Chiral Brønsted acid-catalyzed asymmetric dearomative spirocyclization of alkynyl thioethers

The regioselective transformation of alkynes represents a highly efficient bond-forming strategy in organic synthesis. However, the enantiocontrol in the conversion of alkynes remains challenging, especially for the metal-free approach. Herein, we describe a chiral Bronsted acid-catalyzed enantioselective spirocyclization of alkynyl thioethers via dearomatization of phenols. This metal-free protocol leads to the green and atom-economical preparation of chiral spiro[4.5]decan-6-ones in good to excellent yields with high enantioselectivities. Importantly, this protocol represents the first metal-free example of the asymmetric transformation of alkynyl thioethers. A chiral Bronsted acid-catalyzed asymmetric dearomative spirocyclization of alkynyl thioethers has been developed, leading to the green and atom-economical preparation of chiral sprio[4.5]decan-6-ones in good yields with high enatioselectivities.