A new,convenient and expeditious synthesis of 4-alkyl-5-methyl-1H-pyrazol-3-ols in water through a multicomponent reaction

A new, simple and efficient synthesis of 4-alkyl-5-methyl-1H-pyrazol-3-ols in water by a two-pot four component reaction of ethyl acetoacetate, hydrazine hydrate, aldehyde and ketone in presence K₂CO₃ as the catalyst is described. Use of water as the reaction medium, operational simplicity, mild reaction conditions, application of a cost-effective, nontoxic and easily available catalyst with auto-tandem catalysis, wide substrate scope, easy workup and purification process make the protocol highly attractive.     

A Cheap One-Pot Approach to Tetraethyl Methylenediphosphonate

A cheap procedure for the preparation of tetraethyl methylene-diphosphonate is described.     

Reaction of selenium dioxide with aromatic ketones in the presence of boron triflouride etherate: a protocol for the synthesis of triarylethanones

An efficient regioselective protocol for the C-C bond formation by the unexpected α,α-diarylation of aromatic ketones with unactivated arenes in the presence of selenium dioxide and boron trifluoride etherate has been developed. The generality and functional tolerance of this protocol is demonstrated by the synthesis of a series of triarylethanones.     

New Alq3 derivatives with efficient photoluminescence and electroluminescence properties for organic light-emitting diodes

Two new ligands prepared under solvent free conditions and five aluminum complexes derived from 8-hydroxyquinoline have been synthesized and characterized. The majority of the new aluminum tris(8-hydroxyquinoline) derivatives have nitrogen functionalities at position-4 of the quinolate ligand. The photoluminescence emission wavelengths of the new Alq₃ derivatives are shifted according to the electronic properties of the substituents at position-4. Results from differential scanning calorimetry (DSC) investigations of the new Alq₃ derivatives indicate that the complexes 9 and 10 are non crystalline and have higher transition glass temperatures than the parent Alq₃. The EL measurements of OLED devices with complexes 7, 9, and 10 as emitters revealed that complexes 7, 9, and 10 are efficient emitters in organic light emitting diodes.     

Cationic wood cellulose films with high strength and bacterial anti-adhesive properties

In this work, periodate oxidized birch wood pulp and microfibrillated cellulose (MFC) were cationized using Girard’s reagent T or aminoguanidine. Cationic celluloses were used to obtain films via solvent-casting method, and the effects of the cationization route and the cellulose fiber source on the properties of the films were studied. Thermal and optical properties of the films were measured using differential scanning calorimetry and UV–Vis spectrometry, and the morphology of the films was examined using an optical microscope and a field emission scanning electron microscope. Bacterial anti-adhesive properties of the films were also studied using a modified leaf print method and against Staphylococcus aureus and Escherichia coli. Both cationizing agents exhibited similar reactivity with periodate oxidized celluloses, however, MFC had significantly higher reactivity compared to birch pulp. The films with high tensile strength (39.1–45.3 MPa) and modulus (3.5–7.3 GPa) were obtained from cationized birch pulp, aminoguanidine modification producing a film with slightly better mechanical properties. Modulus of the films was significantly increased (up to 14.0 GPa) when MFC was used as a cellulose fiber source. Compared to the unmodified MFC films, the cationic MFC films were less porous and significantly more transparent; however, they had slightly lower tensile strength values. It was found that aminoguanidine modified celluloses had no culturable bacteria on its surface and also exhibited resistance to microbial degradation, whereas there were culturable bacteria on the surface of Girard’s reagent modified films and they were partially degraded by the bacteria.     

Acid-base titrations of schiff bases in deuteriomethanol as studied by1H NMR

The Schiff bases of salicylaldehyde and pyridoxal 5-phosphate with amino compounds were studied by¹H NMR in CD₃OD by using a glass electrode for the control of acidity. This study makes a new contribution for the elucidation of the structures of pyridoxylidene Schiff bases and gives additional data on the¹H NMR of the compounds that have not been available from the related studies in aqueous solutions.     

Synthesis of 8‐hydroxyquinolines with amino and thioalkyl functionalities at position 4

Six 8‐hydroxyquinolines with amino and thioalkyl functionalities at position 4 have been prepared. The synthesis starts with chlorination of the readily available 4‐hydroxy‐8‐tosyloxyquinoline to give 4‐chloro‐8‐tosyloxyquinoline in 94% yield. Treatment of the 4‐chloro‐8‐tosyloxyquinoline with sulphur and nitrogen nucleophiles produces the target 4‐amino and 4‐thioalkyl‐8‐hydroxyquinolines in more than 70% yield. In case of sulphur nucleophiles and pyrrolidine, the removal of the protecting tosyl group at position 8 occurs simultaneously with the substitution of chlorine at position 4.     

On the hydrolysis step in osmium catalyzed asymmetric dihydroxylations

In order to obtain information about the most important features that affect the efficiency of osmium catalyzed asymmetric dihydroxylation, a series of substituted styrenes have been studied by using a Hammett type approach as well as solvent kinetic isotope effects. A concave shaped Hammett plot with a minimum at X=H revealed a change in the mechanism going from electron-donating to electron-withdrawing substituents for both NaClO2 and K3[Fe(CN)6] asymmetric dihydroxylations. The Hammett plot together with solvent isotope effect results indicates that osmium (mono)glycolates of styrenes with electron-withdrawing substituents are hydrolyzed by a stepwise attack of the nucleophile to the electrophilic osmium-center and subsequent protonation of the alkaline intermediate. Osmium (mono)glycolates in dihydroxylation, using NaClO2 as the stoichiometric oxidant of styrenes with electron-donating substituents, are hydrolyzed by specific acid catalysis. The rate-limiting step is an A1 type process. Differences in the rho values in the Hammett plots for NaClO2 and K3[Fe(CN)6] asymmetric dihydroxylations indicate that in dihydroxylations with NaClO2 as the secondary oxidant, the reactive osmium(VI) mono(glycolate) is oxidized to osmium(VIII) mono(glycolate) prior to hydrolysis. The reaction rate was found to have an effect on the enantioselectivity in asymmetric dihydroxylation. If the hydrolysis step is slow enough, a competitive bis(glycolation) deteriorates the enantioselectivity in K3[Fe(CN)6] asymmetric dihydroxylations and even more so in NaClO2 asymmetric dihydroxylations.