A novel and efficient strategy for the transformation of trifluoromethyl ketones is reported. The selective C(α)–C(β) bond cleavage of trifluoromethyl ketones is realized with amidines under air. This transition-metal free reaction system employs green molecular oxygen as an oxidant as well as an O-source, delivering various useful 5-trifluoromethylated imidazol-4-ones in high yields. Preliminary mechanism studies indicate that this reaction proceeds through a 1,2-aryl migration pathway rather than a radical mechanism.