This study developed a concise and efficient method for synthesizing cytoxazone via the corresponding dihydrooxazine intermediate. A dihydrooxazine ring was formed with high stereoselectivity through a SiO2-promoted intramolecular substitution of a trichloroacetimidate, starting from a known enantiomerically pure diol. The intermediary dihydrooxazine was successively hydrolyzed, yielding cytoxazone