Chiral compounds are ubiquitous in nature and play a pivotal role in biochemical processes, in chiroptical materials and applications, and as chiral drugs. The analysis and determination of the enantiomeric ratio (er) of chiral compounds is of enormous scientific, industrial, and economic importance. Chiral separation techniques and methods have become indispensable tools to separate chiral compounds into their enantiomers on an analytical as well on a preparative level to obtain enantiopure compounds. Chiral gas chromatography and high‐performance liquid chromatography have paved the way and fostered several research areas, that is, asymmetric synthesis and catalysis in organic, medicinal, pharmaceutical, and supramolecular chemistry. The development of highly enantioselective chiral stationary phases was essential. In particular, the elucidation and understanding of the underlying enantioselective supramolecular separation mechanisms led to the design of new chiral stationary phases. This review article focuses on the development of chiral stationary phases for gas chromatography. The fundamental mechanisms of the recognition and separation of enantiomers and the selectors and chiral stationary phases used in chiral gas chromatography are presented. An overview over syntheses and applications of these chiral stationary phases is presented as a practical guidance for enantioselective separation of chiral compound classes and substances by gas chromatography.
Fluoromethyl)triphenylphosphonium iodide has been prepared in a simple and high yield synthesis. The salt was characterized by vibrational, NMR spectroscopy and a single-crystal X-ray structure analysis. The salt crystallizes in an orthorhombic space group Pna2 1 with four formula units in the
Alkylations of simple electron-rich heterocompounds deliver valuable target structures in bioorganic and medicinal chemistry. Herein, we present a straightforward and photosensitizer free approach for the photoinduced CC coupling of electron-rich unsaturated heterocompounds with alkyl bromides using 405 nm and 365 nm irradiation. Comprehensive mechanistic studies indicate the involvement of 2,6-lutidine in the formation of a non-covalently bound intermediate to which the function of a photosensitizer is attributed. UV/Vis spectra reveal the formation of a bathochromic shifted band when the elec-[a
To understand chiral symmetry breaking on the molecular level, we developed a method to efficiently investigate reaction kinetics of single molecules. The model systems include autocatalysis as well as a reaction cascade to gain further insight into the prebiotic origin of homochirality. The simulated reactions start with a substrate and only a single catalyst molecule, and the occurrence of symmetry breaking was examined for its degree of dependence on randomness. The results demonstrate that interlocking processes, which e.g., form catalysts, autocatalytic systems, or reaction cascades that build on each other and lead to a kinetic acceleration, can very well amplify a statistically occurring symmetry breaking. These results suggest a promising direction for the experimental implementation and identification of such processes, which could have led to a shift out of thermodynamic equilibrium in the emergence of life.
The Front Cover shows the photosensitizer free, photoinduced C–C coupling of electron‐rich unsaturated heterocompounds with alkyl bromides using 405 nm and 365 nm irradiation. More information can be found in the Communication by O. Trapp et al.
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