Radical-Polar Crossover Enabled Triple Cleavage of CF₂Br₂: A Multicomponent Tandem Cyclization to 3-Fluoropyrazoles

Abstract

The elaboration of step-economy and catalytic approaches for accessing diverse fluorinated heterocyclics is highly desirable. Described herein is a radical-polar crossover enabled three-component cyclization to polysubstituted fluoropyrazoles by using CF₂Br₂ as a novel C1F1 synthon. Mechanistic experiments revealed that the <i>in situ</i> generation of the reactive intermediate <i>gem</i>-difluorovinylimine ion is the key to this transformation. This protocol unlocks the novel reactivity of CF₂Br₂ and adds significant synthetic values to fluorine chemistry.