was also evaluated on a panel of human cancer cell lines. Among the tested derivatives, compounds 17i (IC50 = 8.64 μM; HEK293T) and 17l (IC50 = 3.41 μM; HeLa) were identified as the most potent analogues of the series. Preliminary mechanism of action studies of thiazole carboxamide 17i suggested that its cytotoxicity against HeLa cells involves the induction of cell death by apoptosis.
2-Iodoxybenzoic Acid (IBX): A Versatile Reagent
(Thieme, 2005) Kumar, Indresh
The importance of hypervalent iodine reagents in organic chemistry has been demonstrated in recent years, and they have been found to have several desirable properties: they are mild, selective, efficient and eco-friendly. [1] 2-Iodoxybenzoic acid (IBX) has been developed as a powerful reagent for several organic transformations, and a recent surge in interest was driven by the publication of an improved method for its synthesis. [2a] IBX is a powerful single-electron transfer oxidant that readily accepts a new heteroatom-based ligand, and has been applied successfully for the construction of novel heterocycles.
2D Nanostructures of CoFe2O4 and NiFe2O4: Efficient Oxygen Evolution Catalyst
(Elsiever, 2018-05-20) Basu, Mrinmoyee
Development of cost-effective, efficient electrocatalyst for oxygen evolution reaction (OER) is a challenging issue as OER has sluggish reaction kinetics due to transfer of multi-electrons. In this study, a new strategy has been developed for the synthesis of 2D nanostructures of CoFe2O4 and NiFe2O4 following a wet-chemical route followed by calcination. Following this method nanoplates of CoFe2O4 and nanosheets of NiFe2O4 have been successfully synthesized. These interconnected 2D structures are very efficient for oxygen evolution reaction and it is observed that CoFe2O4 nanoplates and NiFe2O4 nanosheets are catalytically more active compared to nanocubes and nanobipyramids of CoFe2O4 and NiFe2O4. CoFe2O4 nanoplates require only 1.64 V vs. RHE for generating current density of 10 mA/cm2 whereas nanocubes of CoFe2O4 require 1.68 V vs. RHE. Similarly, NiFe2O4 nanosheets require 1.69 V to generate current density 10 mA/cm2 and NiFe2O4 nanobipyramids require 1.77 V vs. RHE to engender 10 mA/cm2 current density. 2D sheet or Plate-like structure with more exposed surface atoms faces more electrolyte to adsorb and react which results in higher electrocatalytic activity.
2D Thin Sheet Heterostructures of MoS2 on MoSe2 as Efficient Electrocatalyst for Hydrogen Evolution Reaction in Wide pH Range
(ACS, 2020-03-09) Basu, Mrinmoyee
Two-dimensional layered transition metal dichalcogenides, MoSe2 and MoS2, have drawn potential attention in the field of water splitting. Coupling of MoS2 and MoSe2 provides a sustainable route to improve the electrocatalytic activity for the hydrogen evolution reaction (HER). Here, the heterostructures of thin sheets (ts) of MoSe2 and MoS2 are combined to develop the MoSe2-ts@MoS2-ts heterostructure via multiple-step methodology. First, thin sheets of MoSe2 are synthesized following the stepwise hydrothermal method. After the successful synthesis of MoSe2-ts, MoS2-ts is synthesized on it to develop the heterostructure: MoSe2-ts@MoS2-ts. By tuning the amount of MoS2-ts and MoSe2-ts in the heterostructure separately, the optimum condition is obtained for HER. The unique heterostructure is efficient for HER under wide pH conditions like 1 M KOH, pH-7 phosphate buffer, 3.5% saline water, and finally 0.5 M H2SO4. MoSe2-ts@MoS2-ts can generate 10 mA/cm2 current density under the application of −0.186 V vs RHE with a low Tafel value of 71 mV/decade. The formation of the heterojunction plays an essential role in facilitating charge transportation. Furthermore, the heterostructure provides the more active sites for the adsorption of hydrogen to generate H2. An excess amount of any of the bare counter parts in the heterostructure leads to a decrease in electrocatalytic efficiency because of the lowered heterojuction formation. MoSe2-ts@MoS2-ts has very high stability during the electrocatalytic reaction, which is determined from 1000 consecutive cycles and a 24 h prolonged scan. MoSe2-ts@MoS2-ts can generate 147 μmol of H2 in ∼50 min of reaction time with 100% Faradaic efficiency.
3-substitued indoles: one-pot synthesis and evaluation of anticancer and Src kinase inhibitory activities
(Elsiever, 2011-06-15) Kumar, Anil
An efficient and economical method was developed for the synthesis of 3-substituted indoles by one-pot three-component coupling reaction of a substituted or unsubstituted benzaldehyde, N-methylaniline, and indole or N-methylindole using Yb(OTf)3–SiO2 as a catalyst. All the synthesized compounds were evaluated for inhibition of cell proliferation of human colon carcinoma (HT-29), human ovarian adenocarcinoma (SK-OV-3), and c-Src kinase activity. The 4-methylphenyl (4o and 4p) and 4-methoxyphenyl (4q) indole derivatives inhibited the cell proliferation of SK-OV-3 and HT-29 cells by 70–77% at a concentration of 50 μM. The unsubstituted phenyl (4d) and 3-nitrophenyl (4l) derivatives showed the inhibition of c-Src kinase with IC50 values of 50.6 and 58.3 μM, respectively.
4-Methoxy-N-(4-nitrobenzyl)aniline
(ACTA, 2012) Kumar, Indresh
In the title compound, C(14)H(14)N(2)O(3), the nitro group is nearly coplanar with the benzene ring to which it is bonded [dihedral angle = 1.70 (2)°], and this ring is para-substituted by the amino-methyl-ene group. The dihedral angle between the benzene rings is 57.8 (1)°. The crystal structure is stabilized by N-H⋯O and C-H⋯O hydrogen bonds and weak C-H⋯π inter-actions are also observed.
Abnormal NHC Palladium(II) Complex Containing CNN Pincer Skeleton and Its Application to Suzuki-Miyaura Coupling of Aryl Chlorides in Water
(Wiley, 2023-05) Khungar, Bharti
The excellent catalytic activities of abnormal NHC carbene complexes, where the C2 position remains unaffected, and coordination occurs at the C4 or C5 position of the imidazolium ring, is still a fascinating but scarce area of research. This present work reports a palladium complex (LPdBr) bearing abnormal NHC with CNN pincer architecture. It is synthesized from imidazolium-based quinoline ligand (LH) with Pd(OAc)2 via -NH and carbene deprotonation. The complex was fully characterized by NMR spectroscopy (1D and 2D) and high-resolution mass spectrometry (HRMS). The structure and abnormal coordination modes of the complex are further confirmed with the help of single-crystal X-ray diffraction. The studies revealed the abnormal coordination mode in LPdBr where C5 carbon of the imidazolium ring participates in bonding, leaving the C2 position unaffected. The catalytic potential of complex LPdBr was investigated in the Pd-catalyzed Suzuki-Miyaura coupling of various aryl/heteroaryl chlorides with different aryl/naphthyl/phenanthryl boronic acids. The catalyst LPdBr successfully activated various less-activated aryl chloride substrates. LPdBr also exhibited good catalytic activity at 1 mol% Pd loading under microwave irradiation and in green solvent water. The mechanism of the catalytic cycle is investigated and proposed by HRMS.
Accelerated design of gold nanoparticles with enhanced plasmonic performance
(AAAS, 2025-08) Rao, Anish
Finding the optimal dimensions of metal nanoparticles to maximize their plasmonic performance in targeted applications is a complex and time-consuming process that typically requires a trial-and-error approach. Here, we propose a universal pipeline that integrates Bayesian optimization with electrodynamics simulations to find dimensions of gold bipyramids with superior plasmonic performance in photothermal efficiency, enhancement of Raman scattering and photoluminescence, strong coupling between plasmon and exciton, and aggregation-induced color difference. Our workflow is a straightforward tool for plasmonic nanoparticle design, setting their optimal dimensions for targeted applications.
Accelerated reduction of 4-nitrophenol: bridging interaction outplays reducing power in the model nanoparticle-catalyzed reaction
(ACS, 2020-08) Rao, Anish
General chemistry knowledge will intuitively predict that a stronger reducing agent will result in a faster reduction reaction. The present work, however, shows the counterintuitive role of reducing agents in a model reaction of gold nanoparticle (AuNP)-catalyzed reduction of 4-nitrophenol (4-NP) by sodium borohydride. The strength of reducing agents is varied, in situ, by adding appropriate metal ions in the reaction medium. The trend observed in the rate constants does not correlate fully with the strength of reducing agents. Surprisingly, Ca2+ outperforms Mg2+ in accelerating the AuNP-catalyzed reduction of 4-NP, despite Ca2+ forming a comparatively weaker reducing agent. A thorough investigation reveals that the reducing power is an incomplete descriptor, and additional ion-specific bridging interactions should be incorporated to explain the observed trend in the rate constants. The idea of combining increased reducing power with bridging interactions was then utilized to transform a traditionally noncatalytic AuNP to a catalytically active one.
Access to 2-Arylindoles via Decarboxylative C−C Coupling in Aqueous Medium and to Heteroaryl Carboxylates under Base-Free Conditions using Diaryliodonium Salts
(Wiley, 2016-10-13) Kumar, Dalip
Diaryliodonium salts have been successfully employed to construct 2-arylindoles and heteroaryl carboxylates. The indoles are prepared using decarboxylative C−C coupling strategy in water. The carboxylates are produced under base-free conditions
Acetalization and thioacetalization of cabonyl compounds: A case study based on global and local electrophilicity descriptors
(Wiley, 2006-03-08) Roy, Ram Kinkar
Acetalization of benzaldehyde and substituted benzaldehydes (containing both electron-donating and electron-withdrawing groups) is explained qualitatively on the basis of global electrophilicity descriptor, w, as proposed by Parr and coworkers (11). The generated values of w can explain qualitatively the preferential electrophilic addition, and hence, the yield of acetalization obtained in an earlier experimental study carried by Patel and coworkers (17). The present study also reveals that although both steric and electronic factors affect the yield, only later can be taken care of by w. In the case of a competitive formation of cyclic acetals and cyclic thioacetals from a reaction mixture containing p-hydroxybenzaldehyde, p-nitrobenzaldehyde, 1,2-ethanediol (i.e., glycol), and 1,2-ethanedithiol, the relative experimental yields (18) could be explained from the difference of the global electrophilicity values between aldehydes and acetalizing agents in the same line of arguments of Maynard et al.
Adaptable DNA interactions regulate surface triggered self assembly
(RSC, 2020) Jana, Pritam Kumar
DNA-mediated multivalent interactions between colloidal particles have been extensively applied for their ability to program bulk phase behaviour and dynamic processes. Exploiting the competition between different types of DNA–DNA bonds, here we experimentally demonstrate the selective triggering of colloidal self-assembly in the presence of a functionalised surface, which induces changes in particle–particle interactions. Besides its relevance to the manufacturing of layered materials with controlled thickness, the intrinsic signal-amplification features of the proposed interaction scheme make it valuable for biosensing applications
Additive-Driven Rhodium-Catalyzed [4+1]/[4+2] Annulations of N-Arylphthalazine-1,4-dione with α-Diazo Carbonyl Compounds
(ACS, 2018-09-05) Sakhuja, Rajeev
A Rh(III)-catalyzed strategy involving the [4+1] annulation of 2-arylphthalazine-1,4-diones with α-diazo carbonyl compounds was developed, accessing a series of unprecedented hydroxy-dihydroindazolo-fused phthalazines in good to excellent yields. By varying the additive, phthalazino-fused cinnolines were synthesized under Rh-catalyzed conditions via [4+2] annulation between the same starting materials. Notably, such two strategies showed a good functional group tolerance and high atom efficiency.
Advances in Functionalized Ionic Liquids as Reagents and Scavengers in Organic Synthesis
(Bentham Science, 2014) Kumar, Anil
Functionalized ionic liquids (FILs) synthesized with specific desired chemical properties have shown promising results in various areas of organic synthesis. In supported organic synthesis, FILs have become known as a new alternative to commonly used PEG and fluorous soluble supports. This review summarizes the progress of recent development in the synthesis of functionalized ionic liquids with emphasis on their applications as reagents and scavengers in organic synthesis.