Originally discovered by Frost and co-workers, the meta selective sulfonation of 2-phenylpyridine using a sulfonyl chloride coupling partner, utilising a ruthenium(II) catalyst. This reaction has been proposed to proceed via a similar method to that of the meta alkylation reported by Frost and Ackermann which involves a meta-selective C-H bond alkylation reaction with secondary and tertiary alkyl halides catalyzed by ruthenium(II) carboxylate catalysts. The directing group first coordinate to the ruthenium catalyst. A reversible metalation takes place to generate the cycloruthenated complex as the key intermediates. The cycloruthenation activates the aromatic ring to undergo SAr type alkylation at the position para to the C–Ru bond.