Electronic and steric substituent effects on the fluorescence emission of 2-pyrazoline derivatives.

A series of substituted 2-pyrazolines were synthesized, and the steric and electronic effects of substituents on the C - and C -positions of the heterocyclic ring on their fluorescent ability were investigated. Two different conjugative intramolecular charge transfer (ICT) and intramolecular charge transfer through space (spiro-conjugation) affect the fluorescence intensity of these compounds. The extent of the ICT process and spiro-conjugation depends on the electronic nature of the additional substitution and its position on the attached aryl rings.

Photooxidation of 2,3-dihydroquinazolin-4(1H)-ones: retention or elimination of 2-substitution.

A series of mono and disubstituted 2,3-dihydroquinazolin-4(1H)-ones (DHQZs) were synthesized and the electronic and steric effects of the C- and N-substitutions on the retention or elimination of the C-substitution by exposing them to the ultraviolet light were investigated. Electron transfer from photo-excited dihydroquinazolinones to chloroform solvent is proposed, in which both lone pairs on the N- and N-atoms can be involved in this process. The extent of the N- and N-atoms contributions in this electron-transfer process and also the retention or elimination of the C-substitutions are dependent on the nature and steric hindrance of both C- and N-substitutions.

Cyclic Voltammetric Study of 3,5-Diaryl-1-phenyl-2-pyrazolines.

Cyclic voltammetry is used to derive HOMO energies of the 1-phenyl-2-pyrazolines containing electron-donating or electron-withdrawing substituted phenyl rings and or naphthalenyl substitution on the C- or C-positions of the heterocyclic ring to investigate the steric and electronic effects of the aryl substitutions and the type of aryl system on their electrochemical behaviors. The optical HOMO-LUMO gaps needed for the calculation of LUMO (excited state) energies of these compounds are obtained from their UV-vis spectra. Results show that the substitution on the C-aryl ring has significant effect via its π-donor/acceptor ability, compared to the σ-donor/acceptor ability of the C-aryl ring, on the CV oxidation peak and onset potentials.

Thermal electron-transfer-induced oxidation of 2-pyrazolines.

Various 3,5-diaryl-1-phenyl-2-pyrazolines were synthesized, and their thermal oxidation to their corresponding 2-pyrazoles was investigated using tetrabutylammonium peroxydisulfate in acetonitrile solution. Compared to the reported oxidative methods, this oxidizing agent provides a clean and non-expensive oxidative reaction in a short reaction time. Based on the proposed reaction mechanism, the extent of co-planarity of the C-aryl ring toward C=N double bond of the heterocyclic ring affects the electron-donating ability of the heterocyclic ring and decreases the time of oxidative reaction.

Synthesis, Molecular Modelling and Biological Studies of 3-hydroxypyrane- 4-one and 3-hydroxy-pyridine-4-one Derivatives as HIV-1 Integrase Inhibitors.

Background: Despite the progress in the discovery of antiretroviral compounds for treating HIV-1 infection by targeting HIV integrase (IN), a promising and well-known drug target against HIV-1, there is a growing need to increase the armamentarium against HIV, for avoiding the drug resistance issue.

Objective: To develop novel HIV-1 IN inhibitors, a series of 3-hydroxy-pyrane-4-one (HP) and 3- hydroxy-pyridine-4-one (HPO) derivatives have been rationally designed and synthesized.

Methods: To provide a significant characterization of the novel compounds, in-depth computational analysis was performed using a novel HIV-1 IN/DNA binary 3D-model for investigating the binding mode of the newly conceived molecules in complex with IN.