Photocatalytic Hydrazonyl Radical-Mediated Radical Cyclization/Allylation Cascade: Synthesis of Dihydropyrazoles and Tetrahydropyridazines

A novel
photocatalytic hydrazonyl radical-mediated radical cyclization/allylation
cascade reaction of β,γ-unsaturated hydrazones is developed
using allyl sulfones and Morita–Baylis–Hillman adduct
as allyl sources, which provides an efficient and practical access
to various diversely functionalized dihydro­pyrazoles and tetrahydro­pyridazines.
The reaction is enabled by controllable generation of hydrazonyl radicals
via an oxidative deprotonation electron transfer strategy and selective
trapping of the resultant C-centered radicals under visible light
irradiation.