Studies on cardiotonic agents. IV. Synthesis of novel 1-(6,7-dimethoxy-4-quinazolinyl)piperidine derivatives carrying substituted hydantoin and 2-thiohydantoin rings

A series of novel 1-(6,7-dimethoxy-4-quinazolinyl)piperidines carrying substituted hydantoin and 2-thiohydantoin rings was synthesized and examined for cardiotonic activity in anesthetized dogs. Introduction of isopropyl and sec-butyl group at the 5-position of the hydantoin and thiohydantoin rings led to potent inotropic activity. Effects of insertion of an alkyl chain between the piperidine and the hydantoin rings were also examined. The structural requirements necessary for optimal cardiotonic activity within the series were investigated.     

A Spin‐Active,Electrochromic, Solvent‐Free Molecular Liquid Based on Double‐Decker Lutetium Phthalocyanine Bearing Long Branched Alkyl Chains

Synthesis and characterization of a novel, multifunctional, solvent‐free room‐temperature liquid based on alkylated double‐decker lutetium(III) phthalocyanine (Pc₂Lu) are described. Lowering of the melting point and viscosity of intrinsically solid Pc₂Lu compounds has been achieved through the attachment of flexible, bulky, and long branched‐alkyl chains, that is, thio‐2‐octyldodecyl, to the periphery of the Pc₂Lu unit. The embedded Pc₂Lu unit maintains its inherent molecular functions, such as spin‐active nature and electrochromic behavior in the liquid state. Comparison of the properties with a solid‐like Pc₂Lu derivative, functionalized with shorter alkyl chains, that is, thio‐2‐ethylhexyl, underlines the importance of the hampering effect on the π–π interactions of neighboring Pc₂Lu molecules by bulkier and longer branched‐alkyl chains. This study could possibly pave the way for novel multifunctional liquids whose spin‐activities are associated with their rheological or optoelectronic properties.     

Enhanced Electron‐Transfer Properties of Cofacial Porphyrin Dimers through π–π Interactions

π–π assisted : Photoinduced electron transfer from cofacial porphyrin dimers to electron acceptors is prominently accelerated, whereas the back electron transfer is decelerated, relative to the corresponding porphyrin monomer (see figure).

     

Iridium‐Catalyzed Intermolecular Dehydrogenative Silylation of Polycyclic Aromatic Compounds without Directing Groups

This study describes the iridium‐catalyzed intermolecular dehydrogenative silylation of C(sp²)?H bonds of polycyclic aromatic compounds without directing groups. The reaction produced various arylsilanes through both Si?H and C?H bond activation, with hydrogen as the sole byproduct. Reactivity was affected by the electronic nature of the aromatic compounds, and silylation of electron‐deficient and polycyclic aromatic compounds proceeded efficiently. Site‐selectivity was controlled predominantly by steric factors. Therefore, the current functionalization proceeded with opposite chemo‐ and site‐selectivity compared to that observed for general electrophilic functionalization of aromatic compounds.     

Stability of dispersions of colloidal alumina particles in aqueous suspensions

The colloidal stability of suspensions of alumina particles has been investigated by measuring particle size distribution, sedimentation, viscosity, and zeta potential. Alumina particles were found to be optimally dispersed at pH around 3 to 7.8 without dispersant and at pH 8.5 and beyond with dispersant. The above results corroborate zeta potential and viscosity measurement data well. The surface charge of alumina powder changed significantly with anionic polyelectrolyte (ammonium polycarboxylate, APC) and the iep shifted toward more acidic range under different dispersant conditions. It was found that the essential role played by pH and dispersant (APC) on the charge generation and shift in the isoelectric point of alumina manifests two features: (i) the stability decreases on approaching the isoelectric point from either side of pH, and (ii) the maximum instability was found at pH 9.1 for alumina only and at pH 6.8 for alumina/APC, which is close to the isoelectric points for both the system, respectively. Using the model based on the electrical double-layer theory of surfactant adsorption through shift in isoelectric points, the authors could estimate the specific free energy of interaction (7.501 kcal/mol) between particles and dispersant. The interaction energy, zeta potential, sedimentation, and viscosity results, were used to explain the colloidal stability of the suspension.     

Rhenium‐ and Manganese‐Catalyzed Insertion of Alkynes into a Carbon–Carbon Single Bond of Cyclic and Acyclic 1,3‐Dicarbonyl Compounds

Treatment of alkynes with cyclic and acyclic 1,3‐dicarbonyl compounds in the presence of a catalytic amount of a rhenium or manganese complex gives ring‐expanded and carbon‐chain extension products, respectively. In these reactions, alkynes insert into a non‐strained carbon–carbon single bond of 1,3‐dicarbonyl compounds. The ring‐expansion reaction is also promoted by the addition of 4‐Å molecular sieves instead of a catalytic amount of an isocyanide.