Regioselectivity in C-H activation: reagent control in cyclometallation of 2-(1-naphthyl)-pyridineElectronic supplementary information (ESI) available: X-ray data in cif format. CCDC 1404269 and 1404270. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5dt04068j

2-(1-Naphthyl)-pyridine ( 1 ) possesses sp 2 C-H bonds in both the γ- and δ-positions and is therefore a suitable substrate for studying the cyclometallation selectivity with different reagents and conditions. Such selectivity studies are reported. Based on deuterium-exchange experiments it is concluded that cycloruthenation with RuCl 2 ( p -cymene) dimer is reversible with kinetic and thermodynamic preference for γ-substitution. Electrophilic cycloborylation, on the other hand, shows unusual δ-substitution. The previously published cyclopalladation and cycloauration of the substrate was studied in detail and was shown to be irreversible; they proceed under kinetic control and give γ- and δ-substitution for palladium and gold, respectively. The choice of metallating agent completely reverses the regioselectivity in cyclometallation of 2-(1-naphthyl)-pyridine.