Access to Polycyclic Thienoindolines via Formal [2+2+1] Cyclization of Alkynyl Indoles with S₈ and K₂S

The syntheses of polycyclic thienoindolines bearing a dihydrothiophene or tetrahydrothiophene subunit have not been reported, despite the fact that such compounds may have interesting medicinal properties. Herein, we report a protocol for accessing polycyclic dihydrothiophenes by means of formal [2+2+1] intramolecular dearomatizing cyclization of alkynyl indoles with K2S and S8 as the sources of sulfide. In addition, tetrahydrothienoindolines...