Nonsteroidal Anti‐inflammatory Drug‐based N‐Allylidene Benzohydrazides and 1‐Acyl‐2‐pyrazolines: Their Synthesis as Potential Cytotoxic Agents In Vitro

A series of 1‐acyl‐2‐pyrazoline derivatives derived from nonsteroidal anti‐inflammatory drugs was designed as potential anticancer agents. Synthesis of these compounds was carried out via the condensation reaction of chalcones and acid hydrazides under heating. The methodology did not require the use of any costly reagents or catalysts, and the acid hydrazide reactants were readily prepared from mefenamic acid or ibuprofen. A variety of 1‐acyl‐2‐pyrazolines was prepared in good to excellent yields. An N‐allylidene benzohydrazide intermediate was isolated during the reaction optimization study, the structure of which was confirmed unambiguously by X‐ray single crystal data. A range of N‐allylidene benzohydrazides were also prepared in good yields. Some of the compounds synthesized showed promising cytotoxic activities when tested against HCT‐15 human colon cancer cell line in vitro.     

A TFAA-H3PO4-mediated direct, metal-free and high-speed synthesis of aryl carboxylate esters from phenols

An operationally simple, mild and single-step method for the direct and metal-free synthesis of aryl carboxylate esters is described under a solvent free condition. The reaction of phenols including 2-naphthol (or 1-naphthol) with a variety of carboxylic acids in the presence of TFAA and 85% H₃PO₄ provided a range of aryl carboxylate esters in good yields within few minutes.     

Influence of disorder on superconductivity in non-magnetic rare-earth nickel borocarbides

The effect of substitutional disorder on the superconducting properties of YNi₂B₂C was studied by partially replacing yttrium and nickel by Lu and Pt, respectively. For the two series of (Y, Lu)Ni₂B₂C and Y(Ni, Pt)₂B₂C compounds, the upper critical field H _c2(T) and the specific heat c _p(T, H) in the superconducting mixed state have been investigated. Disorder is found to reduce several relevant quantities such as T _c, the upper critical field H _c2(0) at T=0 and a characteristic positive curvature of H _c2(T) observed for these compounds near T _c. The H _c2(T) data point to the clean limit for (Y, Lu) substitutions and to a transition to the quasi-dirty limit for (Ni, Pt) substitutions. The electronic specific heat contribution γ(H) exhibits significant deviations from the usual linear γ(H) law. These deviations reduce with growing substitutional disorder but remain even in the quasidirty limit which is reached in the Y(Ni_1−x , Pt _x )₂B₂C samples for x=0.1.     

An efficient method to prepare sulfoxonium ylides and their reactivity studies using copper powder and Sc(III) as catalysts: Molecular and electronic structure analysis

Sulfoxonium ylides are the viable alternatives for diazo compounds as carbene precursors. Unlike diazo compounds, these are bench-stable and crystalline solids. However, the existing methods for the synthesis of sulfoxonium ylides have disadvantages related to the yields, substrate scope, and usage of expensive catalysts. Therefore, it is necessary to develop efficient and competitive protocols for the preparation of sulfoxonium ylides. In this study, we developed an economically affordable protocol for the synthesis of sulfoxonium ylides from diazo compounds using copper powder as a catalyst. This protocol leads to the efficient multigram-scale synthesis of a wide range of sulfoxonium ylides in good yields. Further, we demonstrated scandium triflate–catalyzed carbene insertion into the N−H bond from sulfoxonium ylide. A variety of anilines and sulfoxonium ylides with various functional groups reacted well and produced the corresponding α-amino esters in good yields. All the synthesized compounds were characterized using various standard spectroscopic and analytical techniques. We also used computational methods to understand the electronic structure of all the sulfoxonium ylides using geometry optimization, frequency calculation, molecular orbital and natural bond orbital analysis, and energy decomposition analysis. Our computational results revealed that the interaction between carbene and dimethyl sulfoxide is covalent in nature and stable enough to handle in the absence of any catalyst.     

Coordination Assisted Distal C−H Alkylation of Fused Heterocycles

Distal C?H bond functionalization of heterocycles remained extremely challenging with covalently attached directing groups (DG). Lack of proper site for DG attachment and inherent catalyst poisoning by heterocycles demand alternate routes for site selective functionalization of their distal C?H bonds. Utilizing non‐productive coordinating property to hold the heterocycle into the cavity of a template system in a host–guest manner, we report distal C?H alkylation (C‐5 of quinoline and thiazole, C‐7 of benzothiazole and benzoxazole) of heterocycles. Upon complexation with heterocyclic substrate, nitrile DG in template directs the metal catalyst towards close vicinity of the specific distal C?H bond of the heterocycles. Our hypothesized pathway has been supported by various X‐ray crystallographically characterized intermediates.     

Novel 1,2,3-triazolo phosphonate derivatives as potential antibacterial agents

We describe the synthesis, characterization, and in vitro antibacterial evaluation of a library of novel compounds based on 1,2,3-triazolo phosphonate framework along with the evaluation of DNA gyrase inhibitory potential of a promising molecule in silico. Preparation of these compounds was carried out via a multistep sequence comprising of the Abramov reaction followed by the Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) as the key steps. Various α-hydroxyphosphonate derivatives containing either a secondary or tertiary alcohol at the α position were prepared. When screened for their antibacterial activities in vitro using a Gram-positive (Staphylococcus aureus) and three Gram-negative (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa) strains, majority of these derivatives exhibited reasonable to good effects with the analogue 5k being active against all the strains. The SAR analysis indicated that the activity was influenced by the position of the α-hydroxyphosphonate moiety as well as the substituent present on the benzene ring attached to the 1,2,3-triazole ring. Moreover, the compound 5k showed strong interactions with the DNA active site when docked into the DNA gyrase in silico. Thus, the 1,2,3-triazolo phosphonate derivative 5k appeared to be a novel and promising hit molecule that deserves further study as a potential antibacterial agent.     

Non-resonant microwave absorption studies of superconducting MgB2 and MgB2 + MgO

Non-resonant microwave absorption (NRMA) studies of superconducting MgB₂ and a sample containing ∼10% by weight of MgO in MgB₂ are reported. The NRMA results indicate near absence of intergranular weak links in the pure MgB₂ sample. A linear temperature dependence of the lower critical field H _c1 is observed indicating a non-s wave superconductivity. However, the phase reversal of the NRMA signal which could suggest d wave symmetry is also not observed. In the MgB₂ + MgO sample, much larger low field dependent absorption is observed indicating the presence of intergranular weak links. The hysteretic behavior of NRMA is compared and contrasted in the two samples. In the pure MgB₂ sample, a large hysteresis is observed between the forward and the reverse scans of the magnetic field indicating strong pinning of flux lines. This hysteresis saturates a few degrees below T _c while in the MgB₂ + MgO sample, a much slower increase of hysteresis with decreasing temperature is observed, a signature of weaker pinning.     

Poly(bis‐2,2,2‐trifluoroethoxymethyl oxetane): Multiple crystal phases,crystallization‐induced surface topological complexity and enhanced hydrophobicity

Semicrystalline poly(bis‐trifluoroethoxymethyl)oxetane, P(B‐3FOx), was prepared by cationic ring‐opening polymerization at ?5 °C with M_n up to 21 kDa. Differences in cooling rates from the melt have substantial effects on crystal phase, percent crystallinity, surface topography, and wetting behavior. DSC and WAXD show that cooling from the melt at slow rates (<5 °C/min) gives α‐P(B‐3FOx) with ΔH_f = 22–27 J/g. Quenching from the melt results in β‐P(B‐3FOx) for which a mesophase structure is suggested. β‐P(B‐3FOx) melts at 53 °C followed by recrystallization to α‐P(B‐3FOx). Solution casting from THF results in third phase, γ‐P(B‐3FOx). TM‐AFM and SEM imaging for α‐P(B‐3FOx) showed that cold crystallization at 25 °C brought about increased crystallinity and surface topologies characterized by sharp asperities and lath‐shaped crystals. Spontaneous surface roughening of α‐P(B‐3FOx) results in a discontinuous three‐phase contact line with water and an increase in water sessile drop contact angle from 106° to 136°. The ～30° increase in water contact angle was attributed primarily to a topological change from a relatively smooth surface (Wenzel state) to an asperity‐rich surface yielding a discontinuous three‐phase contact line (composite of Wenzel and Cassie‐Baxter state). The oleophobicity for this polymer, which contains only a single ? CF₃ end group on each side chain, compares favorably with more highly fluorinated acrylates. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1022–1034, 2010     

Experiments and modeling of iron-particle-filled magnetorheological elastomers

Magnetorheological elastomers (MREs) are ferromagnetic particle impregnated rubbers whose mechanical properties are altered by the application of external magnetic fields. Due to their coupled magnetoelastic response, MREs are finding an increasing number of engineering applications. In this work, we present a combined experimental and theoretical study of the macroscopic response of a particular MRE consisting of a rubber matrix phase with spherical carbonyl iron particles. The MRE specimens used in this work are cured in the presence of strong magnetic fields leading to the formation of particle chain structures and thus to an overall transversely isotropic composite. The MRE samples are tested experimentally under uniaxial stresses as well as under simple shear in the absence or in the presence of magnetic fields and for different initial orientations of their particle chains with respect to the mechanical and magnetic loading direction.Using the theoretical framework for finitely strained MREs introduced by Kankanala and Triantafyllidis (2004), we propose a transversely isotropic energy density function that is able to reproduce the experimentally measured magnetization, magnetostriction and simple shear curves under different prestresses, initial particle chain orientations and magnetic fields. Microscopic mechanisms are also proposed to explain (i) the counterintuitive effect of dilation under zero or compressive applied mechanical loads for the magnetostriction experiments and (ii) the importance of a finite strain constitutive formulation even at small magnetostrictive strains. The model gives an excellent agreement with experiments for relatively moderate magnetic fields but has also been satisfactorily extended to include magnetic fields near saturation.