Abstract:
Functionalization of the bio-relevant heterocycles
2-arylbenzo[d]oxazole and 2-arylbenzo[d]thiazole has been
achieved through Ru(II)-catalyzed alkenylation with unactivated olefins leading to selective formation of the monoalkenylated products. This approach has a broad substrate
scope with respect to the coupling partners, affords high
yields, and works for gram scale synthesis using a readily
available Ru-based catalyst. Mechanistic studies reveal a C H
activation pathway for the dehydrogenative coupling leading
to the alkenylation. However, the results of the ESI-MS-guided
deuterium kinetic isotope effect studies indicate that the C H
activation stage may not be the rate-determining step of the
reaction. The use of a radical scavenging agent such as
TEMPO did not show any detrimental effect on the reaction
outcome, eliminating the possibility of the involvement of a
free-radical path
