Selectfluor‐Mediated N‐Methylation, N‐Methylenesulfonylmethylation and Methylenethiomethylation of Isatins in Dimethyl Sulfoxide

Dimethyl sulfoxide as a reagent and solvent in Selectfluor mediated transformations of isatin is reported. The transformations include N ‐methylation and N ‐methylenesulfonylmethylation of isatin at 100 °C whereas N ‐methylenethiomethylation was observed at 140 °C in addition to N ‐methylation and N ‐methylenesulfonylmethylation of isatins. Electron withdrawing and releasing substituents on isatin were tolerated. Interestingly, dual ( N ‐ and C −)methylenethiomethylation was observed in case of 7‐Bromo‐ and 7‐Iodo isatins at 140 °C. This protocol efficiently afforded various isatin analogs using DMSO/Selectfluor system.