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  • Open access
  • 102 Reads
Greener Synthesis, In-silico and theoretical analysis of hydrazides as potential antituberculosis agents (Part 1)

Since several decades, our healthcare burden has been increased due to tremendous cases of multidrug-resistant (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) infections especially in tropical countries. In present study, we have synthesized ten hydrazides with the use of greener Chitosan-derived catalyst. This catalyst accomplished the said condensation reaction within 15-30 mins at room temperature conditions. All our synthesized compounds showed stronger affinities against mycobacterium tb and bacterial targets, especially towards 1d7u than the standard drug ciprofloxacin. One of our compounds retained with lower toxicity (electrophilicity index (ω) 3.1304), low chemical hardness (η: 2.1740), and high softness (S: 0.4600). In the realm of development of more potent, effective, safer antituberculosis agents with effective greener synthesis; our current study would provide more insights on potent analogues containing hydrazine motifs in them.

  • Open access
  • 38 Reads
Cp2ZrCl2 – Et3Al Reagent System in the Homo-Coupling of Trimethylsilyl-Substituted Alkynes
, , , ,

The reaction of homo-coupling of alkynes using zirconocene reagents is an important basis for the efficient synthesis of polymer, oligomers and macrocycles. The most widely used reagents include Negishi reagent (“Cp2ZrBu2”), Takahashi reagent (“Cp2ZrEt2”), and Rosenthal reagent (Cp2Zr(py)TMSC≡CTMS). Despite detailed studies of the reaction of Et3Al with Cp2ZrCl2, the resulting zirconocene complexes could not be successfully used for intramolecular coupling of alkynes. We found that the reaction of trimethylsilyl-substituted alkynes with 0.5 equivalents of Cp2ZrCl2, 1 equivalents of Et3Al in toluene at room temperature for 18 hours gives, after hydrolysis/deuterolysis or iodination, functionalized products of the homocoupling of silyl-substituted alkynes in good yield. We assume that the reaction proceeds through the stage of intermediate formation of the metalcyclopentadiene, which can be of a ziconocene or organoaluminum nature. The detected reaction is of a general nature and allows the synthesis of previously difficult to obtain and practically important unsaturated bis-trialkylsilanes connected by a conjugated hydrocarbon spacer. The first positive results open the way for the synthesis of macrocyclic polyene compounds through the combination of diyne molecules.

  • Open access
  • 52 Reads
N,N-dimethyl-4-amino-2,1,3-benzothiadiazole: synthesis and luminescent solvatochromism

2,1,3-benzothiadiazole (BTD) derivatives were widely applied as herbicides, fungicides and antibacterial agents. The strong withdrawing ability of BTD and its fluorescent properties make it appealing also for the preparation of luminescent materials. Polymers containing the BTD fragment were successfully exploited for advances applications such as organic light-emitting diodes (OLEDs), dyes, solar and photovoltaic cells, as recently reported by B.A.D. Neto et al. [Eur. J. Org. Chem. (2013) 228].

To the best of our knowledge, a complete synthetic procedure for N,N-dimethyl-4-amino-2,1,3-benzothiadiazole (BTDNMe2) from the commercially available 2,1,3-benzothiadiazole was never reported. The only reference available dates back to 1976 and describes the thermal decomposition of the corresponding ammonium salt [N.M. Slavachevskaja et al., Pharm. Chem. J. 10 (1976) 327]. The synthetic route here proposed involves nitration of BTD in sulfonitric mixture, followed by reduction of the nitro-group and subsequent methylation with iodomethane. BTDNMe2 was isolated as dark red oil and it was fully characterized by means of nuclear magnetic resonance (NMR) and infrared spectroscopy. Solutions of BTDNMe2 in common organic solvents revealed to be appreciably luminescent in the visible range. The increase of dielectric constant caused a non-linear red shift of the absorption and emission maxima, an increase of the Stokes shift and a reduction of the photoluminescence quantum yield. The electronic transitions related to the absorption and emission properties were associated to the HOMO-LUMO energy gap by means of electrochemical measurements and DFT calculations. Finally, BTDNMe2 was successfully used for the preparation of luminescent doped polymethylmethacrylate samples with intense orange emission.

  • Open access
  • 51 Reads
Fullerenyl-1,2,3-triazoles: synthesis and cytotoxic activity

For the first time, the reaction of fullerenyl azide with terminal acetylenes has been used to synthesize previously undescribed 1-butyl-2-triazolylfullerenes, in which the heterocyclic fragment is directly attached to the fullerene backbone. Water-soluble complexes of the synthesized adducts of fullerene with polyvinylpyrrolidone showed high cytotoxic activity towards tumor cells of the Jurkat, K562, U937 lines.

  • Open access
  • 109 Reads
CuBr2/HYmmm – an effective catalyst for the transformation of 1,2-propanediol into 2-ethyl-4-methyl-1,3-dioxolane
, ,

Propanal is an important chemical intermediate used extensively in the manufacture of rubbers, plastics, paints, and pesticides. The ready availability of 1,2-propanediol production from glycerol provides the opportunity for propanal and its derivatives production from biomass resource. We found that pyrolysis of 1,2-propanediol at 200 °C for 4 hin the presence of the supported form of copper (II) bromide on micro-meso-macroporous zeolite HYmmm (5% CuBr2 (20% ) / HYmmm) gives a mixture of cis- and trans-2-ethyl-4-methyl-1,3-dioxolane in 1.5: 1 ratio. New synthetic methodology paves the way to the development of new Cu-based catalytic systems promising for industrial applications.

  • Open access
  • 95 Reads
Synthesis and antimicrobial evaluation of some new pyrazole derivatives containing thiazole scaffold

In the present work, the one-pot synthesis of some new 2,4-disubstituted thiazolyl pyrazole derivatives was carried out. The reaction of different pyrazole aldehydes, thiosemicarbazide, and α-halo ketones in one pot afforded the targeted pyrazolyl thiazole derivatives. The synthesis was carried out by following two different methods. The first one is the conventional method in which pyrazole aldehyde, thiosemicarbazide, and α-halo ketones were refluxed in ethanol. In the second method, the reaction mixture was ground at room temperature. The rate of the reaction, the yield of the products, and the purity of the products were compared for both methods. All the synthesized compounds were tested for their antimicrobial activities. It was found that most of the compounds showed good to moderate antibacterial as well as antifungal activities.

  • Open access
  • 86 Reads
Synthesis and antimicrobial screening of some new thiazole substituted 1,3,4-oxadiazole derivatives

In the present work, the synthesis and antimicrobial activity of new thiazolyl substituted 1,3,4-oxadiazole derivatives were achieved. The reaction of different thioamides with ethyl 4-chloro-3-oxobutanoate (4-chloroethyl acetoacetate) gave derivatives of ethyl 2(2-arylthiazol-4yl)acetate, which on subsequent reaction with hydrazine hydrate in absolute ethanol afforded 2-(2-arylthiazol-4-yl)acetohydrazide derivatives. The obtained 2-(2-arylthiazol-4-yl)acetohydrazide derivatives on reaction with CS2 and KOH in aqueous ethanol cyclized to form 5-((2-arylthiazol-4-yl)methyl)-1,3,4-oxadiazole-2-thiol derivatives. Finally, the obtained 1,3,4-oxadiazoles were further treated with α-halo ketones at room temperature to afford the targeted thiazolyl oxadiazole derivatives. Most of the compounds showed good antibacterial as well as antifungal activity.

  • Open access
  • 69 Reads
Palladacyle as functionalized metal-ligand precursors

One of the most important goals in modern inorganic and organometallic chemistry is the development of well-designed ligand systems that allow the properties of metal centers to be easily varied in a controlled manner. Among the numerous ligand systems described in the chemical literature, derivatives of variously substituted [C, N] Schiff bases, and their complexes have piqued the interest of researchers due to their high stability, activity, and variability. When an organic ligand forms an M-C bond with a metal center, the metal is then further bonded to a donor atom to form a stable, five-membered metallated ring.

  • Open access
  • 166 Reads
Development and Evaluation of Eberconazole Loaded Niosomal Formulation for Sustained Release Application

The invasive fungal infection requires a long treatment schedule; however, treatment becomes more cumbersome due to the development of resistance. Most antifungal moieties show systemic toxicity upon oral administration, leading to delivery of antifungal moiety via topical route. Eberconazole (EBZ) is a BCS class II drug that has poor solubility and high permeability. It is a broad-spectrum imidazole derivative, which acts as both fungicidal and fungistatic by inhibiting ergosterol synthesis. Various topical creams of EBZ are available in the market, but the lack of a proper dosing schedule and rapid removal leads to poor bioavailability. Niosomes are vesicular carriers that can entrap both hydrophilic and lipophilic drugs. Niosomal formulations have been prepared using Span20 (nonionic surfactant) and cholesterol by thin-film hydration (TFH) technique. During the pre-formulation studies, purity of EBZ was ascertained using FT-IR and melting point studies while standard calibration curve was prepared using UV-visible spectroscopy. The prepared niosomal formulations were characterized for their morphology, entrapment efficiency, particle size, and zeta-potential. The formulation has shown 86 ± 0.85% entrapment efficiency while noisome appeared ring-like structure during its microscopic evaluation. The niosomal formulations were also evaluated for their release and release kinetics using the dialysis bag method. The release profile has shown sustained delivery of EBZ up to 120 hrs. In nutshell, EBZ loaded niosomal formulation will be useful and beneficial as compared to currently available marketed preparations by increasing the bioavailability and decreasing the toxicity due to its sustained release behavior.

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