Synthesis of 3,8,13,18-tetrachloro-2,7,12,17-tetramethoxyporphyrin

Vilsmeier-Haack formylation of 3,4-dimethoxypyrrole led to the unprecedented formation of 3-chloro-4-methoxypyrrole-2-aldehyde instead of the desired dialdehyde. Subsequent reduction and acid catalyzed cyclization led to the formation of type I, 3,8,13,18-tetrachloro-2,7,12,17-tetramethoxyporphyrin in approximately 6% yield.     

Thermodynamics of silver—silver halide electrodes and thermodynamic solubility products of silver halides in glycerol + water mixtures at different temperatures

The standard potentials of silver—silver bromide and silver—silver iodide electrodes in glycerol+water mixtures containing 5, 10, 20 and 30 wt% glycerol were determined from electromotive force measurements of the cell Ag(s), AgX(s), KX(c)//KCl(c), AgCl(s), Ag(s), where X is Br or I, at seven different temperatures in the range 5–35°C. The standard potentials in each solvent are represented as a function of temperature. The standard thermodynamic functions for the electrode reactions, the primary medium effects of various solvents upon X⁻, and the standard thermodynamic quantities for the transfer of 1 g-ion of X⁻ from water to the respective glycerol + water media are evaluated and discussed in the light of ion—solvent interactions as well as the structural changes of the solvents. From the values of the Ag/Ag⁺ and Ag/AgX, X⁻ electrodes, the thermodynamic solubility product constants of silver chloride, silver bromide and silver iodide have been determined in glycerol + water solvent mixtures at different temperatures.     

Synthesis of bis(pyrrol-2-yl)arenes by Pd-catalyzed cross coupling

2-Borylpyrrole was prepared from 2-iodopyrrole almost quantitatively and then reacted with dihaloarenes under typical reaction conditions of Suzuki-Miyaura cross coupling to give bis(pyrrol-2-yl)arenes in good yields, while the cross coupling reaction of 2-iodopyrrole with 1,4-phenylenebisboronic acid was susceptible to oxidative self-coupling to produce 4,4′-bis(pyrrol-2-yl)biphenyl as a byproduct. These bis(pyrrol-2-yl)arenes showed strong fluorescence.     

Nonlinear finite element analysis of functionally graded plates integrated with patches of piezoelectric fiber reinforced composite

In this paper, a nonlinear static finite element analysis of simply supported smart functionally graded (FG) plates in the presence/absence of the thermal environment has been presented. The substrate FG plate is integrated with the patches of piezoelectric fiber reinforced composite (PFRC) material which act as the distributed actuators of the plate. The material properties of the FG substrate plate are assumed to be temperature dependent and graded along the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The derivation of this nonlinear thermo-electro-mechanical coupled finite element model is based on the first order shear deformation theory and the Von Karman type geometric nonlinearity. The numerical solutions of the nonlinear equations of the finite element model are obtained by employing the direct iteration method. The numerical illustrations suggest the potential use of the distributed actuator made of the PFRC material for active control of nonlinear deformations of smart FG structures. The effects of volume fraction index of the FG material of the substrate plates and the locations of the PFRC patches on the control authority of the patches are investigated. Emphasis has also been placed on investigating the effect of variation of piezoelectric fiber orientation angle in the PFRC patches on their actuation capability for counteracting the large deflections of FG plates.     

Computer-aided design of chiral ligands. Part 2. Functionality mapping as a method to identify stereocontrol elements for asymmetric reactions

A computational method to determine the energetically favorable positions of functional groups with respect to the transition states of stereoselective reactions based on force field energy minimization is presented. The parameters of this functionality mapping, the characteristics of the target transition states, and the features of the probe structures are outlined. Our method was found to reproduce the positions of the stereodiscriminating fragments for some known chiral ligands including the Masamune dimethylborolane, dimenthylborane, the Corey stien reagent, the Roush allylboronate tartrates, and the secondary amine Diels-Alder catalysts described by MacMillan. Functionality mapping can be used to better understand the specific interactions in the transition states leading to the products by providing a quantitative measure of the stabilization/destabilization afforded by the different ligand components via nonbonded interactions. The method can determine if a chiral ligand imparts the observed selectivity by stabilizing one reaction pathway, by destabilizing a reaction pathway, or by a combination of both. Orientational as well as positional information about potential functional groups is readily obtained. In addition to its utility as an analytical tool, functionality mapping can be used to explore starting points for the design of new chiral ligands.     

Quantum mechanical models correlating structure with selectivity: predicting the enantioselectivity of beta-amino alcohol catalysts in aldehyde alkylation

Quantitative structure selectivity relationship (QSSR) models are described that provide consistently reliable predictions for the asymmetric addition of Et2Zn to PhCHO catalyzed by beta-amino alcohols. Statistically valid two-variable linear regression models that correlate the structures of the chiral catalysts with their enantioselectivities are obtained from three-dimensional physical property grids. The strength of the present method is that statistical models obtained from a small set of experimentally determined selectivities and relatively simple theoretical calculations yield selectivity predictions that are as accurate as those derived from higher-level calculations of transition-structure energies. Only minutes of computing time are required. Simple models are obtained which permit straightforward physical interpretation and generate realistic predictions.     

Structurally characterized acylruthenium organometallics bearing a pendant aldehyde function

By reacting [Ru(RL¹)(PPh₃)₂(CO)Cl], (1) (R = C₆H₄Me, Et) with an excess of CNBu^t in the presence of NH₄PF₆, organometallics of the type [Ru(RL²)(PPh₃)₂(CNBu^t)₂]PF₆, (2) have been isolated in excellent yield [RL¹ = C₆H₂O-2-CHNHR(p)-3-Me-5, RL² = C₆H₂(CO)-O-2-CHNHR(p)-3-Me-5]. These organometallics, on controlled hydrolysis, produce [Ru(L³)(PPh₃)₂(CNBu^t)₂], (3) in very good yield (L³ = C₆H₂(CO)-O-CHO-3-Me-5). In both ([2(C₆H₄Me)] · 2H₂O) and ([3] · 2CH₂Cl₂) the two phosphine ligands lie in trans positions. In ([2(C₆H₄Me)] · 2H₂O) the Ru(C₆H₄MeL²) fragment, excluding the pendant tolyl ring, is a near perfect plane (mean dev ~ 0.02Å) which makes a dihedral angle of 5.2° with the tolyl plane. The acyl chelate ring in ([2(C₆H₄Me)] · 2H₂O) is excellently planar with a mean deviation of 0.006°. In ([3] · 2CH₂Cl₂) the Ru(L³) fragment defines a crystallographic plane of symmetry, the coordinates of the atom being of the type x, 1/4z. The complex ([2C₆H₄Me)] · 2H₂O) displays N–HȮFO (iminium-phenolato) hydrogen bonding while in ([3] · 2CH₂Cl₂) C–H...O hydrogen bonding is present. Characteristic spectral data (u.v.–vis, i.r. and ¹H n.m.r.) of the complexes are reported. A notable feature is that an allowed band near 500 nm due to the t_2g → π^*(azomethine) charge transfer transition, which is diagnostic of the coordinated iminium-phenolato function, is present in (3) but this band is absent in the aldehydic acyl complex (2). In the ¹H n.m.r. spectrum the N⁺–H signal in (2) (near 13.5 ppm) is split into a doublet due to transcoupling with the azomethine proton. The aldehydic proton of (3) resonates as a sharp singlet near 10 ppm. In CH₂Cl₂ solution (2) and (3) display quasireversible a Ru^III/Ru^IIcyclic voltammetric response with E_1/2 near 0.9 and 0.5 V versuss.c.e. The conversion (2) → (3) is accompanied by the nucleophilic attack of water. The complex (3) is also obtained directly from (1) by reaction with CNBu^t in the presence of H₂O. The aldehyde function in (3) is deactivated by the existing acyl moiety; as a result further decarbonylation does not take place.     

In Vitro Antiviral Activity of α-Mangostin against Dengue Virus Serotype-2 (DENV-2)

Dengue virus (DENV), a member of the family Flaviviridae, is a threat for global health as it infects more than 100 million people yearly. Approved antiviral therapies or vaccines for the treatment or prevention of DENV infections are not available. In the present study, natural compounds were screened for their antiviral activity against DENV by in vitro cell line-based assay. α-Mangostin, a xanthanoid, was observed to exert antiviral activity against DENV-2 under pre-, co- and post-treatment testing conditions. The antiviral activity was determined by foci forming unit (FFU) assay, quantitative RT-PCR and cell-based immunofluorescence assay (IFA). A complete inhibition of DENV-2 was observed at 8 µM under the co-treatment condition. The possible inhibitory mechanism of α-Mangostin was also determined by docking studies. The molecular docking experiments indicate that α-Mangostin can interact with multiple DENV protein targets such as the NS5 methyltransferase, NS2B-NS3 protease and the glycoprotein E. The in vitro and in silico findings suggest that α-Mangostin possesses the ability to suppress DENV-2 production at different stages of its replication cycle and might act as a prophylactic/therapeutic agent against DENV-2.     

Green Synthetic Approach: An Efficient Eco-Friendly Tool for Synthesis of Biologically Active Oxadiazole Derivatives

Green synthetic protocol refers to the development of processes for the sustainable production of chemicals and materials. For the synthesis of various biologically active compounds, energy-efficient and environmentally benign processes are applied, such as microwave irradiation technology, ultrasound-mediated synthesis, photo-catalysis (ultraviolet, visible and infrared irradiation), molecular sieving, grinding and milling techniques, etc. Thesemethods are considered sustainable technology and become valuable green protocol to synthesize new drug molecules as theyprovidenumerous benefits over conventional synthetic methods.Based on this concept, oxadiazole derivatives are synthesized under microwave irradiation technique to reduce the formation of byproduct so that the product yield can be increased quantitatively in less reaction time. Hence, the synthesis of drug molecules under microwave irradiation follows a green chemistry approach that employs a set of principles to minimize or remove the utilization and production of hazardous toxic materials during the design, manufacture and application of chemical substances.This approach plays a major role in controlling environmental pollution by utilizing safer solvents, catalysts, suitable reaction conditions and thereby increases the atom economy and energy efficiency. Oxadiazole is a five-membered heterocyclic compound that possesses one oxygen and two nitrogen atoms in the ring system.Oxadiazole moiety is drawing considerable interest for the development of new drug candidates with potential therapeutic activities including antibacterial, antifungal, antiviral, anticonvulsant, anticancer, antimalarial, antitubercular, anti-asthmatic, antidepressant, antidiabetic, antioxidant, antiparkinsonian, analgesic and antiinflammatory, etc. This review focuses on different synthetic approaches of oxadiazole derivatives under microwave heating method and study of their various biological activities.