The Practical Access to Fluoroalkylated Pyrazolo[1,5-c]quinazolines by Fluoroalkyl-Promoted [3 + 2] Cycloaddition Reaction

The efficient synthesis of fluoroalkylated pyrazolo[1,5-c]quinazolines by reactions of 3-diazoindolin-2-ones with methyl β-fluoroalkylpropionates has been achieved. This protocol affords two regioisomers of fluoroalkylated pyrazolo[1,5-c]quinazolines with excellent yields in total. The dipolarophilicity of methyl β-fluoroalkylpropionates enhanced by perfluoroalkyl groups is crucial for the high efficiency of this [3 + 2] cycloaddition reaction.