C–H Arylation of Pyridines: High Regioselectivity as a Consequence of the Electronic Character of C–H Bonds and Heteroarene Ring
作者:Pengfei Guo、Jung Min Joo、Souvik Rakshit、Dalibor Sames
DOI:10.1021/ja206022p
日期:2011.10.19
We report a new catalytic protocol for highly selective C-H arylation of pyridines containing common and synthetically versatile electron-withdrawing substituents (NO(2), CN, F and Cl). The new protocol expands the scope of catalytic azine functionalization as the excellent regioselectivity at the 3- and 4-positions well complements the existing methods for C-H arylation and Ir-catalyzed borylation, as well as classical functionalization of pyridines. Another important feature of the new method is its flexibility to adapt to challenging substrates by a simple modification of the carboxylic acid ligand or the use of silver salts. The regioselectivity can be rationalized on the basis of the key electronic effects (repulsion between the nitrogen lone pair and polarized C-Pd bond at C2-/C6-positions and acidity of the C-H bond) in combination with steric effects (sensitivity to bulky substituents).
Contrasting Anticancer Activity of Half-Sandwich Iridium(III) Complexes Bearing Functionally Diverse 2-Phenylpyridine Ligands
作者:Adam J. Millett、Abraha Habtemariam、Isolda Romero-Canelón、Guy J. Clarkson、Peter J. Sadler
DOI:10.1021/acs.organomet.5b00097
日期:2015.6.8
[(η5-Cp*)Ir(2-(2′-fluorophenyl)pyridine)Cl] (1) and [(η5-Cp*)Ir(2-(4′-fluorophenyl)pyridine)Cl] (2) exhibit the expected “piano-stool” configuration. DFT calculations showed that substituents caused only localized effects on the electrostatic potential surface of the chelating 2-PhPy ligand of the complexes. Hydrolysis of all complexes is rapid, but readily reversed by addition of NaCl. The complexes show preferential