Access to Tetrahydrothiopyrano[2,3‐b]Indole Derivatives via Zinc‐Catalyzed Asymmetric [3+3] Annulation of Indoline‐2‐Thiones with Yne–Enones

Abstract

AbstractWe report herein an enantioselective [3+3] annulation of indoline‐2‐thiones with yne–enones by chiral dinuclear zinc catalysts via a Brønsted base and Lewis acid cooperative activation model. This transformation proceeded through sequential conjugate addition, allenyl ketone formation and intramolecular sulfa‐Michael 6‐endo‐trig cyclization. A range of enantioenriched tetrahydrothiopyrano[2,3‐b]indole derivatives bearing an exocyclic double bond were obtained in moderate yields with excellent stereoselectivities (up to 20 : 1 dr, 20:1 Z/E ratio and 95% ee). Late‐stage functionalization, large‐scale experiment and further derivatizations were also explored.