Synthesis and Structural Characterization of Some New Magnesium Formamidinates

[Mg(Form)₂(THF)] [Form = bis(2,6‐dimethylphenyl)formamidinate (XylForm) ( 1 ), bis(2,6‐diethylphenyl)formamidinate, (EtForm) ( 2 ), bis(2,6‐diisopropylphenyl)formamidinate (DippForm) ( 3 )] are conveniently synthesized by treating bis(2,6‐dimethylphenyl)formamidine, bis(2,6‐diethylphenyl)formamidine, or bis(2,6‐diisopropylphenyl)formamidine, respectively, with half an equivalent of dibutylmagnesium in THF. Compounds 1 – 3 are mononuclear species in the solid state with five coordinate central metal atoms. The ¹H NMR chemical shift of the formamidinate formyl proton exhibits a correlation with ligand sterics wherein increasing bulk leads to a shift to higher field.     

Synthesis of 2‐Unsubstituted 1,3‐Selenazoles by Cyclization of Selenoformamide with α‐Bromocarbonyl Compounds

2‐Unsubstituted 1,3‐selenazoles were prepared by cyclization of selenoformamide with α‐bromoacetophenones. Parent 1,3‐selenazole was prepared by cyclization of selenoformamide with α‐bromoacetaldehyde.     

Thermal Stability and Molecular Ordering of Organic Semiconductor Monolayers: Effect of an Anchor Group

The thermal stability and molecular order in monolayers of two organic semiconductors, PBI‐PA and PBI‐alkyl, based on perylene derivatives with an identical molecular structure except for an anchor group for attachment to the substrate in PBI‐PA, are reported. In situ X‐ray reflectivity measurements are used to follow the stability of these monolayers in terms of order and thickness as temperature is increased. Films have thicknesses corresponding approximately to the length of one molecule; molecules stand upright on the substrate with a defined structure. PBI‐PA monolayers have a high degree of order at room temperature and a stable film exists up to 250 °C, but decomposes rapidly above 300 °C. In contrast, stable physisorbed PBI‐alkyl monolayers only exist up to 100 °C. Above the bulk melting point at 200 °C no more order exists. The results encourage using anchor groups in monolayers for various applications as it allows enhanced stability at the interface with the substrate.     

Antimicrobial activity of newly synthesized thienoquinolizidines derivatives: inspired by natural plant alkaloids

The antimicrobial activity of 16 newly prepared quinolizidines derivatives using bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Proteus sp., Escherichia coli) acid fast bacterium Mycobacterium smegmatis, yeasts (Candida albicans, Candida parapsilosis), and filamentous fungi (Fusarium culmorum, Microsporum gypseum, Aspergillus flavus, Botrytis cinerea, Alternaria alternata) was studied in this paper. The best antibacterial properties were demonstrated by derivatives 11Ba, trans10Bb and 11Bb, and the most sensitive microorganism was found to be the gram-positive bacterium S. epidermidis. The derivative 11Bb showed the best antifungal activity, while C. albicans was resistant to all tested derivatives, and C. parapsilosis was fully inhibited in the presence of the derivative 11Ba and 11Bb. Among the filamentous fungi, only the dermatophyte M. gypseum was partially inhibited. Biofilms represent the most prevalent type of microbial growth in nature and are crucial to the development of clinical infections. Newly synthesized derivatives were also added into the medium throughout the biofilm formation. We have observed a significant decrease of biofilm formation in the presence of quinolizidine derivatives, testifying to their significant antimicrobial activity. It seems that the relationship between antimicrobial activity and the structure is based on the alkaline character due to nitrogen, the saturated basic quinolizidine skeleton, and the position of sulfur in the molecule.     

Necessarily Incompatible Consistent Wants

This paper argues that the wants or desires of a person can be consistent with each other and still necessarily incompatible with each other and for interesting reasons. It is argued here that this problem is not rare and that there is no solution in sight.     

Synthesis of heterocycles from arylacetonitriles: Powerful tools for medicinal chemists

Arylacetonitriles are versatile building blocks for the construction of heterocyclic scaffolds in medicinal chemistry. These intermediates are able to engage in a variety of synthetic transformations, giving rise to diverse biologically active structures. This digest focuses on recent applications of this synthetic methodology by drug discovery teams across several disease areas, with an emphasis on different reaction types.     

Ionization Constants of DL-2-Aminobutyric Acid and DL-Norvaline Under Hydrothermal Conditions by UV–Visible Spectroscopy

The first and second ionization constants for the amino acids DL-2-aminobutyric acid (DL-2-aminobutanoic acid) and DL-norvaline (DL-2-aminopentanoic acid) were determined under hydrothermal conditions, from 175 to 275 °C at 10 MPa, using thermally-stable colorimetric pH indicators (acridine, 4-nitrophenol and 2-naphthoic acid). The measurements were carried out by UV–visible spectroscopy using a high-temperature, high-pressure platinum flow cell with sapphire windows, which minimized the effects of thermal decomposition. The results were combined with literature values from titration calorimetry at 25–130 °C to yield an extended van’t Hoff model for the temperature dependence of the ionization constants for the carboxylic acid and ammonium groups, \( K_{\text{a,COOH}} \) and \( K_{{{\text{a,NH}}_{3}^{ + } }} \), over the entire temperature range. The experimental results for the second ionization constant \( K_{{{\text{a,NH}}_{3}^{ + } }} \) at elevated temperatures are consistent with the predictions from the Yezdimer–Sedlbauer–Wood functional group additivity model, but for the first ionization constant \( K_{\text{a,COOH}} \) are not. This suggests that the group contribution parameters for the standard partial molar heat capacity of the carboxylic acid group are in error, or that nearest neighbor interactions between the –COOH and \( - {\text{NH}}_{3}^{ + } \) groups cause a breakdown in the functional group additivity relationship.