Five-membered Heterocyclic Molecules Research Articles

Recent Advances in Green Approaches for Synthesis of Oxindole Derivatives

Oxindole derivatives are nitrogen-containing, five-membered heterocyclic molecules found in both natural and synthetic substances with diverse biological functions. Owing to their pharmaceutical and therapeutic characteristics, oxindoles have received remarkable attention, and various oxindole-containing substances can be synthesized using many different approaches. With the discovery of the importance of oxindole derivatives in medicinal chemistry, mainly in drug synthesis, the demand for finding sustainable protocols has increased, as most classical methods have their limitations and flaws. Hence, it is crucial to establish efficient and sustainable techniques that are safe, cost-effective, have low energy consumption, and cause minimal environmental impact. Nowadays, the use of green solvents in organic synthesis has received much attention because they prevent the formation of waste, are environmentally friendly, and have easy work-up procedures. Green solvents such as water, deep eutectic solvents, ionic liquids, and polyethylene glycol can substitute hazardous solvents. Microwave irradiation, visible-light irradiation, electrochemical methods, and multi-component synthesis are all described under green approaches. Most of these approaches allow the reaction to proceed rapidly while releasing minimal waste into the environment. Recent discoveries in green chemistry applications can be considered a turning point in organic synthesis. This review focuses on promising green approaches, used for the synthesis of oxindole derivatives, carried out in recent years with typical examples in two sections: green solvents and green techniques.
 Keywords- Oxindole derivatives, Green solvents, Green techniques, Sustainable chemistry, Solvent-free.

Adsorption behavior of furan at Ge(100) surface

The adsorption behavior of furan on the Ge(100) surface was studied using a combination of high-resolution photoemission spectroscopy (HRPES) and density functional theory (DFT) calculations. We identified the two adsorption species produced by the [4 + 2] cycloaddition and deoxygenation reactions of furan with the Ge(100) surface in a ratio of approximately 76:24 at the surveyed coverages, via an analysis of the binding energies and relative area proportions of all the peaks in the C 1s and O 1s core-level spectra. The DFT simulation results revealed that the [4 + 2] cycloaddition and deoxygenation adducts are thermodynamically preferred by the reaction of furan with the Ge(100) surface compared with others, which is consistent with the HRPES results. The findings will further our understanding of the surface reactions of five-membered heterocyclic molecules.

Isoxazole/Isoxazoline Skeleton in the Structural Modification of Natural Products: A Review.

Isoxazoles and isoxazolines are five-membered heterocyclic molecules containing nitrogen and oxygen. Isoxazole and isoxazoline are the most popular heterocyclic compounds for developing novel drug candidates. Over 80 molecules with a broad range of bioactivities, including antitumor, antibacterial, anti-inflammatory, antidiabetic, cardiovascular, and other activities, were reviewed. A review of recent studies on the use of isoxazoles and isoxazolines moiety derivative activities for natural products is presented here, focusing on the parameters that affect the bioactivity of these compounds.

Two-body dissociation of isoxazole following double photoionization - an experimental PEPIPICO and theoretical DFT and MP2 study.

The dissociative double photoionization of isoxazole molecules has been investigated experimentally and theoretically. The experiment has been carried out in the 27.5-36 eV photon energy range using vacuum ultraviolet (VUV) synchrotron radiation excitation combined with ion time-of-flight (TOF) spectrometry and photoelectron-photoion-photoion coincidence (PEPIPICO) technique. Five well-resolved two-body dissociation channels have been identified in the isoxazole's coincidence maps, and their appearance energies have been determined. The coincidence yield curves of these dissociation channels have been obtained in the photon energy ranges from their appearance energies up to 36 eV. The double photoionization of isoxazole produces a C3H3NO2+ transient dication, which decomposes into fragments differing from previously reported photofragmentation products of isoxazole. We have found no evidence of pathways leading to the C3H2NO+, HCN+, C2H2O+, C3HN+, or C2H2+ fragments or their neutral counterparts that have been observed in previous neutral photodissociation and single photoionization studies. Instead, the dissociation of isoxazole after the ejection of two electrons is bond-selective and is governed by two reactions, HCO+ + H2CCN+ and H2CO+ + HCCN+, whose appearance energies are 28.6 (±0.3) and 29.4 (±0.3) eV, respectively. A third dissociation channel turns out to be a variant of the most intense channel (HCO+ + H2CCN+), where one of the fragment ions contains a heavy isotope. Two minor dissociation channels occurring at higher energies, CO+ + CH3CN+ and CN+ + H3CCO+, are also identified. The density functional and ab initio quantum chemical calculations have been performed to elucidate the dissociative charge-separating mechanisms and determine the energies of the observed photoproducts. The present work unravels hitherto unexplored photodissociation mechanisms of isoxazole and thus provides deeper insight into the photophysics of five-membered heterocyclic molecules containing two heteroatoms.

A mini review on recent updates on pharmacological evaluations of molecules based on azetidinones and rhodanines heterocyclic nucleous

Azetidinones is a four member heterocyclic ring system with nitrogen as the hetero atom and a carbonyl group incorporated into it. Rhodanines is five-membered heterocyclic molecules containing thiazole nucleus with carbonyl group on fourth carbon such as rhodanine derivatives have broad spectrum of pharmacological activities. Azetidinones and rhodanines were showed wide spectrum activities including antimicrobial, anti-tubercular, anticonvulsant, anticancer, anti-inflammatory and CNS activities etc. The uses of different azetidinone and rhodanine compounds for synthesizing various biologically active compounds. Substituting the azetidinones and rhodanines with appropriate substitution for showing biological activities. Various biological activities of azetidinones and rhodanines are discussed in this article.

Time-Resolved Photoelectron Studies of Thiophene and 2,5-Dimethylthiophene.

The photoinduced dynamics of thiophene and 2,5-dimethylthiophene (2,5-DMT) were investigated upon excitation at 200 and 255 nm (2,5-DMT only) using time-resolved photoelectron spectroscopy and compared with results from ab initio coupled cluster calculations. For thiophene, depopulation of the initially excited B2(π3π4*) state to the lower-lying A1(π2π4*) state occurs within 25 ± 20 fs, with a subsequent bifurcation into a ring-puckering channel and a ring-opening channel with lifetimes of 80 ± 20 and 450 ± 50 fs, respectively. For 2,5-DMT, the dynamics following excitation at 200 nm is described by a monoexponential decay with a time constant of 120 ± 20 fs, while that following excitation at 255 nm is best fit by a biexponential decay with time constants of 115 ± 20 fs and 15 ± 3 ps, respectively. The fast signal observed after excitation of 2,5-DMT is assigned to the ring-opening channel, which is favored with respect to thiophene due to a lower excited-state barrier along the ring-opening coordinate and an increased inertia toward the ring-puckering channel. Coupled cluster calculations have been undertaken to compare the relaxation dynamics of thiophene to thiazole and isothiazole. For the latter two molecules, we find a strong gradient along the ring-opening coordinate in the Franck-Condon region of the initially populated ππ* state and predict that ring-opening is the dominating relaxation channel after photoexcitation. We use the extracted information for a comparison of the thiophene dynamics with the light-induced processes observed in other five-membered heterocyclic molecules.

Imidazolium-based ionic liquid decorated zinc porphyrin catalyst for converting CO2 into five-membered heterocyclic molecules

The bifunctional zinc(ii) porphyrin complex with flexible quaternary imidazole ionic liquids exhibited improved catalytic activity and reusability for the reaction of CO2with epoxides or aziridines to form five-membered heterocyclic products without any additives under solvent-free conditions.

Selective Alkylation of Aromatic Five-Membered Heterocyclic Molecules

Selective Alkylation of Aromatic Five-Membered Heterocyclic Molecules

The explicit interactions of five-membered saturated heterocyclics containing one and two heteroatoms with single water molecule

In this article, the hydrogen bonding interaction between saturated five-membered heterocyclic molecules and water has been investigated. Molecular orbital and density functional theory methods have been used to evaluate the stabilization energies associated with the adduct formation between heterocyclic molecules and water. The hydrogen bond acceptor ability of O, S, Se, and N as members of five-membered ring has been analyzed. The effect of the presence of second heteroatom N in the ring on the hydrogen bond interaction has also been evaluated. Atoms in molecules theory calculations were carried out to characterize the hydrogen bond through the changes in electron density and Laplacian of electron density. A natural energy decomposition analysis and natural bond orbital analysis is also performed to understand the nature of hydrogen bonding interaction in monohydrated five-membered heterocyclic adducts.

Magnetotropicity of five-membered heterocyclic molecules

Ab initio methods have been employed to obtain models for the current density field induced in the electrons of pentatomic cyclic molecules C4H4X, with X = CH2, NH, O, S, PH, and AsH, in the presence of a static, homogeneous magnetic field normal to the plane containing the four ring carbon atoms. These models are expected to provide simple and valid tools to assess the magnetotropism of these compounds and to interpret their magnetic response.

Electronic and spatial structure of five-membered oxygen-or sulfur-containing cyclic phosphorus and arsenic compounds based on quantum-chemical calculations

We have carried out nonempirical quantum-chemical calculations for five-membered heterocyclic molecules containing O or S atoms and also P or As atoms in the ring, using RHF/6-31G(d) and MP2/6-31G(d) methods with full optimization of their geometry. We have studied their electronic and spatial structure and the characteristics of the interaction between atoms in the molecules.

Can aromaticity be connected with molecular polarizability? A theoretical study of benzene isomers and five-membered heterocyclic molecules

Extended calculations of molecular electric dipole polarizability tensor, at Hartree-Fock and correlated level of accuracy (MP2, CCS, CC2, CCSD, and CCSD(T)) have been carried out to investigate whether aromaticity could be related to the electric dipole polarizability of planar ring systems. The calculations prove the exaltation of the average property of conjugated molecules, which is possibly due to their easily polarizable π-electron cloud. On the other hand, theoretical out-of-plane polarizability components are smaller in benzene than in any other C$_6$H$_6$ isomer. The aromatic stabilization energies of monosubstituted five-membered conjugated cyclic molecules increase in the same direction as theoretical out-of-plane polarizabilities.

High Overtones of C−H Stretching Vibrations in Isoxazole, Thiazole, and Related Methyl and Dimethyl Derivatives

The high overtone spectra of liquid isoxazole and thiazole, two five-membered heterocyclic molecules with different aromaticity characters, have been investigated in the C−H stretching region by visible absorption spectroscopy. The local-mode model describes satisfactorily the C−H stretching vibrations at the fifth and sixth quanta of excitation, where the localized character is increased. Each overtone band generally displays a number of peaks corresponding to the different types of C−H oscillators. Comparison between the overtone spectra of the parent molecules and those of the methyl derivatives provided sufficient information for a conclusive assignment of the progressions. Deconvolution of the fifth overtone bands gave further evidence regarding the shape and the width of the distinct peaks. Anharmonicity values of the overtone vibrations, C−H bond lengths, and force constants were obtained from the local-mode analysis and discussed in comparison with the results obtained from the normal-mode approximation. A correlation between overtone frequencies and chemical shifts in proton magnetic resonance, generally observed in aromatic compounds, has been found only for thiazole, whose aromaticity is responsible for a significant electron current in the ring.

ChemInform Abstract: INFRARED STUDY OF THE C‐H STRETCHING REGION OF FIVE‐MEMBERED HETEROCYCLIC COMPOUNDS

An infrared analysis of the C—H stretching region of some five-membered heterocyclic molecules (pyrrole, furan, thiophene, selenophene, and tellurophene) has been carried out. Spectra were obtained for gas, liquid, solution (CCl4), and crystal samples. Polarised infrared radiation was employed for crystalline oriented films. Band profiles in the gas phase and polarisation values for the crystal spectra have been used in order to get new assignments for this spectral region.

Infrared study of the C—H stretching region of five-membered heterocyclic compounds

An infrared analysis of the C—H stretching region of some five-membered heterocyclic molecules (pyrrole, furan, thiophene, selenophene, and tellurophene) has been carried out. Spectra were obtained for gas, liquid, solution (CCl4), and crystal samples. Polarised infrared radiation was employed for crystalline oriented films. Band profiles in the gas phase and polarisation values for the crystal spectra have been used in order to get new assignments for this spectral region.

Some comments on ring currents in five-membered heterocyclic molecules

Some comments on ring currents in five-membered heterocyclic molecules

Further comments on ring currents in five-membered heterocyclic molecules

Further comments on ring currents in five-membered heterocyclic molecules

Infra-red and Raman spectra of five-membered heterocyclic molecules—oxazole and thiazole

The infra-red and Raman spectra of oxazole and thiazole have been measured in different conditions in order to get definite evidence for a complete assignment of the normal vibrations of these ring compounds. The vibrational assignment of oxazole and thiazole is then discussed on the basis of the collected experimental results. The correlation with the normal modes of similar ring molecules is substantiated and discussed.