Metal controlled regioselectivity in the cyclometallation of 2-(1-naphthyl)-pyridine

Abstract

Cyclometallation of 2-(1-naphthyl)-pyridine is described. While cyclopalladation results in a five-membered metallacycle, cycloauration displays a completely orthogonal regioselectivity, resulting in the six-membered ring analogue. Bromination of the gold metallacycle results in the new C-H functionalisation product 2-(8-bromonaphth-1-yl)pyridine.

Catalytic Gold Chemistry: From Simple Salts to Complexes for Regioselective C−H Bond Functionalization

“…In contrast, Pd(OAc) 2 or IrCl 3 activates the δ CÀ H bond to afford five-membered metallacycles, a result that can be attributed to the control of regiochemistry as a function of the metal catalyst. [124] Similar γ-CÀ H site-selectivity was observed by You et al, while investigating the AuBr 3 catalyzed oxidative Csp 2 -H arylation of 55 with phenylboronic acid. [125] This change in regioselectivity compared to the work of Wendt could be explained by the relative electron density difference at the δ-CÀ H and γ-CÀ H bonds.…”

“…The observed regioselectivity was also attributed to the location of the δ‐C−H within the electron‐rich unsubstituted benzene ring compared to those possessing weakly electron‐withdrawing pyridyl substituents bound to the gold metal center. In contrast, Pd(OAc) 2 or IrCl 3 activates the δ C−H bond to afford five‐membered metallacycles, a result that can be attributed to the control of regiochemistry as a function of the metal catalyst [124] . Similar γ‐C−H site‐selectivity was observed by You et al., while investigating the AuBr 3 catalyzed oxidative Csp 2 ‐H arylation of 55 with phenylboronic acid [125] .…”

Enhancing the Stability of Aromatic PCN Pincer Nickel Complexes by Incorporation of Pyridine as the Nitrogen Side Arm

“…Pyridine is well known as a common directing group that enhances cyclometallation and selective C-H functionalization reactions. [24][25][26][27][28]…”

“…Pyridine has been widely used as a directing group in C-H functionalization reactions due to its strong ability to bind to the metal center, which facilitates the C-H activation step and/or stabilizes the product. [24][25][26][27][28][29][30] Here, we report the synthesis of a new (PCN Py )H pincer ligand bearing pyridine as the nitrogen side arm. The pyridine arm is installed in one synthetic step through a cross-coupling reaction which is a great NCN nickel complex with pyridine side arms was successfully obtained giving a rare example of such type of complexes to be prepared through direct C-H activation.…”

Electronically Divergent Triscyclometalated Iridium(III) 2-(1-naphthyl)pyridine Complexes and Their Application in Three-Component Methoxytrifluoromethylation of Styrene

“…19 To this end, homoleptic tris-C,N iridium complexes have been widely investigated, and these efforts have primarily focused on the prototypical 2-phenylpyridine (ppy) ligand. 16 Although more-conjugated 2-(1naphthyl)pyridine (npy) ligands show promising properties, 20 they remain underexplored.…”