3'-Azido-3'-deoxy-5-fluorocytidine (Compound 12) is a cytidine derivative. 3'-Azido-3'-deoxy-5-fluorocytidine is a click chemistry reagent, it contains an Azide group and can undergo copper-catalyzed azide-alkyne cycloaddition reaction (CuAAc) with molecules containing Alkyne groups. Strain-promoted alkyne-azide cycloaddition (SPAAC) can also occur with molecules containing DBCO or BCN groups.