Synthesis and Characterization of 5‐Cyanotetrazolide‐Based Ionic Liquids

New salts based on imidazolium, pyrrolidinium, phosphonium, guanidinium, and ammonium cations together with the 5‐cyanotetrazolide anion [C₂N₅]^? are reported. Depending on the nature of cation–anion interactions, characterized by XRD, the ionic liquids (ILs) have a low viscosity and are liquid at room temperature or have higher melting temperatures. Thermogravimetric analysis, cyclic voltammetry, viscosimetry, and impedance spectroscopy display a thermal stability up to 230 °C, an electrochemical window of 4.5 V, a viscosity of 25 mPa s at 20 °C, and an ionic conductivity of 5.4 mS cm^?1 at 20 °C for the IL 1‐butyl‐1‐methylpyrrolidinium 5‐cyanotetrazolide [BMPyr][C₂N₅]. On the basis of these results, the synthesized compounds are promising electrolytes for lithium‐ion batteries.     

Iridium-catalyzed regio- and enantioselective allylation of ketone enolates

The regio- and enantioselective alpha-allylation of unstabilized ketone enolates with unsymmetrical allylic carbonates to form the branched substitution products in the presence of metallacyclic iridium catalysts is reported. The products, branched gamma,delta-unsaturated ketones, were obtained from readily available silyl enol ethers and achiral Boc-protected allylic alcohols in high regioselectivities and enantioselectivities (91-96% ee). The combination of CsF and ZnF2 was shown to promote this reaction and suppress the formation of diallylation byproducts. In addition, iridium complexes derived from simple phosphoramidite ligands were shown to catalyze this reaction with excellent selectivities, and spectroscopic data show that a cyclometalated Ir precatalyst is formed in situ. This process provides an enantioselective access to synthetically important bifunctional compounds, which are generally accessible, but in racemic form, through Claisen rearrangements. Ten examples of the reactions of aromatic, as well as aliphatic, substrates are reported.     

Markierungsexperimente zur fragmentierung von 1,2,3-thiadiazolen

The generation of thiirenes in the thermal and photochemical nitrogen elimination of 1,2,3-thiadiazoles is discussed in relation to oxirene formation. Isotope labelling experiments were performed with 4-phenyl-[4-¹³C]-1,2,3-thiadiazole ( 7 ) as the substrate.     

Determination of an aldosterone antagonist in urine by high-performance liquid chromatography using automated column switching

An automated high-performance liquid chromatographic assay for the determination of an aldosterone antagonist (I) is described using column switching for direct injection of urine samples. After dilution with buffered internal standard solution, the sample was injected onto a clean-up column (17 X 4.6 mm I.D.), dry-packed with C18 reversed-phase material (particle size 30 micron). Polar urine components were removed by flushing the clean-up column with water. Retained substances, including I and the internal standard, were desorbed by backflush elution onto a 5-micron ODS-silica analytical column (125 X 4 mm I.D.), separated with water-methanol-tetrahydrofuran, and detected at 295 nm. After backflushing the analytical column and re-equilibrating the clean-up column, the system was ready for the next injection. The limit of quantification was ca. 100 ng/ml, using a 100-microliter specimen of diluted urine. The mean inter-assay precision of the method up to 25.6 micrograms/ml was 2%. Practicability and accuracy of the new method were demonstrated by the application to excretion studies performed with human volunteers.