Flow dearomatization of electron-poor 3-fluoromethylthioindoles by 1,3-dipolar cycloaddition

Indoles substituted by electron-depleted thio groups at positions 1 and 3 react as C2 = C3 dipolarophiles with an electron-rich azomethine ylide dipole under flow conditions. The dearomatizing (3 + 2) cycloadditions readily occur to afford the corresponding fluorinated 3D-pyrrolidinoindolines bearing a tetrasusbtituted carbon centre at the ring junction.