Visible Light-Induced Radical-Cascade Difluoroalkylation/Cyclization of Unsaturated Aldehyde Hydrazones for the Synthesis of Difluoroalkylated Dihydropyrazoles and Tetrahydropyridazines

Visible light-induced radical 5/6-endo-trig difluoroalkylation/cyclization of N-allyl and homoallyl aldehyde hydrazones with various fluoroalkyl bromides has been achieved. The reaction was carried out with alkyl difluoroacetates and difluoroacetamide as difluoroalkylation reagents and Eosin Y as an organic photocatalyst. Various difluoroalkylated dihydropyrazoles and tetrahydropyridazines were obtained under metal-free and mild conditions.