Photoinduced Sequential Trichloromethylation/Cyclization of N -Alkenyl Aldehyde Hydrazones to Access Trichloromethylated Diazaheterocycles

A visible-light-induced trichloromethylation/cyclization reaction of N -homoallyl aldehyde hydrazones with bromotrichloromethane (BrCCl 3 ) using fac -Ir(ppy) 3 as the photocatalyst was developed, providing trichloromethylated tetrahydropyridazines in 38–80% yields. Under similar reaction conditions, the reaction of N -allyl aldehyde hydrazones with BrCCl 3 afforded trichloromethylated dihydropyrazoles in 47–72% yields. In addition, trichloromethylated tetrahydrodiazepines were also achieved in 20–63% yield. This protocol features mild conditions and good functional group compatibility to install a trichloromethyl group into N -heterocyclic structures.