We developed a Ru(II)-catalyzed redox-neutral C-H olefination of N-methoxybenzamides with vinyl sulfones. The reaction is operationally simple and conducted at ambient temperature and does not require silver additives or external oxidants, making it suitable for late-stage functionalization. Notably, we leveraged the leaving group ability of sulfinate anion to synthesize 3-methyleneisoindolin-1-ones through a tandem C-H olefination/cyclization/elimination sequence at ambient temperature. Moreover, we successfully demonstrated the synthetic versatility of 3-methyleneisoindolin-1-one for the construction of an isoindolobenzazepine core.