Efficient synthesis of novel functionalized pyrazolo-pyranoquinoline and tetrahydrodibenzo-[1,8]naphthyridinone derivatives

The facile and efficient synthesis of 1,4-dihydropyrazolo-pyrano-[2,3-b]quinoline derivatives from the reaction of 2-chloroquinoline-3-carbaldehydes and pyrazolones is described. Moreover, a one-pot method for the development of functionalized tetrahydrodibenzo[b,g][1,8]naphthyridinone derivatives is reported by using a three-component reaction of 2-chloroquinoline 3-carbaldehydes, pyrazolone, and enaminones catalyzed by l-proline in EtOH.     

A novel strategy for the synthesis of 6H-chromeno [4, 3-b] quinoline by intramolecular Heck cyclization

A novel procedure for the synthesis of various derivatives of 6H-chromeno [4, 3-b] quinolines from intramolecular Heck reaction of 2-chloro-3-(phenoxymethyl) quinolines is described in this study. Intramolecular cyclization of N-alkylated indoles was efficiently investigated as well. The reaction is catalyzed by bis (triphenylphosphine) palladium (II) dichloride in acetonitrile at 80 °C.     

Mechanistic study of fenoprofen photoisomerization to pure (S)-fenoprofen: a DFT study

Structural Chemistry - This work provides a comprehensive DFT study on the conversion mechanism and photoisomerization of the effective and commonly used nonsteroidal anti-inflammatory medicine...     

Order isomorphisms in cones and a characterization of duality for ellipsoids

We study order isomorphisms in finite-dimensional ordered vector spaces. We generalize theorems of Alexandrov, Zeeman, and Rothaus (valid for ??non-angular?? cones) to wide classes of cones, including in particular polyhedral cones, using a different and novel geometric method. We arrive at the following result: whenever the cone has more than n generic extremal vectors, an order isomorphism must be affine. In the remaining case, of precisely n extremal rays, the transform has a restricted diagonal form. To this end, we prove and use a new version of the well-known Fundamental theorem of affine geometry. We then apply our results to the cone of positive semi-definite matrices and get a characterization of its order isomorphisms. As a consequence, the polarity mapping is, up to a linear map, the only order-reversing isomorphism for ellipsoids.     

Solvent‐Induced Crystal Polymorphism as Studied by Pyroelectric Measurements and Impedance Spectroscopy: Alcohols as Tailor‐Made Inhibitors of α‐Glycine

Metastable polymorphs commonly emerge when the formation of the stable analogues is inhibited by using different solvents or auxiliaries. Herein, we report that when glycine is grown in aqueous solutions in the presence of low concentrations of different co‐solvents, only alcohols and acetone, unlike water and acetic acid, are selectively incorporated in minute amounts within the bulk of the α‐polymorph. These findings demonstrate that although water binds more strongly to the growing face of the crystal, alcohols and acetone are exclusively incorporated, and thus serve as efficient inhibitors of this polymorph, leading to the precipitation of the β‐form. These solvents then create polar domains detectable by pyroelectric measurements and impedance spectroscopy. These results suggest that in the control of crystal polymorphism with co‐solvents, one should consider also the different desolvation rates in addition to the energy of binding to the growing faces of the crystal.     

Magnetic Fe3O4 nanoparticles supported imine/Thiophene‐nickel (II) complex: A new and highly active heterogeneous catalyst for the synthesis of polyhydroquinolines and 2, 3‐dihydroquinazoline‐4(1H)‐ones

A new magnetically separable nickel catalyst (Ni(NO₃)_2?Imine/Thiophene‐Fe₃O₄@SiO₂) was readily prepared and structurally characterized by Fourier transform infrared spectroscopy (FT‐IR), Scanning electron microscopy (SEM), Energy‐dispersive X‐ray spectroscopy (EDX), Vibrating sample magnetometer (VSM), X‐Ray diffraction (XRD) and Atomic absorption spectroscopy (AAS). The Ni(NO₃)_2?Imine/Thiophene‐Fe₃O₄@SiO₂ exhibited efficient catalytic activity in the synthesis of 2,3‐dihydroquinazoline‐4(1H)‐ones and polyhydroquinolines. Catalysis research under water and solvent‐free conditions makes also this synthetic protocol ideal and fascinating from the environmental point of view. The catalyst can be magnetically recovered after the reaction and can be reused for many times without appreciable decrease in activity.     

Quantitative structure-activity relationship analysis of β-amyloid aggregation inhibitors

Inhibiting the aggregation process of the β-amyloid peptide is a promising strategy in treating Alzheimer’s disease. In this work, we have collected a dataset of 80 small molecules with known inhibition levels and utilized them to develop two comprehensive quantitative structure–activity relationship models: a Bayesian model and a decision tree model. These models have exhibited high predictive accuracy: 87% of the training and test sets using the Bayesian model and 89 and 93% of the training and test sets, respectively, by the decision tree model. Subsequently these models were used to predict the activities of several new potential β-amyloid aggregation inhibitors and these predictions were indeed validated by in vitro experiments. Key chemical features correlated with the inhibition ability were identified. These include the electro-topological state of carbonyl groups, AlogP and the number of hydrogen bond donor groups. The results demonstrate the feasibility of the developed models as tools for rapid screening, which could help in the design of novel potential drug candidates for Alzheimer’s disease.     

Heterogeneous Electrofreezing of Super‐Cooled Water on Surfaces of Pyroelectric Crystals is Triggered by Trigonal Planar Ions

Electrofreezing experiments of super‐cooled water (SCW) with different ions, performed directly on the charged hemihedral faces of pyroelectric LiTaO₃ and AgI crystals, in the presence and in the absence of pyroelectric charge are reported. It is demonstrated that bicarbonate (HCO₃^?) ions elevate the icing temperature near the positively charged faces. In contrast, the hydronium (H₃O⁺) slightly reduces the icing temperature. Molecular dynamics simulations suggest that the hydrated trigonal planar HCO₃^? ions self‐assemble with water molecules near the surface of the AgI crystal as clusters of slightly different configuration from those of the ice‐like hexagons. These clusters, however, have a tendency to serve as embryonic nuclei for ice crystallization. Consequently, we predicted and experimentally confirmed that the trigonal planar ions of NO₃^? and guanidinium (Gdm⁺), at appropriate concentrations, elevate the icing temperature near the positive and negative charged surfaces, respectively. On the other hand, the Cl^? and SO₄^2? ions of different configurations reduce the icing temperature.     

Chemoselective Oxidation of Benzylic Alcohols and Hydroquinones with bis-(2,4,6-Trimethylpyridinium) Dichromate (BTMPDC) as an Efficient and New Oxidizing Agent

A simple, efficient, and chemoselective oxidation of benzylic alcohols to the corresponding aldehydes and ketones and also hydroquinones to the benzoquinones using bis-(2,4,6-trimethylpyridinium) dichromate (BTMPDC) in acetonitrile is described. A good range of primary and secondary benzylic alcohols and a limited range of hydroquinones were selectively oxidized under reflux conditions in reasonable yields.