Anionic Cascade Reaction Followed by Silylative Dieckmann Cyclization: A Straightforward Route to Tricyclic Fused Ring Systems Starting from Alkynyl Esters Tethered to Bicyclo[n.2.0]alkanones
The successive addition of sodiumethoxide and TBSOTf (or TMSOTf) to alkynyl esters tethered to bicyclo[n.2.0]alk-anones (n = 3-5) promoted a domino anionic reaction and a Dieckmann condensation, respectively, which led to 5-6-5, 6-6-5, and 7-6-5 tricyclic fused ring systems. These systems represent relevant substructures of numerous bioactive compounds.