Dearomative Addition-Hydrogen Autotransfer for Branch-Selective -Heteroaryl C-H Functionalization via Ruthenium-Catalyzed C-C Couplings of Diene Pronucleophiles.

A novel mechanism for -heteroaryl C-H functionalization via dearomative addition-hydrogen autotransfer is described. Upon exposure to the catalyst derived from RuHCl(CO)(PPh) and Xantphos, dienes - suffer hydroruthenation to form allylruthenium nucleophiles that engage in -heteroaryl addition-β-hydride elimination to furnish branched products of C-C coupling - and -. Oxidative cleavage of isoprene adducts , , , and followed by ruthenium-catalyzed dynamic kinetic asymmetric ketone reduction provides enantiomerically enriched -heteroarylethyl alcohols - and, therefrom, -heteroarylethyl amines -. Density functional theory calculations correlate experimentally observed regioselectivities with the magnitude of the -heteroaryl LUMO coefficients and corroborate rate-determining dearomative allylruthenium addition. In the presence of 2-propanol and trifluoroethanol, dearomatized adducts derived from pyrimidine and quinazoline were isolated and characterized.