Ruthenium catalyzed remote C4-selective C-H functionalisation of carbazoles via σ-activation

We report the C4-selective C-H alkylation of carbazole derivatives furnished with a pyrimidine directing group at N9. This was realized using ruthenium catalyzed sigma-activation methodology, whereby C-H activation at C1 enables the interaction of this ruthenacycle, at the para position to the metal center, with tertiary alkyl radicals.