Sydnones are highly stable mesoionic 1,3‐dipoles that react with cyclooctynes through strain‐promoted sydnone‐alkyne cycloaddition (SPSAC). Although sydnones have been shown to be valuable bioorthogonal chemical reporters for the labeling of proteins and complex glycans, nucleic acids have not yet been tagged by SPSAC. Evaluation of SPSAC kinetics with model substrates showed fast reactions with cyclooctyne probes (up to k =0.59 M −1 s −1 ), and two different sydnones were effectively incorporated into both 2’‐deoxyuridines at position 5, and 7‐deaza‐2’‐deoxyadenosines at position 7. These modified nucleosides were synthetically incorporated into single‐stranded DNAs, which were successfully postsynthetically labeled with cyclooctyne probes both in vitro and in cells. These results show that sydnones are versatile bioorthogonal tags and have the premise to become essential tools for tracking DNA and potentially RNA in living cells.

Stepwise metalation and metathesis reactions with a bulky aminocarbazole were conducted to prepare derivatives of tetravalent group 14 elements. These were regarded as putatively suitable precursors for the formation of doubly bonded group 14/group 15 molecules such as imino species. Starting from an N‐aminocarbazole, deprotonation with benzyl potassium formed the corresponding solvent‐free dimeric amide. Metathesis reactions with EBr4 (E=Si, Ge, Sn) afforded RN(H)EBr3. Deprotonation of RN(SiMe3)H with benzyl potassium afforded the solvent‐free monomeric amide RN(SiMe3)K which was then treated with SiCl4, GeBr4 and SnI4. Both obtained series of compounds, RN(H)EBr3 and RN(SiMe3)EX3, were characterized by multinuclear NMR spectroscopy and SCXRD studies.

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