This presentation has highlighted the value of ACE, aza-ACE and s-tetrazine coupling reactions for the stereoselective preparation of rigid alicyclic structures based on the fusion of norbornenes and 7-hetero norbornenes. In particular, we have demonstrated a new approach to the synthesis of polarofacial molecules where the polar groups originate from the 7-hetero substituent of the component norbornenes. These same BLOCK coupling reactions have been applied with considerable success to the synthesis of U-shaped cavity molecules. By judicious incorporation of functionality, it has been possible to introduce units such as crown ethers into the molecular structures with a full understanding of their positioning, geometry and shape.

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7. Acknowledgements