Dynamic behavior is a fascinating property of natural and artificial systems and its understanding has significantly impacted the transformation of molecular interchanges into controlled molecular motion. In this tutorial, the key descriptors of enantiomeric stability are examined in-depth. Enantiomerization and racemization are discussed and differentiated on a fundamental level proposing a unified and distinct nomenclature. Their mathematical meanings and relations are described and deduced cohesively in the context of atropisomerization. The calculation of inversion barriers from thermodynamic and kinetic data is demonstrated and the interdependences between the latter are explained mathematically. Using current examples from our group, the determination of rate constants and the thermodynamic parameters is shown in a step-by-step manner using the most common techniques. The tutorial is concluded with aspects and considerations concerning statistical data analysis and error determination of measurements including a practical guide to Monte-Carlo simulations.

Macrocycle 1 is assembled as smallest member of a series of “Geländer” oligomers with a conjugated banister comprising exclusively sp2‐ and sp‐hybridized carbon atoms. The synthesis of 1 is based on an acetylene scaffolding approach, comprising Sonogashira cross‐coupling reactions in combination with protection group strategies and a final cyclization based on an oxidative acetylene coupling using Eglinton‐Breslow reaction conditions. Macrocycle 1 serves as model compound for the investigation of the structural integrity of the strained 1,3‐diyne subunit. An enhanced reactivity of the strained 1,3‐diyne subunit is documented by its engagement in Huisgen's (2+3) cycloaddition when exposed to an azide at elevated temperature. Both structures, macrocycle 1 and cycloaddition‐product 2, are fully characterized including their solid‐state structure obtained by X‐ray diffraction analysis.

The novel diacetylene bridged terphenylic macrocycle 1 is presented and discussed in the context of rotationally restricted “Geländer” oligomers. The 1,4‐bis(phenylbuta‐1,3‐diyn‐1‐yl) benzene bridge of diacetylene 1 is significantly longer than its terphenyl backbone, forcing the bridge to bend around the central pylon. The synthesis of molecule 1 is based to a large extent on acetylene scaffolding strategies, profiting from orthogonal alkyne protection groups to close both macrocyclic subunits by oxidative acetylene coupling sequentially. The spatial arrangement and the dynamic enantiomerization process of the bicyclic target structure 1 are analyzed. In‐depth NMR investigations not only reveal an unexpected spatial arrangement with both oligomer strands bent alongside the backbone, but also display the limited stability of the model compound in the presence of molecular oxygen.

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The Front Cover shows two macrocycles, one representing the smallest member of a series of “Geländer” oligomers with a conjugated banister comprising exclusively sp2‐ and sp‐hybridized carbon atoms, and the Huisgen's (2+3) cycloaddition analogue. Both molecules are surrounded by a water slide, representing the helicity of the two macrocycles. The banister of the diethynyl macrocycle shows a continuous helicity, whereas the banister of the cycloaddition product is distorted. More information can be found in the https://doi.org/10.1002/ejoc.201800586

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The Basel Chemistry SymposiumThe symposium was opened by Prof. Andreas Pfaltz with a short introduction on the impact of Prof. Reichstein on the development of the Chemistry Department and the pharma industry in Basel, including some personal reminiscences from the time when Prof. Reichstein was still active in the department as Emeritus.