sp3 C-H bond arylation directed by amidine protecting group:: α-arylation of pyrrolidines and piperidines

A new ruthenium-catalyzed direct sp3 C-H to C-C bond transformation is disclosed. Specifically, a method for the α-arylation of cyclic amines, containing either permanent (pyridine, pyrimidine) or removable (amidine) directing groups, is described. This cross-coupling reaction involves heating amine substrates with arylboronate ester at 150 °C in a ketone solvent with a catalytic amount of ruthenium carbonyl [Ru3(CO)12]. Arylboronate esters containing either electron-withdrawing or electron-donating substituents could be efficiently coupled. Heteroarene boronates were also effective donors. Copyright © 2006 American Chemical Society.