Cytotoxicity profiling of the in situ generated 1F to 39F using a double-dose cell-viability assay. (A) Thirty-nine in situ SuFEx generated fluorosulfurylation products 1F-39F were tested in a cell viability assay with MCF-7 and A549 cells at the final concentrations of 20 μM and 500 nM. After a 72 h treatment, the cytotoxicity of fluorosulfurylation products 1F-39F and their phenol precursors 1–39 were evaluated according to the viability of the compound treated cancer cells relative to that of the vehicle (DMSO) treated control. The color of each unit in the heat maps reflects the increase (red) or decrease (blue) of the cytotoxicity of the corresponding fluorosulfurylation product compared to its phenol precursor (n = 3). (B) Cancer cell viabilities under the treatment of in situ generated 1F, 11F, and 25F and their phenol parents at a final concentration of 20 and 500 nM for 72 h. Cells treated with DMSO (0.2%) as the vehicle control. The structures of 1F, 11F, and 25F were confirmed by NMR after flash column chromatography purification. P-Values were calculated using two-way ANOVA. Error bars represent the mean ± SEM (n = 3); ns: P ≥ 0.05; *P ≤ 0.1; ** P ≤ 0.01; *** P ≤ 0.001; **** P ≤ 0.0001.