An Easy Access to 4‐Trifluoromethylated 7‐(4‐Substitued‐1H‐1,2,3‐Triazol‐1‐yl)Pyrimido[1,2‐b]Pyridazin‐2‐One Systems

Efficient synthesis of 7‐(1H‐1,2,3‐triazol‐1‐yl)‐4‐trifluoromethyl‐2H‐pyrimido[1,2‐b]pyridazin‐2‐ones from 7‐chloro‐4‐trifluoromethylpyrimido[1,2‐b]pyridazin‐2‐one by a consecutive SNAr reaction with azide, followed by copper‐catalyzed [3+2] cycloaddition is described. An efficient and very easy methodology for the synthesis of fluorinated 7‐(1H‐1,2,3‐triazol‐1‐yl)‐2H‐pyrimido[1,2‐b]pyridazin‐2‐ones has been developed. The new trifluoromethylated pyrimido[1,2‐b]pyridazin‐2‐one embedded with 1,4‐disubstituted‐[1,2,3]‐triazole are obtained regioselectively from 7‐chloro‐4‐trifluoromethylpyrimido[1,2‐b]pyridazin‐2‐one by a consecutive SNAr reaction with azide, followed by copper‐catalyzed [3+2] cycloaddition. This methodology can be used to easily prepare, with good to excellent yields, a library of potentially bioactive trifluoromethylated 7‐(1H‐1,2,3‐triazol‐1‐yl)‐2H‐pyrimido[1,2‐b]pyridazin‐2‐ones.