The development of synthetic host-guest chemistry to investigate and quantify weak, non-covalent interactions has been key to unraveling the complexity of molecular recognition in chemical and biological systems. Macrocycles have shown great utility in the design of receptors, enabling the development of highly preorganized structures. Among macrocycles, resorcin[4]arene-based cavitands have become privileged scaffolds due to their synthetic tunability, which allows access to structures with precisely defined geometries, as well as receptors that display conformational switching between two distinct states with a large difference in guest-binding properties. Here, we highlight three case studies demonstrating redox- and photoredox-controlled switching of molecular recognition properties, the formation of guest-binding supramolecular capsules based solely on halogen-bonding interactions, and enantioselective encapsulation of chiral, substituted cyclohexanes by enantiopure cage compounds as a result of perfect shape complementarity, dispersion interactions, and halogen bonding. The high geometrical and conformational control that can be achieved with resorcin[4]arene-derived host systems will continue to be a powerful resource in future molecular recognition studies.

The Z-selective cross metathesis of allylic-substituted olefins is explored with recently developed ruthenium-based metathesis catalysts. The reaction proceeds with excellent stereoselectivity for the Z-isomer (typically >95%) and yields of up to 88% for a variety of allylic substituents. This includes the first synthesis of Z-α,β-unsaturated acetals by cross metathesis and their elaboration to Z-α,β-unsaturated aldehydes. In addition, the reaction is tolerant of a variety of cross partners, varying in functionality and steric profile.

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