Biocompatible SuFEx Click Chemistry: Thionyl Tetrafluoride (SOF4) Derived Connective Hubs For Bioconjugation to DNA and Proteins.

We report here the development of a suite of biocompatible SuFEx transformations from the SOF4-derived iminosulfur oxydifluoride hub in aqueous buffer conditions. These biocompatible SuFEx reactions of iminosulfur oxydifluorides (R-N=SOF2) with primary amines give sulfamides (8 examples, up to 98 %), while the reaction with secondary amines furnish sulfuramidimidoyl fluoride products (8 examples, up to 97 %). Likewise, under mild buffered conditions, phenols react with the iminosulfur oxydifluorides (Ar-N=SOF2) to produce sulfurofluoridoimidates (13 examples, up to 99 %), which can themselves be further modified by nucleophiles. These transformations open the potential for asymmetric and trisubstituted linkages projecting from the sulfur(VI) center, including versatile S-N and S-O connectivity (9 examples, up to 94 %). Finally, the SuFEx bioconjugation of iminosulfur oxydifluorides to amine-tagged single-stranded DNA and to BSA protein demonstrate the potential of SOF4-derived SuFEx click chemistry in biological applications.