Intramolecular Pd-Catalyzed Formal anti-Carboalkoxylation of Alkynes: Access to Tetrasubstituted Enol Ethers.

An intramolecular Pd-catalyzed formal anti-carboalkoxylation reaction is presented that provides access to tetrasubstituted enol ethers. The key to success is a cascade consisting of a formal anti-carbopalladation of a carbon-carbon triple bond followed by a nucleophilic attack of a hydroxy group at the emerging vinyl organopalladium species. The desired transformation proceeded smoothly with primary, secondary, and tertiary alcohols, and even with phenols. Depending on the substitution pattern of the enol ethers, a further Tsuji-Trost-type step may occur resulting in oligocyclic ketals.