-Substitutions at Five-Membered Hetarenes Enabled by Sulfonium Salts.

We report a nucleophilic substitution reaction of five-membered hetarylsulfonium salts that results in a change of the substitution pattern on the arene. The products of these -substitutions are hard to access synthetically otherwise. The sulfonium salts that serve as starting materials are generated by a highly site-selective C-H functionalization reaction.

Site-Selective C-H Oxygenation via Aryl Sulfonium Salts.

Herein, we report a two-step process forming arene C-O bonds in excellent site-selectivity at a late-stage. The C-O bond formation is achieved by selective introduction of a thianthrenium group, which is then converted into C-O bonds using photoredox chemistry. Electron-rich, -poor and -neutral arenes as well as complex drug-like small molecules are successfully transformed into both phenols and various ethers.

C-N Cross-Couplings for Site-Selective Late-Stage Diversification via Aryl Sulfonium Salts.

We report diverse C-N cross-coupling reactions of aryl thianthrenium salts that are formed site-selectively by direct C-H functionalization. The scope of N-nucleophiles ranges from primary and secondary alkyl and aryl amines to various N-containing heterocycles, and the overall transformation is applicable to late-stage functionalization of complex, drug-like small molecules.

Exploiting and Understanding the Selectivity of Ru-N-Heterocyclic Carbene Metathesis Catalysts for the Ethenolysis of Cyclic Olefins to α,ω-Dienes.

A library of 29 homologous Ru-based olefin metathesis catalysts has been tested for ethenolysis of cyclic olefins toward the goal of selectively forming α,ω-diene using cis-cyclooctene as a prototypical substrate. Dissymmetry at the N-heterocyclic carbene (NHC) ligand was identified as a key parameter for controlling the selectivity. The best-performing catalyst bearing an N-CF group significantly outperformed the benchmark second-generation Grubbs catalyst in the ethenolysis of cis-cyclooctene.