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PdII‐catalyzed CN‐directed addition of isocyanides to C(sp2)–SMe bonds of thiophenes (generated in situ) effectively recycles the SMe activating group into thioimidate products. The catalytic sequence includes selective C(sp2)–SMe bond activation/migratory insertion of isocyanides into C(sp2)–PdIV and subsequent C(sp2)–SMe bond‐forming reductive elimination from imidoyl–PdIV–SMe complexes. Through these transition‐metal‐catalyzed addition reactions we have established isocyanides as a new template for atom‐transfer reactions. This groundbreaking research avoids the use of ancillary ligands that is a constant feature of all previously reported addition reactions with C–S bonds. This process proceeds through a high‐valent PdII/IV catalytic cycle, which – to the best of our knowledge – has not been previously reported in this regard. Isocyanide insertion into C(Ar)–S bonds through addition is also unprecedented. Finally, the resulting thioimidates were demonstrated to be convenient precursors for the synthesis of thieno[2,3‐c]pyrroles by targeting the recycled SMe group for the second time in a cascade reaction process.

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Despite the development of many novel carriers for the delivery of various types of genetic material, the lack of a delivery system with high efficiency and low cytotoxicity is a major bottleneck. Herein, low molecular weight polyethylenimine (PEI1.8k) was functionalized with saponin residues using phenylboronic acid (PBA) as an ATP-responsive cross-linker, and a fluorinated side chain to construct PEI-PBA-SAP-F polycation as a highly efficient delivery vector. This vehicle could transfect small plasmid DNA ( 3 kb) with outstanding efficiency into various cells, including HEK293T, NIH3T3, A549, PC12, MCF7 and HT-29, as well as robust transfection of a large plasmid ( 9 kb) into HEK293T cells. The carrier could maintain transfection efficacy even at high concentration of serum and low doses of plasmid. The use of green fluorescent protein (GFP) knock-out analysis demonstrated transfection of different types of CRISPR/Cas9 complexes (Cas9/sgRNA ribonucleoproteins RNP, plasmid encoding Cas9 plus sgRNA targeting GFP, Cas9 expression plasmid plus in vitro-prepared sgRNA). The transfection of a large plasmid into local mouse brain tissue was also shown. In summary, we report an effective PEI-PBA-SAP-F gene carrier with the appropriate lipophilic/cationic balance for biomedical applications.

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