Visible-light-induced photocatalytic formyloxylation reactions of 3-bromooxindoles with water and DMF: the scope and mechanism

The formyloxylation reaction of 3-bromooxindoles with water and N,N-dimethylformamide (DMF) has been developed in the presence of the photoredox catalyst fac-Ir(ppy)3 under irradiation of visible light at ambient temperature. The reaction provides a straightforward approach to pharmaceutically and synthetically useful 3-formyloxyoxindoles in high yields. The mechanism of this transformation was investigated by fluorescence quenching experiments, “on–off” switching of the light source, labeling experiments, mass spectral analyses and in situ IR experiments.