Synthesis of Benzo[ <i>b</i> ]thiophene 1,1-Dioxides via Pd-Catalyzed Sulfinylation of Aryl Triflates and Their Use as Large Stokes Shift Fluorophores for Multicolor Live-Cell Imaging with Self-Labeling Tags

]-thiophene 1,1-dioxides, including 6-dialkylamino "push-pull" type fluorophores possessing large (>140 nm) Stokes shifts. Fluorescent labels derived from this core structure are compatible with live-cell imaging using self-labeling protein tags (HaloTag, SNAP-tag, and CLIP-tag). Together with the established live-cell fluorescent labels and orthogonal self-labeling tags, they allow for simultaneous observation of up to three intracellular targets below the diffraction limit using fluorescence microscopy with three excitation lasers (485, 561, and 640 nm) and stimulated emission depletion (STED) at 775 nm.