Rh(iii)-catalyzed redox-neutral C–H [4 + 1] annulation of sulfoximines with α,α-difluoromethylene alkynes: diastereoselective synthesis of E-monofluoroalkenyl benzoisothiazole 1-oxides†

Novel cyclic fluorinated sulfoximines featuring an E-monofluoroalkenyl benzoisothiazole 1-oxide moiety as single diastereomers can be facilely accessed by Rh(III)-catalyzed redox-neutral [4 + 1] annulation of sulfoximines with α,α-difluoromethylene alkynes. The reaction proceeds with sequential selective cleavage of both C–H and C–F bonds, thus exhibiting high step and atom economy. Through a combined experimental and computational mechanistic study, the origins of annulative chemoselectivity, unconventional E-selectivity, and excellent diastereoselectivity have been revealed accordingly.