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  • Open access
  • 26 Reads
Cp2TiCl2 – Catalyzed synthesis of tertiary alcohols by the reaction of AlCl3 with ketones and arylolefins

We have previously obtained significant results on the cycloalumination of olefins with EtAlCl2 in the presence of magnesium and Cp2ZrCl2 or Cp2TiCl2 catalyst. Here we report the development of an efficient one-pot catalytic method for the synthesis of tertiary alcohols from AlCl3, arylolefins, and ketones under the action of Cp2TiCl2. The developed method for producing tertiary alcohols has a general character and allows to convert styrene and substituted styrenes (ortho-, para-methylstyrenes) into aryl-substituted tertiary alcohols with yields up to 76% in the reaction with acetone or methylethylketone. We assume that the reaction proceeds through the formation of titanacyclopropane intermediate.

  • Open access
  • 39 Reads
Peculiarities of obtaining and modeling the structure of nimesulide clathrate complexes with β- and γ- cyclodextrins
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This work investigates the inclusion of the nimesulide molecule into the beta- and gamma- cyclodextrin cavity and explores the application of molecular modelling for the purposes of proving the host-guest complexation process.

The experiment was carried out according to the author's method, based on the main methods for obtaining clathrate complexes. To confirm the structural features of the complexes, a set of physicochemical methods of analysis was used. It was decided that the focus will be on figuring out the possibility applying computer modeling. The characteristics of the molecular systems under study were calculated using the «Gaussian 09W» software package. The functionality of this software package allowed us to apply both the restricted Hartree-Fock method - RHF, and the hybrid density functional method - B3LYP. The-31G split-valence basis set was utilized for all subsequent calculations , to quantify the influence of the additional polarization and diffuse functions on the calculations. Using computational chemistry, the structures of γ-, β- cyclodextrin, nimesulide, and surface complex compounds were constructed and optimized. The possible structures of nimesulide inclusion complexes with β-, γ-cyclodextrin were also designed. The results obtained will influence the evaluation of the possibility of obtaining the clathrate complex.

The crystal structure of the nimesulide inclusion complex obtained by us with γ-cyclodextrin was experimentally confirmed by X-ray diffraction analysis. To date, not many works are known to utilize these molecular modeling techniques in the field of supramolecular chemistry based on an independently synthesized inclusion complex.

  • Open access
  • 75 Reads
Graphitic carbon nitride-supported L-arginine: synthesis, charachterization, and catalytic activity in multi-component reactions

Graphitic carbon nitride-supported L-arginine (g-C3N4@L-arginine) has been prepared as a heterogeneous catalyst for synthesizing heterocyclic compounds such as pyranopyrazole and acridinedione derivatives. High efficiency, short reaction time, and easy separation are major assets for using g-C3N4@L-arginine as a catalyst in one-pot multicomponent reactions. Numerous analyses were used to detect synthesized compounds such as FE-SEM (Field Emission Scanning Electron Microscopy), EDX (Energy Dispersive X-ray spectroscopy), XRD (X-Ray Diffraction analysis), TGA (Thermo Gravimetric Analysis), and FT-IR (Fourier Transform Infrared Spectroscopy). g-C3N4@L-arginine nanocatalyst was reused five times in the reaction with no apparent decrease in reaction yield, which shows acceptable recyclability.

  • Open access
  • 22 Reads
Multiple pathways in Cp2TiCl2 - catalyzed reaction of tetraalkyl-substituted pyrazines with EtAlCl2 and Mg.

There exist a number of classical methods for the synthesis of substituted pyrazines. Among this variety of reactions, the synthesis of substituted pyrazines from nitriles stands out neither in the number of known examples nor in product yields. However, the one-stage character of the transformation, together with the uncertainty of its mechanism, aroused our interest in this catalytic reaction. Here we report the successful implementation of Cp2TiCl2 -catalyzed reaction of aliphatic nitriles with EtAlCl2 and Mg, which led to the selective preparation of 2,3,5,6-tetraalkyl-substituted pyrazines, 2,4,5-trisubstituted-1H-imidazole or 2-aminocyclopent-1-ene-carbonitrile depending on reaction conditions and substituents.

  • Open access
  • 33 Reads
CuBr2-Catalyzed alkenylation of 1-adamantanol with isopropanol

The electrophilic adamantylation of olefins is one of the few synthetic approaches to polycyclic framework compounds with the side chains. The reaction of adamantane with lower olefins on aluminosilicate catalysts leads to alkyladamantanes, and in the case of propylene, a noticeable amount of alkenyladamantanes is formed. In a solution of trifluoromethanesulfonic acid, the reaction of adamantane with olefins gives a mixture of mono- and polysubstituted alkyladamantanes in ~10 % yield. In order to elaborate convenient preparative methods for the selective introduction of a three-carbon fragment into the adamantane framework, we undertook a study of the reaction of 1-adamantanol with isopropanol in the presence of metal-complex catalysts. We have developed for the first time a CuBr2-catalyzed method for the alkenylation of 1-adamantanol with isopropanol. The reaction proceeds for 4 hours at 220 oC giving the corresponding trans-1-adamantylpropene in high yield.

  • Open access
  • 30 Reads
Use of Phenyl Formate as a CO Surrogate for the Reductive Cyclization of Organic Nitro Compounds to yield Different N-Heterocycles: Avoiding the Use of Autoclaves and Pressurized Gases

The reductive cyclization of different organic nitro compounds by carbon monoxide, catalyzed by transition metal complexes, is a very efficient and clean strategy for the synthesis of many N-heterocycles. Indeed, only CO2 is formed as a stoichiometric byproduct. Most often, suitably substituted nitroarenes are employed as substrates, but the use of b-nitrostyrenes and nitrodienes has also been described and a few cases of inter-molecular reactions of a nitroarene with a separate alkene or diene have been reported. Despite the advantages these reactions have with respect to alternative procedures, their use has not spread out of the few groups which developed them, undoubtedly mainly because they require the use of autoclaves and pressurized CO lines, which are not available in most synthetic laboratories. In this talk, the author will present the results obtained in his laboratories on the use of phenyl formate as a convenient CO surrogate, able to liberate carbon monoxide under the reaction conditions and allowing the use of a standard and cheap glass pressure tube as a reaction vessel. This way, both the need for autoclaves and pressurized CO lines are released. Four examples will be discussed: the synthesis of indoles from o-nitrostyrenes, the synthesis of indoles from b-nitrostyrenes, the synthesis of oxazines from nitroarenes and conjugated dienes, and the synthesis of carbazoles from o-nitrobiphenyls. In most cases, yields were better than those previously reported by the use of pressurized CO, proving that the use of CO surrogates can be a viable alternative to the gaseous reagent and not just a second-choice strategy.

  • Open access
  • 30 Reads

Insects are unable to synthesize cholesterol de novo from acetyl-CoA, but most of them require it as a component of cell membranes and a precursor for the synthesis of the hormone ecdysone. In the case of herbivorous insects, a three-step oxidative removal of the 24-ethyl group of beta-sitosterol is carried out to convert it to 24-dehydrocholesterol and then to cholesterol. It is important to note that in the biosynthesis of ecdysone, the oxidation of cholesterol is carried out by Neverlend Reiske monooxygenase and little-studied “black box” enzymes. Intracellular transport of cholesterol and other steroids in insects is also important for survival, as illustrated by the steroid transfer protein SCP-2. Since fluorescent 3beta-hydroxy-5-ene steroids are used to study the distribution and metabolism of cholesterol, and in the literature, as far as we know, such studies were carried out only for a pair of SCP-2 with commercial 22-NBD-cholesterol, we performed calculations in silico for obtained 7-nitrobenzoxadiazole (NBD) derivatives codenamed DAM-NBD ​​and NBD-pip-CCF.

Synthesis of NBD-pip-CCF was carried out by conjugation of cholesteryl chloroformate (CCF) and 4-Chloro-7-nitrobenzofurazan through a piperazine (Pip) fragment. To obtain DAM-NBD, dehydroepiandrosterone was converted to 17-methylamino derivative (DAM), after which it was subjected to acid treatment, neutralization and NBD-ylation. Biological properties were predicted in silico using Autodock Vina and FYTdock.

The results of computer simulation showed the possibility of binding synthetic DAM-NBD and CCFNBDpip. The data obtained open up prospects for the use of the obtained substances in vitro to search for mechanisms to control the viability of insects.

  • Open access
  • 21 Reads
Cyclic 1H-phospolane oxides as a potential candidate for cancer therapy

Organophosphorus compounds have been investigated for applications in agricultural and medicinal applications for decades, and a considerable number of phosphorus-containing drugs have achieved commercial success. Recently by P. Finkbeiner atc in review have shown, that phosphine oxides and related phosphorus-containing functional groups are valuable polar structural elements and that they deserve to be considered as a routine part of every medicinal chemist’s toolbox. A new approach to the synthesis of previously hard-to-obtained 3-alkyl-1H-phospholanes oxides was developed by us. In order to assess the potential of five-membered cyclic organophosphorus compounds in cancer therapy, we carried out docking 3-buthyl-1H-phospholanes oxide and 2,3-dihydrophosphole in the binding site of 24 human proteins involved in oncogenesis processes. Proteins were selected using the PharmMapper in-house pharmacophore model database. The results are presented in the article.

  • Open access
  • 38 Reads
New 2,6-Bis(5-phenyloxazolyl)pyridine Ligands for Luminescent LnIII Complexes

Lanthanide (Ln(III)) luminescent complexes have been attracting a lot of interest for technological applications and molecular imaging. The luminescence of Ln(III)) ions is weak and depends on the use of light absorbing coordination ligands which sensitizes the lanthanide ion. [1,2] A large variety of coordination ligands has been screened such as dipicolinates, oligopyridines, cyclen and crown ether derivatives, porphyrins, cryptands or calixarenes. [1]

In our research group we have developed an expeditious methodology to prepare bis(oxazolyl)pyridine ligands for LnIII from threonine and 2,6-pyridinedicarbonyl dichloride.[2] In this work, two new pyridine-bis-oxazolyl ligands with an aromatic ring in position 5 of the oxazole ring (Figure 1) were prepared from phenylserine and 2,6-pyridinedicarbonyl dichloride. The photophysical properties of compounds 1 and 2 were studied in acetonitrile and in Tris-HCl buffer (0.1 M, pH 7.1). These compounds were used for complexation with Eu(III) and/or Tb(III) ions, and the photophysical properties of the complexes studied. Luminescence titrations with anhydrous EuCl3 and TbCl3 allowed the determination of the stoichiometry of the complexes and of the stability constants.

[1] A. Bettencourt-Dias, P. S. Barber, S. Bauer, J. Am. Chem. Soc., 2012, 134, 6987

[2] G. Pereira, M.F. Ferreira, E.M.S. Castanheira, J.A. Martins, P.M.T. Ferreira, Eur. J. Org. Chem. 2012, 3905

  • Open access
  • 31 Reads
Development of easy and practical access of novel imidazo[2,1-b]thiazole derivatives

The scientific discoveries exposed the privileged skeleton of the imidazo[2,1‐b]thiazole heterocycles for the development of pharmacological compounds. Imidazo[2,1‐b]thiazoles showed interesting potency against a bord range of biological activities such as antibacterial, antifungal, antiviral, anti‐ inflammatory, antihypertensive, anticancer and antioxidant, also used as drug that has significant immunomodulatory properties (Levamisole). Encouraged by these bioactivities, we report herein a new easy and efficient procedure for the preparation of imidazo[2,1-b]thiazole derivatives under green chemistry conditions.