Lewis acid-catalyzed intramolecular condensation of ynol ether-acetals. Synthesis of alkoxycycloalkene carboxylates

Treatment of ynol ether-tethered dialkyl acetals with catalytic quantities of scandium triflate in CH3CN gives rise to five-, six-, and seven-membered alkoxycycloalkene carboxylates in good to excellent yields. Trisubstituted and tetrasubsituted carbocyclic and heterocyclic alkenes may be formed by this method, and the products obtained may serve as useful intermediates for natural product synthesis.