Synthesis of Eight‐Membered Lactones: Intermolecular [6+2] Cyclization of Amphoteric Molecules with Siloxy Alkynes

That's about the size of it : The title molecules react with siloxy alkynes in the presence of a Brønsted acid to deliver medium‐sized lactones through a [6+2] cyclization (see scheme; TIPS=triisopropylsilyl). This process is the first intermolecular synthesis of such lactones and involves a sequence of several selective ring‐opening/ring‐closing events.