An Efficient Difluorohydroxylation of Indoles Using Selectfluor as a Fluorinating Reagent

An efficient difluorohydroxylation of substituted indoles leading to 3,3-difluoroindolin-2-ols with good yields by using Selectfluor as the electrophilic fluorinating reagent has been developed. In this methodology, the indole rings were difluorinated highly regioselectively at the C3 carbon site. This protocol is practically convenient, easily handled under mild conditions, and provides an efficient way to produce the unique difluorinated indolin-2-ol structure. When alcohols were used as the nucleophiles instead of H2O, the corresponding products were obtained in moderate yields. Based on the experimental observations, a plausible mechanism is proposed.