Stereoelectronic Model To Explain Highly Stereoselective Reactions of Seven‐Membered‐Ring Oxocarbenium‐Ion Intermediates

Nucleophilic attack on seven-membered-ring oxocarbenium ions is generally highly stereoselective. The preferred mode of nucleophilic attack forms the product in a conformation that minimizes transannular interactions, thus leading to different stereoselectivity as compared to that of reactions involving six-membered-ring oxocarbenium ions.