Herein, we report the ruthenium-catalyzed ortho C–H alkenylation of a wide range of N-aryloxazolidinone scaffolds. Alkenylation was achieved with complete monoselectivity with a scope of 27 examples in 2-MeTHF. Yields ranged from 23 to 94%, producing highly decorated oxazolidinone scaffolds. A kinetically relevant C–H cleavage was also observed with a kinetic isotope effect (KIE) of ∼2. Density functional theory calculations provided information about mechanism, detailing the β-hydride elimination as the most energetically challenging step of 13.5 kcal mol–1. In-depth computational kinetic studies also predicted a KIE of 2.17 for C–H cleavage and an intrinsic KIE for the reaction of 2.22, in line with the experimentally observed value.