Molecular switches are ubiquitous in Nature and provide the basis of many forms of transport and signalling. Single synthetic molecules that change conformation, and thus function, reversibly in a stimulus-dependent manner are of great interest not only to chemists but society in general; myriad applications exist in storage, display, sensing and medicine. Here we describe recent developments in the area of ion-mediated switching.

This critical review offers an overview of asymmetric electrocyclic processes, where diastereo- or enantioselectivity is a consequence of the influence of a chiral component (be it substrate or catalyst) on the electrocyclic bond-forming process (195 references).

Molecules containing an atropisomeric C–N biaryl axis are gaining increasing attention in catalytic and medicinal chemistry. Despite this rising interest, relatively few approaches towards their catalytic enantioselective synthesis have been reported. Here we review these approaches, with a focus on the mechanism of asymmetric induction. Some common themes emerge: Brønsted acid catalysed cyclo-condensation and palladium-catalysed ring-closure are the most common and successful approaches. Meanwhile, the more direct but challenging axial C–N bond formation strategy remains in its infancy, with just two reports to-date. We hope this review will inform and inspire other researchers to develop new creative approaches to this important chemical motif.1 Introduction2 Cyclo-Condensation3 Proximal C–N Bond Formation4 Desymmetrisation of Intact Axes5 ortho-C–H Functionalisation6 Cycloaddition7 Axial C–N Bond Formation8 Atropisomeric N–N Axes: An Emerging Class of Heterobiaryls9 Conclusion and Outlook

A catalytic enantioselective electrocyclic cascade leads to the construction of topologically complex systems comprising multiple rings with up to three stereocentres. This phase-transfer catalysed process offers a new strategy for the rapid and enantioselective generation of complex products bearing all-carbon quaternary stereogenic centres.